A case-crossover study of fine particulate matter air pollution and onset of congestive heart failure symptom exacerbation leading to hospitalization

A case-crossover analysis to quantify the impact of wildfire smoke on hospital respiratory admissions in the Rogue Valley, Oregon

Background

With the increasing prevalence of wildfire smoke in the Pacific Northwest, it is important to quantify health impacts to plan for adequate health services. The Rogue Valley region has historically faced some of the greatest wildfire threats in the state. Health impacts from smoke have been estimated in several recent studies that include Oregon's Rogue Valley, but the results between studies are conflicting.

Objective

The objective is to critically examine impacts of wildfire smoke on health in the Rogue Valley area and translate the results to support hospital staffing decisions.

Study design

The study adopts a case-crossover approach.

Methods

Apply a conditional Poisson regression to analyze time stratified counts while controlling for mean temperature.

Results

Every 10 μ/m3 increase in PM2.5 is associated with a 2% increase in same-day hospital or emergency room admission rates for respiratory conditions during fire season after adjusting for temperature and time (OR = 1.020; 95% CI: 1.004-1.034); a 10 μ/m3 increase in PM2.5 lasting nine days is associated with a 4% increase in admission rates (OR = 1.041; 95% CI: 1.018-1.065). In other words, for each 10 μ/m3 single day increase in pollution from smoke, an additional 0.26 respiratory patients would be expected in the area hospitals. With a single day increase from 10 μ/m3 to 150 μ/m3, hospitals could expect an additional four patients.

Conclusions

There are small but significant health impacts in the Rogue Valley. These impacts are smaller than some statewide estimates. We need further research to understand these differences.

A case-crossover study on the effect of short-term exposure to moderate levels of air pollution on the risk of heart failure

Aims

Exposure to high levels of air pollution in industrialized urban areas is associated with an increased risk of heart failure (HF). On most days, the majority of European cities are only moderately affected by air pollution. The aim of this study was to evaluate the association between short‐term exposure to moderate levels of air pollution with the risk of HF in a city with good air quality.

Methods and results

We recruited 576 patients (median age 82 years; 58.2% men) admitted to a large university hospital in Central Germany for HF to participate in a hospital‐based, bidirectional, case‐crossover study. Diagnosis of HF and symptom onset were verified individually. The effect of short‐term exposure to nitrogen dioxide (NO₂), particulate matter (PM₁₀), and ozone (O₃) on the risk of HF was estimated using linear and non‐linear (categorized) multivariate analyses for three different lag times (1, 2, and 3 days before HF onset). Air pollution variables were adjusted to the date of HF symptom onset. During the study period, the average daily concentration of air pollutants was only moderate and reflects the average European background air pollution. In particular, the concentration of air pollutants ranged from 2 to 63.39 μg/m³ (median = 17.46 μg/m³) for NO₂, from 2 to 125.88 μg/m³ (median = 44.61 μg/m³) for O₃, and from 2.21 to 166.79 μg/m³ (median = 18.67 μg/m³) for PM₁₀. We did not find a linear or non‐linear association between short‐term exposure to NO₂, O₃, or PM₁₀ and risk for HF at all lag times in the overall population and subgroups.

Conclusions

In an area with only moderate air pollution, short‐term exposure to major air pollutants does not increase the risk for HF. Future studies should focus on a potential threshold effect of air pollution on HF risk as a basis for evidence‐based development of statutory limits in highly polluted areas.

Relationship between air pollution and hospitalizations for congestive heart failure in elderly people in the city of São Paulo

To evaluate the effects of air pollutants on hospitalizations of elderly people for congestive heart failure (CHF) in the city of São Paulo, stratified by sex, exploring lag structures, from 2000 to 2013. Ecological time series study using information on hospitalization of elderly patients for CHF (ICD-10th: I50) obtained from DATASUS for the city of São Paulo. Information on O₃, PM₁₀, NO₂, SO₂, CO, temperature and humidity was obtained from CETESB. Descriptive analyses, Pearson correlation, and generalized linear Poisson regression model were applied to estimate the effects of pollutants. The interquartile variations of O₃ (52.45 μg/m³), PM₁₀ (24.28 μg/m³), NO₂ (7.63 μg/m³), SO₂ (50.22 μg/m³), and CO (1.28 ppm) were associated with increased hospitalizations for CHF. Air pollutants continue to be a factor that contributes to the increase in the number of hospitalizations due to CHF.

Contribution of Satellite-Derived Aerosol Optical Depth PM2.5 Bayesian Concentration Surfaces to Respiratory-Cardiovascular Chronic Disease Hospitalizations in Baltimore, Maryland

The fine particulate matter baseline (PMB), which includes PM_2.5 monitor readings fused with Community Multiscale Air Quality (CMAQ) model predictions, using the Hierarchical Bayesian Model (HBM), is less accurate in rural areas without monitors. To address this issue, an upgraded HBM was used to form four experimental aerosol optical depth (AOD)-PM_2.5 concentration surfaces. A case-crossover design and conditional logistic regression evaluated the contribution of the AOD-PM_2.5 surfaces and PMB to four respiratory-cardiovascular hospital events in all 99 12 km² CMAQ grids, and in grids with and without ambient air monitors. For all four health outcomes, only two AOD-PM_2.5 surfaces, one not kriged (PMC) and the other kriged (PMCK), had significantly higher Odds Ratios (ORs) on lag days 0, 1, and 01 than PMB in all grids, and in grids without monitors. In grids with monitors, emergency department (ED) asthma PMCK on lag days 0, 1 and 01 and inpatient (IP) heart failure (HF) PMCK ORs on lag days 01 were significantly higher than PMB ORs. Warm season ORs were significantly higher than cold season ORs. Independent confirmation of these results should include AOD-PM_2.5 concentration surfaces with greater temporal-spatial resolution, now easily available from geostationary satellites, such as GOES-16 and GOES-17.

Short term exposure to fine particulate matter and hospital admission risks and costs in the Medicare population: time stratified, case crossover study

OBJECTIVE

To assess risks and costs of hospital admission associated with short term exposure to fine particulate matter with diameter less than 2.5 µm (PM2.5) for 214 mutually exclusive disease groups.

DESIGN

Time stratified, case crossover analyses with conditional logistic regressions adjusted for non-linear confounding effects of meteorological variables.

SETTING

Medicare inpatient hospital claims in the United States, 2000-12 (n=95 277 169).

PARTICIPANTS

All Medicare fee-for-service beneficiaries aged 65 or older admitted to hospital.

MAIN OUTCOME MEASURES

Risk of hospital admission, number of admissions, days in hospital, inpatient and post-acute care costs, and value of statistical life (that is, the economic value used to measure the cost of avoiding a death) due to the lives lost at discharge for 214 disease groups.

RESULTS

Positive associations between short term exposure to PM2.5 and risk of hospital admission were found for several prevalent but rarely studied diseases, such as septicemia, fluid and electrolyte disorders, and acute and unspecified renal failure. Positive associations were also found between risk of hospital admission and cardiovascular and respiratory diseases, Parkinson's disease, diabetes, phlebitis, thrombophlebitis, and thromboembolism, confirming previously published results. These associations remained consistent when restricted to days with a daily PM2.5 concentration below the WHO air quality guideline for the 24 hour average exposure to PM2.5. For the rarely studied diseases, each 1 µg/m3 increase in short term PM2.5 was associated with an annual increase of 2050 hospital admissions (95% confidence interval 1914 to 2187 admissions), 12 216 days in hospital (11 358 to 13 075), US$31m (£24m, €28m; $29m to $34m) in inpatient and post-acute care costs, and $2.5bn ($2.0bn to $2.9bn) in value of statistical life. For diseases with a previously known association, each 1 µg/m3 increase in short term exposure to PM2.5 was associated with an annual increase of 3642 hospital admissions (3434 to 3851), 20 098 days in hospital (18 950 to 21 247), $69m ($65m to $73m) in inpatient and post-acute care costs, and $4.1bn ($3.5bn to $4.7bn) in value of statistical life.

CONCLUSIONS

New causes and previously identified causes of hospital admission associated with short term exposure to PM2.5 were found. These associations remained even at a daily PM2.5 concentration below the WHO 24 hour guideline. Substantial economic costs were linked to a small increase in short term PM2.5.

Ozone effects on blood biomarkers of systemic inflammation, oxidative stress, endothelial function, and thrombosis: The Multicenter Ozone Study in oldEr Subjects (MOSES)

The evidence that exposure to ozone air pollution causes acute cardiovascular effects is mixed. We postulated that exposure to ambient levels of ozone would increase blood markers of systemic inflammation, prothrombotic state, oxidative stress, and vascular dysfunction in healthy older subjects, and that absence of the glutathione S-transferase Mu 1 (GSTM1) gene would confer increased susceptibility. This double-blind, randomized, crossover study of 87 healthy volunteers 55-70 years of age was conducted at three sites using a common protocol. Subjects were exposed for 3 h in random order to 0 parts per billion (ppb) (filtered air), 70 ppb, and 120 ppb ozone, alternating 15 min of moderate exercise and rest. Blood was obtained the day before, approximately 4 h after, and approximately 22 h after each exposure. Linear mixed effect and logistic regression models evaluated the impact of exposure to ozone on pre-specified primary and secondary outcomes. The definition of statistical significance was p<0.01. There were no effects of ozone on the three primary markers of systemic inflammation and a prothrombotic state: C-reactive protein, monocyte-platelet conjugates, and microparticle-associated tissue factor activity. However, among the secondary endpoints, endothelin-1, a potent vasoconstrictor, increased from pre- to post-exposure with ozone concentration (120 vs 0 ppb: 0.07 pg/mL, 95% confidence interval [CI] 0.01, 0.14; 70 vs 0 ppb: -0.03 pg/mL, CI -0.09, 0.04; p = 0.008). Nitrotyrosine, a marker of oxidative and nitrosative stress, decreased with increasing ozone concentrations, with marginal significance (120 vs 0 ppb: -41.5, CI -70.1, -12.8; 70 vs 0 ppb: -14.2, CI -42.7, 14.2; p = 0.017). GSTM1 status did not modify the effect of ozone exposure on any of the outcomes. These findings from healthy older adults fail to identify any mechanistic basis for the epidemiologically described cardiovascular effects of exposure to ozone. The findings, however, may not be applicable to adults with cardiovascular disease.

Acute effects of fine particulate matter (PM2.5) on hospital admissions for cardiovascular disease in Beijing, China: a time-series study

BACKGROUND

Air pollution and cardiovascular disease are increasing problems in China. However, the short-term association between fine particulate matter (PM_2.5) and cardiovascular disease (CVD) is not well documented. The purpose of this study is to estimate the short-term effects of PM_2.5 on CVD admissions in Beijing, China.

METHODS

In total, 460,938 electronic hospitalization summary reports for CVD between 2013 and 2017 were obtained. A generalized additive model using a quasi-Poisson distribution was used to investigate the association between exposure to PM_2.5 and hospitalizations for total and cause-specific CVD, including coronary heart disease (CHD), atrial fibrillation (AF), and heart failure (HF) after controlling for the season, the day of the week, public holidays, and weather conditions. A stratified analysis was also conducted for age (18-64 and ≥ 65 years), sex and season.

RESULTS

For every 10 μg/m³ increase in the PM_2.5 concentration from the previous day to the current (lag 0-1) there was a significant increase in total CVD admissions (0.30, 95% CI: 0.20, 0.39%), with a strong association for older adults (aged ≥65 years), CHD (0.34, 95% CI: 0.22 to 0.45%) and AF (0.29, 95% CI, 0.03 to 0.55%). However, the observed increased risk was not statistically significant for HF hospitalizations. The associations in the single-pollutant models were robust to the inclusion of other pollutants in a two-pollutant model. No differences were found after stratification by sex and season.

CONCLUSIONS

Exposure to PM_2.5 increased the risk of hospitalizations from CVD, especially for CHD, and appeared to have more influence in the elderly. Precautions and protective measures and efforts to reduce exposure to PM_2.5 should be strengthened, especially for the elderly.

Association Between PM2.5 and Daily Hospital Admissions for Heart Failure: A Time-Series Analysis in Beijing

There is little evidence that acute exposure to fine particulate matter (PM_2.5) impacts the rate of hospitalization for congestive heart failure (CHF) in developing countries. The primary purpose of the present retrospective study was to evaluate the short-term association between ambient PM_2.5 and hospitalization for CHF in Beijing, China. A total of 15,256 hospital admissions for CHF from January 2010 to June 2012 were identified from Beijing Medical Claim Data for Employees and a time-series design with generalized additive Poisson model was used to assess the obtained data. We found a clear significant exposure response association between PM_2.5 and the number of hospitalizations for CHF. Increasing PM_2.5 daily concentrations by 10 μg/m³ caused a 0.35% (95% CI, 0.06⁻0.64%) increase in the number of CHF admissions on the same day. We also found that female and older patients were more susceptible to PM_2.5. These associations remained significant in sensitivity analyses involving changing the degrees of freedom of calendar time, temperature, and relative humidity. PM_2.5 was associated with significantly increased risk of hospitalization for CHF in this citywide study. These findings may contribute to the limited scientific evidence about the acute impacts of PM_2.5 on CHF in China.

Cardiovascular function and ozone exposure: The Multicenter Ozone Study in oldEr Subjects (MOSES)

BACKGROUND

To date, there have been relatively few studies of acute cardiovascular responses to controlled ozone inhalation, although a number of observational studies have reported significant positive associations between both ambient ozone levels and acute cardiovascular events and long-term ozone exposure and cardiovascular mortality.

OBJECTIVES

We hypothesized that short-term controlled exposure to low levels of ozone in filtered air would induce autonomic imbalance, repolarization abnormalities, arrhythmia, and vascular dysfunction.

METHODS

This randomized crossover study of 87 healthy volunteers 55-70 years of age was conducted at three sites using a common protocol, from June 2012 to April 2015. Subjects were exposed for 3 h in random order to 0 ppb (filtered air), 70 ppb ozone, and 120 ppb ozone, alternating 15 min of moderate exercise with 15 min of rest. A suite of cardiovascular endpoints was measured the day before, the day of, and up to 22 h after each exposure. Mixed effect linear and logit models evaluated the impact of exposure to ozone on pre-specified primary and secondary outcomes. Site and time were included in the models.

RESULTS

We found no significant effects of ozone exposure on any of the primary or secondary measures of autonomic function, repolarization, ST segment change, arrhythmia, or vascular function (systolic blood pressure and flow-mediated dilation).

CONCLUSIONS

In this multicenter study of older healthy women and men, there was no convincing evidence for acute effects of 3-h, relatively low-level ozone exposures on cardiovascular function. However, we cannot exclude the possibility of effects with higher ozone concentrations, more prolonged exposure, or in subjects with underlying cardiovascular disease. Further, we cannot exclude the possibility that exposure to ambient ozone and other pollutants in the days before the experimental exposures obscured or blunted cardiovascular biomarker response to the controlled ozone exposures.

Associations between ambient air pollution and daily mortality in a cohort of congestive heart failure: Case-crossover and nested case-control analyses using a distributed lag nonlinear model

BACKGROUND

Persons with congestive heart failure may be at higher risk of the acute effects related to daily fluctuations in ambient air pollution. To meet some of the limitations of previous studies using grouped-analysis, we developed a cohort study of persons with congestive heart failure to estimate whether daily non-accidental mortality were associated with spatially-resolved, daily exposures to ambient nitrogen dioxide (NO₂) and ozone (O₃), and whether these associations were modified according to a series of indicators potentially reflecting complications or worsening of health.

METHODS

We constructed the cohort from the linkage of administrative health databases. Daily exposure was assigned from different methods we developed previously to predict spatially-resolved, time-dependent concentrations of ambient NO₂ (all year) and O₃ (warm season) at participants' residences. We performed two distinct types of analyses: a case-crossover that contrasts the same person at different times, and a nested case-control that contrasts different persons at similar times. We modelled the effects of air pollution and weather (case-crossover only) on mortality using distributed lag nonlinear models over lags 0 to 3 days. We developed from administrative health data a series of indicators that may reflect the underlying construct of "declining health", and used interactions between these indicators and the cross-basis function for air pollutant to assess potential effect modification.

RESULTS

The magnitude of the cumulative as well as the lag-specific estimates of association differed in many instances according to the metric of exposure. Using the back-extrapolation method, which is our preferred exposure model, we found for the case-crossover design a cumulative mean percentage changes (MPC) in daily mortality per interquartile increment in NO₂ (8.8 ppb) of 3.0% (95% CI: -0.4, 6.6%) and for O₃ (16.5 ppb) 3.5% (95% CI: -4.5, 12.1). For O₃ there was strong confounding by weather (unadjusted MPC = 7.1%; 95% CI: 1.7, 12.7%). For the nested case-control approach the cumulative MPC for NO₂ in daily mortality was 2.9% (95% CI: -0.9, 6.9%) and for O₃ 7.3% (95% CI: 3.0, 11.9%). We found evidence of effect modification between daily mortality and cumulative NO₂ and O₃ according to the prescribed dose of furosemide in the nested case-control analysis, but not in the case-crossover analysis.

CONCLUSIONS

Mortality in congestive heart failure was associated with exposure to daily ambient NO₂ and O₃ predicted from a back-extrapolation method using a land use regression model from dense sampling surveys. The methods used to assess exposure can have considerable influence on the estimated acute health effects of the two air pollutants.

Where do uncertainties reside within environmental risk assessments? Testing UnISERA, a guide for uncertainty assessment

A means for identifying and prioritising the treatment of uncertainty (UnISERA) in environmental risk assessments (ERAs) is tested, using three risk domains where ERA is an established requirement and one in which ERA practice is emerging. UnISERA's development draws on 19 expert elicitations across genetically modified higher plants, particulate matter, and agricultural pesticide release and is stress tested here for engineered nanomaterials (ENM). We are concerned with the severity of uncertainty; its nature; and its location across four accepted stages of ERAs. Using an established uncertainty scale, the risk characterisation stage of ERA harbours the highest severity level of uncertainty, associated with estimating, aggregating and evaluating expressions of risk. Combined epistemic and aleatory uncertainty is the dominant nature of uncertainty. The dominant location of uncertainty is associated with data in problem formulation, exposure assessment and effects assessment. Testing UnISERA produced agreements of 55%, 90%, and 80% for the severity level, nature and location dimensions of uncertainty between the combined case studies and the ENM stress test. UnISERA enables environmental risk analysts to prioritise risk assessment phases, groups of tasks, or individual ERA tasks and it can direct them towards established methods for uncertainty treatment.

Association of air pollution sources and aldehydes with biomarkers of blood coagulation, pulmonary inflammation, and systemic oxidative stress

Using data collected before, during, and after the 2008 Summer Olympic Games in Beijing, this study examines associations between biomarkers of blood coagulation (vWF, sCD62P and sCD40L), pulmonary inflammation (EBC pH, EBC nitrite, and eNO), and systemic oxidative stress (urinary 8-OHdG) with sources of air pollution identified utilizing principal component analysis and with concentrations of three aldehydes of health concern. Associations between the biomarkers and the air pollution source types and aldehydes were examined using a linear mixed effects model, regressing through seven lag days and controlling for ambient temperature, relative humidity, gender, and day of week for the biomarker measurements. The biomarkers for pulmonary inflammation, particularly EBC pH and eNO, were most consistently associated with vehicle and industrial combustion, oil combustion, and vegetative burning. The biomarkers for blood coagulation, particularly vWF and sCD62p, were most consistently associated with oil combustion. Systemic oxidative stress biomarker (8-OHdG) was most consistently associated with vehicle and industrial combustion. The associations of the biomarkers were generally not significant or consistent with secondary formation of pollutants and with the aldehydes. The findings support policies to control anthropogenic pollution sources rather than natural soil or road dust from a cardio-respiratory health standpoint.

Risk of Cardiovascular Hospitalizations from Exposure to Coarse Particulate Matter (PM10) Below the European Union Safety Threshold

The association between exposure to air pollution and acute cardiovascular (CV) events is well documented; however, limited data are available evaluating the public health safety of various "doses" of particular matter (PM) below currently accepted safety thresholds. We explored the cross-sectional association between PM with aerodynamic diameter <10 μm (PM10) and daily CV hospitalizations in Brescia, Italy, using Poisson regression models adjusted for age, gender, and meteorologic indices. Average daily exposure to PM10 obtained from arithmetic means of air pollution data were captured by 4 selected monitoring stations. PM10 data were expressed as daily means (lag 0-day) or 3-day moving averages (lag 3-day) and categorized according to the European Union daily limit value of 50 μg/m(3). From September 2004 to September 2007, data from 6,000 acute CV admissions to a tertiary referral center were collected. An increase of 1 μg/m(3) PM10 at lag 0-day was independently associated with higher rates of acute hospitalizations for composite CV-related events (relative risk [RR] 1.004, 95% confidence interval [CI] 1.002 to 1.006), acute heart failure (RR 1.004, 95% CI 1.001 to 1.008), acute coronary syndromes (RR 1.002, 95% CI 0.999 to 1.005), malignant ventricular arrhythmias (RR 1.004, 95% CI 0.999 to 1.010), and atrial fibrillation (RR 1.008, 95% CI 1.003 to 1.012). Similar results were obtained using PM10 lag 3-day data. The excess PM10 CV hospitalization risk (by lag 0-day and lag 3-day) did not vary significantly above and below the 50 μg/m(3) safety threshold or by age and gender. In conclusion, increased levels of PM10, even below the current limits set by the European Union, were associated with excess risk for admissions for acute CV events.

Effects of Air Pollution on Hospital Emergency Room Visits for Respiratory Diseases: Urban-Suburban Differences in Eastern China

A study on the relationships between ambient air pollutants (PM_2.5, SO₂ and NO₂) and hospital emergency room visits (ERVs) for respiratory diseases from 2013 to 2014 was performed in both urban and suburban areas of Jinan, a heavily air-polluted city in Eastern China. This research was analyzed using generalized additive models (GAM) with Poisson regression, which controls for long-time trends, the “day of the week” effect and meteorological parameters. An increase of 10 μg/m³ in PM_2.5, SO₂ and NO₂ corresponded to a 1.4% (95% confidence interval (CI): 0.7%, 2.1%), 1.2% (95% CI: 0.5%, 1.9%), and 2.5% (95%: 0.8%, 4.2%) growth in ERVs for the urban population, respectively, and a 1.5% (95%: 0.4%, 2.6%), 0.8% (95%: −0.7%, 2.3%), and 3.1% (95%: 0.5%, 5.7%) rise in ERVs for the suburban population, respectively. It was found that females were more susceptible than males to air pollution in the urban area when the analysis was stratified by gender, and the reverse result was seen in the suburban area. Our results suggest that the increase in ERVs for respiratory illnesses is linked to the levels of air pollutants in Jinan, and there may be some urban-suburban discrepancies in health outcomes from air pollutant exposure.

Air pollution and diastolic function in elderly women - Results from the SALIA study cohort

BACKGROUND

Studies linking particulate matter (PM) with heart failure (HF) show inconsistent results. However, the association of air pollution with diastolic function, an important determinant of heart failure, has not been studied yet and is addressed in the presented study.

METHODS

402 women (69-79 years) of the clinical follow-up (2007-2010) of the ongoing population-based prospective SALIA (Study on the influence of Air pollution on Lung function, Inflammation and Ageing) cohort were examined using Doppler echocardiography: Of the 291 women with preserved ejection fraction, the ratio of peak early diastolic filling velocity and peak early diastolic mitral annulus velocity (E/E') was collected in 264 and left atrial volume index (LAVI) in 262 women. Residential long-term air pollution exposure (nitrogen oxides, size-fractioned PM) was modeled at baseline and at follow-up, applying land use regression models. We used linear regression to model the cross-sectional associations of air pollutants per interquartile range (IQR) with different measures of diastolic function, adjusting for personal risk factors.

RESULTS

Median concentrations of annual NOx, NO2, PM2.5, and PM10 at follow-up were 37.7, 25.9, 17.4 and 26.4μg/m(3), respectively. In the fully adjusted models, LAVI was associated with an IQR increase in PM2.5 (1.05 [0.99; 1.12]) and NOx (1.04 [1.00; 1.09]) at follow-up, and with NOx and NO2 (both 1.05 [1.00; 1.11]) at baseline. None of the pollutants were clearly associated with E/E'.

CONCLUSIONS

In this analysis of elderly women, we found suggestive evidence for an association of air pollution with impaired diastolic function.

Physiological and perceived health effects from daily changes in air pollution and weather among persons with heart failure: a panel study

We carried out this daily diary panel study in Montreal, Quebec, to determine whether oxygen saturation, pulse rate, blood pressure, self-rated health, and shortness of breath at night were associated with concentrations of indoor carbon monoxide (CO), and indoor and outdoor fine particles (PM2.5), temperature, and relative humidity. Over a 2-month consecutive period between 2008 and 2010, we measured daily indoor and outdoor levels of the air pollutants and weather variables and 55 subjects measured their daily health and other variables. To estimate the associations between the health outcomes and the environmental exposures, we used a mixed effects regression model using an autoregressive model of order-one and we adjusted for month and day and personal variables. The general pattern of associations can be summarized as follows: oxygen saturation was reduced for increases in indoor- and outdoor-PM2.5 and temperature. Pulse rate increased on the concurrent day for increases in indoor CO and PM2.5. Diastolic blood pressure increased with increasing indoor and outdoor PM2.5 and relative humidity. Systolic blood pressure increased with indoor PM2.5 and decreased with increasing indoor and outdoor temperature. Self-rated health diminished with increases in outdoor PM2.5 and indoor and outdoor temperature. Self-reported shortness of breath at night increased with increasing indoor and outdoor temperatures. Health in heart failure is affected in the short term by personal and environmental conditions that are manifest in intermediate physiological parameters.

Short-term effects of fine particulate air pollution on hospital admissions for cardiovascular diseases: a case-crossover study in a tropical city

This study was undertaken to determine whether there was an association between fine particles (PM2.5) levels and hospital admissions for cardiovascular diseases (CVD) in Kaohsiung, Taiwan. Hospital admissions for CVD (including ischemic heart disease [IHD], stroke, congestive heart failure [CHF], and arrhythmias) and ambient air pollution data for Kaohsiung were obtained for the period from 2006-2010. The relative risk of hospital admissions for CVD was estimated using a case-crossover approach, controlling for weather variables, day of the week, seasonality, and long-term time trends. For the single-pollutant model (without adjustment for other pollutants), elevated number of admissions for CVD were significantly associated with higher PM2.5 levels only on cool days (<25°C), with an interquartile range rise associated with a 47% (95% CI = 39-56%), 48% (95% CI = 40-56%), 47% (95% CI = 34-61%), and 51% (95% CI = 34-70%) increase in IHD, stroke, CHF, and arrhythmias admissions, respectively. No significant associations between PM2.5 and hospital admissions for CVD were observed on warm days. In the two-pollutant models, PM2.5 levels remained significant even controlling for sulfur dioxide, nitrogen dioxide, carbon monoxide, or ozone on cool days. This study provides evidence that higher levels of PM2.5 enhance the risk of hospital admissions for CVD in Kaohsiung, Taiwan.

Fine particulate air pollution and hospital admissions for congestive heart failure: a case-crossover study in Taipei

This study was undertaken to determine whether there was an association between fine particles (PM₂.₅) levels and hospital admissions for congestive heart failure (CHF) in Taipei, Taiwan. Hospital admissions for CHF and ambient air pollution data for Taipei were obtained for the period 2006-2010. The relative risk of hospital admissions was estimated using a case-crossover approach, controlling for weather variables, day of the week, seasonality and long-term time trends. For the single pollutant model (without adjustment for other pollutants), increased CHF admissions were significantly associated with PM₂.₅ both on warm days (>23 °C) and cool days (<23 °C), with an interquartile range increase associated with a 13% (95% CI = 9-17%) and 3% (95% CI = 0-7%) increase in CHF admissions, respectively. In the two-pollutant models, PM₂.₅ remained significant after the inclusion of SO₂ or O₃ both on warm and cool days. This study provides evidence that higher levels of PM₂.₅ increase the risk of hospital admissions for CHF.

Effects of exposure to particles and ozone on hospital admissions for cardiorespiratory diseases in SetúBal, Portugal

In recent years, the adverse health effects attributed to air pollution have been a focus of intense study. Exposure to pollutants such as airborne particulate matter (PM) and ozone (O3) has been associated with increases in morbidity and mortality due to respiratory and cardiovascular diseases. The aim of this study was to determine a correlation between particles (PM10, PM2.5) and O3 with hospital admissions in Setúbal, a densely populated Portuguese urban region that coexists with a heavy industrial area. A database with daily air quality and hospital admission data over 5 years (2005-2009) was assembled and associations were investigated by ordinary least squares linear regression. Results showed positive significant associations between PM10 and respiratory diseases for ages below 14 yr and above 64 yr, and between PM2.5 and respiratory diseases for ages above 64 yr.

Association of air pollution and use of glyceryl trinitrate against angina pectoris: a population-based case-crossover study

BACKGROUND

Ambient air pollution has been associated with increased cardiovascular morbidity and mortality. In Reykjavik, Iceland, air pollutant concentrations exceed official health limits several times every year. The aim was to study the association of concentrations of NO2, O3, PM10, and H2S in the Reykjavik capital area with the dispensing of anti-angina pectoris medication, glyceryl trinitrate to the inhabitants.

METHODS

Data on daily dispensing of glyceryl trinitrate, were retrieved from the Icelandic Medicines Registry. Data on hourly concentrations of NO2, O3, PM10, and H2S were obtained from the Environment Agency of Iceland. A case-crossover design was used, based on the dispensing of glyceryl trinitrate to 5,246 individuals (≥18 years) between 2005 and 2009.

RESULTS

For every 10 μg/m3 increase of NO2 and O3 3-day mean concentrations, the odds ratio (OR) for daily dispensing of glyceryl trinitrates was 1.136 (95% confidence intervals (CI) 1.069-1.207) and 1.094 (95% CI 1.029-1.163) at lag 0, and OR was 1.096 (95% CI 1.029-1.168) and 1.094 (95% CI 1.028-1.166) at lag 1, respectively.

CONCLUSIONS

These findings suggest that NO2 and O3 ambient air concentrations may adversely affect cardiovascular health, as measured by the dispensing of glyceryl trinitrates for angina pectoris. Further, the findings suggest that data on the dispensing of medication may be a valuable health indicator when studying the effect of air pollution on cardiovascular morbidity.

Acute and chronic effects of particles on hospital admissions in New-England

Background

Many studies have reported significant associations between exposure to PM_2.5 and hospital admissions, but all have focused on the effects of short-term exposure. In addition all these studies have relied on a limited number of PM_2.5 monitors in their study regions, which introduces exposure error, and excludes rural and suburban populations from locations in which monitors are not available, reducing generalizability and potentially creating selection bias.

Methods

Using our novel prediction models for exposure combining land use regression with physical measurements (satellite aerosol optical depth) we investigated both the long and short term effects of PM_2.5 exposures on hospital admissions across New-England for all residents aged 65 and older. We performed separate Poisson regression analysis for each admission type: all respiratory, cardiovascular disease (CVD), stroke and diabetes. Daily admission counts in each zip code were regressed against long and short-term PM_2.5 exposure, temperature, socio-economic data and a spline of time to control for seasonal trends in baseline risk.

Results

We observed associations between both short-term and long-term exposure to PM_2.5 and hospitalization for all of the outcomes examined. In example, for respiratory diseases, for every10-µg/m³ increase in short-term PM_2.5 exposure there is a 0.70 percent increase in admissions (CI = 0.35 to 0.52) while concurrently for every10-µg/m³ increase in long-term PM_2.5 exposure there is a 4.22 percent increase in admissions (CI = 1.06 to 4.75).

Conclusions

As with mortality studies, chronic exposure to particles is associated with substantially larger increases in hospital admissions than acute exposure and both can be detected simultaneously using our exposure models.

A review of low-level air pollution and adverse effects on human health: implications for epidemiological studies and public policy

The aim of this study was to review original scientific articles describing the relationship between atmospheric pollution and damage to human health. We also aimed to determine which of these studies mentioned public policy issues. Original articles relating to atmospheric pollution and human health published between 1995 and 2009 were retrieved from the PubMed database and analyzed. This study included only articles dealing with atmospheric pollutants resulting primarily from vehicle emissions. Three researchers were involved in the final selection of the studies, and the chosen articles were approved by at least two of the three researchers. Of the 84 non-Brazilian studies analyzed, 80 showed an association between atmospheric pollution and adverse effects on human health. Moreover, 66 showed evidence of adverse effects on human health, even at levels below the permitted emission standards. Three studies mentioned public policies aimed at changing emission standards. Similarly, the 29 selected Brazilian studies reported adverse associations with human health, and 27 showed evidence of adverse effects even at levels below the legally permitted emission standards. Of these studies, 16 mentioned public policies aimed at changing emission standards. Based on the Brazilian and non-Brazilian scientific studies that have been conducted, it can be concluded that, even under conditions that are compliant with Brazilian air quality standards, the concentration of atmospheric pollutants in Brazil can negatively affect human health. However, as little discussion of this topic has been generated, this finding demonstrates the need to incorporate epidemiological evidence into decisions regarding legal regulations and to discuss the public policy implications in epidemiological studies.

Case-crossover analysis of air pollution health effects: a systematic review of methodology and application

BACKGROUND

Case-crossover is one of the most used designs for analyzing the health-related effects of air pollution. Nevertheless, no one has reviewed its application and methodology in this context.

OBJECTIVE

We conducted a systematic review of case-crossover (CCO) designs used to study the relationship between air pollution and morbidity and mortality, from the standpoint of methodology and application.

DATA SOURCES AND EXTRACTION

A search was made of the MEDLINE and EMBASE databases.Reports were classified as methodologic or applied. From the latter, the following information was extracted: author, study location, year, type of population (general or patients), dependent variable(s), independent variable(s), type of CCO design, and whether effect modification was analyzed for variables at the individual level.

DATA SYNTHESIS

The review covered 105 reports that fulfilled the inclusion criteria. Of these, 24 addressed methodological aspects, and the remainder involved the design's application. In the methodological reports, the designs that yielded the best results in simulation were symmetric bidirectional CCO and time-stratified CCO. Furthermore, we observed an increase across time in the use of certain CCO designs, mainly symmetric bidirectional and time-stratified CCO. The dependent variables most frequently analyzed were those relating to hospital morbidity; the pollutants most often studied were those linked to particulate matter. Among the CCO-application reports, 13.6% studied effect modification for variables at the individual level.

CONCLUSIONS

The use of CCO designs has undergone considerable growth; the most widely used designs were those that yielded better results in simulation studies: symmetric bidirectional and time-stratified CCO. However, the advantages of CCO as a method of analysis of variables at the individual level are put to little use.

Impact of fine and ultrafine particles on emergency hospital admissions for cardiac and respiratory diseases

BACKGROUND

Little is known about the short-term effects of ultrafine particles.

METHODS

We evaluated the effect of particulate matter with an aerodynamic diameter <or=10 microm (PM10), <or=2.5 microm (PM2.5), and ultrafine particles on emergency hospital admissions in Rome 2001-2005. We studied residents aged >or=35 years hospitalized for acute coronary syndrome, heart failure, lower respiratory tract infections, and chronic obstructive pulmonary disease (COPD). Information was available for factors indicating vulnerability, such as age and previous admissions for COPD. Particulate matter data were collected daily at one central fixed monitor. A case-crossover analysis was performed using a time-stratified approach. We estimated percent increases in risk per 14 microg/m PM10, per 10 microg/m PM2.5, and per 9392 particles/mL.

RESULTS

An immediate impact (lag 0) of PM2.5 on hospitalizations for acute coronary syndrome (2.3% [95% confidence interval = 0.5% to 4.2%]) and heart failure (2.4% [0.3% to 4.5%]) was found, whereas the effect on lower respiratory tract infections (2.8% [0.5% to 5.2%]) was delayed (lag 2). Particle number concentration showed an association only with admissions for heart failure (lag 0-5; 2.4% [0.2% to 4.7%]) and COPD (lag 0; 1.6% [0.0% to 3.2%]). The effects were generally stronger in the elderly and during winter. There was no clear effect modification with previous COPD.

CONCLUSIONS

We found sizeable acute health effects of fine and ultrafine particles. Although differential reliability in exposure assessment, in particular of ultrafine particles, precludes a firm conclusion, the study indicates that particulate matter of different sizes tends to have diverse outcomes, with dissimilar latency between exposure and health response.

Short-term effect of concentrations of fine particulate matter on hospital admissions due to cardiovascular and respiratory causes among the over-75 age group in Madrid, Spain

OBJECTIVES

This study sought to analyse the effect of daily mean concentrations of fine particulate matter (diameter <2.5 microm; PM(2.5)) on hospital admissions due to circulatory and respiratory causes among an elderly population (>75 years) in Madrid between 2003 and 2005.

STUDY DESIGN

Ecological longitudinal time-series study.

METHODS

The dependent variable used was the daily number of emergency hospital admissions registered at the Gregorio Marañón University Teaching Hospital. The following causes were analysed: all causes [International Classification of Diseases 9th Version (ICD-9:1-799)], respiratory causes (ICD-9: 460-519) and circulatory causes (ICD-9: 390-459). Analysis focused on subjects over 75 years of age. Daily records of mean concentrations of PM(2.5), PM(10), NO(2), NO(x), SO(2) and O(3) in Madrid were used as independent variables. The control variables were seasonalities, trend, influenza epidemics, noise and pollen concentrations. Poisson regression models were constructed to calculate the relative risk (RR) and attributable risk (AR). Analyses were performed for the entire year and for the winter and summer.

RESULTS

PM(2.5) was the single primary pollutant that proved statistically significant in all models. The functional relationship with hospital admissions was linear and had no threshold. Taking the year as a whole, the RRs among people over 75 years of age for an increase of 10 microg/m(3) in PM(2.5) concentrations were: 1.038 [95% confidence interval (CI) 1.022-1.053] for all causes at lag 0; 1.062 (95% CI 1.036-1.089) for circulatory causes at lag 0; and 1.049 (95% CI 1.019-1.078) for respiratory causes at lag 3. The ARs were 3.6%, 5.9% and 4.6%, respectively. These risks increased in winter and no statistically significant associations were observed in summer. PM(2.5) was the only primary pollutant that showed a statistically significant association with hospital admissions among people over 75 years of age in Madrid across the study period.

CONCLUSION

Measures should be implemented to reduce PM(2.5) concentrations in Madrid.

Surveillance of the short-term impact of fine particle air pollution on cardiovascular disease hospitalizations in New York State

BACKGROUND

Studies have shown that the effects of particulate matter on health vary based on factors including the vulnerability of the population, health care practices, exposure factors, and the pollutant mix.

METHODS

We used time-stratified case-crossover to estimate differences in the short-term impacts of PM2.5 on cardiovascular disease hospital admissions in New York State by geographic area, year, age, gender, co-morbid conditions, and area poverty rates.

RESULTS

PM2.5 had a stronger impact on heart failure than other cardiovascular diagnoses, with 3.1% of heart failure admissions attributable to short-term PM2.5 exposure over background levels of 5 ug/m3. Older adults were significantly more susceptible to heart failure after short-term ambient PM2.5 exposure than younger adults.

CONCLUSION

The short-term impact of PM2.5 on cardiovascular disease admissions, and modifications of that impact, are small and difficult to measure with precision. Multi-state collaborations will be necessary to attain more precision to describe spatiotemporal differences in health impacts.

The association between fine particulate air pollution and hospital emergency room visits for cardiovascular diseases in Beijing, China

BACKGROUND

Because epidemiological studies have yielded different results, the association between exposure to fine particulate matter less than 2.5 microm in aerodynamic diameter (PM(2.5)) and acute events of cardiovascular diseases (CVD) is unknown. Additionally, no research has been conducted to explore the association between PM(2.5) and hospital emergency room (ER) visits of cardiovascular diseases in Beijing, China.

OBJECTIVE

To explore the association between PM(2.5) and the hospital ER visits in Beijing, China for CVD {(International Classification of Diseases, 10th vision (ICD-10): I00-I99)}.

METHODS

We collected data for daily hospital ER visits for CVD from the Peking University Third Hospital, daily ambient PM(2.5) data from a fixed monitor site at Peking University, and data on the daily level of gaseous air pollutants {sulfur dioxide (SO(2)) and nitrogen dioxide (NO(2))} from the Beijing Municipal Environmental Monitoring Center between June 1, 2004 and December 31, 2006. A time-stratified case-crossover design was used to evaluate associations between CVD health outcomes and ambient air pollutants.

RESULTS

8377 hospital ER visits of CVD were collected in our study. After adjusting the temperature and the relative humidity, the associations for 10 microg/m(3) increases in levels of PM(2.5), SO(2), or NO(2) and hospital ER visits for cardiovascular diseases were statistically significant with odds ratios (ORs) of 1.005{95% confidence interval (CI): 1.001-1.009}, 1.014(95% CI: 1.004-1.024), and 1.016(95% CI: 1.003-1.029), respectively.

CONCLUSION

These findings suggest that elevated levels of ambient air pollutants are associated with the increase in hospital ER visits for CVD in Beijing, China.

Tracking associations between ambient ozone and asthma-related emergency department visits using case-crossover analysis

Traditional environmental public health surveillance consists of separately measuring hazards, exposures, and health outcomes. The Environmental Public Health Tracking (EPHT) Network seeks to accrue additional information by linking hazard or exposure data to health outcomes data. A natural progression is to consider tracking the "link" itself, that is, to track the association between an environmental hazard and a health outcome. The Maine EPHT Program conducted a case-crossover analysis to measure associations between daily estimated ambient ozone and particulate matter (PM2.5) and asthma-related emergency department (ED) visits for 2000-2003. We found an overall association of 7 percent (95% confidence interval, 4-11) excess asthma-related ED visits per 10-ppb increase in ozone averaged over 4 days (lag 0-3). The association was positive in the first 3 years and negative in the last. The excess risk was concentrated among females aged 15 to 34 and males younger than 15. The methodology for tracking associations between ambient air quality and acute morbidity is not generalizable to most other EPHT topic areas, but there are ample reasons to pursue this activity. The analysis can potentially help evaluate the effectiveness of regulatory and intervention programs, as well as inform us about trends, sensitive subpopulations, and changing potency of air constituents.

Shortness of breath at night and health status in congestive heart failure: effects of environmental conditions and health-related and dietary factors

OBJECTIVES

Recent studies suggest that persons with congestive heart failure (CHF) may be at higher risk for the short-term effects of air pollution. We carried out this daily diary panel study in Montreal, Quebec, to determine whether indicators of self-reported health status and shortness of breath at night were associated with selected health-related and dietary factors, weather conditions, and air pollution.

METHODS

Thirty-one subjects with CHF participated in this study in 2002 and 2003. Over a 2-month period, they measured their oxygen saturation, pulse rate, weight, and temperature each morning and recorded these and other data in a daily diary. Every morning they recorded on visual analogue scales their assessments of their general health, shortness of breath, and weakness, their weight, temperature and other data in a daily diary. Air pollution and weather conditions were obtained from fixed-site monitoring stations. This paper deals only with the daily self-reported health outcomes of general health and shortness of breath. We made use of mixed regression models, adjusting for within-subject serial correlation and temporal trends, to determine the association between oxygen saturation and pulse rate and health-related, dietary and environmental variables. Depending on the model, we accounted for the effects of a variety of health-related and dietary variables as well as NO(2), ozone, maximum temperature and change in barometric pressure at 8:00AM from the previous day.

RESULTS

Of the many associations for self-reported general health and shortness of breath, we found only a few statistically significant predictors, although increases in many variables showed decrements in self-reported general health and shortness of breath. The statistically significant associations with general health were increases in daily pulse rate and body weight, higher maximum ambient air temperature, higher relative humidity, and ozone (on the concurrent day). Statistically significant predictors of worsened shortness of breath at night were increases in blood pressure, body weight, and higher maximum ambient air temperature (lag 0 and 1 days). We also found that there was little confounding between environmental variables and health and dietary factors.

CONCLUSIONS

The findings from the present investigation suggest that certain health-related indices and environmental conditions affect self-reported health and shortness of breath in CHF patients, although larger studies are needed to confirm these findings.

Right heart pressure increases after acute increases in ambient particulate concentration

OBJECTIVES

We explored the association between acute changes in daily mean pulmonary artery (PA) and right ventricular (RV) pressures and concentrations of ambient fine particulate matter [PM with aerodynamic diameter < or = 2.5 microm (PM(2.5))] as an explanation for previous associations between congestive heart failure (HF) hospital admissions and PM.

MATERIALS AND METHODS

In the Chronicle Offers Management to Patients with Advanced Signs and Symptoms of Heart Failure (COMPASS-HF) trial, to see whether management of ambulatory HF could be improved by providing continuous right heart pressure monitoring to physicians, the Chronicle Implantable Hemodynamic Monitor (Medtronic, Inc., Minneapolis, MN, USA) continuously measured multiple right heart hemodynamic parameters, heart rate, and activity trends in subjects with moderate/severe HF. Using these trial data, we calculated daily mean pressures, using only those time intervals where the subject was not physically active (n = 5,807 person-days; n = 11 subjects). We then studied the association between mean daily PA/RV pressures and mean ambient PM(2.5) concentrations on the same day and previous 6 days.

RESULTS

Each 11.62-microg/m(3) increase in same-day mean PM(2.5) concentration was associated with small but significant increases in estimated PA diastolic pressure [0.19 mmHg; 95% confidence interval (CI), 0.05-0.33] and RV diastolic pressure (0.23 mmHg; 95% CI, 0.11-0.34). Although we saw considerable differences in the magnitude of response by COMPASS-HF randomization group (total data access for physicians vs. blocked clinician access), season, left ventricular ejection fraction, and obesity, these effects were not significantly different.

CONCLUSIONS

These pilot study findings provide a potential mechanism for previous findings of increased risk of HF associated with ambient PM. However, because of the small number of subjects, a larger study is needed for confirmation.

Effects of diesel exhaust particles on left ventricular function in isoproterenol-induced myocardial injury and healthy rats

The associations between ambient particulate matter with an aerodiameter less than 2.5 mu m (PM(2.5)) and congestive heart failure (CHF) have been reported. However, the underlying mechanisms remain unclear. We investigated the effect of diesel exhaust particles (DEPs) on left ventricular function in isoproterenol (ISO)-induced myocardial injury and healthy rats. Male Sprague-Dawley (SD) rats were injected with ISO or normal saline. Seven days later, both groups were further assigned to receive either DEPs or normal saline by intratracheal instillation (IT). Echocardiography was used to measure fractional shortening (FS) and left ventricular end-diastolic diameter (LVDd) 24 h before and after IT in each rat. Fractional shortening (FS) was significantly decreased in SD rats treated with ISO as compared to those treated with normal saline (p < .05, t-test). When FS and LVDd before and after treatment were compared in each rat, there was no difference for normal saline treatment in healthy or ISO groups. However, there was significantly lower FS before and after DEPs exposure in both groups (p < .05, paired t-test). When using SD rats treated with normal saline as a reference group, both SD rats treated with DEPs and ISO rats treated with normal saline had lower FS (p < .05 and .0001, respectively, t-test), while ISO rats treated with DEPs had the lowest FS (p < .0001, t-test). Echocardiographic assessment revealed that left ventricular function was impaired by acute DEPs exposure, and this LV function was further compromised in rats with preexisting ISO-induced myocardial injury.

[Contribution of case-crossover design to the analysis of short-term health effects of air pollution: reanalysis of air pollution and health data]

BACKGROUND

During the last decades, numerous studies have shown significant links between short-term exposure to air pollution and health. Time series design have been widely used in order to study these associations. In recent years, the case-crossover design has been applied to the analysis of acute effects of environmental exposures, especially air pollution. The aims of this paper are to describe the case-crossover design and to compare this approach with time series design to assess the association between air pollution and health.

METHODS

In the case-crossover approach, a case-control study is conducted whereby each person who had a health event (case period) is matched with himself/herself on a nearby time period where he/she did not have the event (control period). Review of the literature shows that the referent selection strategies can be associated to a bias in the estimation of the health effect of air pollution. In comparison with time series design, the case-crossover design is easier to conduct, and individual factors can be taken into account. Nevertheless, it is not possible to take into account the overdispersion in the health indicator with this approach.

RESULTS AND CONCLUSION

In conclusion, we suggest to use time series analysis with population data and case-crossover design with individual data.

Effects of ambient air pollution on functional status in patients with chronic congestive heart failure: a repeated-measures study

BACKGROUND

Studies using administrative data report a positive association between ambient air pollution and the risk of hospitalization for congestive heart failure (HF). Circulating levels of B-type natriuretic peptide (BNP) are directly associated with cardiac hemodynamics and symptom severity in patients with HF and, therefore, serves as a marker of functional status. We tested the hypothesis that BNP levels would be positively associated with short-term changes in ambient pollution levels among 28 patients with chronic stable HF and impaired systolic function.

METHODS

BNP was measured in whole blood at 0, 6, and 12 weeks. We used linear mixed models to evaluate the association between fine particulate matter (PM2.5), carbon monoxide, sulfur dioxide, nitrogen dioxide, ozone, and black carbon and log(BNP). Lags of 0 to 3 days were considered in separate models. We calculated the intraclass correlation coefficient and within-subject coefficient of variation as measures of reproducibility.

RESULTS

We found no association between any pollutant and measures of BNP at any lag. For example, a 10 microg/m3 increase in PM2.5 was associated with a 0.8% (95% CI: -16.4, 21.5; p = 0.94) increase in BNP on the same day. The within-subject coefficient of variation was 45% on the natural scale and 9% on the log scale.

CONCLUSION

These results suggest that serial BNP measurements are unlikely to be useful in a longitudinal study of air pollution-related acute health effects. The magnitude of expected ambient air pollution health effects appears small in relation to the considerable within-person variability in BNP levels in this population.