PM2.5 constituents and related air quality variables as predictors of survival in a cohort of U.S. military veterans

An overview of atmospheric aerosol and their effects on human health

Epidemiologic investigations have previously been published in more than 200 papers, and several studies have examined the impacts of particle air pollution on health. The main conclusions now being made about the epidemiological evidence of particle pollution-induced health impacts are discussed in this article. Although there is no universal agreement, most reviewers conclude that particulate air pollution, particularly excellent combustion-cause contamination prevalent in many municipal and manufacturing environments, is a significant risk for cardiopulmonary sickness and mortality. Most epidemiological research has concentrated on the impacts of acute exposure, although the total public health implications of chronic acquaintance's outcome may be more extraordinarily significant. According to some reviewers, prolonged, repeated exposure raises the risk of cardiorespiratory death and chronic respiratory illness. A more general (but still universal) agreement is that short-term particle pollution exposure has been shown to aggravate pre-existing pulmonary and cardiovascular diseases and increase the number of community members who become sick, require medical treatment, or die. Several in-depth studies conducted in the global and Indian regions are addressed.

Long-term exposure to ambient ozone and mortality in a population-based cohort of South Korea: Considering for an alternative exposure time metric

Studies on the health effects of long-term ozone exposure remain limited with mixed results. One potential source of this inconsistency is the difference in exposure time metrics. This study aimed to investigate the association between long-term exposure to ambient ozone and mortality in South Korea, using different exposure metrics. We also examined whether heterogeneity between previous studies was due to the different exposure metrics. The study population comprised 179,806 participants from the National Health Insurance Service-National Sample Cohort (2002-2015) residing in seven major cities in South Korea. Several ozone exposure metrics (year-round 24-h, year-round 8-h, warm-season 24-h, and warm-season 8-h) were calculated. Time-varying Cox proportional hazards models were used to estimate the association between ozone and all-cause and cause-specific mortalities. Random-effect meta-analysis and meta-regression analysis were performed to pool the effect estimates of previous studies and examine whether the exposure metric can explain the between-study heterogeneity. The hazard ratios (HRs) per 10 ppb increment in year-round 24-h ozone for all-cause (HR, 1.18; 95% CI, 1.07-1.29) and circulatory (HR, 1.52; 95% CI, 1.25-1.84) mortality were higher than those of the other metrics. Year-round 8-h ozone exhibited the largest association with respiratory mortality (HR, 1.43; 95% CI, 1.04-1.96). A meta-analysis of 29 previous studies and the present study showed the largest HR for all-cause mortality from studies using year-round 8-h exposure (HR, 1.014; 95% CI, 0.994-1.033). The exposure metric was significantly associated with effect estimates in the multivariable meta-regression model. In conclusion, in the population-based cohort in South Korea, we found positive associations between several long-term ozone exposure metrics and mortality. The different ozone exposure metrics exhibited heterogeneous effect estimates. A year-round 24-h average ozone metric also could be considered an alternative long-term standard for ozone.

Integrated molecular response of exposure to traffic-related pollutants in the US trucking industry

Exposure to traffic-related pollutants, including diesel exhaust, is associated with increased risk of cardiopulmonary disease and mortality; however, the precise biochemical pathways underlying these effects are not known. To investigate biological response mechanisms underlying exposure to traffic related pollutants, we used an integrated molecular response approach that included high-resolution metabolomic profiling and peripheral blood gene expression to identify biological responses to diesel exhaust exposure. Plasma samples were collected from 73 non-smoking males employed in the US trucking industry between February 2009 and October 2010, and analyzed using untargeted high-resolution metabolomics to characterize metabolite associations with shift- and week-averaged levels of elemental carbon (EC), organic carbon (OC) and particulate matter with diameter ≤ 2.5 μm (PM2.5). Metabolic associations with EC, OC and PM2.5 were evaluated for biochemical processes known to be associated with disease risk. Annotated metabolites associated with exposure were then tested for relationships with the peripheral blood transcriptome using multivariate selection and network correlation. Week-averaged EC and OC levels, which were averaged across multiple shifts during the workweek, resulted in the greatest exposure-associated metabolic alterations compared to shift-averaged exposure levels. Metabolic changes associated with EC exposure suggest increased lipid peroxidation products, biomarkers of oxidative stress, thrombotic signaling lipids, and metabolites associated with endothelial dysfunction from altered nitric oxide metabolism, while OC exposures were associated with antioxidants, oxidative stress biomarkers and critical intermediates in nitric oxide production. Correlation with whole blood RNA gene expression provided additional evidence of changes in processes related to endothelial function, immune response, inflammation, and oxidative stress. We did not detect metabolic associations with PM2.5. This study provides an integrated molecular assessment of human exposure to traffic-related air pollutants that includes diesel exhaust. Metabolite and transcriptomic changes associated with exposure to EC and OC are consistent with increased risk of cardiovascular diseases and the adverse health effects of traffic-related air pollution.

Indoor Particulate Matter in Urban Households: Sources, Pathways, Characteristics, Health Effects, and Exposure Mitigation

Particulate matter (PM) is a complex mixture of solid particles and liquid droplets suspended in the air with varying size, shape, and chemical composition which intensifies significant concern due to severe health effects. Based on the well-established human health effects of outdoor PM, health-based standards for outdoor air have been promoted (e.g., the National Ambient Air Quality Standards formulated by the U.S.). Due to the exchange of indoor and outdoor air, the chemical composition of indoor particulate matter is related to the sources and components of outdoor PM. However, PM in the indoor environment has the potential to exceed outdoor PM levels. Indoor PM includes particles of outdoor origin that drift indoors and particles that originate from indoor activities, which include cooking, fireplaces, smoking, fuel combustion for heating, human activities, and burning incense. Indoor PM can be enriched with inorganic and organic contaminants, including toxic heavy metals and carcinogenic volatile organic compounds. As a potential health hazard, indoor exposure to PM has received increased attention in recent years because people spend most of their time indoors. In addition, as the quantity, quality, and scope of the research have expanded, it is necessary to conduct a systematic review of indoor PM. This review discusses the sources, pathways, characteristics, health effects, and exposure mitigation of indoor PM. Practical solutions and steps to reduce exposure to indoor PM are also discussed.

Environmental and health hazards of military metal pollution

An increasing body of literature has demonstrated that armed conflicts and military activity may contribute to environmental pollution with metals, although the existing data are inconsistent. Therefore, in this paper, we discuss potential sources of military-related metal emissions, environmental metal contamination, as well as routes of metal exposure and their health hazards in relation to military activities. Emission of metals into the environment upon military activity occurs from weapon residues containing high levels of particles containing lead (Pb; leaded ammunition), copper (Cu; unleaded), and depleted uranium (DU). As a consequence, military activity results in soil contamination with Pb and Cu, as well as other metals including Cd, Sb, Cr, Ni, Zn, with subsequent metal translocation to water, thus increasing the risk of human exposure. Biomonitoring studies have demonstrated increased accumulation of metals in plants, invertebrates, and vertebrate species (fish, birds, mammals). Correspondingly, military activity is associated with human metal exposure that results from inhalation or ingestion of released particles, as well as injuries with subsequent metal release from embedded fragments. It is also notable that local metal accumulation following military injury may occur even without detectable fragments. Nonetheless, data on health effects of military-related metal exposures have yet to be systematized. The existing data demonstrate adverse neurological, cardiovascular, and reproductive outcomes in exposed military personnel. Moreover, military-related metal exposures also result in adverse neurodevelopmental outcome in children living within adulterated territories. Experimental in vivo and in vitro studies also demonstrated toxic effects of specific metals as well as widely used metal alloys, although laboratory data report much wider spectrum of adverse effects as compared to epidemiological studies. Therefore, further epidemiological, biomonitoring and laboratory studies are required to better characterize military-related metal exposures and their underlying mechanisms of their adverse toxic effects.

Household air pollution and blood markers of inflammation: A cross-sectional analysis

Household air pollution (HAP) from biomass stoves is a leading risk factor for cardiopulmonary outcomes; however, its toxicity pathways and relationship with inflammation markers are poorly understood. Among 180 adult women in rural Peru, we examined the cross-sectional exposure-response relationship between biomass HAP and markers of inflammation in blood using baseline measurements from a randomized trial. We measured markers of inflammation (CRP, IL-6, IL-10, IL-1β, and TNF-α) with dried blood spots, 48-h kitchen area concentrations and personal exposures to fine particulate matter (PM_2.5 ), black carbon (BC), and carbon monoxide (CO), and 48-h kitchen concentrations of nitrogen dioxide (NO₂ ) in a subset of 97 participants. We conducted an exposure-response analysis between quintiles of HAP levels and markers of inflammation. Markers of inflammation were more strongly associated with kitchen area concentrations of BC than PM_2.5 . As expected, kitchen area BC concentrations were positively associated with TNF-α (pro-inflammatory) concentrations and negatively associated with IL-10, an anti-inflammatory marker, controlling for confounders in single- and multi-pollutant models. However, contrary to expectations, kitchen area BC and NO₂ concentrations were negatively associated with IL-1β, a pro-inflammatory marker. No associations were identified for IL-6 or CRP, or for any marker in relation to personal exposures.

The Role of Fossil Fuel Combustion Metals in PM2.5 Air Pollution Health Associations

In this review, we elucidate the central role played by fossil fuel combustion in the health-related effects that have been associated with inhalation of ambient fine particulate matter (PM2.5). We especially focus on individual properties and concentrations of metals commonly found in PM air pollution, as well as their sources and their adverse health effects, based on both epidemiologic and toxicological evidence. It is known that transition metals, such as Ni, V, Fe, and Cu, are highly capable of participating in redox reactions that produce oxidative stress. Therefore, particles that are enriched, per unit mass, in these metals, such as those from fossil fuel combustion, can have greater potential to produce health effects than other ambient particulate matter. Moreover, fossil fuel combustion particles also contain varying amounts of sulfur, and the acidic nature of the resulting sulfur compounds in particulate matter (e.g., as ammonium sulfate, ammonium bisulfate, or sulfuric acid) makes transition metals in particles more bioavailable, greatly enhancing the potential of fossil fuel combustion PM2.5 to cause oxidative stress and systemic health effects in the human body. In general, there is a need to further recognize particulate matter air pollution mass as a complex source-driven mixture, in order to more effectively quantify and regulate particle air pollution exposure health risks.

Long-term exposure to iron and copper in fine particulate air pollution and their combined impact on reactive oxygen species concentration in lung fluid: a population-based cohort study of cardiovascular disease incidence and mortality in Toronto, Canada

BACKGROUND

Exposure to fine particulate (PM2.5) air pollution is associated with increased cardiovascular disease (CVD), but less is known about its specific components, such as metals originating from non-tailpipe emissions. We investigated the associations of long-term exposure to metal components [iron (Fe) and copper (Cu)] in PM2.5 with CVD incidence.

METHODS

We conducted a population-based cohort study in Toronto, Canada. Exposures to Fe and Cu in PM2.5 and their combined impact on the concentration of reactive oxygen species (ROS) in lung fluid were estimated using land use regression models. Incidence of acute myocardial infarction (AMI), congestive heart failure (CHF) and CVD death was ascertained using health administrative datasets. We used mixed-effects Cox regression models to examine the associations between the exposures and health outcomes. A series of sensitivity analyses were conducted, including indirect adjustment for individual-level cardiovascular risk factors (e.g. smoking), and adjustment for PM2.5 and nitrogen dioxide (NO2).

RESULTS

In single-pollutant models, we found positive associations between the three exposures and all three outcomes, with the strongest associations detected for the estimated ROS. The associations of AMI and CHF were sensitive to indirect adjustment, but remained robust for CVD death in all sensitivity analyses. In multi-pollutant models, the associations of the three exposures generally remained unaltered. Interestingly, adjustment for ROS did not substantially change the associations between PM2.5 and CVD, but attenuated the associations of NO2.

CONCLUSIONS

Long-term exposure to Fe and Cu in PM2.5 and their combined impact on ROS were consistently associated with increased CVD death.

COVID-19 and the Environment, Review and Analysis

We reviewed studies linking COVID-19 cases and deaths with the environment, focusing on relationships with air pollution. We found both short- and long-term observational relationships with a range of regulated pollutants, although only two studies considered both cases (i.e., infections) and deaths within a common analytical framework. Most of these studies were limited to a few months of the pandemic period. Statistically significant relationships were found more often for PM2.5 and NO2 than for other regulated pollutants, but no rationale was suggested for such short-term relationships; latency was seldom considered for long-term relationships. It was also unclear whether confounding had been adequately controlled in either type of study. Studies of air quality improvement following lockdowns found more robust relationships with local (CO, NO2) rather than regional (PM2.5, O3) pollutants, but meteorological confounding was seldom considered. Only one of seven studies of airborne virus transmission reported actual measurements. Overall, we found the existing body of literature to be more suggestive than definitive. Due to these various deficiencies, we assembled a new state-level database of cumulative COVID-19 cases and deaths through March 2021 with a range of potential predictor variables and performed linear regression analyses on various combinations. As single predictors, we found significant (p < 0.05) relationships between cumulative cases and household crowding (+), education (−), face-mask usage (−), or voting Republican (+). For cumulative deaths, we found significant relationships with education (−), black race (+), or previous levels of PM2.5 (+). NOx (+), and elemental carbon (EC, +). We found no relationships between long-term air quality and cumulative COVID-19 cases. Our associations linking air pollution with COVID-19 mortality were not statistically different from those for all-cause mortality in previous studies. In multiple mortality regressions combining air pollution, race, and education, NOx and EC remained significant but PM2.5 did not. We concluded that the current worldwide emphasis on PM2.5 is misplaced. We predicted air pollutant effects of a few percentage points, but individual differences between races, political identification, and post-graduate education were of the order of factors of 2 to 4. In general, the factors predicting infection were personal and related to COVID-19 exposure, while those predicting subsequent mortality tended to be more situational and related to geography. Overall, we concluded that how you live is more important than where you live.

Systematic review and meta-analysis of cohort studies of long term outdoor nitrogen dioxide exposure and mortality

Objective

To determine whether long term exposure to outdoor nitrogen dioxide (NO₂) is associated with all-cause or cause-specific mortality.

Methods

MEDLINE, Embase, CENTRAL, Global Health and Toxline databases were searched using terms developed by a librarian. Screening, data extraction and risk of bias assessment were completed independently by two reviewers. Conflicts were resolved through consensus and/or involvement of a third reviewer. Pooling of results across studies was conducted using random effects models, heterogeneity among included studies was assessed using Cochran’s Q and I² measures, and sources of heterogeneity were evaluated using meta-regression. Sensitivity of pooled estimates to individual studies was examined and publication bias was evaluated using Funnel plots, Begg’s and Egger’s tests, and trim and fill.

Results

Seventy-nine studies based on 47 cohorts, plus one set of pooled analyses of multiple European cohorts, met inclusion criteria. There was a consistently high degree of heterogeneity. After excluding studies with probably high or high risk of bias in the confounding domain (n = 12), pooled hazard ratios (HR) indicated that long term exposure to NO₂ was significantly associated with mortality from all/ natural causes (pooled HR 1.047, 95% confidence interval (CI), 1.023–1.072 per 10 ppb), cardiovascular disease (pooled HR 1.058, 95%CI 1.026–1.091), lung cancer (pooled HR 1.083, 95%CI 1.041–1.126), respiratory disease (pooled HR 1.062, 95%CI1.035–1.089), and ischemic heart disease (pooled HR 1.111, 95%CI 1.079–1.144). Pooled estimates based on multi-pollutant models were consistently smaller than those from single pollutant models and mostly non-significant.

Conclusions

For all causes of death other than cerebrovascular disease, the overall quality of the evidence is moderate, and the strength of evidence is limited, while for cerebrovascular disease, overall quality is low and strength of evidence is inadequate. Important uncertainties remain, including potential confounding by co-pollutants or other concomitant exposures, and limited supporting mechanistic evidence. (PROSPERO registration number CRD42018084497)

Long-term exposure to NO2 and O3 and all-cause and respiratory mortality: A systematic review and meta-analysis

BACKGROUND

WHO has published several volumes of Global Air Quality Guidelines to provide guidance on the health risks associated with exposure to outdoor air pollution. As new scientific evidence is generated, air quality guidelines need to be periodically revised and, where necessary, updated.

OBJECTIVES

The aims of the study were 1) to summarise the available evidence on the effect of long-term exposure to ozone (O3) and nitrogen dioxide (NO2) on mortality; 2) and to assess concentration response functions (CRF), their shape and the minimum level of exposures measured in studies to support WHO's update of the global air quality guidelines.

DATA SOURCES

We conducted a systematic literature search of the Medline, Embase and Web of Science databases following a protocol proposed by WHO and applied Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) guidelines for reporting our results.

STUDY ELIGIBILITY CRITERIA

Cohort studies in human populations (including sub-groups at risk) exposed to long-term concentrations of NO2 and O3. Outcomes assessed were all-cause, respiratory, Chronic Obstructive Pulmonary Disease (COPD) and Acute Lower Respiratory Infection (ALRI) mortality.

STUDY APPRAISAL AND SYNTHESIS METHODS

Studies included in the meta-analyses were assessed using a new Risk of Bias instrument developed by a group of experts convened by WHO. Study results are presented in forest plots and quantitative meta-analyses were conducted using random effects models. The certainty of evidence was assessed using a newly developed adaptation of GRADE.

RESULTS

The review identified 2068 studies of which 95 were subject to full-text review with 45 meeting the inclusion criteria. An update in September 2018 identified 159 studies with 1 meeting the inclusion criteria. Of the 46 included studies, 41 reported results for NO2 and 20 for O3. The majority of studies were from the USA and Europe with the remainder from Canada, China and Japan. Forty-two studies reported results for all-cause mortality and 22 for respiratory mortality. Associations for NO2 and mortality were positive; random-effects summary relative risks (RR) were 1.02 (95% CI: 1.01, 1.04), 1.03 (1.00, 1.05), 1.03 (1.01, 1.04) and 1.06 (1.02, 1.10) per 10 μg/m3 for all-cause (24 cohorts), respiratory (15 cohorts), COPD (9 cohorts) and ALRI (5 cohorts) mortality respectively. The review identified high levels of heterogeneity for all causes of death except COPD. A small number of studies investigated the shape of the concentration-response relationship and generally found little evidence to reject the assumption of linearity across the concentration range. Studies of O3 using annual metrics showed the associations with all-cause and respiratory mortality were 0.97 (0.93, 1.02) and 0.99 (0.89, 1.11) per 10 μg/m3 respectively. For studies using peak O3 metrics, the association with all-cause mortality was 1.01 (1.00, 1.02) and for respiratory mortality 1.02 (0.99, 1.05), each per 10 μg/m3. The review identified high levels of heterogeneity. Few studies investigated the shape of the concentration-response relationship. Certainty in the associations (adapted GRADE) with mortality was rated low to moderate for each exposure-outcome pair, except for NO2 and COPD mortality which was rated high.

LIMITATIONS

The substantial heterogeneity for most outcomes in the review requires explanation. The evidence base is limited in terms of the geographical spread of the study populations and, for some outcomes, the small number of independent cohorts for meta-analysis precludes meaningful meta-regression to explore causes of heterogeneity. Relatively few studies assessed specifically the shape of the CRF or multi-pollutant models.

CONCLUSIONS

The short-comings in the existing literature base makes determining the precise nature (magnitude and linearity) of the associations challenging. Certainty of evidence assessments were moderate or low for both NO2 and O3 for all causes of mortality except for NO2 and COPD mortality where the certainty of the evidence was judged as high.

The toxicity of respirable South African mine tailings dust in relation to their physicochemical properties

INTRODUCTION

Decades of mining in South Africa has given rise to hundreds of tailings storage facilities (TSFs) and several tonnes of waste. These TSFs have contributed to air pollution due to the lack of proper rehabilitation measures. Currently, it is not known whether tailings emissions could be the cause of respiratory-related ill effects. In addition, the physicochemical properties that may govern their toxicity have not yet been identified.

AIM

The aim of this research was to determine the toxicity of tailings dust and identify the physicochemical properties likely to govern toxicity.

METHODS

Dust samples were collected from five TSFs in the Gauteng and North West Provinces of South Africa and sieved to enrich the airborne particle fraction more likely to be inhaled. Thereafter, their physicochemical characteristics were assessed i.e. size distribution, specific surface area, shape, surface elemental composition, mineral composition, total elemental composition and surface activity. In addition, the toxicity and cellular internalization of the particles were assessed using the BEAS-2B epithelial and U937 monocytic-macrophage cell lines.

Results: The results showed that all tailings dusts showed toxicity, particularly in the BEAS-2B cell line. This toxicity could have been governed by either their elemental composition, e.g. high transition elements e.g. Fe, Cu, Cr and V in the dusts from TSF 4, or a combination of other physicochemical properties, e.g. higher quartz content, lower size and higher surface area in the dusts from TSF 1.

CONCLUSION

These results provide mechanistic evidence to support future epidemiological studies attempting to link tailings dust exposure to adverse health effects.

Long-term exposure to PM and all-cause and cause-specific mortality: A systematic review and meta-analysis

As new scientific evidence on health effects of air pollution is generated, air quality guidelines need to be periodically updated. The objective of this review is to support the derivation of updated guidelines by the World Health Organization (WHO) by performing a systematic review of evidence of associations between long-term exposure to particulate matter with diameter under 2.5 µm (PM_2.5) and particulate matter with diameter under 10 µm (PM₁₀), in relation to all-cause and cause-specific mortality. As there is especially uncertainty about the relationship at the low and high end of the exposure range, the review needed to provide an indication of the shape of the concentration-response function (CRF). We systematically searched MEDLINE and EMBASE from database inception to 9 October 2018. Articles were checked for eligibility by two reviewers. We included cohort and case-control studies on outdoor air pollution in human populations using individual level data. In addition to natural-cause mortality, we evaluated mortality from circulatory diseases (ischemic heart disease (IHD) and cerebrovascular disease (stroke) also specifically), respiratory diseases (Chronic Obstructive Pulmonary Disease (COPD) and acute lower respiratory infection (ALRI) also specifically) and lung cancer. A random-effect meta-analysis was performed when at least three studies were available for a specific exposure-outcome pair. Risk of bias was assessed for all included articles using a specifically developed tool coordinated by WHO. Additional analyses were performed to assess consistency across geographic region, explain heterogeneity and explore the shape of the CRF. An adapted GRADE (Grading of Recommendations Assessment, Development and Evaluation) assessment of the body of evidence was made using a specifically developed tool coordinated by WHO. A large number (N = 107) of predominantly cohort studies (N = 104) were included after screening more than 3000 abstracts. Studies were conducted globally with the majority of studies from North America (N = 62) and Europe (N = 25). More studies used PM_2.5 (N = 71) as the exposure metric than PM₁₀ (N = 42). PM_2.5 was significantly associated with all causes of death evaluated. The combined Risk Ratio (RR) for PM_2.5 and natural-cause mortality was 1.08 (95%CI 1.06, 1.09) per 10 µg/m³. Meta analyses of studies conducted at the low mean PM_2.5 levels (<25, 20, 15, 12, 10 µg/m³) yielded RRs that were similar or higher compared to the overall RR, consistent with the finding of generally linear or supra-linear CRFs in individual studies. Pooled RRs were almost identical for studies conducted in North America, Europe and Western Pacific region. PM₁₀ was significantly associated with natural-cause and most but not all causes of death. Application of the risk of bias tool showed that few studies were at a high risk of bias in any domain. Application of the adapted GRADE tool resulted in an assessment of "high certainty of evidence" for PM_2.5 with all assessed endpoints except for respiratory mortality (moderate). The evidence was rated as less certain for PM₁₀ and cause-specific mortality ("moderate" for circulatory, IHD, COPD and "low" for stroke mortality. Compared to the previous global WHO evaluation, the evidence base has increased substantially. However, studies conducted in low- and middle- income countries (LMICs) are still limited. There is clear evidence that both PM_2.5 and PM₁₀ were associated with increased mortality from all causes, cardiovascular disease, respiratory disease and lung cancer. Associations remained below the current WHO guideline exposure level of 10 µg/m³ for PM_2.5. Systematic review registration number (PROSPERO ID): CRD42018082577.

Long-term Exposure to Low Air Pollutant Concentrations and the Relationship with All-Cause Mortality and Stroke in Older Men

BACKGROUND

Long-term air pollution exposure has been associated with increased risk of mortality and stroke. Less is known about the risk at lower concentrations. The association of long-term exposure to PM2.5, PM2.5 absorbance, NO2, and NOx with all-cause mortality and stroke was investigated in a cohort of men aged ≥ 65 years who lived in metropolitan Perth, Western Australia.

METHODS

Land use regression models were used to estimate long-term exposure to air pollutants at participant's home address (n = 11,627) over 16 years. Different metrics of exposure were assigned: baseline; year before the outcome event; and average exposure across follow-up period. The Mortality Register and Hospital Morbidity Data from the Western Australia Data Linkage System were used to ascertain mortality and stroke cases. Hazard ratios (HRs) and 95% confidence intervals were estimated using Cox proportional hazard models, adjusting for age, smoking, education, and body mass index for all-cause mortality. For fatal and hospitalized stroke, the models included variables controlled for all-cause mortality plus hypertension.

RESULTS

Fifty-four percent of all-participants died, 3% suffered a fatal stroke, and 14% were hospitalized stroke cases. PM2.5 absorbance increased the risk of all-cause mortality with adjusted HR of 1.12 (1.02-1.23) for baseline and average exposures, and 1.14 (1.02-1.24) for past-year exposure. There were no associations between PM2.5 absorbance, NO2, and NOx and stroke outcomes. However, PM2.5 was associated with reduced risks of fatal stroke.

CONCLUSION

Long-term exposure to PM2.5 absorbance was associated with all-cause mortality among older men exposed to low concentrations; and exposure to PM2.5 was associated with reduced risk of fatal stroke.

Attributable Risk to Assess the Health Impact of Air Pollution: Advances, Controversies, State of the Art and Future Needs

Despite the increased attention given to the health impact assessment of air pollution and to the strategies to control it in both scientific literature and concrete interventions, the results of the implementations, especially those involving traffic, have not always been satisfactory and there is still disagreement about the most appropriate interventions and the methods to assess their effectiveness. This state-of-the-art article reviews the recent interpretation of the concepts that concern the impact assessment, and compares old and new measurements of attributable risk and attributable fraction. It also summarizes the ongoing discussion about the designs and methods for assessing the air pollution impact with particular attention to improvements due to spatio-temporal analysis and other new approaches, such as studying short term effects in cohorts, and the still discussed methods of predicting the values of attributable risk (AR). Finally, the study presents the more recent analytic perspectives and the methods for directly assessing the effects of not yet implemented interventions on air quality and health, in accordance with the suggestion in the strategic plan 2020-2025 from the Health Effect Institute.

Environmental predictors of survival in a cohort of U.S. military veterans: A multi-level spatio-temporal analysis stratified by race

We analyzed racial differences in all-cause mortality rates associated with air pollution in a cohort of military veterans in which 37% of the 70,000 members identified as African-American (black). In this comprehensive analysis, spatial levels comprised individuals, zip-codes, and counties. Temporal levels comprised the 26-y follow-up period (1976-2001) and 4 subperiods. Proportional hazard regression models were used, controlling for individual age, race (white, black), smoking (current, ever), education, height, body-mass index, and systolic and diastolic blood pressure; zipcode-average socioeconomic indicators; and county-average climate. County-level air quality measures included vehicular traffic density as a surrogate for all traffic-related pollutants including noise. The model accounted for nonlinear mortality relationships with age, body-mass index, blood pressure and zip-code racial composition. Relative to whites, more of the black veterans smoked, had slightly higher blood pressure, and lived in predominately black zip-codes that had more poverty than whites. The black veterans lived in counties that had slightly worse ambient air quality and substantially higher levels of vehicular traffic density. We analyzed all-cause mortality associations with county-level average ozone, nitrogen dioxide, sulfur dioxide, carbon monoxide for 1975-81, and subsequent data on particulates by particle size. We also considered sulfate and elemental carbon particles, benzene, SO2, and NOx based on nationwide modeling for 2002. We had no information on indoor air quality or personal exposures; our risk estimates should thus be regarded as characterizing the counties of residence rather than individual exposures of inhabitants. In addition to age, the strongest predictors of veterans' survival were residence in high-poverty zip-codes, smoking, and diastolic blood pressure, to all of which black veterans were less sensitive than whites. Black veterans had significantly lower mortality risks from aging, smoking, and elevated diastolic blood pressure, but larger risks from excessive body-mass index. They were less at risk from living a high-poverty zip-code than whites. We assumed these risk factors to be stable during follow-up and thus applicable to chronic health effects. After controlling for them, the all-cause mortality risk for black veterans was 10% lower than whites. In an effort to reduce random scatter we computed mean risks associated with overlapping groups of similar pollutants. These means were statistically significant for both black and white veterans for traffic-related, gaseous, and NOx-O3 pollutants, for which the overall mean relative risk was 1.076 (1.057-1.090). Grouped mean risks for particulate pollutants, sulfur compounds, and non-traffic pollutants were not significant for either race. Black veterans carried more of the traffic-related risks than whites because of their greater exposures and risk coefficients. PM2.5 risk estimates were negative for black veterans (0.82 [0.75-0.89]) but positive for whites (1.05 [1.005-1.10]) which is consistent with regional differences in overall mortality. The temporal analyses compared mortality rates by follow-up subperiod for the pollutants measured at enrollment. We expected increasing (cumulative) risks for chronic effects and decreasing risks for delayed acute effects, but found no significant trend for either race. We concluded that the higher exposures and mortality risks associated with vehicular traffic posed environmental injustice for the black veterans.

The impact of long-term PM2.5 exposure on specific causes of death: exposure-response curves and effect modification among 53 million U.S. Medicare beneficiaries

BACKGROUND

The shape of the exposure-response curve for long-term ambient fine particulate (PM_2.5) exposure and cause-specific mortality is poorly understood, especially for rural populations and underrepresented minorities.

METHODS

We used hybrid machine learning and Cox proportional hazard models to assess the association of long-term PM_2.5 exposures on specific causes of death for 53 million U.S. Medicare beneficiaries (aged ≥65) from 2000 to 2008. Models included strata for age, sex, race, and ZIP code and controlled for neighborhood socio-economic status (SES) in our main analyses, with approximately 4 billion person-months of follow-up, and additionally for warm season average of 1-h daily maximum ozone exposures in a sensitivity analysis. The impact of non-traffic PM_2.5 on mortality was examined using two stage models of PM_2.5 and nitrogen dioxide (NO₂).

RESULTS

A 10 μg /m³ increase in 12-month average PM_2.5 prior to death was associated with a 5% increase in all-cause mortality, as well as an 8.8, 5.6, and 2.5% increase in all cardiovascular disease (CVD)-, all respiratory-, and all cancer deaths, respectively, in age, gender, race, ZIP code, and SES-adjusted models. PM_2.5 exposures, however, were not associated with lung cancer mortality. Results were not sensitive to control for ozone exposures. PM_2.5-mortality associations for CVD- and respiratory-related causes were positive and significant for beneficiaries irrespective of their sex, race, age, SES and urbanicity, with no evidence of a lower threshold for response or of lower Risk Ratios (RRs) at low PM_2.5 levels. Associations between PM_2.5 and CVD and respiratory mortality were linear and were higher for younger, Black and urban beneficiaries, but were largely similar by SES. Risks associated with non-traffic PM_2.5 were lower than that for all PM_2.5 and were null for respiratory and lung cancer-related deaths.

CONCLUSIONS

PM_2.5 was associated with mortality from CVD, respiratory, and all cancer, but not lung cancer. PM_2.5-associated risks of CVD and respiratory mortality were similar across PM_2.5 levels, with no evidence of a threshold. Blacks, urban, and younger beneficiaries were most vulnerable to the long-term impacts of PM_2.5 on mortality.

Evaluation of the Impact of Black Carbon on the Worsening of Allergic Respiratory Diseases in the Region of Western Serbia: A Time-Stratified Case-Crossover Study

Background and Objectives: Many epidemiological studies have shown a positive association between black carbon (BC) and the exacerbation of allergic rhinitis and allergic asthma. However, none of the studies in Serbia examined this relationship yet. The aim of this study was to examine the associations between BC and emergency department (ED) visits for allergic rhinitis and allergic asthma in the Užice region of Serbia. Materials and Methods: A time-stratified case-crossover design was applied to 523 ED visits for allergic rhinitis and asthma exacerbation that occurred in the Užice region of Serbia between 2012–2014. Data regarding ED visits were routinely collected in the Health Center of Užice. The daily average concentrations of BC were measured by automatic ambient air quality monitoring stations. Odds ratios (ORs) and their corresponding 95% confidence intervals (CIs) were estimated using conditional logistic regression adjusted for the potential confounding influence of weather variables (temperature, humidity, and air pressure). Results: Statistically significant associations were observed between ED visits for allergic rhinitis and 2-day lagged exposure to BC (OR = 3.20; CI = 1.00–10.18; p = 0.049) and allergic asthma and 3-day lagged exposure to BC (OR = 3.23; CI = 1.05–9.95; p = 0.041). Conclusion: Exposure to BC in the Užice region increases the risk of ED visits for allergic rhinitis and asthma, particularly during the heating season.

Mitigation impact of roadside trees on fine particle pollution

Fine particulate matter (PM_2.5) is an important air pollutant due to its adverse health effects. Vehicle emissions make a large contribution to particle concentrations in urban areas. Exposure to particles especially near roadways increases the risk of public health problems. Planting vegetation might be used to capture the fine particles at the roadside, which can lower the health risks for the urban population. Istanbul is the most populous city in Turkey, where the number of non-electric cars is increasing rapidly, resulting in decreasing air quality, especially at the roadsides. Recent studies show that cardiovascular, respiratory and total non-accidental mortality is increasing with short-term exposure to outdoor air pollution in Istanbul. In this study, roadside trees were investigated for the mitigation effect on vehicle-related PM_2.5 and heavy metal (HM). Cupressus sempervirens (Mediterranean Cypress trees) were planted in three different cases (i.e., no trees-C1, trees with gaps-C2 and thick trees with no gaps-C3) at the study site. Location of the site is on a dense-traffic roadside in Istanbul, where thousands of people are living, working and walking through two sides of this road. PM_2.5 samples and tree leaves were examined in the performed experiments. C2 and C3 showed the importance of roadside tree plantation by reducing the exposure to significantly low levels. Roadside PM_2.5 concentrations were reduced by 17% in C3, equivalent to urban background levels in the city. Maximum removal of HMs is observed in nickel from 26.4 ± 7.8 to 7.5 ± 2.4 μg m^-3. Pedestrian exposure is calculated with the measured data in three experiments and exposure is significantly reduced (e.g., >50% for cadmium and lead exposure) in experiment C3. In conclusion, three experiments showed that Mediterranean Cypress trees significantly decreased particle pollution at roadsides in Istanbul.

Long-term NO2 exposures and cause-specific mortality in American older adults

BACKGROUND

The impact of long-term exposure to nitrogen dioxide (NO₂) on cause-specific mortality is poorly understood.

OBJECTIVE

To assess mortality risks associated with long-term NO₂ exposure and evaluate confounding of this association.

METHODS

We examined the association between 12-month moving average NO₂ exposure and cause-specific mortality in 14.1 million US Medicare beneficiaries between 2000 and 2008. Associations were examined using age, gender, and race-stratified and state-adjusted Poisson regression models. We assessed the potential for confounding by PM_2.5 and behavioral covariates and unmeasured confounding by decomposing NO₂ into its spatial and spatio-temporal components.

RESULTS

We found significant associations between 12-month NO₂ exposure and increased mortality from all-causes [risk ratio (RR): 1.052; 95% CI: 1.051, 1.054; per 10 ppb], cardiovascular (CVD) (1.133; 95% CI: 1.130, 1.137) and respiratory disease (1.050; 95% CI: 1.044, 1.056), all cancers (1.021; 95% CI: 1.017, 1.025), ischemic heart disease (IHD) (1.221; 95% CI: 1.217, 1.226), cerebrovascular (CBV) disease (1.092; 95% CI: 1.085, 1.100), and for the first time pneumonia (1.275; 95% CI: 1.263, 1.287). Associations generally remained positive and statistically significant after adjustment for PM_2.5 and behavioral factors.

CONCLUSIONS

Our findings provide additional evidence of the increased risk posed by long-term NO₂ exposures on increased mortality from all-causes, CVD, respiratory disease, IHD, CBV, and cancer and provide new evidence of their impact on mortality from pneumonia. Unmeasured confounding of these associations was present, however, demonstrating the need to understand sources of this confounding.

Long-term Concentrations of Nitrogen Dioxide and Mortality: A Meta-analysis of Cohort Studies

Supplemental Digital Content is available in the text.

Background:

Concentrations of outdoor nitrogen dioxide (NO₂) have been associated with increased mortality. Hazard ratios (HRs) from cohort studies are used to assess population health impact and burden. We undertook meta-analyses to derive concentration–response functions suitable for such evaluations and assessed their sensitivity to study selection based upon cohort characteristics.

Methods:

We searched online databases and existing reviews for cohort studies published to October 2016 that reported HRs for NO₂ and mortality. We calculated meta-analytic summary estimates using fixed/random-effects models.

Results:

We identified 48 articles analyzing 28 cohorts. Meta-analysis of HRs found positive associations between NO₂ and all cause (1.02 [95% confidence interval (CI): 1.01, 1.03]; prediction interval [PI]: [0.99, 1.06] per 10 µg/m³ increment in NO₂), cardiovascular (1.03 [95% CI: 1.02, 1.05]; PI: [0.98, 1.08]), respiratory (1.03 [95% CI: 1.01, 1.05]; PI: [0.97, 1.10]), and lung cancer mortality (1.05 [95% CI: 1.02, 1.08]; PI: [0.94, 1.17]) with evidence of substantial heterogeneity between studies. In subgroup analysis, summary HRs varied by age at cohort entry, spatial resolution of pollution estimates, and adjustment for smoking and body mass index at the individual level; for some subgroups, the HR was close to unity, with lower confidence limits below 1.

Conclusions:

Given the many uncertainties inherent in the assessment of this evidence base and the sensitivity of health impact calculations to small changes in the magnitude of the HRs, calculation of the impact on health of policies to reduce long-term exposure to NO₂ should use prediction intervals and report ranges of impact rather than focusing upon point estimates.

Revisiting the Veterans Cohort Mortality Study: New results and synthesis

The Veterans Cohort Mortality Study began in 1999 in collaboration with Washington University in St. Louis, comprising ~70,000 male military veterans. We published six research papers on this cohort, considering the dynamics of all-cause mortality as the subjects aged and environmental parameters changed. This paper summarizes those results and presents new results by age group. Pollutants included monitored and modeled criteria pollutants, vehicular traffic density (annual km driven per unit of county land area), and modeled nationwide levels of hazardous species. In addition to spatial relationships, we examined the effects of exposure timing through separate analyses of sequential follow-up and exposure periods from 1976 to 2001. Risks associated with peak ozone decreased with lag between exposure and response, suggesting acute effects. Risks associated with traffic were invariant over time and consistent across five exposure databases. Associations with ozone were also coherent across databases; we found no consistent associations with particulate matter. Epidemiology considers both spatial and temporal relationships; most long-term studies focus on spatial gradients at a given time, thus masking effects of cohort aging and other trends during follow-up. Our new analyses distinguished between these temporal effects by analyzing age deciles for which separate mortality risks had been estimated for nationwide levels of nitrogen oxides (NO_x), benzene, and traffic density during four sequential follow-up subperiods, thus providing 40 sets of mortality risk coefficients. We used ordinary least squares regression to define relationships with subject age and follow-up year for the data set of 40 coefficients. We found strong nonlinear relationships between subject age and mortality coefficients for smoking, climate, poverty status, and air pollution; only smoking and climate coefficients changed over time as well. We concluded that these pollutant-mortality relationships reflected differences among the veterans' residential locations rather than changes in their pollution exposures during follow-up. We saw no evidence that cleaner air reduced mortality. Implications: Recent air pollution mortality studies emphasize PM_2.5 (particulate matter with an aerodynamic diameter <2.5 μm); we show associations with many other pollutants and a measure of traffic intensity. Control policies should thus be based on multipollutant analyses. We found no reduced risks with improved air quality after distinguishing cohort aging from purely temporal effects; longitudinal studies of accountability must thus account for changes in demography and exposures. Our studies of exposure timing indicate mainly coincident responses and no evidence for cumulative effects typical of smoking; we had no information on personal exposures. We found the strongest risks were associated with high-traffic locations rather than outdoor air quality per se.

Identifying the socioeconomic determinants of population exposure to particulate matter (PM2.5) in China using geographically weighted regression modeling

Air pollution contributes significantly to premature death in China. However, only a limited number of studies have identified the potential determinants of population exposure to PM_2.5 from a socioeconomic perspective. This paper analyses the socioeconomic determinants of population exposure at the city level in China. We first estimated population exposure to PM_2.5 by integrating high resolution spatial distribution maps of PM_2.5 concentrations and population density, using data for 2013. Then, geographically weighted regression (GWR) modeling was undertaken to explore the strength and direction of relationships between the selected socioeconomic factors and population exposure. The results indicate that approximately 75% of the population of China lived in an area where PM_2.5 concentrations were over 35 μg/m³ in 2013. From the GWR models, we found that the percentages for cities that showed a statistically significant relationship (p < 0.05) between population exposure and each of the six factors were: urbanization, 91.92%; industry share, 91.58%; construction level, 88.55%; urban expansion, 73.40%; income disparity, 64.98%; and private vehicles, 27.27%. The R-squared value for the six factors in the multivariable GWR model was 0.88, and all cities demonstrated a statistically significant relationship. More importantly, the association between the six factors and population exposure was found to be spatially heterogeneous at the local geographic level. Consideration of these six drivers of population exposure can help policy makers and epidemiologists to evaluate and reduce population exposure risks.

The concentration-response between long-term PM2.5 exposure and mortality; A meta-regression approach

BACKGROUND

Long-term exposure to ambient fine particulate matter (≤ 2.5 μg/m³ in aerodynamic diameter; PM_2.5) is significantly associated with increased risk of premature mortality. Our goal was to provide an updated meta-analysis of all-cause and cause-specific mortality associated with exposure to PM_2.5 and to better estimate the risk of death as a function of air pollution levels.

METHODS

We systematically searched all published cohort studies examining the association between long term exposure to PM_2.5 and mortality. We applied multivariate linear random effects meta-analysis with random effects for cohort, and study within cohort. Meta-regression techniques were used to test whether study population or analytic characteristics modify the PM_{2.5 -}mortality association and to estimate the shape of the concentration-response curve.

RESULTS

A total of 53 studies that provided 135 estimates of the quantitative association between the risk of mortality and exposure to PM_2.5 were included in the meta-analysis. There were 39 studies from North America, 8 from Europe, and 6 from Asia. Since 2015, 17 studies of long-term air pollution exposure have been published, covering, wider geographic areas with a wider range of mean exposures (e.g. <12 or > 20 μg/m³). A penalized spline showed the slope decreased at higher concentrations but appeared to level off. We found that the inverse transform of average PM_2.5 well approximated that spline and provided a parametric estimate that fit better than a linear or logarithmic term for average PM_2.5. In addition, we found that studies using space time exposure models or fixed monitors at Zip-code scale (as compared to land use regression method), or additionally controlling for area level socio-economic status, or with mean exposure less than 10 μg/m³ were associated with higher mortality effect estimates.

CONCLUSIONS

This meta-analysis provides strong evidence for the adverse effect of PM_2.5 on mortality, that studies with poorer exposure have lower effect size estimates, that more control for SES increases effect size estimates, and that significant effects are seen below 10 µg/m³. The concentration -response function produced here can be further applied in the global health risk assessment of air particulate matter.

The gains in life expectancy by ambient PM2.5 pollution reductions in localities in Nigeria

Global burden of disease estimates reveal that people in Nigeria are living shorter lifespan than the regional or global average life expectancy. Ambient air pollution is a top risk factor responsible for the reduced longevity. But, the magnitude of the loss or the gains in longevity accruing from the pollution reductions, which are capable of driving mitigation interventions in Nigeria, remain unknown. Thus, we estimate the loss, and the gains in longevity resulting from ambient PM_2.5 pollution reductions at the local sub-national level using life table approach. Surface average PM_2.5 concentration datasets covering Nigeria with spatial resolution of ∼1 km were obtained from the global gridded concentration fields, and combined with ∼1 km gridded population of the world (GPWv4), and global administrative unit layers (GAUL) for territorial boundaries classification. We estimate the loss or gains in longevity using population-weighted average pollution level and baseline mortality data for cardiopulmonary disease and lung cancer in adults ≥25 years and for respiratory infection in children under 5. As at 2015, there are six "highly polluted", thirty "polluted" and one "moderately polluted" States in Nigeria. People residing in these States lose ∼3.8-4.0, 3.0-3.6 and 2.7 years of life expectancy, respectively, due to the pollution exposure. But, assuming interventions achieve global air quality guideline of 10 μg/m³, longevity would increase by 2.6-2.9, 1.9-2.5 and 1.6 years for people in the State-categories, respectively. The longevity gains are indeed high, but to achieve them, mitigation interventions should target emission sources having the highest population exposures.

The effects of ozone on human health

Ozone is a highly reactive, oxidative gas associated with adverse health outcome, including mortality and morbidity. Data from monitoring sites worldwide show levels of ozone often exceeding EU legislation threshold and the more restrictive WHO guidelines for the protection of human health. Well-established evidence has been produced for short-term effects, especially on respiratory and cardiovascular systems, associated to ozone exposure. Less conclusive is the evidence for long-term effects, reporting suggestive associations with respiratory mortality, new-onset asthma in children and increased respiratory symptom effects in asthmatics. The growing epidemiological evidence and the increasing availability of routinely collected data on air pollutant concentrations and health statistics allow to produce robust estimates in health impact assessment routine. Most recent estimates indicate that in 2013 in EU-28, 16,000 premature deaths, equivalent to 192,000 years of life lost, are attributable to ozone exposure. Italy shows very high health impact estimates among EU countries, reporting 3380 premature deaths and 61 years of life lost (per 100,000 inhabitants) attributable to ozone exposure.

Ischemic Heart Disease Mortality and Long-Term Exposure to Source-Related Components of U.S. Fine Particle Air Pollution

BACKGROUND

Fine particulate matter (PM2.5) air pollution exposure has been identified as a global health threat. However, the types and sources of particles most responsible are not yet known.

OBJECTIVES

We sought to identify the causal characteristics and sources of air pollution underlying past associations between long-term PM2.5 exposure and ischemic heart disease (IHD) mortality, as established in the American Cancer Society's Cancer Prevention Study-II cohort.

METHODS

Individual risk factor data were evaluated for 445,860 adults in 100 U.S. metropolitan areas followed from 1982 through 2004 for vital status and cause of death. Using Cox proportional hazard models, we estimated IHD mortality hazard ratios (HRs) for PM2.5, trace constituents, and pollution source-associated PM2.5, as derived from air monitoring at central stations throughout the nation during 2000-2005.

RESULTS

Associations with IHD mortality varied by PM2.5 mass constituent and source. A coal combustion PM2.5 IHD HR = 1.05 (95% CI: 1.02, 1.08) per microgram/cubic meter, versus an IHD HR = 1.01 (95% CI: 1.00, 1.02) per microgram/cubic meter PM2.5 mass, indicated a risk roughly five times higher for coal combustion PM2.5 than for PM2.5 mass in general, on a per microgram/cubic meter PM2.5 basis. Diesel traffic-related elemental carbon (EC) soot was also associated with IHD mortality (HR = 1.03; 95% CI: 1.00, 1.06 per 0.26-μg/m3 EC increase). However, PM2.5 from both wind-blown soil and biomass combustion was not associated with IHD mortality.

CONCLUSIONS

Long-term PM2.5 exposures from fossil fuel combustion, especially coal burning but also from diesel traffic, were associated with increases in IHD mortality in this nationwide population. Results suggest that PM2.5-mortality associations can vary greatly by source, and that the largest IHD health benefits per microgram/cubic meter from PM2.5 air pollution control may be achieved via reductions of fossil fuel combustion exposures, especially from coal-burning sources.

CITATION

Thurston GD, Burnett RT, Turner MC, Shi Y, Krewski D, Lall R, Ito K, Jerrett M, Gapstur SM, Diver WR, Pope CA III. 2016. Ischemic heart disease mortality and long-term exposure to source-related components of U.S. fine particle air pollution. Environ Health Perspect 124:785-794; http://dx.doi.org/10.1289/ehp.1509777.

Long-term exposure to ambient ozone and mortality: a quantitative systematic review and meta-analysis of evidence from cohort studies

OBJECTIVES

While there is good evidence for associations between short-term exposure to ozone and a range of adverse health outcomes, the evidence from narrative reviews for long-term exposure is suggestive of associations with respiratory mortality only. We conducted a systematic, quantitative evaluation of the evidence from cohort studies, reporting associations between long-term exposure to ozone and mortality.

METHODS

Cohort studies published in peer-reviewed journals indexed in EMBASE and MEDLINE to September 2015 and PubMed to October 2015 and cited in reviews/key publications were identified via search strings using terms relating to study design, pollutant and health outcome. Study details and estimate information were extracted and used to calculate standardised effect estimates expressed as HRs per 10 ppb increment in long-term ozone concentrations.

RESULTS

14 publications from 8 cohorts presented results for ozone and all-cause and cause-specific mortality. We found no evidence of associations between long-term annual O3 concentrations and the risk of death from all causes, cardiovascular or respiratory diseases, or lung cancer. 4 cohorts assessed ozone concentrations measured during the warm season. Summary HRs for cardiovascular and respiratory causes of death derived from 3 cohorts were 1.01 (95% CI 1.00 to 1.02) and 1.03 (95% CI 1.01 to 1.05) per 10 ppb, respectively.

CONCLUSIONS

Our quantitative review revealed a paucity of independent studies regarding the associations between long-term exposure to ozone and mortality. The potential impact of climate change and increasing anthropogenic emissions of ozone precursors on ozone levels worldwide suggests further studies of the long-term effects of exposure to high ozone levels are warranted.

Assessing public health burden associated with exposure to ambient black carbon in the United States

Black carbon (BC) is a significant component of fine particulate matter (PM2.5) air pollution, which has been linked to a series of adverse health effects, in particular premature mortality. Recent scientific research indicates that BC also plays an important role in climate change. Therefore, controlling black carbon emissions provides an opportunity for a double dividend. This study quantifies the national burden of mortality and morbidity attributable to exposure to ambient BC in the United States (US). We use GEOS-Chem, a global 3-D model of atmospheric composition to estimate the 2010 annual average BC levels at 0.5×0.667° resolution, and then re-grid to 12-km grid resolution across the continental US. Using PM2.5 mortality risk coefficient drawn from the American Cancer Society cohort study, the numbers of deaths due to BC exposure were estimated for each 12-km grid, and then aggregated to the county, state and national level. Given evidence that BC particles may pose a greater risk on human health than other components of PM2.5, we also conducted sensitivity analysis using BC-specific risk coefficients drawn from recent literature. We estimated approximately 14,000 deaths to result from the 2010 BC levels, and hundreds of thousands of illness cases, ranging from hospitalizations and emergency department visits to minor respiratory symptoms. Sensitivity analysis indicates that the total BC-related mortality could be even significantly larger than the above mortality estimate. Our findings indicate that controlling BC emissions would have substantial benefits for public health in the US.

Exploring the Uncertainty Associated with Satellite-Based Estimates of Premature Mortality due to Exposure to Fine Particulate Matter

The negative impacts of fine particulate matter (PM_2.5) exposure on human health are a primary motivator for air quality research. However, estimates of the air pollution health burden vary considerably and strongly depend on the datasets and methodology. Satellite observations of aerosol optical depth (AOD) have been widely used to overcome limited coverage from surface monitoring and to assess the global population exposure to PM_2.5 and the associated premature mortality. Here we quantify the uncertainty in determining the burden of disease using this approach, discuss different methods and datasets, and explain sources of discrepancies among values in the literature. For this purpose we primarily use the MODIS satellite observations in concert with the GEOS-Chem chemical transport model. We contrast results in the United States and China for the years 2004-2011. Using the Burnett et al. (2014) integrated exposure response function, we estimate that in the United States, exposure to PM_2.5 accounts for approximately 2% of total deaths compared to 14% in China (using satellite-based exposure), which falls within the range of previous estimates. The difference in estimated mortality burden based solely on a global model vs. that derived from satellite is approximately 14% for the U.S. and 2% for China on a nationwide basis, although regionally the differences can be much greater. This difference is overshadowed by the uncertainty in the methodology for deriving PM_2.5 burden from satellite observations, which we quantify to be on the order of 20% due to uncertainties in the AOD-to-surface-PM_2.5 relationship, 10% due to the satellite observational uncertainty, and 30% or greater uncertainty associated with the application of concentration response functions to estimated exposure.

Impact of air pollutants from surface transport sources on human health: A modeling and epidemiological approach

This study adopted an integrated 'source-to-receptor' assessment paradigm in order to determine the effects of emissions from passenger transport on urban air quality and human health in the megacity, Delhi. The emission modeling was carried out for the base year 2007 and three alternate (ALT) policy scenarios along with a business as usual (BAU) scenario for the year 2021. An Activity-Structure-Emission Factor (ASF) framework was adapted for emission modeling, followed by a grid-wise air quality assessment using AERMOD and a health impact assessment using an epidemiological approach. It was observed that a 2021-ALT-III scenario resulted in a maximum concentration reduction of ~24%, ~42% and ~58% for carbon monoxide (CO), nitrogen dioxide (NO2) and particulate matter (PM), respectively, compared to a 2021-BAU scenario. Further, it results in significant reductions in respiratory and cardiovascular mortality, morbidity and Disability Adjusted Life Years (DALY) by 41% and 58% on exposure to PM2.5 and NO2 concentrations when compared to the 2021-BAU scenario, respectively. In other words, a mix of proposed policy interventions namely the full-phased introduction of the Integrated Mass Transit System, fixed bus speed, stringent vehicle emission norms and a hike in parking fees for private vehicles would help in strengthening the capability of passenger transport to cater to a growing transport demand with a minimum health burden in the Delhi region. Further, the study estimated that the transport of goods would be responsible for ~5.5% additional VKT in the 2021-BAU scenario; however, it will contribute ~49% and ~55% additional NO2 and PM2.5 concentrations, respectively, in the Delhi region. Implementation of diesel particulate filters for goods vehicles in the 2021-ALT-IV-O scenario would help in the reduction of ~87% of PM2.5 concentration, compared to the 2021-BAU scenario; translating into a gain of 1267 and 505 DALY per million people from exposure to PM2.5 and NO2 concentrations, respectively. These findings suggest that significant health benefits are possible if goods transport is also included while designing strategies and policies in order to improve the overall urban air quality and minimize health impacts in city areas.

Long-term effects of elemental composition of particulate matter on inflammatory blood markers in European cohorts

BACKGROUND

Epidemiological studies have associated long-term exposure to ambient particulate matter with increased mortality from cardiovascular and respiratory disorders. Systemic inflammation is a plausible biological mechanism behind this association. However, it is unclear how the chemical composition of PM affects inflammatory responses.

OBJECTIVES

To investigate the association between long-term exposure to elemental components of PM and the inflammatory blood markers high-sensitivity C-reactive protein (hsCRP) and fibrinogen as part of the European ESCAPE and TRANSPHORM multi-center projects.

METHODS

In total, 21,558 hsCRP measurements and 17,428 fibrinogen measurements from cross-sections of five and four cohort studies were available, respectively. Residential long-term concentrations of particulate matter <10μm (PM10) and <2.5μm (PM2.5) in diameter and selected elemental components (copper, iron, potassium, nickel, sulfur, silicon, vanadium, zinc) were estimated based on land-use regression models. Associations between components and inflammatory markers were estimated using linear regression models for each cohort separately. Cohort-specific results were combined using random effects meta-analysis. As a sensitivity analysis the models were additionally adjusted for PM mass.

RESULTS

A 5ng/m(3) increase in PM2.5 copper and a 500ng/m(3) increase in PM10 iron were associated with a 6.3% [0.7; 12.3%] and 3.6% [0.3; 7.1%] increase in hsCRP, respectively. These associations between components and fibrinogen were slightly weaker. A 10ng/m(3) increase in PM2.5 zinc was associated with a 1.2% [0.1; 2.4%] increase in fibrinogen; confidence intervals widened when additionally adjusting for PM2.5.

CONCLUSIONS

Long-term exposure to transition metals within ambient particulate matter, originating from traffic and industry, may be related to chronic systemic inflammation providing a link to long-term health effects of particulate matter.

Assessing the role of chemical components in cellular responses to atmospheric particle matter (PM) through chemical fractionation of PM extracts

In order to further our understanding of the influence of chemical components and ultimately specific sources of atmospheric particulate matter (PM) on pro-inflammatory and other adverse cellular responses, we promulgate and apply a suite of chemical fractionation tools to aqueous aerosol extracts of PM samples for analysis in toxicity assays. We illustrate the approach with a study that used water extracts of quasi-ultrafine PM (PM0.25) collected in the Los Angeles Basin. Filtered PM extracts were fractionated using Chelex, a weak anion exchanger diethylaminoethyl (DEAE), a strong anion exchanger (SAX), and a hydrophobic C18 resin, as well as by desferrioxamine (DFO) complexation that binds iron. The fractionated extracts were then analyzed using high-resolution sector field inductively coupled plasma mass spectrometry (SF-ICPMS) to determine elemental composition. Cellular responses to the fractionated extracts were probed in an in vitro rat alveolar macrophages model with measurement of reactive oxygen species (ROS) production and the cytokine tumor necrosis factor-α (TNF-α). The DFO treatment that chelates iron was very effective at reducing the cellular ROS activity but had only a small impact on the TNF-α production. In contrast, the hydrophobic C18 resin treatment had a small impact on the cellular ROS activity but significantly reduced the TNF-α production. The use of statistical methods to integrate the results across all treatments led to the conclusion that sufficient iron must be present to participate in the chemistry needed for ROS activity, but the amount of ROS activity is not proportional to the iron solution concentration. ROS activity was found to be most related to cationic mono- and divalent metals (i.e., Mn and Ni) and oxyanions (i.e., Mo and V). Although the TNF-α production was not significantly affected by the chelexation of iron, it was greatly impacted by the removal of organics with the C18 resin and all other metal removal methods, suggesting that iron is not a critical pathway leading to TNF-α production, but a wide range of soluble metals and organic compounds in particulate matter play a role. Although the results are specific to the Los Angeles Basin, where the samples used in the study were collected, the method employed in the study can be widely employed to study the role of components of particulate matter in in vitro or in vivo assays.

Air pollution and risk of uterine leiomyomata

BACKGROUND

Air pollution, particularly from vehicle exhaust, has been shown to influence hormonal activity. However, it is unknown whether air pollution exposure is associated with the occurrence of uterine leiomyomata, a hormonally sensitive tumor of the uterus.

METHODS

For 85,251 women 25-42 years of age at enrollment in the Nurses' Health Study II, we examined proximity to major roadways and outdoor levels of particulate matter less than 10 microns (PM10) or 2.5 microns (PM2.5) or between 10 and 2.5 microns (PM10-2.5) in diameter for all residential addresses from September 1989 to May 2007. To be eligible for this analysis, a woman had to be alive and respond to questionnaires, premenopausal with an intact uterus, and without diagnoses of cancer or prevalent uterine leiomyomata. Incidence of ultrasound- or hysterectomy-confirmed uterine leiomyomata and covariates were reported on biennial questionnaires sent through May 2007. Multivariable time-varying Cox proportional hazard models were used to estimate the relationship between distance to road or PM exposures and uterine leiomyomata risk.

RESULTS

During 837,573 person-years of follow-up, there were 7760 incident cases of uterine leiomyomata. Living close to a major road and exposures to PM10 or PM10-2.5 were not associated with an increased risk of uterine leiomyomata. However, each 10 μg/m increase in 2-year average, 4-year average, or cumulative average PM2.5 was associated with an adjusted hazard ratio of 1.08 (95% confidence interval = 1.00-1.17), 1.09 (0.99-1.19), and 1.11 (1.03-1.19), respectively.

CONCLUSIONS

Chronic exposure to PM2.5 may be associated with a modest increased risk of uterine leiomyomata.

Enhancing the Characterization of Epistemic Uncertainties in PM2.5 Risk Analyses

The Environmental Benefits Mapping and Analysis Program (BenMAP) is a software tool developed by the U.S. Environmental Protection Agency (EPA) that is widely used inside and outside of EPA to produce quantitative estimates of public health risks from fine particulate matter (PM2.5 ). This article discusses the purpose and appropriate role of a risk analysis tool to support risk management deliberations, and evaluates the functions of BenMAP in this context. It highlights the importance in quantitative risk analyses of characterization of epistemic uncertainty, or outright lack of knowledge, about the true risk relationships being quantified. This article describes and quantitatively illustrates sensitivities of PM2.5 risk estimates to several key forms of epistemic uncertainty that pervade those calculations: the risk coefficient, shape of the risk function, and the relative toxicity of individual PM2.5 constituents. It also summarizes findings from a review of U.S.-based epidemiological evidence regarding the PM2.5 risk coefficient for mortality from long-term exposure. That review shows that the set of risk coefficients embedded in BenMAP substantially understates the range in the literature. We conclude that BenMAP would more usefully fulfill its role as a risk analysis support tool if its functions were extended to better enable and prompt its users to characterize the epistemic uncertainties in their risk calculations. This requires expanded automatic sensitivity analysis functions and more recognition of the full range of uncertainty in risk coefficients.

Respiratory and cardiovascular effects of metals in ambient particulate matter: a critical review

In this review, we critically evaluated the epidemiological and toxicological evidence for the role of specific transition metals (As. Cr. Cu. Fe. Mn. Ni. Sc. Ti. V and Zn) in causing or contributing to the respiratory and cardiovascular health effects associated with ambient PM. Although the epidemiologic studies arc suggestive. and both the in vivo and in vitro laboratory studies document the toxicity of specific metals (Fe. Ni. V and Zn). the overall weight of evidence does not convincingly implicate metals as major contributors to health effects. None of the epidemiology studies that we reviewed conclusively implicated specific transition metals as having caused the respiratory and cardiovascular effects associated with ambient levels of PM. However, the studies reviewed tended to be internal ly consistent in identifying some metals (Fe, Ni, V and Zn) more frequently than others (As, Cu, Mn and Sc) as having positive associations wi th health effects. The major problem wi th which the epidemiological studies were faced was classifying and quantifying exposure. Community and population exposures to metals or other components of ambient PM were inferred from centrally- located samplers that may not accurately represent individual level exposures. Only a few authors reported findings that did not support the stated premise of the study; indeed, statistic ally significant associations are not necessarily biologically significant. It is likely that ·'negative studies" are under-represented in the published literature, making it a challenge to achieve a balanced evaluation of the role of metals in causing health effects associated with ambient PM. Both the in vivo and in vitro study results demonstrated that individual metals (Cu. Fe. Ni. V and Zn) and extracts of metals from ambient PM sources can produce acute inflammatory responses. However. the doses administered to laboratory animals were many orders of magnitude greater than what humans experience from breathing ambient air. The studies that used intratracheal instillation have the advantage of delivering a known dose to a specific anatomical location. but arc not analogous to an inhaled dose that is distributed over the surface area of the respiratory tract. Studies. in which laboratory animals or human volunteers inhaled CAPs best represent exposures to the general human population. The in vivo and in vitro studies reviewed provide indications that the probable mechanisms involved in the respiratory and cardiac effects from high metal exposures include: an inflammatory response mediated by formation of ROS, upregulation of genes coding for inflammatory cytokines, altered expression of genes involved in cell signaling pathways and maintenance of metals homeostasis.The fact that doses of metals many orders of magnitude greater than those existing in ambient air were required to produce measurable adverse effects in animals makes it doubtful that metals play any major role in respiratory and cardiovascular effects produced from human exposure to ambient PM. We suggest that future research priorities should focus on testing at more environmentally relevant exposure levels and that any new toxicological studies be written to include dosages in units that can be easily compared to human exposure levels.

Particulate matter air pollution exposure, distance to road, and incident lung cancer in the nurses' health study cohort

BACKGROUND

A body of literature has suggested an elevated risk of lung cancer associated with particulate matter and traffic-related pollutants.

OBJECTIVE

We examined the relation of lung cancer incidence with long-term residential exposures to ambient particulate matter and residential distance to roadway, as a proxy for traffic-related exposures.

METHODS

For participants in the Nurses' Health Study, a nationwide prospective cohort of women, we estimated 72-month average exposures to PM2.5, PM2.5-10, and PM10 and residential distance to road. Follow-up for incident cases of lung cancer occurred from 1994 through 2010. Cox proportional hazards models were adjusted for potential confounders. Effect modification by smoking status was examined.

RESULTS

During 1,510,027 person-years, 2,155 incident cases of lung cancer were observed among 103,650 participants. In fully adjusted models, a 10-μg/m3 increase in 72-month average PM10 [hazard ratio (HR) = 1.04; 95% CI: 0.95, 1.14], PM2.5 (HR = 1.06; 95% CI: 0.91, 1.25), or PM2.5-10 (HR = 1.05; 95% CI: 0.92, 1.20) was positively associated with lung cancer. When the cohort was restricted to never-smokers and to former smokers who had quit at least 10 years before, the associations appeared to increase and were strongest for PM2.5 (PM10: HR = 1.15; 95% CI: 1.00, 1.32; PM2.5: HR = 1.37; 95% CI: 1.06, 1.77; PM2.5-10: HR = 1.11; 95% CI: 0.90, 1.37). RESULTS were most elevated when restricted to the most prevalent subtype, adenocarcinomas. Risks with roadway proximity were less consistent.

CONCLUSIONS

Our findings support those from other studies indicating increased risk of incident lung cancer associated with ambient PM exposures, especially among never- and long-term former smokers.

Public health and components of particulate matter: the changing assessment of black carbon

In 2012, the WHO classified diesel emissions as carcinogenic, and its European branch suggested creating a public health standard for airborne black carbon (BC). In 2011, EU researchers found that life expectancy could be extended four to nine times by reducing a unit of BC, vs reducing a unit of PM2.5. Only recently could such determinations be made. Steady improvements in research methodologies now enable such judgments. In this Critical Review, we survey epidemiological and toxicological literature regarding carbonaceous combustion emissions, as research methodologies improved over time. Initially, we focus on studies of BC, diesel, and traffic emissions in the Western countries (where daily urban BC emissions are mainly from diesels). We examine effects of other carbonaceous emissions, e.g., residential burning of biomass and coal without controls, mainly in developing countries. Throughout the 1990s, air pollution epidemiology studies rarely included species not routinely monitored. As additional PM2.5. chemical species, including carbonaceous species, became more widely available after 1999, they were gradually included in epidemiological studies. Pollutant species concentrations which more accurately reflected subject exposure also improved models. Natural "interventions"--reductions in emissions concurrent with fuel changes or increased combustion efficiency; introduction of ventilation in highway tunnels; implementation of electronic toll payment systems--demonstrated health benefits of reducing specific carbon emissions. Toxicology studies provided plausible biological mechanisms by which different PM species, e.g, carbonaceous species, may cause harm, aiding interpretation of epidemiological studies. Our review finds that BC from various sources appears to be causally involved in all-cause, lung cancer and cardiovascular mortality, morbidity, and perhaps adverse birth and nervous system effects. We recommend that the US. EPA rubric for judging possible causality of PM25. mass concentrations, be used to assess which PM2.5. species are most harmful to public health.

IMPLICATIONS

Black carbon (BC) and correlated co-emissions appear causally related with all-cause, cardiovascular, and lung cancer mortality, and perhaps with adverse birth outcomes and central nervous system effects. Such findings are recent, since widespread monitoring for BC is also recent. Helpful epidemiological advances (using many health relevant PM2.5 species in models; using better measurements of subject exposure) have also occurred. "Natural intervention" studies also demonstrate harm from partly combusted carbonaceous emissions. Toxicology studies consistently find biological mechanisms explaining how such emissions can cause these adverse outcomes. A consistent mechanism for judging causality for different PM2.5 species is suggested.

Toxicological and epidemiological studies of cardiovascular effects of ambient air fine particulate matter (PM2.5) and its chemical components: coherence and public health implications

Recent investigations on PM2.5 constituents' effects in community residents have substantially enhanced our knowledge on the impacts of specific components, especially the HEI-sponsored National Particle Toxicity Component (NPACT) studies at NYU and UW-LRRI that addressed the impact of long-term PM2.5 exposure on cardiovascular disease (CVD) effects. NYU's mouse inhalation studies at five sites showed substantial variations in aortic plaque progression by geographic region that was coherent with the regional variation in annual IHD mortality in the ACS-II cohort, with both the human and mouse responses being primarily attributable to the coal combustion source category. The UW regressions of associations of CVD events and mortality in the WHI cohort, and of CIMT and CAC progression in the MESA cohort, indicated that [Formula: see text] had stronger associations with CVD-related human responses than OC, EC, or Si. The LRRI's mice had CVD-related biomarker responses to [Formula: see text]. NYU also identified components most closely associated with daily hospital admissions (OC, EC, Cu from traffic and Ni and V from residual oil). For daily mortality, they were from coal combustion ([Formula: see text], Se, and As). While the recent NPACT research on PM2.5 components that affect CVD has clearly filled some major knowledge gaps, and helped to define remaining uncertainties, much more knowledge is needed on the effects in other organ systems if we are to identify and characterize the most effective and efficient means for reducing the still considerable adverse health impacts of ambient air PM. More comprehensive speciation data are needed for better definition of human responses.

Air pollution exposures during adulthood and risk of endometriosis in the Nurses' Health Study II

BACKGROUND

Particulate matter and proximity to large roadways may promote disease mechanisms, including systemic inflammation, hormonal alteration, and vascular proliferation, that may contribute to the development and severity of endometriosis.

OBJECTIVE

Our goal was to determine the association of air pollution exposures during adulthood, including distance to road, particulate matter<2.5 μm, between 2.5 and 10 μm, and <10 μm, (PM2.5, PM10-2.5, PM10), and timing of exposure with risk of endometriosis in the Nurses' Health Study II.

METHODS

Proximity to major roadways and outdoor levels of PM2.5, PM10-2.5, and PM10 were determined for all residential addresses from 1993 to 2007. Multivariable-adjusted time-varying Cox proportional hazard models were used to estimate the relation between these air pollution exposures and endometriosis risk.

RESULTS

Among 84,060 women, 2,486 incident cases of surgically confirmed endometriosis were identified over 710,230 person-years of follow-up. There was no evidence of an association between endometriosis risk and distance to road or exposure to PM2.5, PM10-2.5, or PM10 averaged over follow-up or during the previous 2- or 4-year period.

CONCLUSIONS

Traffic and air pollution exposures during adulthood were not associated with incident endometriosis in this cohort of women.

Changes in traffic exposure and the risk of incident myocardial infarction and all-cause mortality

BACKGROUND

Traffic-related exposures, such as air pollution and noise, have been associated with increased cardiovascular morbidity and mortality. Few studies, however, have been able to examine the effects of changes in exposure on changes in risk. Our objective was to explore the associations of changes in traffic exposure with changes in risk between 1990 and 2008 in the Nurses' Health Study.

METHODS

Incident myocardial infarction (MI) and all-cause mortality were prospectively identified. As a proxy for traffic exposure, we calculated residential distance to roads at all residential addresses 1986-2006 and considered addresses to be "close" or "far" based on distance and road type. To examine the effect of changes in exposure, each consecutive pair of addresses was categorized as: (1) consistently close, (2) consistently far, (3) change from close to far, and (4) change from far to close. We also examined the change in NO2 levels between address pairs.

RESULTS

In time-varying Cox proportional hazards models adjusted for a variety of risk factors, women living at residences consistently close to traffic were at a higher risk of an incident MI (hazard ratio [HR] = 1.11; 95% confidence interval [CI] = 1.01-1.22) and a higher risk of all-cause mortality (1.05; 1.00-1.10), compared with those consistently far. The highest risks were seen among women who moved from being far from traffic to close (incident MI: HR = 1.50 [95% CI = 1.11-2.03]; all-cause mortality: HR = 1.17 [95% CI = 1.00-1.37]). Each 1 ppb increase in NO2 compared with the previous address was associated with a HR = 1.22 for incident MI (95% CI = 0.99-1.50) and 1.03 for all-cause mortality (95% CI = 0.92-1.15).

CONCLUSIONS

Our results suggest that changes in traffic exposure (measured as roadway proximity or change in NO2 levels) are associated with changes in risk of MI and all-cause mortality.

Mortality associations with long-term exposure to outdoor air pollution in a national English cohort

RATIONALE

Cohort evidence linking long-term exposure to outdoor particulate air pollution and mortality has come largely from the United States. There is relatively little evidence from nationally representative cohorts in other countries.

OBJECTIVES

To investigate the relationship between long-term exposure to a range of pollutants and causes of death in a national English cohort.

METHODS

A total of 835,607 patients aged 40-89 years registered with 205 general practices were followed from 2003-2007. Annual average concentrations in 2002 for particulate matter with a median aerodynamic diameter less than 10 (PM(10)) and less than 2.5 μm (PM(2.5)), nitrogen dioxide (NO(2)), ozone, and sulfur dioxide (SO(2)) at 1 km(2) resolution, estimated from emission-based models, were linked to residential postcode. Deaths (n = 83,103) were ascertained from linkage to death certificates, and hazard ratios (HRs) for all- and cause-specific mortality for pollutants were estimated for interquartile pollutant changes from Cox models adjusting for age, sex, smoking, body mass index, and area-level socioeconomic status markers.

MEASUREMENTS AND MAIN RESULTS

Residential concentrations of all pollutants except ozone were positively associated with all-cause mortality (HR, 1.02, 1.03, and 1.04 for PM(2.5), NO(2), and SO(2), respectively). Associations for PM(2.5), NO(2), and SO(2) were larger for respiratory deaths (HR, 1.09 each) and lung cancer (HR, 1.02, 1.06, and 1.05) but nearer unity for cardiovascular deaths (1.00, 1.00, and 1.04).

CONCLUSIONS

These results strengthen the evidence linking long-term ambient air pollution exposure to increased all-cause mortality. However, the stronger associations with respiratory mortality are not consistent with most US studies in which associations with cardiovascular causes of death tend to predominate.

A meta-analysis and multisite time-series analysis of the differential toxicity of major fine particulate matter constituents

Health risk assessments of particulate matter less than 2.5 μm in diameter (PM(2.5)) often assume that all constituents of PM(2.5) are equally toxic. While investigators in previous epidemiologic studies have evaluated health risks from various PM(2.5) constituents, few have conducted the analyses needed to directly inform risk assessments. In this study, the authors performed a literature review and conducted a multisite time-series analysis of hospital admissions and exposure to PM(2.5) constituents (elemental carbon, organic carbon matter, sulfate, and nitrate) in a population of 12 million US Medicare enrollees for the period 2000-2008. The literature review illustrated a general lack of multiconstituent models or insight about probabilities of differential impacts per unit of concentration change. Consistent with previous results, the multisite time-series analysis found statistically significant associations between short-term changes in elemental carbon and cardiovascular hospital admissions. Posterior probabilities from multiconstituent models provided evidence that some individual constituents were more toxic than others, and posterior parameter estimates coupled with correlations among these estimates provided necessary information for risk assessment. Ratios of constituent toxicities, commonly used in risk assessment to describe differential toxicity, were extremely uncertain for all comparisons. These analyses emphasize the subtlety of the statistical techniques and epidemiologic studies necessary to inform risk assessments of particle constituents.

Reducing personal exposure to particulate air pollution improves cardiovascular health in patients with coronary heart disease

BACKGROUND

Air pollution exposure increases cardiovascular morbidity and mortality and is a major global public health concern.

OBJECTIVES

We investigated the benefits of reducing personal exposure to urban air pollution in patients with coronary heart disease.

METHODS

In an open randomized crossover trial, 98 patients with coronary heart disease walked on a predefined route in central Beijing, China, under different conditions: once while using a highly efficient face mask, and once while not using the mask. Symptoms, exercise, personal air pollution exposure, blood pressure, heart rate, and 12-lead electrocardiography were monitored throughout the 24-hr study period.

RESULTS

Ambient air pollutants were dominated by fine and ultrafine particulate matter (PM) that was present at high levels [74 μg/m³ for PM(2.5) (PM with aerodynamic diamater <2.5 µm)]. Consistent with traffic-derived sources, this PM contained organic carbon and polycyclic aromatic hydrocarbons and was highly oxidizing, generating large amounts of free radicals. The face mask was well tolerated, and its use was associated with decreased self-reported symptoms and reduced maximal ST segment depression (-142 vs. -156 μV, p = 0.046) over the 24-hr period. When the face mask was used during the prescribed walk, mean arterial pressure was lower (93 ± 10 vs. 96 ± 10 mmHg, p = 0.025) and heart rate variability increased (high-frequency power: 54 vs. 40 msec², p = 0.005; high-frequency normalized power: 23.5 vs. 20.5 msec, p = 0.001; root mean square successive differences: 16.7 vs. 14.8 msec, p = 0.007). However, mask use did not appear to influence heart rate or energy expenditure.

CONCLUSIONS

Reducing personal exposure to air pollution using a highly efficient face mask appeared to reduce symptoms and improve a range of cardiovascular health measures in patients with coronary heart disease. Such interventions to reduce personal exposure to PM air pollution have the potential to reduce the incidence of cardiovascular events in this highly susceptible population.

Burden of mortality due to ambient fine particulate air pollution (PM2.5) in interior and Northern BC

OBJECTIVES

Our objective was to estimate the burden of mortality attributable to long-term exposure to ambient fine particulate matter (PM2.5) among adults in two rural regions of British Columbia, the Interior and the North, in order to provide information for public health professionals setting health priorities.

METHODS

We used the standard method to calculate the fraction of all-cause mortality among adults (> or = 30 years old) attributable to long-term exposure to ambient PM2.5 as described in the World Health Organization global burden of disease study. PM2.5 concentration was either locally measured using tapered element oscillating microbalance (TEOM) continuous monitors or estimated for unmonitored cities. For the base case, we used a conservative PM2.5 threshold (5.0 ug/m3); for sensitivity analysis, we set the threshold to estimate all mortality attributable to anthropogenic PM2.5 (3.1 ug/m3). We conducted sensitivity analysis for PM2.5 concentrations estimated in unmonitored cities.

RESULTS AND CONCLUSIONS

Mean annual PM2.5 concentration ranged from 3.1 to 7.4 ug/m3 across local health areas in Northern and Interior BC. Sixty percent of the adult population lived in monitored regions. PM2.5 was estimated to cause 0.20% of all-cause mortality among adults (16 deaths/year). Anthropogenic PM2.5 was estimated to cause 0.93% of all-cause mortality among adults (74 deaths/year). Estimates were sensitive to both PM2.5 threshold and estimated PM2.5 in unmonitored communities. This demonstrates that ambient PM2.5 air pollution does have an important mortality burden, even in a region with relatively low PM2.5 concentrations.

Black carbon as an additional indicator of the adverse health effects of airborne particles compared with PM10 and PM2.5

BACKGROUND

Current air quality standards for particulate matter (PM) use the PM mass concentration [PM with aerodynamic diameters ≤ 10 μm (PM(10)) or ≤ 2.5 μm (PM(2.5))] as a metric. It has been suggested that particles from combustion sources are more relevant to human health than are particles from other sources, but the impact of policies directed at reducing PM from combustion processes is usually relatively small when effects are estimated for a reduction in the total mass concentration.

OBJECTIVES

We evaluated the value of black carbon particles (BCP) as an additional indicator in air quality management.

METHODS

We performed a systematic review and meta-analysis of health effects of BCP compared with PM mass based on data from time-series studies and cohort studies that measured both exposures. We compared the potential health benefits of a hypothetical traffic abatement measure, using near-roadway concentration increments of BCP and PM(2.5) based on data from prior studies.

RESULTS

Estimated health effects of a 1-μg/m3 increase in exposure were greater for BCP than for PM(10) or PM(2.5), but estimated effects of an interquartile range increase were similar. Two-pollutant models in time-series studies suggested that the effect of BCP was more robust than the effect of PM mass. The estimated increase in life expectancy associated with a hypothetical traffic abatement measure was four to nine times higher when expressed in BCP compared with an equivalent change in PM(2.5) mass.

CONCLUSION

BCP is a valuable additional air quality indicator to evaluate the health risks of air quality dominated by primary combustion particles.

Spatial and seasonal distribution of aerosol chemical components in New York City: (2) road dust and other tracers of traffic-generated air pollution

We describe spatial and temporal patterns of seven chemical elements commonly observed in fine particulate matter (PM) and thought to be linked to roadway emissions that were measured at residential locations in New York City (NYC). These elements, that is, Si, Al, Ti, Fe, Ba, Br, and black carbon (BC), were found to have significant spatial and temporal variability at our 10 residential PM(2.5) sampling locations. We also describe pilot study data of near-roadway samples of both PM(10-2.5) and PM(2.5) chemical elements of roadway emissions. PM(2.5) element concentrations collected on the George Washington Bridge (GWB) connecting NYC and New Jersey were higher that similar elemental concentration measured at residential locations. Coarse-particle elements (within PM(10-2.5)) on the GWB were 10-100 times higher in concentration than their PM(2.5) counterparts. Roadway elements were well correlated with one another in both the PM(2.5) and PM(10-2.5) fractions, suggesting common sources. The same elements in the PM(2.5) collected at residential locations were less correlated, suggesting either different sources or different processing mechanisms for each element. Despite the fact that these elements are only a fraction of total PM(2.5) or PM(10-2.5) mass, the results have important implications for near-roadway exposures where elements with known causal links to health effects are shown to be at elevated concentrations in both the PM(2.5) and PM(10-2.5) size ranges.