Gaseous pollutants in particulate matter epidemiology: confounders or surrogates?

Alzheimer's Related Neurodegeneration Mediates Air Pollution Effects on Medial Temporal Lobe Atrophy

Exposure to ambient air pollution, especially particulate matter with aerodynamic diameter <2.5 μm (PM2.5) and nitrogen dioxide (NO2), are environmental risk factors for Alzheimer's disease and related dementia. The medial temporal lobe (MTL) is an important brain region subserving episodic memory that atrophies with age, during the Alzheimer's disease continuum, and is vulnerable to the effects of cerebrovascular disease. Despite the importance of air pollution it is unclear whether exposure leads to atrophy of the MTL and by what pathways. Here we conducted a longitudinal study examining associations between ambient air pollution exposure and MTL atrophy and whether putative air pollution exposure effects resembled Alzheimer's disease-related neurodegeneration or cerebrovascular disease-related neurodegeneration. Participants included older women (n = 627; aged 71-87) who underwent two structural brain MRI scans (MRI-1: 2005-6; MRI-2: 2009-10) as part of the Women's Health Initiative Memory Study of Magnetic Resonance Imaging. Regionalized universal kriging was used to estimate annual concentrations of PM2.5 and NO2 at residential locations aggregated to 3-year averages prior to MRI-1. The outcome was 5-year standardized change in MTL volumes. Mediators included voxel-based MRI measures of the spatial pattern of neurodegeneration of Alzheimer's disease (Alzheimer's disease pattern similarity scores [AD-PS]) and whole-brain white matter small-vessel ischemic disease (WM-SVID) volume as a proxy of global cerebrovascular damage. Structural equation models were constructed to examine whether the associations between exposures with MTL atrophy were mediated by the initial level or concurrent change in AD-PS score or WM-SVID while adjusting for sociodemographic, lifestyle, clinical characteristics, and intracranial volume. Living in locations with higher PM2.5 (per interquartile range [IQR]=3.17μg/m3) or NO2 (per IQR=6.63ppb) was associated with greater MTL atrophy (βPM2.5 = -0.29, 95% confidence interval [CI]=[-0.41,-0.18]; βNO2 =-0.12, 95%CI=[-0.23,-0.02]). Greater PM2.5 was associated with larger increases in AD-PS (βPM2.5 = 0.23, 95%CI=[0.12,0.33]) over time, which partially mediated associations with MTL atrophy (indirect effect= -0.10; 95%CI=[-0.15, -0.05]), explaining approximately 32% of the total effect. NO2 was positively associated with AD-PS at MRI-1 (βNO2=0.13, 95%CI=[0.03,0.24]), which partially mediated the association with MTL atrophy (indirect effect= -0.01, 95% CI=[-0.03,-0.001]). Global WM-SVID at MRI-1 or concurrent change were not significant mediators between exposures and MTL atrophy. Findings support the mediating role of Alzheimer's disease-related neurodegeneration contributing to MTL atrophy associated with late-life exposures to air pollutants. Alzheimer's disease-related neurodegeneration only partially explained associations between exposure and MTL atrophy suggesting the role of multiple neuropathological processes underlying air pollution neurotoxicity on brain aging.

Long-Term Exposure to Ambient PM2.5 and Hospitalizations for Myocardial Infarction Among US Residents: A Difference-in-Differences Analysis

Background Air pollution has been recognized as an untraditional risk factor for myocardial infarction (MI). However, the MI risk attributable to long-term exposure to fine particulate matter ≤2.5 μm in aerodynamic diameter (PM2.5) is unclear, especially in younger populations, and few studies have represented the general population or had power to examine comorbidities. Methods and Results We applied the difference-in-differences approach to estimate the relationship between annual PM2.5 exposure and hospitalizations for MI among US residents and further identified potential susceptible subpopulations. All hospital admissions for MI in 10 US states over the period 2002 to 2016 were obtained from the Healthcare Cost and Utilization Project State Inpatient Database. In total, 1 914 684 MI hospital admissions from 8106 zip codes were included in this study. We observed a 1.35% (95% CI, 1.11-1.59) increase in MI hospitalization rate for 1-μg/m3 increase in annual PM2.5 exposure. The estimate was robust to adjustment for surface pressure, relative humidity, and copollutants. In the population exposed to ≤12 μg/m3, there was a larger increment of 2.17% (95% CI, 1.79-2.56) in hospitalization rate associated with 1-μg/m3 increase in PM2.5. Young people (0-34 years of age) and elderly people (≥75 years of age) were the 2 most susceptible age groups. Residents living in more densely populated or poorer areas and individuals with comorbidities were observed to be at a greater risk. Conclusions This study indicates long-term residential exposure to PM2.5 could increase risk of MI among the general US population, people with comorbidities, and poorer individuals. The association persists below current standards.

Stronger susceptibilities to air pollutants of influenza A than B were identified in subtropical Shenzhen, China

Air pollution was indicated to be a key factor contributing to the aggressive spread of influenza viruses, whereas uncertainty still exists regarding to whether distinctions exist between influenza subtypes. Our study quantified the impact of five air pollutants on influenza subtype outbreaks in Shenzhen, China, a densely populated and highly urbanized megacity. Daily influenza outbreak data of laboratory-confirmed positive cases were obtained from the Shenzhen CDC, from May 1, 2013 to Dec 31, 2015. Concentrations of nitrogen dioxide (NO₂), sulfur dioxide (SO₂), particulate matters ≤2.5 μm (PM_2.5), particulate matters ≤10 μm (PM₁₀), and ozone (O₃), were retrieved from the 18 national monitoring stations. The generalized additive model (GAM) and distributed lag non-linear model (DLNM) were used to calculate the concentration-response relationships between environmental inducers and outbreak epidemics, respectively for influenza A (Flu-A) and B (Flu-B). There were 1687 positive specimens were confirmed during the study period. The cold season was restricted from Nov. 4th to Apr. 20th, covering all seasons other than the long-lasting summer. Relatively heavy fine particle matter (PM_2.5) and NO₂ pollution was observed in cold months, with mean concentrations of 46.06 μg/m³ and 40.03 μg/m³, respectively. Time-series analysis indicated that high concentrations of NO₂, PM_2.5, PM₁₀, and O₃ were associated with more influenza outbreaks at short lag periods (0-5 d). Although more Flu-B (679 cases) epidemics occurred than Flu-A (382 cases) in the cold season, Flu-A generally showed higher susceptibility to air pollutants. A 10 μg/m³ increment in concentrations of PM_2.5, PM₁₀, and O₃ at lag 04, was associated with a 2.103 (95%CI: 1.528-2.893), 1.618 (95%CI: 1.311-1.996), and 1.569 (95%CI: 1.214-2.028) of the relative risk (RR) of Flu-A, respectively. A 5 μg/m³ increase in NO₂ was associated with higher risk of Flu-A at lag 03 (RR = 1.646, 95%CI: 1.295-2.092) and of Flu-B at lag 04 (RR = 1.319, 95%CI: 1.095-1.588). Nevertheless, barely significant effect of particulate matters (PM_2.5, PM₁₀) on Flu-B and SO₂ on both subtypes was detected. Further, the effect estimates of NO₂ increased for both subtypes when coexisting with other pollutants. This study provides evidence that declining concentrations of main pollutants including NO₂, O₃, and particulate matters, could substantially decrease influenza risk in subtropical Shenzhen, especially for influenza A.

Impacts of traffic-related particulate matter pollution on semen quality: A retrospective cohort study relying on the random forest model in a megacity of South China

BACKGROUND

Emerging evidence shows the detrimental impacts of particulate matter (PM) on poor semen quality. High-resolution estimates of PM concentrations are conducive to evaluating accurate associations between traffic-related PM exposure and semen quality.

METHODS

In this study, we firstly developed a random forest model incorporating meteorological factors, land-use information, traffic-related variables, and other spatiotemporal predictors to estimate daily traffic-related PM concentrations, including PM_2.5, PM₁₀, and PM₁. Then we enrolled 1310 semen donors corresponding to 4912 semen samples during the study period from January 1, 2019, and December 31, 2019 in Guangzhou city, China. Linear mixed models were employed to associate individual exposures to traffic-related PM during the entire (0-90 lag days) and key periods (0-37 and 34-77 lag days) with semen quality parameters, including sperm concentration, sperm count, progressive motility and total motility.

RESULTS

The results showed that decreased sperm concentration was associated with PM₁₀ exposures (β: -0.21, 95 % CI: -0.35, -0.07), sperm count was inversely related to both PM_2.5 (β: -0.19, 95 % CI: -0.35, -0.02) and PM₁₀ (β: -0.19, 95 % CI: -0.33, -0.05) during the 0-90 days lag exposure window. Besides, PM_2.5 and PM₁₀ might diminish sperm concentration by mainly affecting the late phase of sperm development (0-37 lag days). Stratified analyses suggested that PBF and drinking seemed to modify the associations between PM exposure and sperm motility. We did not observe any significant associations of PM₁ exposures with semen parameters.

CONCLUSION

Our results indicate that exposure to traffic-related PM_2.5 and PM₁₀ pollution throughout spermatogenesis may adversely affect semen quality, especially sperm concentration and count. The findings provided more evidence for the negative associations between traffic-related PM exposure and semen quality, highlighting the necessity to reduce ambient air pollution through environmental policy.

Air pollution and risk of respiratory and cardiovascular hospitalizations in a large city of the Mekong Delta Region

It is important to explore air pollution and health effects in developing cities for early prevention rather than waiting for conditions to deteriorate as in the current megacities. This study aims to investigate the short-term health effects of air pollution in a large city in the Mekong Delta Region (MDR) of Vietnam. Air pollution data from January 2015 to December 2018 were collected from the Environmental Monitoring Centre of Can Tho City. The data of respiratory and cardiovascular disease (CVD) admissions in 18 hospitals and medical centers were collected. A time-series regression analysis was conducted using distributed lag models to examine the relationship between the air pollutants and hospitalizations including the delayed effect up to 7 days. The research findings reveal that a 10 μg increase in PM₁₀ was associated with an increase of 2.5% in the risk of respiratory admission for all people and 2.2% in the risk of CVD admission for the elderly on the same day. The analysis stratified by age and sex indicates that PM10 resulted in a higher risk of respiratory admission among children (0-5 years old) and males compared with other groups. PM10 and NO₂ were significantly associated with CVD admission among the elderly at lag 4 and 6 days. The effects of other air pollutants (SO₂, O₃) were not observed in this study. As development continues in this region, there is an urgent need for intervention measures to minimize the health impacts associated with the expected increases in air pollution in the MDR.

Synergistic or Antagonistic Health Effects of Long- and Short-Term Exposure to Ambient NO2 and PM2.5: A Review

Studies on adverse health effects associated with air pollution mostly focus on individual pollutants. However, the air is a complex medium, and thus epidemiological studies face many challenges and limitations in the multipollutant approach. NO₂ and PM_2.5 have been selected as both originating from combustion processes and are considered to be the main pollutants associated with traffic; moreover, both elicit oxidative stress responses. An answer to the question of whether synergistic or antagonistic health effects of combined pollutants are demonstrated by pollutants monitored in ambient air is not explicit. Among the analyzed studies, only a few revealed statistical significance. Exposure to a single pollutant (PM_2.5 or NO₂) was mostly associated with a small increase in non-accidental mortality (HR:1.01-1.03). PM_2.5 increase of <10 µg/m³ adjusted for NO₂ as well as NO₂ adjusted for PM_2.5 resulted in a slightly lower health risk than a single pollutant. In the case of cardiovascular heart disease, mortality evoked by exposure to PM_2.5 or NO₂ adjusted for NO₂ and PM_2.5, respectively, revealed an antagonistic effect on health risk compared to the single pollutant. Both short- and long-term exposure to PM_2.5 or NO₂ adjusted for NO₂ and PM_2.5, respectively, revealed a synergistic effect appearing as higher mortality from respiratory diseases.

Long-Term Effects of Ambient Particulate and Gaseous Pollutants on Serum High-Sensitivity C-Reactive Protein Levels: A Cross-Sectional Study Using KoGES-HEXA Data

Ambient air pollutants reportedly increase inflammatory responses associated with multiple chronic diseases. We investigated the effects of long-term exposure to ambient air pollution on high-sensitivity C-reactive protein (hs-CRP) using data from 60,581 participants enrolled in the Korean Genome and Epidemiology Study-Health Examinees Study between 2012 and 2017. Community Multiscale Air Quality System with surface data assimilation was used to estimate the participants' exposure to criteria air pollutants based on geocoded residential addresses. Long-term exposure was defined as the 2-year moving average concentrations of PM₁₀, PM_2.5, SO₂, NO₂, and O₃. Multivariable linear and logistic regression models were utilized to estimate the percent changes in hs-CRP and odds ratios of systemic low-grade inflammation (hs-CRP > 3 mg/L) per interquartile range increment in air pollutants. We identified positive associations between hs-CRP and PM₁₀ (% changes: 3.75 [95% CI 2.68, 4.82]), PM_2.5 (3.68, [2.57, 4.81]), SO₂ (1.79, [1.10, 2.48]), and NO₂ (3.31, [2.12, 4.52]), while negative association was demonstrated for O₃ (-3.81, [-4.96, -2.65]). Elevated risks of low-grade inflammation were associated with PM₁₀ (odds ratio: 1.07 [95% CI 1.01, 1.13]), PM_2.5 (1.08 [1.02, 1.14]), and SO₂ (1.05 [1.01, 1.08]). The odds ratios reported indicated that the exposures might be risk factors for inflammatory conditions; however, they did not reflect strong associations. Our findings suggest that exposure to air pollutants may play a role in the inflammation process.

Comparing human exposure to fine particulate matter in low and high-income countries: A systematic review of studies measuring personal PM2.5 exposure

BACKGROUND

Due to the adverse health effects of air pollution, researchers have advocated for personal exposure measurements whereby individuals carry portable monitors in order to better characterise and understand the sources of people's pollution exposure.

OBJECTIVES

The aim of this systematic review is to assess the differences in the magnitude and sources of personal PM2.5 exposures experienced between countries at contrasting levels of income.

METHODS

This review summarised studies that measured participants personal exposure by carrying a PM2.5 monitor throughout their typical day. Personal PM2.5 exposures were summarised to indicate the distribution of exposures measured within each country income category (based on low (LIC), lower-middle (LMIC), upper-middle (UMIC), and high (HIC) income countries) and between different groups (i.e. gender, age, urban or rural residents).

RESULTS

From the 2259 search results, there were 140 studies that met our criteria. Overall, personal PM2.5 exposures in HICs were lower compared to other countries, with UMICs exposures being slightly lower than exposures measured in LMICs or LICs. 34% of measured groups in HICs reported below the ambient World Health Organisation 24-h PM2.5 guideline of 15 μg/m3, compared to only 1% of UMICs and 0% of LMICs and LICs. There was no difference between rural and urban participant exposures in HICs, but there were noticeably higher exposures recorded in rural areas compared to urban areas in non-HICs, due to significant household sources of PM2.5 in rural locations. In HICs, studies reported that secondhand smoke, ambient pollution infiltrating indoors, and traffic emissions were the dominant contributors to personal exposures. While, in non-HICs, household cooking and heating with biomass and coal were reported as the most important sources.

CONCLUSION

This review revealed a growing literature of personal PM2.5 exposure studies, which highlighted a large variability in exposures recorded and severe inequalities in geographical and social population subgroups.

Inverse association between ambient particulate matter and semen quality in Central China: Evidence from a prospective cohort study of 15,112 participants

Emerging evidence indicates that ambient particulate matter (PM) is harmful to male fertility, but the associations between ambient PM exposure and semen quality were inconsistent. This study aimed to quantitatively evaluate the association between ambient PM exposure and semen quality based on a large prospective cohort. Using data from the prospective assisted reproduction cohort in Anhui province, China, we included 15,112 males with 28,267 semen tests, whose partner has undergone assisted reproductive technology from September 1, 2015 to September, 22 2020. Individual ambient PM, gaseous air pollutants, and temperature exposures of the participants during 0-90, 0-9, 10-14, and 70-90 days before semen quality tests were evaluated using inverse distance weighting interpolation. Linear mixed-effects models were conducted to evaluate the relationship between PM_2.5 and PM₁₀ exposures and standardized semen quality parameters. Models were adjusted for age, body mass index, smoking, drinking, education attainment, occupation type, sampling month, temperature and the principal component of gaseous air pollutants. PM_2.5 and PM₁₀ were inversely associated with sperm concentration, total sperm count, total motility, progressive motility, total motile sperm count, and progressively motile sperm count during 0-90, 0-9, and 70-90 days period (all p < 0.05), but not 10-14 days period. The regression coefficients of PM_2.5 exposure on semen quality parameters during 0-90 days period were larger than 0-9 and 70-90 days periods, and the effects of PM_2.5 on semen quality parameters were stronger than PM₁₀. Our results showed that ambient PM_2.5 and PM₁₀ exposures were associated with semen quality, during 70-90 days and 0-9 days before sampling, and the entire spermatogenesis process. The effects of PM_2.5 on semen quality parameters were stronger than PM₁₀, and the long-term effects of PM_2.5 and PM₁₀, throughout spermatogenesis, were stronger than the short-term effects.

A Bayesian Multi-Outcome Analysis of Fine Particulate Matter and Cardiorespiratory Hospitalizations

BACKGROUND

Short-term fine particulate matter (PM2.5) exposure is positively associated with acute cardiovascular and respiratory events. Understanding whether this association varies across specific cardiovascular and respiratory conditions has important biologic, clinical, and public health implications.

METHODS

We conducted a time-stratified case-crossover study of hospitalizations from 2000 through 2014 among United States Medicare beneficiaries aged 65+. The outcomes were hospitalizations with any of 57 cardiovascular and 32 respiratory discharge diagnoses. We estimated associations with two-day moving average PM2.5 as a piecewise linear term with a knot at PM2.5 = 25 g/m3. We used Multi-Outcome Regression with Tree-structured Shrinkage (MOReTreeS) to identify de novo groups of related diseases such that PM2.5 associations are: (1) similar within outcome groups; but (2) different between outcome groups. We adjusted for temperature, humidity, and individual-level characteristics. We introduce an R package, moretrees.

RESULTS

Our dataset included 16,007,293 cardiovascular and 8,690,837 respiratory hospitalizations. Of 57 cardiovascular diseases, 51 were grouped and positively associated with PM2.5. We observed a stronger positive association for heart failure, which formed a separate group. We observed negative associations for groups containing the outcomes other aneurysm and intracranial hemorrhage. Of 32 respiratory outcomes, 31 were grouped and were positively associated with PM2.5. Influenza formed a separate group with a negative association.

CONCLUSIONS

We used a new statistical approach, MOReTreeS, to uncover variation in the association between short-term PM2.5 exposure and hospitalizations for cardiovascular and respiratory causes controlling for patient characteristics, time trends, and environmental confounders.

A review and analysis of personal and ambient PM2.5 measurements: Implications for epidemiology studies

BACKGROUND

In epidemiology studies, ambient measurements of PM_2.5 are often used as surrogates for personal exposures. However, it is unclear the degree to which ambient PM_2.5 reflects personal exposures.

OBJECTIVE

In order to examine potential sources of bias in epidemiology studies, we conducted a review and meta-analysis of studies to determine the extent to which short-term measurements of ambient PM_2.5 levels are related to short-term measurements of personal PM_2.5 levels.

METHODS

We conducted a literature search of studies reporting both personal and ambient measurements of PM_2.5 published in the last 10 years (2009-2019) and incorporated studies published prior to 2009 from reviews.

RESULTS

Seventy-one studies were identified. Based on 17 studies reporting slopes, a meta-analysis revealed an overall slope of 0.56 μg/m³ (95% CI: [0.39, 0.73]) personal PM_2.5 per μg/m³ increase in ambient PM_2.5. Slopes for summer months were higher (slope = 0.73, 95% CI: [0.64, 0.81]) than for winter (slope = 0.46, 95% CI: [0.36, 0.57]). Based on 44 studies reporting correlations, we calculated an overall personal-ambient PM_2.5 correlation of 0.63 (95% CI: [0.55, 0.71]). Correlations were stronger in studies conducted in Canada (r = 0.86, 95% CI: [0.67, 0.94]) compared to the USA (r = 0.60, 95% CI: [0.49, 0.70]) and China (r = 0.60, 95% CI: [0.46, 0.71]). Correlations also were stronger in urban areas (r = 0.53, 95% CI: [0.43, 0.62]) vs. suburban areas (r = 0.36, 95% CI: [0.21, 0.49]).

SIGNIFICANCE

Our results suggest a large degree of variability in the personal-ambient PM_2.5 association and the potential for exposure misclassification and measurement error in PM_2.5 epidemiology studies.

Mutual effects of fine particulate matter, nitrogen dioxide, and fireworks on cause-specific acute cardiovascular mortality: A case-crossover study in communities affected by aircraft noise

Ambient air pollution is the leading cause of environmental mortality and morbidity worldwide. However, the individual contributions to acute mortality of traffic-related air pollutants such as nitrogen dioxide (NO₂) and fine particulate matter (PM_2.5) are still debated. We conducted a time-stratified case-crossover study for a population located around Zurich airport in Switzerland, including 24,886 adult cardiovascular deaths from the Swiss National Cohort. We estimated the risk of cause-specific cardiovascular mortality associated with daily NO₂ and PM_2.5 concentrations at home using distributed lag models up to 7 days preceding death, adjusted for daily temperature, precipitation, acute night-time aircraft noise, firework celebrations, and holidays. Cardiovascular mortality was associated with NO₂, whereas the association with PM_2.5 disappeared upon adjustment for NO₂. The strongest association was observed between NO₂ and ischemic stroke mortality (odds ratio = 1.55 per 10 μg/m³, 95% confidence intervals = 1.20-2.00). Cause-specific mortality analyses showed differences in terms of delayed effect: odds ratios were highest at 1-3 days after exposure for most outcomes but at lags of 3-5 days for heart failure. Individual vulnerabilities to NO₂ associated cardiovascular mortality also varied by cause of death, possibly highlighting the role of different behaviours and risk factors in the most susceptible groups. The risk of cardiovascular mortality was also increased on firework days and after public holidays, independent from NO₂ and PM_2.5 concentrations. This study confirms the association between ambient NO₂, as a marker for primary emissions, and acute cardiovascular mortality in a specific setting around a major airport. Future research should clarify the role of additional air pollutants including ultra-fine particles on cardiovascular diseases to inform most efficient control measures.

Quantifying the short-term effects of air pollution on health in the presence of exposure measurement error: a simulation study of multi-pollutant model results

BACKGROUND

Most epidemiological studies estimate associations without considering exposure measurement error. While some studies have estimated the impact of error in single-exposure models we aimed to quantify the effect of measurement error in multi-exposure models, specifically in time-series analysis of PM_2.5, NO₂, and mortality using simulations, under various plausible scenarios for exposure errors. Measurement error in multi-exposure models can lead to effect transfer where the effect estimate is overestimated for the pollutant estimated with more error to the one estimated with less error. This complicates interpretation of the independent effects of different pollutants and thus the relative importance of reducing their concentrations in air pollution policy.

METHODS

Measurement error was defined as the difference between ambient concentrations and personal exposure from outdoor sources. Simulation inputs for error magnitude and variability were informed by the literature. Error-free exposures with their consequent health outcome and error-prone exposures of various error types (classical/Berkson) were generated. Bias was quantified as the relative difference in effect estimates of the error-free and error-prone exposures.

RESULTS

Mortality effect estimates were generally underestimated with greater bias observed when low ratios of the true exposure variance over the error variance were assumed (27.4% underestimation for NO₂). Higher ratios resulted in smaller, but still substantial bias (up to 19% for both pollutants). Effect transfer was observed indicating that less precise measurements for one pollutant (NO₂) yield more bias, while the co-pollutant (PM_2.5) associations were found closer to the true. Interestingly, the sum of single-pollutant model effect estimates was found closer to the summed true associations than those from multi-pollutant models, due to cancelling out of confounding and measurement error bias.

CONCLUSIONS

Our simulation study indicated an underestimation of true independent health effects of multiple exposures due to measurement error. Using error parameter information in future epidemiological studies should provide more accurate concentration-response functions.

The association of air pollutants exposure with subclinical inflammation and carotid atherosclerosis

BACKGROUND

Air pollution is a well-described environmental factor with evidence suggesting a firm association with cardiovascular diseases. The purpose of this study was to determine the association of exposure to gaseous air pollutants on atherosclerosis burden.

METHODS

1955 inhabitants of the Corinthia region, aged 40 years or older, underwent clinical and biochemical assessment as well as carotid ultrasonography to evaluate carotid intima-media thickness (cIMT) and plaque burden. Analyzers recording time series concentration of CO, NO₂, and SO₂ were located at 4 different open sites (Regions 1, 2, 3 and 4) based on their proximity to industries, highways or shipyards.

RESULTS

A higher concentration of CO, NO2, and SO2 was observed in Region 4 compared to the other regions. Mean cIMT (Region 1: 0.93 ± 0.24 mm; Region 2: 0.96 ± 0.40 mm; Region 3: 0.94 ± 0.39 mm; Region 4: 1.14 ± 0.55 mm, p < 0.001), maximum cIMT (p < 0.001) as well as carotid plaque burden (Region 1: 13.3%; Region 2: 18.8%; Region 3: 22.4%; Region 4: 38.6%, p < 0.001) were significantly higher in individuals of Region 4. Inhabitants of Region 4 had also higher levels of C reactive protein (Region 1: 4.56 ± 4.85 mg/l; Region 2: 3.49 ± 4.46 mg/l; Region 3: 4.03 ± 3.32 mg/l, Region 4: 5.16 ± 8.26 mg/l, p < 0.001). Propensity score analysis revealed higher inter-area differences in mean cIMT of individuals with coronary artery disease (CAD) (high vs low air pollution area: 1.56 ± 0.80 mm; vs. 1.18 ± 0.54 mm, p < 0.001) while there was no difference in cIMT of the matched population without CAD (p = 0.52).

CONCLUSIONS

An increased carotid atherosclerotic and inflammatory burden is observed in inhabitants of areas with the highest concentration of air pollutants.

PM2.5 and NO2 exposure errors using proxy measures, including derived personal exposure from outdoor sources: A systematic review and meta-analysis

BACKGROUND

The use of proxy exposure estimates for PM_2.5 and NO₂ in air pollution studies instead of personal exposures, introduces measurement error, which can produce biased epidemiological effect estimates. Most studies consider total personal exposure as the gold standard. However, when studying the effects of ambient air pollution, personal exposure from outdoor sources is the exposure of interest.

OBJECTIVES

We assessed the magnitude and variability of exposure measurement error by conducting a systematic review of the differences between personal exposures from outdoor sources and the corresponding measurements for ambient concentrations in order to increase understanding of the measurement error structures of the pollutants.

DATA SOURCES AND ELIGIBILITY CRITERIA

We reviewed the literature (ISI Web of Science, Medline, 2000-2016) for English language studies (in any age group in any location (NO₂) or Europe and North America (PM_2.5)) that reported repeated measurements over time both for personal and ambient PM_2.5 or NO₂ concentrations. Only a few studies reported personal exposure from outdoor sources. We also collected data for infiltration factors and time-activity patterns of the individuals in order to estimate personal exposures from outdoor sources in every study.

STUDY APPRAISAL AND SYNTHESIS METHODS

Studies using modelled rather than monitored exposures were excluded. Type of personal exposure monitor was assessed. Random effects meta-analysis was conducted to quantify exposure error as the mean difference between "true" and proxy measures.

RESULTS

Thirty-two papers for PM_2.5 and 24 for NO₂ were identified. Outdoor sources were found to contribute 44% (range: 33-55%) of total personal exposure to PM_2.5 and 74% (range: 57-88%) to NO₂. Overall estimates of personal exposure (24-hour averages) from outdoor sources were 9.3 μg/m³ and 12.0 ppb for PM_2.5 and NO₂ respectively, while the corresponding difference between these exposures and the ambient concentrations (i.e. the measurement error) was 5.72 μg/m³ and 7.17 ppb. Our findings indicated also higher error variability for NO₂ than PM_2.5. Large heterogeneity was observed which was not explained sufficiently by geographical location or age group of the study sample.

LIMITATIONS, CONCLUSIONS AND IMPLICATIONS OF KEY FINDINGS

Relying only on information available in published studies led to some limitations: the contribution of outdoor sources to total personal exposure for NO₂ had to be inferred, individual variation in exposure misclassification was unavailable and instrument error could not be addressed. The larger magnitude and variability of errors for NO₂ compared with PM_2.5 has implications for biases in the health effect estimates of multi-pollutant epidemiological models. Results suggest that further research is needed regarding personal exposure studies and measurement error bias in epidemiological models.

Air pollution exposure and risk of spontaneous abortion in the Nurses' Health Study II

STUDY QUESTION

Is there an association between air pollution exposures and the risk of spontaneous abortion (SAB)?

SUMMARY ANSWER

Higher exposure to particulate matter (PM) air pollution above and beyond a woman's average exposure may be associated with greater risk of SAB, particularly among women experiencing at least one SAB during follow-up.

WHAT IS KNOWN ALREADY

There is sufficient biologic plausibility to suggest that air pollution adversely affects early pregnancy outcomes, particularly pregnancy loss; however, the evidence is limited.

STUDY DESIGN, SIZE, DURATION

Our prospective cohort study included 19 309 women in the Nurses' Health Study II who contributed a total of 35 025 pregnancies between 1990 and 2008. We also conducted a case-crossover analysis among 3585 women (11 212 pregnancies) with at least one SAB and one live birth during follow-up.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Proximity to major roadways and exposure to PM <10 microns (PM10), 2.5-10 microns (PM2.5-10) and <2.5 microns (PM2.5) were determined for residential addresses between 1989 and 2007. Pregnancy outcomes were self-reported biannually throughout follow-up and comprehensively in 2009. Multivariable log-binomial regression models with generalized estimating equations were used to estimate the risk ratios and 95% CIs of SAB. Conditional logistic regression was used for the case-crossover analysis.

MAIN RESULTS AND THE ROLE OF CHANCE

During the 19 years of follow-up, 6599 SABs (18.8% of pregnancies) were reported. In the main analysis, living closer to a major roadway and average exposure to PM10, PM10-2.5 or PM2.5 in the 1 or 2 years prior to pregnancy were not associated with an increased risk of SAB. However, small positive associations between PM exposures and SAB were observed when restricting the analysis to women experiencing at least one SAB during follow-up. In the case-crossover analysis, an increase in PM10 (per 3.9 μg/m3), PM2.5-10 (per 2.3 μg/m3) and PM2.5 (per 2.0 μg/m3) in the year prior to pregnancy was associated with 1.12 (95% CI 1.06, 1.19), 1.09 (95% CI 1.03, 1.14) and 1.10 (95% CI 1.04, 1.17) higher odds of SAB, respectively.

LIMITATIONS, REASONS FOR CAUTION

We did not have information on the month or day of SAB, which precluded our ability to examine specific windows of susceptibility or acute exposures. We also used ambient air pollution exposures as a proxy for personal exposure, potentially leading to exposure misclassification.

WIDER IMPLICATIONS OF THE FINDINGS

In our case-crossover analysis (but not in the entire cohort) we observed positive associations between exposure to all size fractions of PM exposure and risk of SAB. This may suggest that changes in PM exposure confer greater risk of SAB or that women with a history of SAB are a particularly vulnerable subgroup.

STUDY FUNDING/COMPETING INTEREST(S)

The authors are supported by the following NIH grants UM1CA176726, R00ES026648 and P30ES000002. The authors have no actual or potential competing financial interests to disclose.

The Impact of Particulate Matter on Outdoor Activity and Mental Health: A Matching Approach

Exposure to air pollution affects human activity and health. Particularly, in Asian countries, the influence of particulate matter on humans has received wide attention. However, there is still a lack of research about the effects of particulate matter on human outdoor activities and mental health. Therefore, we aimed to explore the association between exposure to particulate matter with a diameter of less than 10 µm (PM10) and outdoor activity along with mental health in South Korea where issues caused by particulate matter increasingly have social and economic impacts. We examined this relationship by combining the physical and habitual factors of approximately 100,000 people in 2015 from the Korean National Health Survey. To measure each individual’s exposure to particulate matter, we computed the total hours exposed to a high PM10 concentration (>80 μg/m³) in a given district one month before the survey was conducted. After dividing all districts into six groups according to the exposed level of the high PM10, we applied the propensity score-weighting method to control for observable background characteristics. We then estimated the impact of the high PM10 on outdoor activity and mental health between the weighted individuals in each group. Our main findings suggest that the impact of PM10 on outdoor activity and stress shows an inverted-U shaped function, which is counterintuitive. Specifically, both outdoor activity and stress levels tend to be worsened when the exposure time to a high PM10 (>80 μg/m³) was more than 20 h. Related policy implications are discussed.

Bibliometric analysis of cardiometabolic disorders studies involving NO2, PM2.5 and noise exposure

BACKGROUND

This study uses bibliometric analysis to describe the state of research about the association of NO2, PM2.5 and noise exposures - three traffic-related pollutants - with cardiometabolic disorders.

METHODS

We retrieved references published 1994-2017 from Scopus and classified references with respect to exposure, health outcome and study design using index keywords. Temporal trend, top cited references, used index keywords and the number of hypothesis testing and non-hypothesis testing study design for each group were identified.

RESULTS

Results show PM2.5 is the most frequently studied exposure (47%), followed by both NO2 and PM2.5 exposure (29%). Only 3% of references considered multiple exposures between NO2 and/or PM2.5 and noise, and these were published after 2008. While we observed a growing trend in studies with NO2 and/or PM2.5 and noise and diabetes in the last decade, there is a diminishing trend in studies with noise and diabetes. Different patterns of study designs were found through H/NH ratio, the number of references classified as having a hypothesis (H)-testing design relative to the number of references classified as having a non-hypothesis (NH)-testing design. Studies with NO2 and/or PM2.5 exposure are more likely to have a H-testing design, while those with noise exposure are more likely to have a NH-testing design, such as cross-sectional study design.

CONCLUSIONS

We conclude with three themes about research trends. First, the study of simultaneous exposures to multiple pollutants is a current trend, and likely to continue. Second, the association between traffic-related pollutants and diabetes and metabolic symptoms is an area for growth in research. Third, the transition to the use of H-testing study designs to explore associations between noise and cardiometabolic outcomes may be supported by improved understanding of the mechanism of action, and/or improvements to the accuracy and precision of air pollution and noise exposure assessments for environmental health research.

Gaseous pollutant exposure affects semen quality in central China: a cross-sectional study

BACKGROUND

Limited studies have explored the association between gaseous pollutant exposures and male reproductive outcomes, and findings remained inconsistent.

OBJECTIVES

To evaluate the potential association  between gaseous pollutants and semen quality within different exposure windows. MATERIALS AND METHODS: We adopted semen quality data of 1852 subjects who attended the Reproductive Medicine Center of Renmin Hospital at Wuhan University during January 1st, 2013, to August 3rd, 2015. A generalized linear model was employed to assess the relationship between each exposure variable and sperm parameters in different exposure windows.

RESULTS

SO₂ exposure with lag 0-90 days was significantly associated with decreased sperm concentration (β: -1.362; 95% CI: -1.844, -0.879), sperm count (β: -2.979; 95% CI: -4.267, -1.691), and PR (β: -0.551; 95% CI: -0.710, -0.393). Similar trends were observed for SO₂ exposure with three other key periods (lag 0-9, 10-14, and 70-90 days). NO₂ exposure with lag 0-90 days was also associated with decreased sperm concentration (β: -0.517; 95% CI: -1.006, -0.027), sperm count (β: -1.914; 95% CI: -3.214, -0.615), and PR (β: -0.264; 95% CI: -0.425, -0.102). No relationship between gaseous pollutant exposure and ejaculate volume was observed in any exposure window.

DISCUSSION AND CONCLUSION

Our study indicated a strong adverse effect of gaseous pollutants on semen quality outcomes during the sperm development. Gaseous pollution exposure appeared to be more detrimental in the initial phase of spermatogenesis.

Estimation of personal exposure to fine particles (PM2.5) of ambient origin for healthy adults in Hong Kong

Personal exposure and ambient fine particles (PM_2.5) measurements for 13 adult subjects (ages 19-57) were conducted in Hong Kong between April 2014 and June 2015. Six to 21 personal samples (mean = 19) per subject were obtained throughout the study period. Samples were analyzed for mass by gravimetric analysis, and 19 elements (from Na to Pb) were analyzed using X-Ray Fluorescence. Higher subject-specific correlations between personal and ambient sulfur (r_s = 0.92; p < 0.001) were found as compared to PM_2.5 mass (r_s = 0.79; p < 0.001) and other elements (0.06 < r_s < 0.86). Personal vs. ambient sulfur regression yielded an average exposure factor (F_pex) of 0.73 ± 0.02, supporting the use of sulfur as a surrogate to estimate personal exposure to PM_2.5 of ambient origin (E_a). E_a accounted for 41-82% and 57-73% of total personal PM_2.5 exposures (P) by season and by subject, respectively. The importance of both E_a and non-ambient exposures (E_na, 11.2 ± 5.6 μg/m³; 32.5 ± 10.9%) are noted. Mixed-effects models were applied to estimate the relationships between ambient PM_2.5 concentrations and their corresponding exposure variables (E_a, P). Higher correlations for E_a (0.90; p < 0.001) than for P (0.58; p < 0.01) were found. A calibration coefficient < 1 suggests an attenuation of 22% (ranging 16-28%) of the true effect estimates when using average ambient concentrations at central monitoring stations as surrogates for E_a. Stationary ambient data can be used to assess population exposure only if PM exposure is dominated by E_a.

What Are the Net Benefits of Reducing the Ozone Standard to 65 ppb? An Alternative Analysis

In October 2015, the United States Environmental Protection Agency (EPA) lowered the level of the ozone National Ambient Air Quality Standard (NAAQS) from 0.075 ppm to 0.070 ppm (annual 4th highest daily maximum 8-h concentration, averaged over three years). The EPA estimated a 2025 annual national non-California net benefit of $1.5 to $4.5 billion (2011$, 7% discount rate) for a 0.070 ppm standard, and a −$1.0 to $14 billion net benefit for an alternative 0.065 ppm standard. The purpose of this work is to present a combined toxicological and economic assessment of the EPA’s benefit-cost analysis of the 2015 ozone NAAQS. Assessing the quality of the epidemiology studies based on considerations of bias, confounding, chance, integration of evidence, and application of the studies for future population risk estimates, we derived several alternative benefits estimates. We also considered the strengths and weaknesses of the EPA’s cost estimates (e.g., marginal abatement costs), as well as estimates completed by other authors, and provided our own alternative cost estimate. Based on our alternative benefits and cost calculations, we estimated an alternative net benefit of between −$0.3 and $1.8 billion for a 0.070 ppm standard (2011 $, 7% discount rate) and between −$23 and −$17 billion for a 0.065 ppm standard. This work demonstrates that alternative reasonable assumptions can generate very difference cost and benefits estimates that may impact how policy makers view the outcomes of a major rule.

The relationship between fine particulate matter (PM2.5) and schizophrenia severity

PURPOSE

Although particulate matter (PM) is reported to affect the rate of emergency admissions for schizophrenia, no study has examined the relationship between particulate matter less than 2.5 μm in diameter (PM_2.5) and the severity of schizophrenia.

METHODS

We obtained data on patients with schizophrenia at a psychiatric hospital, and on air pollution in Sakai, Japan between Feb 1, 2013 and April 30, 2016. Multivariate logistic regression analyses were used to estimate the relationship between PM_2.5 concentrations and scores on the Brief Psychiatric Rating Scale (BPRS) of schizophrenia patients at admission, with a lag of up to 7 days.

RESULTS

During the study period, there were 1193 schizophrenia cases. The odds ratio (OR) for a BPRS score ≥ 50 at admission was 1.05 [95% confidence interval 1.00-1.10] and the effect of PM_2.5 concentration was significant for lag period of 2 days. The ORs associated with PM_2.5 concentration increased substantially for patients over 65 years of age.

CONCLUSIONS

Ambient PM_2.5 concentration was associated with exacerbation of schizophrenia. Our results suggest that protection for several days should be considered for controlling PM_2.5-related schizophrenia, especially among elderly patients.

Temporal trends in respiratory mortality and short-term effects of air pollutants in Shenyang, China

Short-term exposures to air pollution are associated with acute effects on respiratory health. This study aimed to describe 10-year temporal trends in respiratory mortality in the urban areas of Shenyang, China, according to gender and age and estimate the effects of air pollution on respiratory diseases (ICD-10J00-J99) and lung cancer (ICD-10 C33-C34) using a case-crossover design. During the study period 2013-2015, the exposure-response relationship between ambient air pollutants and mortality data was fitted by a quasi-Poisson model. Age-standardized mortality rates for a combined number of respiratory diseases and for lung cancer declined in Shenyang; however, death counts increased with aging. Deaths from respiratory diseases increased by 4.7% (95% CI, 0.00-9.9), and lung cancer mortality increased by 6.5% (95% CI, 1.2-12.0), both associated with a 10 μg/m³ increase in exposure to particulate matter < 2.5 μg in diameter (PM2.5). Moreover, males in Shenyang's urban areas were more susceptible to the acute effects of PM2.5 and SO₂ exposure; people aged ≥ 65 years had a high susceptibility to ozone, and those aged < 65 years were more susceptible to other air pollutants. These results provided an updated estimate of the short-term effects of air pollution in Shenyang. Since population aging is also associated with increasing mortality from respiratory diseases and lung cancer, reinforcing air quality control measures and health-promoting behaviors is urgent and necessary in Shenyang.

Ozone exposure and pulmonary effects in panel and human clinical studies: Considerations for design and interpretation

A wealth of literature exists regarding the pulmonary effects of ozone, a photochemical pollutant produced by the reaction of nitrogen oxide and volatile organic precursors in the presence of sunlight. This paper focuses on epidemiological panel studies and human clinical studies of ozone exposure, and discusses issues specific to this pollutant that may influence study design and interpretation as well as other, broader considerations relevant to ozone-health research. The issues are discussed using examples drawn from the wider literature. The recent panel and clinical literature is also reviewed. Health outcomes considered include lung function, symptoms, and pulmonary inflammation. Issues discussed include adversity, reversibility, adaptation, variability in ozone exposure metric used and health outcomes evaluated, co-pollutants in panel studies, influence of temperature in panel studies, and multiple comparisons. Improvements in and standardization of panel study approaches are recommended to facilitate comparisons between studies as well as meta-analyses. Additional clinical studies at or near the current National Ambient Air Quality Standard (NAAQS) of 70 ppb are recommended, as are clinical studies in sensitive subpopulations such as asthmatics.

IMPLICATIONS

The pulmonary health impacts of ozone exposure have been well documented using both epidemiological and chamber study designs. However, there are a number of specific methodological and related issues that should be considered when interpreting the results of these studies and planning additional research, including the standardization of exposure and health metrics to facilitate comparisons among studies.

A National County-Level Assessment of U.S. Nursing Facility Characteristics Associated with Long-Term Exposure to Traffic Pollution in Older Adults

Long-term exposure to ambient air pollution increases disease risk in older adults. Nursing facilities located near major roadways potentially expose older adults to traffic pollution. No studies, however, have described the association between nursing facilities and traffic pollution. We obtained data on facility- and census-tract-level characteristics of 15,706 U.S. facilities from the Medicare Nursing Home Compare datasets. We calculated distance to major roadways and traffic density for each facility. In the contiguous U.S. (as of 2014), 345,792 older adults, about 27% of residents in non-hospital facilities, lived within 150 m major roadways (A1 or A2) in 3876 (28% of sampled) facilities. Nationally, for-profit facilities, high-occupancy facilities, and facilities in census tracts with higher percentages of minorities were more likely to have higher exposure to traffic. Counties in Virginia, New York City, and Rhode Island have the highest percent of residents and facilities near major roads. Nationally, over one-quarter of sampled facilities are located near major roadways. Attributes potentially associated with higher exposure to traffic included “for-profit” and “higher minority census tract”. Proximity to major roadways may be an important factor to consider in siting nursing facilities. Our results inform potential intervention strategy at both county and facility level.

Inverse Association between Ambient Sulfur Dioxide Exposure and Semen Quality in Wuhan, China

Evidence concerning the association between ambient gaseous air pollutant exposures and semen quality is sparse, and findings in previous studies remain largely inconsistent. We enrolled 1759 men and performed 2184 semen examinations at a large reproductive medical center in Wuhan, China, between 2013 and 2015. Inverse distance weighting interpolation was performed to estimate individual exposures to SO₂, NO₂, CO, and O₃ during the entire period (lag 0-90 days) and key periods (lag 0-9, 10-14, 70-90 days) of sperm development. Linear mixed models were used to analyze exposure-response relationships. SO₂ exposure with 0-90 days lag was significantly associated with monotonically decreased sperm concentration (β for each interquartile range increase of exposure: -0.14; 95% CI: -0.23, -0.05), sperm count (-0.21; -0.30, -0.12) and total motile sperm count (-0.16; -0.25, -0.08). Significant associations were observed for total and progressive motility only when SO₂ exposure was at the highest quintile (all P_trend < 0.05). Similar trends were observed for SO₂ exposure with 70-90 days lag. NO₂, CO, or O₃ exposure was not significantly associated with semen quality. Our results suggest that ambient SO₂ exposure adversely affects semen quality and highlight the potential to improve semen quality by reducing ambient SO₂ exposure during early stages of sperm development.

Seasonal Effect on Association between Atmospheric Pollutants and Hospital Emergency Room Visit for Stroke

BACKGROUND

The relationship between air pollution and stroke is conflicting. This study was conducted to document the relationship between daily changes in atmospheric pollutants and hospital emergency room visits (ERVs) for stroke.

METHODS

Data of daily hospital ERVs for stroke and atmospheric pollutants in Changsha city between 2008 and 2009 were collected. Using a time-stratified bidirectional case-crossover design, we analyzed the association between atmospheric pollutants and stroke incidence in 4 seasons.

RESULTS

In the single-pollutant model, we found changes in sulfur dioxide (SO₂), nitrogen dioxide (NO₂), and particulate matters (PM₁₀) were significantly associated with cerebral hemorrhage and cerebral infarction (P < .05) in lags of 0-2 days in autumn. A 10-µg/m³ increase in SO₂ in autumn was significantly associated with ERVs for both cerebral hemorrhage (odds ratio [OR], 1.166; 95% confidence interval [CI], 1.012-1.343) and cerebral infarction (OR, 1.214; 95% CI, 1.018-1.448). NO₂ in autumn was significantly associated with ERVs for cerebral hemorrhage and infarction with OR = 1.162 (95% CI, 1.005-1.344) and OR = 1.137 (95% CI, 1.011-1.279), respectively. PM₁₀ in autumn was significantly associated with ERVs for cerebral hemorrhage and infarction with OR = 1.147 (95% CI, 1.045-1.259) and OR = 1.091 (95% CI, 1.019-1.168), respectively. Results of the multipollutant model showed that in autumn after PM₁₀ and NO₂ adjustment, only a 10-µg/m³ increase in SO₂ was significantly associated with ERVs for cerebral infarction (OR, 1.158; 95% CI, 1.006-1.333; P < .05). SO₂, NO₂, and PM₁₀ were not associated with ERVs for cerebral hemorrhage (P > .05).

CONCLUSIONS

This study demonstrates that the change in atmospheric SO₂ levels in Changsha is significantly associated with the stroke incidence in autumn.

Maternal Exposure to Nitrogen Dioxide, Intake of Methyl Nutrients, and Congenital Heart Defects in Offspring

Nutrients that regulate methylation processes may modify susceptibility to the effects of air pollutants. Data from the National Birth Defects Prevention Study (United States, 1997-2006) were used to estimate associations between maternal exposure to nitrogen dioxide (NO2), dietary intake of methyl nutrients, and the odds of congenital heart defects in offspring. NO2 concentrations, a marker of traffic-related air pollution, averaged across postconception weeks 2-8, were assigned to 6,160 nondiabetic mothers of cases and controls using inverse distance-squared weighting of air monitors within 50 km of maternal residences. Intakes of choline, folate, methionine, and vitamins B6 and B12 were assessed using a food frequency questionnaire. Hierarchical regression models, which accounted for similarities across defects, were constructed, and relative excess risks due to interaction were calculated. Relative to women with the lowest NO2 exposure and high methionine intake, women with the highest NO2 exposure and lowest methionine intake had the greatest odds of offspring with a perimembranous ventricular septal defect (odds ratio = 3.23, 95% confidence interval: 1.74, 6.01; relative excess risk due to interaction = 2.15, 95% confidence interval: 0.39, 3.92). Considerable departure from additivity was not observed for other defects. These results provide modest evidence of interaction between nutrition and NO2 exposure during pregnancy.

Association between Exposure to Traffic-Related Air Pollution and Prevalence of Allergic Diseases in Children, Seoul, Korea

Although there has been suggestive evidence of the association between TRAP and ADs, findings remained inconsistent possibly due to limited population. We investigated the association between TRAP and ADs in a large population of children with rich spatial coverage and expanded age span in Seoul, Korea. TRAP exposures were estimated by categorized proximity to the nearest major road (≤150, 150–300, 300–500, and >500 m) and density of major roads within 300 meters from children's residences. We estimated the association between two TRAP exposures and three ADs using generalized mixed model after adjusting for individual characteristics. We also investigated whether the association varied by household and regional socioeconomic status. We found associations of atopic eczema with road density [OR = 1.08; 95% CI = 1.01–1.15] and road proximity [1.15, 1.01–1.32; 1.17, 1.03–1.34; and 1.16, 1.01–1.34 for ≤150, 150–300, and 300–500 m, resp., compared to >500 m]. There was no association with asthma and allergic rhinitis. Effect estimates were generally the highest in the low socioeconomic region. Children living in areas surrounded by large and busy roads were likely to be at greater risks for atopic eczema, with increased vulnerability when living in deprived areas.

Systematic Review and Meta-Analysis of the Association between Ambient Nitrogen Dioxide and Respiratory Disease in China

Objective: This study aimed to assess the quantitative effects of short-term exposure of ambient nitrogen dioxide (NO₂) on respiratory disease (RD) mortality and RD hospital admission in China through systematic review and meta-analysis. Methods: A total of 29 publications were finally selected from searches in PubMed, Web of Science, CNKI and Wanfang databases. Generic inverse variance method was used to pool effect estimates. Pooled estimates were used to represent the increased risk of RD mortality and RD hospital admission per 10 μg/m³ increase in NO₂ concentration. Results: Positive correlations were found between short-term NO₂ exposure and RD in China. RD mortality and RD hospital admission respectively increased by 1.4% (95% CI: 1.1%, 1.7%) and 1.0% (95% CI: 0.5%, 1.5%) per 10 μg/m³ increase in NO₂ concentration. Differences were observed across geographic regions of China. The risk of RD mortality due to NO₂ was higher in the southern region (1.7%) than in the north (0.7%). Conclusions: Evidence was found that short-term exposure to NO₂ was associated with an increased risk of RD mortality and RD hospital admission in China and these risks were more pronounced in the southern regions of the country, due in part to a larger proportion of elderly persons with increased susceptibility to NO₂ in the population compared with the north.

Fine particulate matter on hospital admissions for acute exacerbation of chronic obstructive pulmonary disease in southwestern Taiwan during 2006-2012

This study explored the effects of PM_2.5 on hospital admissions (HAs) for acute exacerbation of chronic obstructive pulmonary disease (AECOPD) in southwestern Taiwan. Data on HAs for AECOPD, pollutants, and meteorological variables were obtained from the National Health Insurance Research Database and Environmental Protection Administration. The relative risks (RRs) of HAs for AECOPD was estimated using the Quasi-Poisson generalized additive model. A total of 38,715 HAs for AECOPD were recorded. The average daily HAs for AECOPD and mean 24-h average level of PM_2.5 were 15.2 and 38.8 µg/m³, respectively. For both single and multiple pollutant (adjusted for O₃ and NO₂) models, increased AECOPD admissions were significantly associated with PM_2.5 during cold season, with the RRs for every 10 µg/m³ increase in PM_2.5 being 1.02 (95% CI = 1.007-1.040) at lag 0-1 in single-pollutant, and 1.02 (95 % CI = 1.001-1.042) at lag 0 day in multiple pollutant model. People 65 years of age and older had higher risk of HAs for AECOPD after PM_2.5 exposure. The RRs of PM_2.5 on HAs for AECOPD were robust after adjusting for O₃ and NO₂. Findings reveal an association between PM_2.5 and HAs for AECOPD in southwestern Taiwan, particularly during cold season.

Health risk of inhalation exposure to sub-10 µm particulate matter and gaseous pollutants in an urban-industrial area in South Africa: an ecological study

OBJECTIVE

To assess the health risks associated with exposure to particulate matter (PM10), sulphur dioxide (SO2), nitrogen dioxide (NO2), carbon monoxide (CO) and ozone (O3).

DESIGN

The study is an ecological study that used the year 2014 hourly ambient pollution data.

SETTING

The study was conducted in an industrial area located in Pretoria West, South Africa. The area accommodates a coal-fired power station, metallurgical industries such as a coke plant and a manganese smelter.

DATA AND METHOD

Estimate of possible health risks from exposure to airborne PM10, SO2, NO2, CO and O3 was performed using the US Environmental Protection Agency human health risk assessment framework. A scenario-assessment approach where normal (average exposure) and worst-case (continuous exposure) scenarios were developed for intermediate (24-hour) and chronic (annual) exposure periods for different exposure groups (infants, children, adults). The normal acute (1-hour) exposure to these pollutants was also determined.

OUTCOME MEASURES

Presence or absence of adverse health effects from exposure to airborne pollutants.

RESULTS

Average annual ambient concentration of PM10, NO2 and SO2 recorded was 48.3±43.4, 11.50±11.6 and 18.68±25.4 µg/m3, respectively, whereas the South African National Ambient Air Quality recommended 40, 40 and 50 µg/m3 for PM10, NO2 and SO2, respectively. Exposure to an hour's concentration of NO2, SO2, CO and O3, an 8-hour concentration of CO and O3, and a 24-hour concentration of PM10, NO2 and SO2 will not likely produce adverse effects to sensitive exposed groups. However, infants and children, rather than adults, are more likely to be affected. Moreover, for chronic annual exposure, PM10, NO2 and SO2 posed a health risk to sensitive individuals, with the severity of risk varying across exposed groups.

CONCLUSIONS

Long-term chronic exposure to airborne PM10, NO2 and SO2 pollutants may result in health risks among the study population.

Association between ambient particulate matter exposure and semen quality in Wuhan, China

BACKGROUND

Health effects of exposure to particulate matter (PM) on male reproductive health remain unclear. Only a limited number of studies have investigated the effects of PM_2.5 or PM₁₀ exposure on semen quality, and the results were largely inconsistent.

OBJECTIVES

To quantitatively assess the exposure-response association between PM exposure and semen quality in Chinese men who were exposed to a wide concentration range of PM.

METHODS

We investigated 1759 men from Wuhan, China, who were partners of women undergoing assisted reproductive technology procedures, and had semen examined at least once between 2013 and 2015. Individual PM_2.5 and PM₁₀ exposures during 0-90, 0-9, 10-14 and 70-90days before each semen examination (corresponding to the entire and three key periods of sperm development, respectively) were retrospectively estimated by inverse distance weighting interpolation. Linear mixed models were used to assess exposure-response relations of PM exposure with sperm concentration, count and motility.

RESULTS

PM_2.5 exposure during 0-90 lag days ranged from 27.3 to 172.4μg/m³. It was linearly and inversely associated with sperm concentration (β: -0.20; 95% CI: -0.34, -0.07) and count (-0.22; -0.35, -0.08). For the three key exposure periods, only PM_2.5 exposure during the 70-90 lag days was significantly associated with sperm concentration (-0.12; -0.22, -0.03) and count (-0.12; -0.21, -0.02). Sensitivity analyses for a subgroup (n=1146) excluding subjects with abnormal sperm concentration, count or motility yielded similar results. Compared with PM_2.5, we found generally similar associations for PM₁₀ exposure in relation to sperm concentration and count, except that the associations appeared to be nonlinear with inverted J-shaped relationships. Neither PM_2.5 nor PM₁₀ exposure was significantly associated with sperm motility (all p>0.05).

CONCLUSIONS

Our results suggest that ambient PM exposure during sperm development adversely affects semen quality, in particular sperm concentration and count.

Acute Effects of Nitrogen Dioxide on Cardiovascular Mortality in Beijing: An Exploration of Spatial Heterogeneity and the District-specific Predictors

The exploration of spatial variation and predictors of the effects of nitrogen dioxide (NO₂) on fatal health outcomes is still sparse. In a multilevel case-crossover study in Beijing, China, we used mixed Cox proportional hazard model to examine the citywide effects and conditional logistic regression to evaluate the district-specific effects of NO₂ on cardiovascular mortality. District-specific predictors that could be related to the spatial pattern of NO₂ effects were examined by robust regression models. We found that a 10 μg/m³ increase in daily mean NO₂ concentration was associated with a 1.89% [95% confidence interval (CI): 1.33–2.45%], 2.07% (95% CI: 1.23–2.91%) and 1.95% (95% CI: 1.16–2.72%) increase in daily total cardiovascular (lag03), cerebrovascular (lag03) and ischemic heart disease (lag02) mortality, respectively. For spatial variation of NO₂ effects across 16 districts, significant effects were only observed in 5, 4 and 2 districts for the above three outcomes, respectively. Generally, NO₂ was likely having greater adverse effects on districts with larger population, higher consumption of coal and more civilian vehicles. Our results suggested independent and spatially varied effects of NO₂ on total and subcategory cardiovascular mortalities. The identification of districts with higher risk can provide important insights for reducing NO₂ related health hazards.

Outdoor air pollution and human infertility: a systematic review

Air pollution is a current research priority because of its adverse effects on human health, including on fertility. However, the mechanisms through which air pollution impairs fertility remain unclear. In this article, we perform a systematic review to evaluate currently available evidence on the impact of air pollution on fertility in humans. Several studies have assessed the impact of air pollutants on the general population, and have found reduced fertility rates and increased risk of miscarriage. In subfertile patients, women exposed to higher concentrations of air pollutants while undergoing IVF showed lower live birth rates and higher rates of miscarriage. After exposure to similar levels of air pollutants, comparable results have been found regardless of the mode of conception (IVF versus spontaneous conception), suggesting that infertile women are not more susceptible to the effects of pollutants than the general population. In addition, previous studies have not observed impaired embryo quality after exposure to air pollution, although evidence for this question is sparse.

Short-Term Exposure to Air Pollution and Cardiac Arrhythmia: A Meta-Analysis and Systematic Review

The objective was to assess the transient association between air pollution and cardiac arrhythmia. Five databases were searched for studies investigating the association between daily increases in air pollutants (PM2.5, PM10, carbon monoxide, nitrogen dioxide, sulfur dioxide and ozone) and arrhythmia hospitalization or arrhythmia mortality. Two reviewers independently selected studies, extracted data, and assessed risk of bias. Outcomes were analyzed via a random-effects model and reported as relative risk and 95% confidence interval. 25 studies satisfied our inclusion criteria and 23 contributed to the meta-analysis. Arrhythmia hospitalization or mortality were associated with increases in PM2.5 (RR = 1.015 per 10 μg/m³, 95% CI: 1.006-1.024), PM10 (RR = 1.009 per 10 μg/m³, 95% CI: 1.004-1.014), carbon monoxide (RR = 1.041 per 1 ppm, 95% CI: 1.017-1.065), nitrogen dioxide (RR = 1.036 per 10 ppb, 95% CI: 1.020-1.053), and sulfur dioxide (RR = 1.021 per 10 ppb, 95% CI: 1.003-1.039), but not ozone (RR = 1.012 per 10 ppb, 95% CI: 0.997-1.027). Both particulate and gaseous components, with the exception of ozone, have a temporal association with arrhythmia hospitalization or mortality. Compared with Europe and North America, a stronger association was noted in Asia.

Adult air pollution exposure and risk of infertility in the Nurses' Health Study II

STUDY QUESTION

Is there an association between air pollution exposures and incident infertility?

SUMMARY ANSWER

Increased exposure to air pollution is associated with an increased incidence of infertility.

WHAT IS KNOWN ALREADY

Exposures to air pollution have been associated with lower conception and fertility rates. However, the impact of pollution on infertility incidence is unknown.

STUDY DESIGN, SIZE, DURATION

Prospective cohort study using data collected from 116 430 female nurses from September 1989 to December 2003 as part of the Nurses' Health Study II cohort.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Infertility was defined by report of attempted conception for ≥12 months without success. Participants were able to report if evaluation was sought and if so, offer multiple clinical indications for infertility. After exclusion, 36 294 members were included in the analysis. Proximity to major roadways and ambient exposures to particulate matter less than 10 microns (PM10), between 2.5 and 10 microns (PM2.5-10), and less than 2.5 microns (PM2.5) were determined for residential addresses for the 36 294 members between the years of 1993 and 2003. Hazard ratios (HR) and 95% confidence intervals (CI) were calculated using multivariable adjusted Cox proportional hazard models with time-varying covariates.

MAIN RESULTS AND THE ROLE OF CHANCE

Over 213 416 person-years, there were 2508 incident reports of infertility. Results for overall infertility were inconsistent across exposure types. We observed a small increased risk for those living closer to compared to farther from a major road, multivariable adjusted HR = 1.11 (CI: 1.02-1.20). This was consistent for those reporting primary or secondary infertility. For women living closer to compared to farther from a major road, for primary infertility HR = 1.05 (CI: 0.94-1.17), while for secondary infertility HR = 1.21 (CI: 1.07-1.36). In addition, the HR for every 10 µg/m(3) increase in cumulative PM2.5-10 among women with primary infertility was 1.10 (CI: 0.96-1.27), and similarly was 1.10 (CI: 0.94-1.28) for those with secondary infertility.

LIMITATIONS, REASONS FOR CAUTION

Within the 2 year window of infertility diagnosis, we do not have the exact date of diagnosis or the exact timing of the start of attempting conception. As infertility status and subtypes of infertility were prospectively collected biennially, we were unable to tightly examine the timing of exposures on incidence of infertility. In terms of exposure quantification, we used ambient air pollution exposures as a proxy for personal exposures, potentially leading to exposure misclassification. However, several studies suggest that ambient measurements are an acceptable surrogate for individual level exposures in most populations.

WIDER IMPLICATIONS OF THE FINDINGS

We observed an association between all size fractions of PM exposure, as well as traffic-related air pollution, and incidence of infertility. Of note, the strongest association was observed between cumulative average exposures over the course of follow-up and the risk of infertility, suggesting that chronic exposures may be of greater importance than short-term exposures.

STUDY FUNDING/COMPETING INTERESTS

The work for this paper was supported by the following: S.M.: Reproductive Scientist Development Program HD000849, and the Building Interdisciplinary Research Careers in Women's Health HD043444, the Boston University CTSI 1UL1TR001430, and a research grant from the Boston University Department of Obstetrics and Gynecology, S.A.M.: R01HD57210 from the National Institute of Child Health and Human Development and the Massachusetts Institute of Technology Center for Environmental Health Sciences Translational Pilot Project Program, R01CA50385 from the National Cancer Institute, J.E.H. and F.L.: 5R01ES017017 from the National Institute for Environmental Health Sciences, 5 P42 ES007381 from the National Institute of Environmental Health at the National Institute of Health. L.V.F.: T32HD060454 in reproductive, perinatal, and pediatric epidemiology from the Eunice Kennedy Shriver National Institute of Child Health and Human Development. The Nurses' Health Study II is additionally supported by infrastructure grant UM1CA176726 from the National Cancer Institute, NIH, U.S. Department of Health and Human Services. The authors have no actual or potential competing financial interests to disclose.

Ethnic differences in ambient air pollution and risk of acute ischemic stroke

OBJECTIVES

To investigate the association between short-term changes in ambient pollution (particulate matter <2.5 μm in aerodynamic diameter (PM2.5) and ozone (O3)) and the risk of ischemic stroke among individuals living in a bi-ethnic community and whether this association is modified by ethnicity.

METHODS

We identified incident ischemic stroke cases from the population-based Brain Attack Surveillance in Corpus Christi (BASIC) project between 2000 and 2012. Associations between PM2.5 (mean 24-h) and O3 (maximal 8-h) levels, measured on the same-day and lags of 1-3 days, and odds of ischemic stroke were assessed using a time-stratified case-crossover design and modeled using conditional logistic regression. We explored race/ethnicity (Mexican American versus non-Hispanic white) as a modifier by including interaction terms in the models.

RESULTS

There were 2948 ischemic strokes with median age 71 years (IQR: 59-80). We observed no overall associations between the air pollutants and odds of ischemic stroke at any lag. When stratified by ethnicity, higher O3 was consistently associated with greater odds of ischemic stroke for non-Hispanic whites, but not for Mexican Americans. Higher PM2.5 was generally associated with lower odds of ischemic stroke for non-Hispanic whites but modestly greater odds for Mexican Americans.

CONCLUSION

Ethnic differences in the associations between ischemic stroke and short-term exposures to O3 and PM2.5 were suggested indicating that further study in diverse populations may be warranted.

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.

Are the elements of the proposed ozone National Ambient Air Quality Standards informed by the best available science?

The United States Environmental Protection Agency (US EPA) issues National Ambient Air Quality Standards (NAAQS) for six criteria pollutants, including ozone. Each standard has four elements: an indicator, level, averaging time, and form. Ozone levels (i.e., air concentrations) alone in scientific studies are not directly comparable to the "level" element of the NAAQS because the standard considers the level in the context of its relation to the remaining elements. Failure to appreciate this has led to misunderstandings regarding NAAQS that would be health-protective. This can be seen with controlled human ozone exposure studies, which often involved small numbers of people exercising quasi-continuously for a long duration at an intensity not common in the general population (and unlikely achievable by most sensitive individuals), under worst-case exposure profiles. In addition, epidemiology studies have used different averaging times and have had methodological limitations that may have biased results. Such considerations can make it difficult to compare ozone levels and results across studies and to appropriately apply them in a NAAQS evaluation. Relating patterns and circumstances of exposure, and exposure measurements, to all elements of the NAAQS can be challenging, but if US EPA fully undertook this, it would be evident that available evidence does not indicate that proposed lower ozone standards would be more health protective than the current one.

Acute air pollution exposure and risk of suicide completion

Research into environmental factors associated with suicide has historically focused on meteorological variables. Recently, a heightened risk of suicide related to short-term exposure to airborne particulate matter was reported. Here, we examined the associations between short-term exposure to nitrogen dioxide, particulate matter, and sulfur dioxide and completed suicide in Salt Lake County, Utah (n = 1,546) from 2000 to 2010. We used a time-stratified case-crossover design to estimate adjusted odds ratios for the relationship between suicide and exposure to air pollutants on the day of the suicide and during the days preceding the suicide. We observed maximum heightened odds of suicide associated with interquartile-range increases in nitrogen dioxide during cumulative lag 3 (average of the 3 days preceding suicide; odds ratio (OR) = 1.20, 95% confidence interval (CI): 1.04, 1.39) and fine particulate matter (diameter ≤2.5 μm) on lag day 2 (day 2 before suicide; OR = 1.05, 95% CI: 1.01, 1.10). Following stratification by season, an increased suicide risk was associated with exposure to nitrogen dioxide during the spring/fall transition period (OR = 1.35, 95% CI: 1.09, 1.66) and fine particulate matter in the spring (OR = 1.28, 95% CI: 1.01, 1.61) during cumulative lag 3. Findings of positive associations between air pollution and suicide appear to be consistent across study locations with vastly different meteorological, geographical, and cultural characteristics.

Proximity to traffic, ambient air pollution, and community noise in relation to incident rheumatoid arthritis

BACKGROUND

The risk of rheumatoid arthritis (RA) has been associated with living near traffic; however, there is evidence suggesting that air pollution may not be responsible for this association. Noise, another traffic-generated exposure, has not been studied as a risk factor for RA.

OBJECTIVES

We investigated proximity to traffic, ambient air pollution, and community noise in relation to RA in the Vancouver and Victoria regions of British Columbia, Canada.

METHODS

Cases and controls were identified in a cohort of adults that was assembled using health insurance registration records. Incident RA cases from 1999 through 2002 were identified by diagnostic codes in combination with prescriptions and type of physician (e.g., rheumatologist). Controls were matched to RA cases by age and sex. Environmental exposures were assigned to each member of the study population by their residential postal code(s). We estimated relative risks using conditional logistic regression, with additional adjustment for median income at the postal code.

RESULTS

RA incidence was increased with proximity to traffic, with an odds ratio (OR) of 1.37 (95% CI: 1.11, 1.68) for residence ≤ 50 m from a highway compared with residence > 150 m away. We found no association with traffic-related exposures such as PM2.5, nitrogen oxides, or noise. Ground-level ozone, which was highest in suburban areas, was associated with an increased risk of RA (OR = 1.26; 95% CI: 1.18, 1.36 per interquartile range increase).

CONCLUSIONS

Our study confirms a previously observed association of RA risk with proximity to traffic and suggests that neither noise levels nor traffic-related air pollutants are responsible for this relationship. Additional investigation of neighborhood and individual correlates of residence near roadways may provide new insight into risk factors for RA.

Urban air pollution and respiratory infections

Public awareness of the impact of air quality on health is increasing worldwide. Indoor and outdoor air pollutants impair children's growing lungs, and increase the risk of respiratory infections. In many cities, children face indoor air pollution from fuels used for cooking and heating, as well as outdoor pollution from vehicle exhausts. Research identifies at-risk groups and seeks to establish biological plausibility for the associations already observed; and looks towards identifying the harmful pollutants that are responsible for respiratory morbidity and mortality. These findings may then serve to influence public debate and future policy at national and international level to improve air quality in cities, and improve children's health.

Multiple exposures to airborne pollutants and hospital admissions due to diseases of the circulatory system in Santiago de Chile

BACKGROUND

High concentrations of various air pollutants have been associated with hospitalization due to development and exacerbation of cardiovascular diseases.

OBJECTIVES

We aimed to assess associations between airborne exposures by particulate matter as well as gaseous air pollutants and hospital admissions due to different cardiovascular disease groups in Santiago de Chile.

METHODS

The study was performed in the metropolitan area of Santiago de Chile during 2004-2007. We applied a time-stratified case-crossover analysis taking temporal variation, meteorological conditions and autocorrelation into account. We computed associations between daily ambient concentrations of carbon monoxide (CO), nitrogen dioxide (NO2), particulate matter (PM10 and PM2.5--particulate matter with aerodynamic diameters less than 10 or 2.5 μm, respectively) or ozone (O3) and hospital admissions for cardiovascular illnesses.

RESULTS

We found for CO, NO2, PM10 and PM2.5 adverse relationships to cardiovascular admissions while effect strength and lag depended on the pollutant and on the disease group. By trend, in 1-pollutant models most adverse pollutants were NO2 and particulate matter (PM10 and PM2.5) followed by CO, while in 2-pollutant models effects of PM10 persisted in most cases whereas other effects weakened. In addition the strongest effects seemed to be immediate or with a delay of up to 2 days. Adverse effects of ozone could not be detected.

CONCLUSIONS

Our results provided evidence for adverse health effects of combined exposure to airborne pollutants. Different pollutants accounted for varying adverse effects within different cardiovascular disease groups. Taking case numbers and effect strength of all cardiovascular diseases into account, mitigation measures should address all pollutants but especially NO2, PM10, and CO.

The Effects of Air Pollution on Cardiovascular and Respiratory Causes of Emergency Admission

INTRODUCTION

Today, air pollution is one of the critical problems in metropolitans and necessary preparations are needed for confronting this crisis. The present study was based on the goal of determining the relationship of air pollutant levels with the rate of emergency admissions for respiratory and cardiovascular patients.

METHODS

In the present retrospective cross-sectional study, all respiratory and cardiovascular patients, referred to emergency department during 2012, were assessed. The meteorological and air pollution data were collected. Information regarding the numbers and dates (month, day) of admission for respiratory and cardiovascular diseases was achieved from the hospital's electronic registration system. The relation of air pollution and respiratory and cardiovascular admissions were analyzed by generalize additive model (GAM).

RESULTS

5922 patients were assessed which included 4048 (68.36%) cardiovascular and 1874 (31.64%) respiratory. Carbon monoxide (CO) level was an independent risk factor of cardiovascular disease on the same day (RR=1.49; 95% CI: 1.25- 1.77; P<0.001), the day before (RR=1.22; 95% CI: 1.02- 1.45; P=0.03), and the last two days (RR=1.3; 95% CI: 1.09- 1.54; P<0.001). The same process was repeated for ozone (O3). In addition, the O3 level on the same day (RR=1.49; 95% CI: 1.25- 1.77; P<0.001), the day before (RR=1.22; 95% CI: 1.02- 1.45; P=0.03), the last two days (RR=1.3; 95% CI: 1.09- 1.54; P<0.001), and the last week (RR=1.004; 95% CI: 1.0007-1.008; P=0.02) were independent risk factors of respiratory admissions. The increased level of particulate matter less than 2.5 micrometers in diameter (PM2.5) like O3 led to growth in the admissions to emergency department.

CONCLUSION

The findings of the present study suggested that rising levels of CO and O3 during two days leads to a significant increase in cardiovascular admission on the third day. Furthermore, increase in O3, PM2.5, nitrogen dioxide (NO2), and CO levels causes a rise in respiratory admissions to emergency department.

Development and evaluation of alternative approaches for exposure assessment of multiple air pollutants in Atlanta, Georgia

Measurements from central site (CS) monitors are often used as estimates of exposure in air pollution epidemiological studies. As these measurements are typically limited in their spatiotemporal resolution, true exposure variability within a population is often obscured, leading to potential measurement errors. To fully examine this limitation, we developed a set of alternative daily exposure metrics for each of the 169 ZIP codes in the Atlanta, GA, metropolitan area, from 1999 to 2002, for PM(2.5) and its components (elemental carbon (EC), SO(4)), O(3), carbon monoxide (CO), and nitrogen oxides (NOx). Metrics were applied in a study investigating the respiratory health effects of these pollutants. The metrics included: (i) CS measurements (one CS per pollutant); (ii) air quality model results for regional background pollution; (iii) local-scale AERMOD air quality model results; (iv) hybrid air quality model estimates (a combination of (ii) and (iii)); and (iv) population exposure model predictions (SHEDS and APEX). Differences in estimated spatial and temporal variability were compared by exposure metric and pollutant. Comparisons showed that: (i) both hybrid and exposure model estimates exhibited high spatial variability for traffic-related pollutants (CO, NO(x), and EC), but little spatial variability among ZIP code centroids for regional pollutants (PM(2.5), SO(4), and O(3)); (ii) for all pollutants except NO(x), temporal variability was consistent across metrics; (iii) daily hybrid-to-exposure model correlations were strong (r>0.82) for all pollutants, suggesting that when temporal variability of pollutant concentrations is of main interest in an epidemiological application, the use of estimates from either model may yield similar results; (iv) exposure models incorporating infiltration parameters, time-location-activity budgets, and other exposure factors affect the magnitude and spatiotemporal distribution of exposure, especially for local pollutants. The results of this analysis can inform the development of more appropriate exposure metrics for future epidemiological studies of the short-term effects of particulate and gaseous ambient pollutant exposure in a community.

Evaluation of the causal framework used for setting national ambient air quality standards

Abstract A scientifically sound assessment of the potential hazards associated with a substance requires a systematic, objective and transparent evaluation of the weight of evidence (WoE) for causality of health effects. We critically evaluated the current WoE framework for causal determination used in the United States Environmental Protection Agency's (EPA's) assessments of the scientific data on air pollutants for the National Ambient Air Quality Standards (NAAQS) review process, including its methods for literature searches; study selection, evaluation and integration; and causal judgments. The causal framework used in recent NAAQS evaluations has many valuable features, but it could be more explicit in some cases, and some features are missing that should be included in every WoE evaluation. Because of this, it has not always been applied consistently in evaluations of causality, leading to conclusions that are not always supported by the overall WoE, as we demonstrate using EPA's ozone Integrated Science Assessment as a case study. We propose additions to the NAAQS causal framework based on best practices gleaned from a previously conducted survey of available WoE frameworks. A revision of the NAAQS causal framework so that it more closely aligns with these best practices and the full and consistent application of the framework will improve future assessments of the potential health effects of criteria air pollutants by making the assessments more thorough, transparent, and scientifically sound.

Examining the effects of air pollution composition on within region differences in PM2.5 mortality risk estimates

Multi-city population-based epidemiological studies have observed significant heterogeneity in both the magnitude and direction of city-specific risk estimates, but tended to focus on regional differences in PM2.5 mortality risk estimates. Interpreting differences in risk estimates is complicated by city-to-city heterogeneity observed within regions due to city-to-city variations in the PM2.5 composition and the concentration of gaseous pollutants. We evaluate whether variations in PM2.5 composition and gaseous pollutant concentrations have a role in explaining the heterogeneity in PM2.5 mortality risk estimates observed in 27 US cities from 1997 to 2002. Within each region, we select the two cities with the largest and smallest mortality risk estimate. We compare for each region the within- and between-city concentrations and correlations of PM2.5 constituents and gaseous pollutants. We also attempt to identify source factors through principal component analysis (PCA) for each city. The results of this analysis indicate that identifying a PM constituent(s) that explains the differences in the PM2.5 mortality risk estimates is not straightforward. The difference in risk estimates between cities in the same region may be attributed to a group of pollutants, possibly those related to local sources such as traffic.