Isolated and synergistic effects of PM10 and average temperature on cardiovascular and respiratory mortality

OBJECTIVE

To analyze the effect of air pollution and temperature on mortality due to cardiovascular and respiratory diseases.

METHODS

We evaluated the isolated and synergistic effects of temperature and particulate matter with aerodynamic diameter < 10 µm (PM₁₀) on the mortality of individuals > 40 years old due to cardiovascular disease and that of individuals > 60 years old due to respiratory diseases in Sao Paulo, SP, Southeastern Brazil, between 1998 and 2008. Three methodologies were used to evaluate the isolated association: time-series analysis using Poisson regression model, bidirectional case-crossover analysis matched by period, and case-crossover analysis matched by the confounding factor, i.e., average temperature or pollutant concentration. The graphical representation of the response surface, generated by the interaction term between these factors added to the Poisson regression model, was interpreted to evaluate the synergistic effect of the risk factors.

RESULTS

No differences were observed between the results of the case-crossover and time-series analyses. The percentage change in the relative risk of cardiovascular and respiratory mortality was 0.85% (0.45;1.25) and 1.60% (0.74;2.46), respectively, due to an increase of 10 μg/m³ in the PM₁₀ concentration. The pattern of correlation of the temperature with cardiovascular mortality was U-shaped and that with respiratory mortality was J-shaped, indicating an increased relative risk at high temperatures. The values for the interaction term indicated a higher relative risk for cardiovascular and respiratory mortalities at low temperatures and high temperatures, respectively, when the pollution levels reached approximately 60 μg/m³.

CONCLUSIONS

The positive association standardized in the Poisson regression model for pollutant concentration is not confounded by temperature, and the effect of temperature is not confounded by the pollutant levels in the time-series analysis. The simultaneous exposure to different levels of environmental factors can create synergistic effects that are as disturbing as those caused by extreme concentrations.     

Mortality in the Medicare Population and Chronic Exposure to Fine Particulate Air Pollution in Urban Centers (2000–2005)

Background

Prospective cohort studies constitute the major source of evidence about the mortality effects of chronic exposure to particulate air pollution. Additional studies are needed to provide evidence on the health effects of chronic exposure to particulate matter ≤ 2.5 μm in aerodynamic diameter (PM_2.5) because few studies have been carried out and the cohorts have not been representative.

Objectives

This study was designed to estimate the relative risk of death associated with long-term exposure to PM_2.5 by region and age groups in a U.S. population of elderly, for the period 2000–2005.

Methods

By linking PM_2.5 monitoring data to the Medicare billing claims by ZIP code of residence of the enrollees, we have developed a new retrospective cohort study, the Medicare Cohort Air Pollution Study. The study population comprises 13.2 million participants living in 4,568 ZIP codes having centroids within 6 miles of a PM_2.5 monitor. We estimated relative risks adjusted by socioeconomic status and smoking by fitting log-linear regression models.

Results

In the eastern and central regions, a 10-μg/m³ increase in 6-year average of PM_2.5 is associated with 6.8% [95% confidence interval (CI), 4.9–8.7%] and 13.2% (95% CI, 9.5–16.9) increases in mortality, respectively. We found no evidence of an association in the western region or for persons ≥ 85 years of age.

Conclusions

We established a cohort of Medicare participants for investigating air pollution and mortality on longer-term time frames. Chronic exposure to PM_2.5 was associated with mortality in the eastern and central regions, but not in the western United States.     

Global Estimates of Ambient Fine Particulate Matter Concentrations from Satellite-Based Aerosol Optical Depth: Development and Application

Background

Epidemiologic and health impact studies of fine particulate matter with diameter < 2.5 μm (PM_2.5) are limited by the lack of monitoring data, especially in developing countries. Satellite observations offer valuable global information about PM_2.5 concentrations.

Objective

In this study, we developed a technique for estimating surface PM_2.5 concentrations from satellite observations.

Methods

We mapped global ground-level PM_2.5 concentrations using total column aerosol optical depth (AOD) from the MODIS (Moderate Resolution Imaging Spectroradiometer) and MISR (Multiangle Imaging Spectroradiometer) satellite instruments and coincident aerosol vertical profiles from the GEOS-Chem global chemical transport model.

Results

We determined that global estimates of long-term average (1 January 2001 to 31 December 2006) PM_2.5 concentrations at approximately 10 km × 10 km resolution indicate a global population-weighted geometric mean PM_2.5 concentration of 20 μg/m³. The World Health Organization Air Quality PM_2.5 Interim Target-1 (35 μg/m³ annual average) is exceeded over central and eastern Asia for 38% and for 50% of the population, respectively. Annual mean PM_2.5 concentrations exceed 80 μg/m³ over eastern China. Our evaluation of the satellite-derived estimate with ground-based in situ measurements indicates significant spatial agreement with North American measurements (r = 0.77; slope = 1.07; n = 1057) and with noncoincident measurements elsewhere (r = 0.83; slope = 0.86; n = 244). The 1 SD of uncertainty in the satellite-derived PM_2.5 is 25%, which is inferred from the AOD retrieval and from aerosol vertical profile errors and sampling. The global population-weighted mean uncertainty is 6.7 μg/m³.

Conclusions

Satellite-derived total-column AOD, when combined with a chemical transport model, provides estimates of global long-term average PM_2.5 concentrations.     

Are day-to-day variations of airborne particles associated with emergency ambulance dispatches?

Background:

Much of the evidence on the health effects of airborne particles is based on mortality and hospital admissions, while the evidence from other morbidity indicators is still limited.

Objective:

To measure the relationship between particles with diameter below 10 μm (PM₁₀) and emergency ambulance dispatches (EAD).

Methods:

Daily EAD for six towns of the Emilia-Romagna region (Italy) were obtained from a database collecting real-time data. Time series analyses were performed, and city-specific estimates were combined using meta-analytic techniques.

Results:

We found a significant percentage change of EAD associated with a 10 μg/m³ increase of PM₁₀ for non-traumatic diseases (0.86%, 95%CI: 0.61,1.1%). A positive relationship was also found for cardiovascular and respiratory diseases without reaching statistical significance. The risks were much higher in the warm (April–September) than in the cold season (January–March and October–December).

Conclusions:

Emergency ambulance dispatches provide useful insight into the health effects of air pollution and may be useful to establish surveillance systems.     

Time-series analysis of mortality effects of fine particulate matter components in Detroit and Seattle

Background

Recent toxicological and epidemiological studies have shown associations between particulate matter (PM) and adverse health effects, but which PM components are most influential is less well known.

Objectives

In this study, we used time-series analyses to determine the associations between daily fine PM [PM ≤ 2.5 μm in aerodynamic diameter (PM_2.5)] concentrations and daily mortality in two U.S. cities—Seattle, Washington, and Detroit, Michigan.

Methods

We obtained daily PM_2.5 filters for the years of 2002–2004 and analyzed trace elements using X-ray fluorescence and black carbon using light reflectance as a surrogate measure of elemental carbon. We used Poisson regression and distributed lag models to estimate excess deaths for all causes and for cardiovascular and respiratory diseases adjusting for time-varying covariates. We computed the excess risks for interquartile range increases of each pollutant at lags of 0 through 3 days for both warm and cold seasons.

Results

The cardiovascular and respiratory mortality series exhibited different source and seasonal patterns in each city. The PM_2.5 components and gaseous pollutants associated with mortality in Detroit were most associated with warm season secondary aerosols and traffic markers. In Seattle, the component species most closely associated with mortality included those for cold season traffic and other combustion sources, such as residual oil and wood burning.

Conclusions

The effects of PM_2.5 on daily mortality vary with source, season, and locale, consistent with the hypothesis that PM composition has an appreciable influence on the health effects attributable to PM.     

Association Between PM10 and O3 Levels and Hospital Visits for Cardiovascular Diseases in Bangkok,Thailand

Background

The association between air pollution and cardiovascular diseases is well known, but previous studies only assessed mortality and hospital admissions in North America, Europe, and Northeast Asia. Few studies have been conducted in less-developed countries in regions with a tropical climate. This study evaluated whether short-term exposures to fine particulate matter (PM₁₀) and ozone (O₃) were associated with hospital visits for cardiovascular diseases (CVD; ICD-10th, I00–I99) in central Bangkok, Thailand.

Methods

Data from hospital records were obtained from 3 major government hospitals. All hospital visits were stratified by age group and category of CVD. Daily PM₁₀ and O₃ levels reported by the Pollution Control Department from April 2002 to December 2006 (1736 days) were used in a time-series analysis with a generalized additive model procedure.

Results

Exposure on the previous day to PM₁₀ and O₃ had a positive association with hospital visits for CVD among elderly (≥65 years) individuals. The increase in CVD hospital visits in this age group was 0.10% (95% CI, 0.03–0.19) with a 10 µg/m³ increase in PM₁₀, and 0.50% (95% CI, 0.19–0.81) with an increase in O₃.

Conclusions

In central Bangkok, a short-term association was observed between increases in daily levels of PM₁₀ and O₃ and the number of daily emergency hospital visits for CVD, particularly among individuals aged ≥65 years.Key words: PM₁₀, ozone, cardiovascular diseases, hospital visits, Bangkok, air pollution     

Survival analysis of long-term exposure to different sizes of airborne particulate matter and risk of infant mortality using a birth cohort in Seoul, Korea

Background

Several studies suggest that airborne particulate matter (PM) is associated with infant mortality; however, most focused on short-term exposure to larger particles.

Objectives

We evaluated associations between long-term exposure to different sizes of particles [total suspended particles (TSP), PM ≤ 10 μm in aerodynamic diameter (PM₁₀), ≤ 10–2.5 μm (PM_10–2.5), and ≤ 2.5 μm (PM_2.5)] and infant mortality in a cohort in Seoul, Korea, 2004–2007.

Methods

The study includes 359,459 births with 225 deaths. We applied extended Cox proportional hazards modeling with time-dependent covariates to three mortality categories: all causes, respiratory, and sudden infant death syndrome (SIDS). We calculated exposures from birth to death (or end of eligibility for outcome at 1 year of age) and pregnancy (gestation and each trimester) and treated exposures as time-dependent variables for subjects’ exposure for each pollutant. We adjusted by sex, gestational length, season of birth, maternal age and educational level, and heat index. Each cause of death and exposure time frame was analyzed separately.

Results

We found a relationship between gestational exposures to PM and infant mortality from all causes or respiratory causes for normal-birth-weight infants. For total mortality (all causes), risks were 1.44 (95% confidence interval, 1.06–1.97), 1.65 (1.18–2.31), 1.53 (1.22–1.90), and 1.19 (0.83–1.70) per interquartile range increase in TSP, PM₁₀, PM_2.5, and PM_10–2.5, respectively; for respiratory mortality, risks were 3.78 (1.18–12.13), 6.20 (1.50–25.66), 3.15 (1.26–7.85), and 2.86 (0.76–10.85). For SIDS, risks were 0.92 (0.33–2.58), 1.15 (0.38–3.48), 1.42 (0.71–2.87), and 0.57 (0.16–1.96), respectively.

Conclusions

Our findings provide supportive evidence of an association of long-term exposure to PM air pollution with infant mortality.     

Chronic Fine and Coarse Particulate Exposure,Mortality, and Coronary Heart Disease in the Nurses’ Health Study

Background

The relationship of fine particulate matter < 2.5 μm in diameter (PM_2.5) air pollution with mortality and cardiovascular disease is well established, with more recent long-term studies reporting larger effect sizes than earlier long-term studies. Some studies have suggested the coarse fraction, particles between 2.5 and 10 μm (PM_10–2.5), may also be important. With respect to mortality and cardiovascular events, questions remain regarding the relative strength of effect sizes for chronic exposure to fine and coarse particles.

Objectives

We examined the relationship of chronic PM_2.5 and PM_10–2.5 exposures with all-cause mortality and fatal and nonfatal incident coronary heart disease (CHD), adjusting for time-varying covariates.

Methods

The current study included women from the Nurses’ Health Study living in metropolitan areas of the northeastern and midwestern United States. Follow-up was from 1992 to 2002. We used geographic information systems–based spatial smoothing models to estimate monthly exposures at each participant’s residence.

Results

We found increased risk of all-cause mortality [hazard ratio (HR), 1.26; 95% confidence interval (CI), 1.02–1.54] and fatal CHD (HR = 2.02; 95% CI, 1.07–3.78) associated with each 10-μg/m³ increase in annual PM_2.5 exposure. The association between fatal CHD and PM_10–2.5 was weaker.

Conclusions

Our findings contribute to growing evidence that chronic PM_2.5 exposure is associated with risk of all-cause and cardiovascular mortality.     

An Estimate of the Global Burden of Anthropogenic Ozone and Fine Particulate Matter on Premature Human Mortality Using Atmospheric Modeling

Background

Ground-level concentrations of ozone (O₃) and fine particulate matter [≤ 2.5 μm in aerodynamic diameter (PM_2.5)] have increased since preindustrial times in urban and rural regions and are associated with cardiovascular and respiratory mortality.

Objectives

We estimated the global burden of mortality due to O₃ and PM_2.5 from anthropogenic emissions using global atmospheric chemical transport model simulations of preindustrial and present-day (2000) concentrations to derive exposure estimates.

Methods

Attributable mortalities were estimated using health impact functions based on long-term relative risk estimates for O₃ and PM_2.5 from the epidemiology literature. Using simulated concentrations rather than previous methods based on measurements allows the inclusion of rural areas where measurements are often unavailable and avoids making assumptions for background air pollution.

Results

Anthropogenic O₃ was associated with an estimated 0.7 ± 0.3 million respiratory mortalities (6.3 ± 3.0 million years of life lost) annually. Anthropogenic PM_2.5 was associated with 3.5 ± 0.9 million cardiopulmonary and 220,000 ± 80,000 lung cancer mortalities (30 ± 7.6 million years of life lost) annually. Mortality estimates were reduced approximately 30% when we assumed low-concentration thresholds of 33.3 ppb for O₃ and 5.8 μg/m³ for PM_2.5. These estimates were sensitive to concentration thresholds and concentration–mortality relationships, often by > 50%.

Conclusions

Anthropogenic O₃ and PM_2.5 contribute substantially to global premature mortality. PM_2.5 mortality estimates are about 50% higher than previous measurement-based estimates based on common assumptions, mainly because of methodologic differences. Specifically, we included rural populations, suggesting higher estimates; however, the coarse resolution of the global atmospheric model may underestimate urban PM_2.5 exposures.     

California Wildfires of 2008: Coarse and Fine Particulate Matter Toxicity

Background

During the last week of June 2008, central and northern California experienced thousands of forest and brush fires, giving rise to a week of severe fire-related particulate air pollution throughout the region. California experienced PM_10–2.5 (particulate matter with mass median aerodynamic diameter > 2.5 μm to < 10 μm; coarse ) and PM_2.5 (particulate matter with mass median aerodynamic diameter < 2.5 μm; fine) concentrations greatly in excess of the air quality standards and among the highest values reported at these stations since data have been collected.

Objectives

These observations prompt a number of questions about the health impact of exposure to elevated levels of PM_10–2.5 and PM_2.5 and about the specific toxicity of PM arising from wildfires in this region.

Methods

Toxicity of PM_10–2.5 and PM_2.5 obtained during the time of peak concentrations of smoke in the air was determined with a mouse bioassay and compared with PM samples collected under normal conditions from the region during the month of June 2007.

Results

Concentrations of PM were not only higher during the wildfire episodes, but the PM was much more toxic to the lung on an equal weight basis than was PM collected from normal ambient air in the region. Toxicity was manifested as increased neutrophils and protein in lung lavage and by histologic indicators of increased cell influx and edema in the lung.

Conclusions

We conclude that the wildfire PM contains chemical components toxic to the lung, especially to alveolar macrophages, and they are more toxic to the lung than equal doses of PM collected from ambient air from the same region during a comparable season.     

The Effect of Fine and Coarse Particulate Air Pollution on Mortality: A National Analysis

Background

Although many studies have examined the effects of air pollution on mortality, data limitations have resulted in fewer studies of both particulate matter with an aerodynamic diameter of ≤ 2.5 μm (PM_2.5; fine particles) and of coarse particles (particles with an aerodynamic diameter > 2.5 and < 10 μm; PM coarse). We conducted a national, multicity time-series study of the acute effect of PM_2.5 and PM coarse on the increased risk of death for all causes, cardiovascular disease (CVD), myocardial infarction (MI), stroke, and respiratory mortality for the years 1999–2005.

Method

We applied a city- and season-specific Poisson regression in 112 U.S. cities to examine the association of mean (day of death and previous day) PM_2.5 and PM coarse with daily deaths. We combined the city-specific estimates using a random effects approach, in total, by season and by region.

Results

We found a 0.98% increase [95% confidence interval (CI), 0.75–1.22] in total mortality, a 0.85% increase (95% CI, 0.46–1.24) in CVD, a 1.18% increase (95% CI, 0.48–1.89) in MI, a 1.78% increase (95% CI, 0.96–2.62) in stroke, and a 1.68% increase (95% CI, 1.04–2.33) in respiratory deaths for a 10-μg/m³ increase in 2-day averaged PM_2.5. The effects were higher in spring. For PM coarse, we found significant but smaller increases for all causes analyzed.

Conclusions

We conclude that our analysis showed an increased risk of mortality for all and specific causes associated with PM_2.5, and the risks are higher than what was previously observed for PM₁₀. In addition, coarse particles are also associated with more deaths.     

Estimating Regional Spatial and Temporal Variability of PM2.5 Concentrations Using Satellite Data,Meteorology, and Land Use Information

Background

Studies of chronic health effects due to exposures to particulate matter with aerodynamic diameters ≤ 2.5 μm (PM_2.5) are often limited by sparse measurements. Satellite aerosol remote sensing data may be used to extend PM_2.5 ground networks to cover a much larger area.

Objectives

In this study we examined the benefits of using aerosol optical depth (AOD) retrieved by the Geostationary Operational Environmental Satellite (GOES) in conjunction with land use and meteorologic information to estimate ground-level PM_2.5 concentrations.

Methods

We developed a two-stage generalized additive model (GAM) for U.S. Environmental Protection Agency PM_2.5 concentrations in a domain centered in Massachusetts. The AOD model represents conditions when AOD retrieval is successful; the non-AOD model represents conditions when AOD is missing in the domain.

Results

The AOD model has a higher predicting power judged by adjusted R² (0.79) than does the non-AOD model (0.48). The predicted PM_2.5 concentrations by the AOD model are, on average, 0.8–0.9 μg/m³ higher than the non-AOD model predictions, with a more smooth spatial distribution, higher concentrations in rural areas, and the highest concentrations in areas other than major urban centers. Although AOD is a highly significant predictor of PM_2.5, meteorologic parameters are major contributors to the better performance of the AOD model.

Conclusions

GOES aerosol/smoke product (GASP) AOD is able to summarize a set of weather and land use conditions that stratify PM_2.5 concentrations into two different spatial patterns. Even if land use regression models do not include AOD as a predictor variable, two separate models should be fitted to account for different PM_2.5 spatial patterns related to AOD availability.     

Diurnal Temperature Range is a Risk Factor for Coronary Heart Disease Death

Background

Although the relation between day-to-day temperature change and coronary heart disease (CHD) mortality is well established, it is unknown whether temperature variation within 1 day, ie, diurnal temperature range (DTR), is an independent risk factor for acute CHD death.

Methods

We used time-series and case-crossover approaches to assess the relation between DTR and daily CHD mortality between 2001 and 2004 in Shanghai, China. Specifically, we used exposures averaged over periods varying from 1 to 5 days to assess the effects of DTR on CHD mortality. We estimated the percent increase in the number of daily deaths related to CHD that were associated with DTR, after adjustment for daily meteorologic conditions (temperature and relative humidity) and levels of outdoor air pollutants.

Results

Both time-series and case-crossover analyses showed that DTR was significantly associated with the number of daily deaths related to CHD. A 1 °C increase in 2-day lagged DTR corresponded to a 2.46% (95% CI, 1.76% to 3.16%) increase in CHD mortality on time-series analysis, a 3.21% (95% CI, 2.23% to 4.19%) increase on unidirectional case-crossover analysis, and a 2.13% (95% CI, 1.04% to 3.22%) increase on bidirectional case-crossover analysis.

Conclusions

Our findings suggest that DTR is an independent risk factor for acute CHD death.Key words: diurnal temperature range, coronary heart disease, mortality, time-series, case-crossover     

Coarse particulate matter and emergency ambulance dispatches in Fukuoka,Japan: a time-stratified case-crossover study

Objectives

There is no conclusive evidence of adverse health effects caused by short-term exposure to coarse particulate matter, so in this case-crossover study we looked for an association between exposure and emergency ambulance dispatches (as a proxy of acute health outcomes).

Methods

We used data on emergency ambulance dispatches in Fukuoka City, Japan between 2005 and 2010. After excluding ambulance dispatches related to external injuries and pregnancy/childbirth, we analyzed data on 176,123 dispatches. Citywide daily mean concentrations of suspended particulate matter (SPM) and fine particulate matter (PM_2.5) were calculated from ambient monitoring data, and the differences between concentrations of SPM and PM_2.5 were used as an exposure surrogate of coarse particulate matter. Using a conditional logistic regression model, we estimated the ambient temperature and relative humidity adjusted odds ratios (ORs) per 10 μg/m³ increase in coarse particulate matter.

Results

The average daily concentration of coarse particulate matter over the study period was 9.9 μg/m³, representing 33 % of the total concentration of SPM. Elevated concentrations of coarse particulate matter were associated with an increase in respiratory disease-related emergency ambulance dispatches for adults aged 65 years or older (9,716 dispatches, OR for lag0–1 = 1.065, 95 % confidence interval = 1.023–1.109). After additional adjustment for exposure to PM_2.5, we observed a statistically non-significant increased risk (OR = 1.035, 0.986–1.086).

Conclusions

We found weak evidence of adverse effects of short-term exposure to coarse particulate matter on human health.     

Associations between PM2.5 and Heart Rate Variability Are Modified by Particle Composition and Beta-Blocker Use in Patients with Coronary Heart Disease

Background

It has been hypothesized that ambient particulate air pollution is able to modify the autonomic nervous control of the heart, measured as heart rate variability (HRV). Previously we reported heterogeneous associations between particulate matter with aerodynamic diameter < 2.5 μm (PM_2.5) and HRV across three study centers.

Objectives

We evaluated whether exposure misclassification, effect modification by medication, or differences in particle composition could explain the inconsistencies.

Methods

Subjects with coronary heart disease visited clinics biweekly in Amsterdam, the Netherlands; Erfurt, Germany; and Helsinki, Finland for 6–8 months. The standard deviation (SD) of NN intervals on an electrocardiogram (ECG; SDNN) and high frequency (HF) power of HRV was measured with ambulatory ECG during paced breathing. Outdoor levels of PM_2.5 were measured at a central site. In Amsterdam and Helsinki, indoor and personal PM_2.5 were measured during the 24 hr preceding the clinic visit. PM_2.5 was apportioned between sources using principal component analyses. We analyzed associations of indoor/personal PM_2.5, elements of PM_2.5, and source-specific PM_2.5 with HRV using linear regression.

Results

Indoor and personal PM_2.5 were not associated with HRV. Increased outdoor PM_2.5 was associated with decreased SDNN and HF at lags of 2 and 3 days only among persons not using beta-blocker medication. Traffic-related PM_2.5 was associated with decreased SDNN, and long-range transported PM_2.5 with decreased SDNN and HF, most strongly among persons not using beta blockers. Indicators for PM_2.5 from traffic and long-range transport were also associated with decreased HRV.

Conclusions

Our results suggest that differences in the composition of particles, beta-blocker use, and obesity of study subjects may explain some inconsistencies among previous studies on HRV.     

Triggering of Transmural Infarctions,but Not Nontransmural Infarctions,by Ambient Fine Particles

Background

Previous studies have reported increased risk of myocardial infarction (MI) after increases in ambient particulate matter (PM) air pollution concentrations in the hours and days before MI onset.

Objectives

We hypothesized that acute increases in fine PM with aerodynamic diameter ≤ 2.5 μm (PM_2.5) may be associated with increased risk of MI and that chronic obstructive pulmonary disease (COPD) and diabetes may increase susceptibility to PM_2.5. We also explored whether both transmural and nontransmural infarctions were acutely associated with ambient PM_2.5 concentrations.

Methods

We studied all hospital admissions from 2004 through 2006 for first acute MI of adult residents of New Jersey who lived within 10 km of a PM_2.5 monitoring site (n = 5,864), as well as ambient measurements of PM_2.5, nitrogen dioxide, sulfur dioxide, carbon monoxide, and ozone.

Results

Using a time-stratified case-crossover design and conditional logistic regression showed that each interquartile-range increase in PM_2.5 concentration (10.8 μg/m³) in the 24 hr before arriving at the emergency department for MI was not associated with an increased risk of MI overall but was associated with an increased risk of a transmural infarction. We found no association between the same increase in PM_2.5 and risk of a nontransmural infarction. Further, subjects with COPD appeared to be particularly susceptible, but those with diabetes were not.

Conclusions

This PM–transmural infarction association is consistent with earlier studies of PM and MI. The lack of association with nontransmural infarction suggests that future studies that investigate the triggering of MI by ambient PM_2.5 concentrations should be stratified by infarction type.     

Acute Effects of Ambient Particulate Matter on Mortality in Europe and North America: Results from the APHENA Study

Background

The APHENA (Air Pollution and Health: A Combined European and North American Approach) study is a collaborative analysis of multicity time-series data on the effect of air pollution on population health, bringing together data from the European APHEA (Air Pollution and Health: A European Approach) and U.S. NMMAPS (National Morbidity, Mortality and Air Pollution Study) projects, along with Canadian data.

Objectives

The main objective of APHENA was to assess the coherence of the findings of the multicity studies carried out in Europe and North America, when analyzed with a common protocol, and to explore sources of possible heterogeneity. We present APHENA results on the effects of particulate matter (PM) ≤ 10 μm in aerodynamic diameter (PM₁₀) on the daily number of deaths for all ages and for those < 75 and ≥ 75 years of age. We explored the impact of potential environmental and socioeconomic factors that may modify this association.

Methods

In the first stage of a two-stage analysis, we used Poisson regression models, with natural and penalized splines, to adjust for seasonality, with various degrees of freedom. In the second stage, we used meta-regression approaches to combine time-series results across cites and to assess effect modification by selected ecologic covariates.

Results

Air pollution risk estimates were relatively robust to different modeling approaches. Risk estimates from Europe and United States were similar, but those from Canada were substantially higher. The combined effect of PM₁₀ on all-cause mortality across all ages for cities with daily air pollution data ranged from 0.2% to 0.6% for a 10-μg/m³ increase in ambient PM₁₀ concentration. Effect modification by other pollutants and climatic variables differed in Europe and the United States. In both of these regions, a higher proportion of older people and higher unemployment were associated with increased air pollution risk.

Conclusions

Estimates of the increased mortality associated with PM air pollution based on the APHENA study were generally comparable with results of previous reports. Overall, risk estimates were similar in Europe and in the United States but higher in Canada. However, PM₁₀ effect modification patterns were somewhat different in Europe and the United States.     

Low-Concentration PM2.5 and Mortality: Estimating Acute and Chronic Effects in a Population-Based Study

Background

Both short- and long-term exposures to fine particulate matter (≤ 2.5 μm; PM_2.5) are associated with mortality. However, whether the associations exist at levels below the new U.S. Environmental Protection Agency (EPA) standards (12 μg/m³ of annual average PM_2.5, 35 μg/m³ daily) is unclear. In addition, it is not clear whether results from previous time series studies (fit in larger cities) and cohort studies (fit in convenience samples) are generalizable.

Objectives

We estimated the effects of low-concentration PM_2.5 on mortality.

Methods

High resolution (1 km × 1 km) daily PM_2.5 predictions, derived from satellite aerosol optical depth retrievals, were used. Poisson regressions were applied to a Medicare population (≥ 65 years of age) in New England to simultaneously estimate the acute and chronic effects of exposure to PM_2.5, with mutual adjustment for short- and long-term exposure, as well as for area-based confounders. Models were also restricted to annual concentrations < 10 μg/m³ or daily concentrations < 30 μg/m³.

Results

PM_2.5 was associated with increased mortality. In the study cohort, 2.14% (95% CI: 1.38, 2.89%) and 7.52% (95% CI: 1.95, 13.40%) increases were estimated for each 10-μg/m³ increase in short- (2 day) and long-term (1 year) exposure, respectively. The associations held for analyses restricted to low-concentration PM_2.5 exposure, and the corresponding estimates were 2.14% (95% CI: 1.34, 2.95%) and 9.28% (95% CI: 0.76, 18.52%). Penalized spline models of long-term exposure indicated a larger effect for mortality in association with exposures ≥ 6 μg/m³ versus those < 6 μg/m³. In contrast, the association between short-term exposure and mortality appeared to be linear across the entire exposure distribution.

Conclusions

Using a mutually adjusted model, we estimated significant acute and chronic effects of PM_2.5 exposure below the current U.S. EPA standards. These findings suggest that improving air quality with even lower PM_2.5 than currently allowed by U.S. EPA standards may benefit public health.

Citation

Shi L, Zanobetti A, Kloog I, Coull BA, Koutrakis P, Melly SJ, Schwartz JD. 2016. Low-concentration PM_2.5 and mortality: estimating acute and chronic effects in a population-based study. Environ Health Perspect 124:46–52; http://dx.doi.org/10.1289/ehp.1409111     

Emergency Admissions for Cardiovascular and Respiratory Diseases and the Chemical Composition of Fine Particle Air Pollution

Background

Population-based studies have estimated health risks of short-term exposure to fine particles using mass of PM_2.5 (particulate matter ≤ 2.5 μm in aerodynamic diameter) as the indicator. Evidence regarding the toxicity of the chemical components of the PM_2.5 mixture is limited.

Objective

In this study we investigated the association between hospital admission for cardiovascular disease (CVD) and respiratory disease and the chemical components of PM_2.5 in the United States.

Methods

We used a national database comprising daily data for 2000–2006 on emergency hospital admissions for cardiovascular and respiratory outcomes, ambient levels of major PM_2.5 chemical components [sulfate, nitrate, silicon, elemental carbon (EC), organic carbon matter (OCM), and sodium and ammonium ions], and weather. Using Bayesian hierarchical statistical models, we estimated the associations between daily levels of PM_2.5 components and risk of hospital admissions in 119 U.S. urban communities for 12 million Medicare enrollees (≥ 65 years of age).

Results

In multiple-pollutant models that adjust for the levels of other pollutants, an interquartile range (IQR) increase in EC was associated with a 0.80% [95% posterior interval (PI), 0.34–1.27%] increase in risk of same-day cardiovascular admissions, and an IQR increase in OCM was associated with a 1.01% (95% PI, 0.04–1.98%) increase in risk of respiratory admissions on the same day. Other components were not associated with cardiovascular or respiratory hospital admissions in multiple-pollutant models.

Conclusions

Ambient levels of EC and OCM, which are generated primarily from vehicle emissions, diesel, and wood burning, were associated with the largest risks of emergency hospitalization across the major chemical constituents of PM_2.5.     

Risk-Based Prioritization among Air Pollution Control Strategies in the Yangtze River Delta,China

Background

The Yangtze River Delta (YRD) in China is a densely populated region with recent dramatic increases in energy consumption and atmospheric emissions.

Objectives

We studied how different emission sectors influence population exposures and the corresponding health risks, to inform air pollution control strategy design.

Methods

We applied the Community Multiscale Air Quality (CMAQ) Modeling System to model the marginal contribution to baseline concentrations from different sectors. We focused on nitrogen oxide (NO_x) control while considering other pollutants that affect fine particulate matter [aerodynamic diameter ≤ 2.5 μm (PM_2.5)] and ozone concentrations. We developed concentration–response (C-R) functions for PM_2.5 and ozone mortality for China to evaluate the anticipated health benefits.

Results

In the YRD, health benefits per ton of emission reductions varied significantly across pollutants, with reductions of primary PM_2.5 from the industry sector and mobile sources showing the greatest benefits of 0.1 fewer deaths per year per ton of emission reduction. Combining estimates of health benefits per ton with potential emission reductions, the greatest mortality reduction of 12,000 fewer deaths per year [95% confidence interval (CI), 1,200–24,000] was associated with controlling primary PM_2.5 emissions from the industry sector and reducing sulfur dioxide (SO₂) from the power sector, respectively. Benefits were lower for reducing NO_x emissions given lower consequent reductions in the formation of secondary PM_2.5 (compared with SO₂) and increases in ozone concentrations that would result in the YRD.

Conclusions

Although uncertainties related to C-R functions are significant, the estimated health benefits of emission reductions in the YRD are substantial, especially for sectors and pollutants with both higher health benefits per unit emission reductions and large potential for emission reductions.