Acute Adverse Effects of Fine Particulate Air Pollution on Ventricular Repolarization

Background

The mechanisms for the relationship between particulate pollution and cardiac disease are not fully understood.

Objective

We examined the effects and time course of exposure to fine particulate matter ≤ 2.5 μm in aerodynamic diameter (PM_2.5) on ventricular repolarization of 106 nonsmoking adults who were living in communities in central Pennsylvania.

Methods

The 24-hr beat-to-beat electrocardiogram (ECG) data were obtained using a high-resolution 12-lead Holter system. After visually identifying and removing artifacts and arrhythmic beats, we summarized normal beat-to-beat QTs from each 30-min segment as heart rate (HR)-corrected QT measures: QT prolongation index (QTI), Bazett’s HR-corrected QT (QTcB), and Fridericia’s HR-corrected QT (QTcF). A personal PM_2.5 monitor was used to measure individual-level real-time PM_2.5 exposures for 24 hr. We averaged these data and used 30-min time-specific average PM_2.5 exposures.

Results

The mean age of the participants was 56 ± 8 years, with 41% male and 74% white. The means ± SDs for QTI, QTcB, and QTcF were 111 ± 6.6, 438 ± 23 msec, and 422 ± 22 msec, respectively; and for PM_2.5, the mean ± SD was 14 ± 22 μg/m³. We used distributed lag models under a framework of linear mixed-effects models to assess the autocorrelation-corrected regression coefficients (β) between 30-min PM_2.5 and the HR-corrected QT measures. Most of the adverse ventricular repolarization effects from PM_2.5 exposure occurred within 3–4 hr. The multivariable adjusted β (SE, p-value) due to a 10-μg/m³ increase in lag 7 PM_2.5 on QTI, QTcB, and QTcF were 0.08 (0.04, p < 0.05), 0.22 (0.08, p < 0.01), and 0.09 (0.05, p < 0.05), respectively.

Conclusions

Our results suggest a significant adverse effect of PM_2.5 on ventricular repolarization. The time course of the effect is within 3–4 hr of elevated PM_2.5.     

Three measures of forest fire smoke exposure and their associations with respiratory and cardiovascular health outcomes in a population-based cohort

Background: During the summer of 2003 numerous fires burned in British Columbia, Canada.Objectives: We examined the associations between respiratory and cardiovascular physician visits and hospital admissions, and three measures of smoke exposure over a 92-day study period (1 July to 30 September 2003).Methods: A population-based cohort of 281,711 residents was identified from administrative data. Spatially specific daily exposure estimates were assigned to each subject based on total measurements of particulate matter (PM) ≤ 10 μm in aerodynamic diameter (PM₁₀) from six regulatory tapered element oscillating microbalance (TEOM) air quality monitors, smoke-related PM₁₀ from a CALPUFF dispersion model run for the study, and a SMOKE exposure metric for plumes visible in satellite images. Logistic regression with repeated measures was used to estimate associations with each outcome.Results: The mean (± SD) exposure based on TEOM-measured PM₁₀ was 29 ± 31 μg/m³, with an interquartile range of 14–31 μg/m³. Correlations between the TEOM, smoke, and CALPUFF metrics were moderate (0.37–0.76). Odds ratios (ORs) for a 30-μg/m³ increase in TEOM-based PM₁₀ were 1.05 [95% confidence interval (CI), 1.03–1.06] for all respiratory physician visits, 1.16 (95% CI, 1.09–1.23) for asthma-specific visits, and 1.15 (95% CI, 1.00–1.29) for respiratory hospital admissions. Associations with cardiovascular outcomes were largely null.Conclusions: Overall we found that increases in TEOM-measured PM₁₀ were associated with increased odds of respiratory physician visits and hospital admissions, but not with cardiovascular health outcomes. Results indicating effects of fire smoke on respiratory outcomes are consistent with previous studies, as are the null results for cardiovascular outcomes. Some agreement between TEOM and the other metrics suggests that exposure assessment tools that are independent of air quality monitoring may be useful with further refinement.     

Carotid Intima-Media Thickness and Long-Term Exposure to Traffic-Related Air Pollution in Middle-Aged Residents of Taiwan: A Cross-Sectional Study

Background

Associations between long-term exposure to air pollution and carotid intima-media thickness (CIMT) have inconsistent findings.

Objectives

In this study we aimed to evaluate association between 1-year average exposure to traffic-related air pollution and CIMT in middle-aged adults in Asia.

Methods

CIMT was measured in Taipei, Taiwan, between 2009 and 2011 in 689 volunteers 35–65 years of age who were recruited as the control subjects of an acute coronary heart disease cohort study. We applied land-use regression models developed by the European Study of Cohorts for Air Pollution Effects (ESCAPE) to estimate each subject’s 1-year average exposure to traffic-related air pollutants with particulate matter diameters ≤ 10 μm (PM₁₀) and ≤ 2.5 μm (PM_2.5) and the absorbance levels of PM_2.5 (PM_2.5abs), nitrogen dioxide (NO₂), and nitrogen oxides (NO_x) in the urban environment.

Results

One-year average air pollution exposures were 44.21 ± 4.19 μg/m³ for PM₁₀, 27.34 ± 5.12 μg/m³ for PM_2.5, and (1.97 ± 0.36) × 10^–5/m for PM_2.5abs. Multivariate regression analyses showed average percentage increases in maximum left CIMT of 4.23% (95% CI: 0.32, 8.13) per 1.0 × 10^–5/m increase in PM_2.5abs; 3.72% (95% CI: 0.32, 7.11) per 10-μg/m³ increase in PM₁₀; 2.81% (95% CI: 0.32, 5.31) per 20-μg/m³ increase in NO₂; and 0.74% (95% CI: 0.08, 1.41) per 10-μg/m³ increase in NO_x. The associations were not evident for right CIMT, and PM_2.5 mass concentration was not associated with the outcomes.

Conclusions

Long-term exposures to traffic-related air pollution of PM_2.5abs, PM₁₀, NO₂, and NO_x were positively associated with subclinical atherosclerosis in middle-aged adults.

Citation

Su TC, Hwang JJ, Shen YC, Chan CC. 2015. Carotid intima–media thickness and long-term exposure to traffic-related air pollution in middle-aged residents of Taiwan: a cross-sectional study. Environ Health Perspect 123:773–778; http://dx.doi.org/10.1289/ehp.1408553     

Outdoor Air Pollution,Preterm Birth,and Low Birth Weight: Analysis of the World Health Organization Global Survey on Maternal and Perinatal Health

Background: Inhaling fine particles (particulate matter with diameter ≤ 2.5 μm; PM_2.5) can induce oxidative stress and inflammation, and may contribute to onset of preterm labor and other adverse perinatal outcomes.Objectives: We examined whether outdoor PM_2.5 was associated with adverse birth outcomes among 22 countries in the World Health Organization Global Survey on Maternal and Perinatal Health from 2004 through 2008.Methods: Long-term average (2001–2006) estimates of outdoor PM_2.5 were assigned to 50-km–radius circular buffers around each health clinic where births occurred. We used generalized estimating equations to determine associations between clinic-level PM_2.5 levels and preterm birth and low birth weight at the individual level, adjusting for seasonality and potential confounders at individual, clinic, and country levels. Country-specific associations were also investigated.Results: Across all countries, adjusting for seasonality, PM_2.5 was not associated with preterm birth, but was associated with low birth weight [odds ratio (OR) = 1.22; 95% CI: 1.07, 1.39 for fourth quartile of PM_2.5 (> 20.2 μg/m³) compared with the first quartile (< 6.3 μg/m³)]. In China, the country with the largest PM_2.5 range, preterm birth and low birth weight both were associated with the highest quartile of PM_2.5 only, which suggests a possible threshold effect (OR = 2.54; CI: 1.42, 4.55 and OR = 1.99; CI: 1.06, 3.72 for preterm birth and low birth weight, respectively, for PM_2.5 ≥ 36.5 μg/m³ compared with PM_2.5 < 12.5 μg/m³).Conclusions: Outdoor PM_2.5 concentrations were associated with low birth weight but not preterm birth. In rapidly developing countries, such as China, the highest levels of air pollution may be of concern for both outcomes.Citation: Fleischer NL, Merialdi M, van Donkelaar A, Vadillo-Ortega F, Martin RV, Betran AP, Souza JP, O´Neill MS. 2014. Outdoor air pollution, preterm birth, and low birth weight: analysis of the World Health Organization Global Survey on Maternal and Perinatal Health. Environ Health Perspect 122:425–430; http://dx.doi.org/10.1289/ehp.1306837     

Indoor air pollution and blood pressure in adult women living in rural China

Background: Almost half of the world’s population uses coal and biomass fuels for domestic energy. Limited evidence suggests that exposure to air pollutants from indoor biomass combustion may be associated with elevated blood pressure (BP).Objective: Our aim was to assess the relationship between air pollution exposure from indoor biomass combustion and BP in women in rural China.Methods: We measured 24-hr personal integrated gravimetric exposure to fine particles < 2.5 µm in aerodynamic diameter (PM_2.5) and systolic BP (SBP) and diastolic BP (DBP) in the winter and summer among 280 women ≥ 25 years of age living in rural households using biomass fuels in Yunnan, China. We investigated the association between PM_2.5 exposure and SBP and DBP using mixed-effects models with random intercepts to account for correlation among repeated measures.Results: Personal average 24-hr exposure to PM_2.5 ranged from 22 to 634 µg/m³ in winter and from 9 to 492 µg/m³ in summer. A 1-log-µg/m³ increase in PM_2.5 exposure was associated with 2.2 mm Hg higher SBP [95% confidence interval (CI), 0.8 to 3.7; p = 0.003] and 0.5 mm Hg higher DBP (95% CI, –0.4 to 1.3; p = 0.31) among all women; estimated effects varied by age group. Among women > 50 years of age, a 1-log-µg/m³ increase in PM_2.5 exposure was associated with 4.1 mm Hg higher SBP (95% CI, 1.5 to 6.6; p = 0.002) and 1.8 mm Hg higher DBP (95% CI, 0.4 to 3.2; p = 0.01). PM_2.5 exposure was positively associated with SBP among younger women, but the association was not statistically significant.Conclusion: PM_2.5 exposure from biomass combustion may be a risk factor for elevated BP and hence for cardiovascular events. Our findings should be corroborated in longitudinal studies.     

Long-term Exposure to PM2.5 and Incidence of Acute Myocardial Infarction

Background: A number of studies have shown associations between chronic exposure to particulate air pollution and increased mortality, particularly from cardiovascular disease, but fewer studies have examined the association between long-term exposure to fine particulate air pollution and specific cardiovascular events, such as acute myocardial infarction (AMI).Objective: We examined how long-term exposure to area particulate matter affects the onset of AMI, and we distinguished between area and local pollutants.Methods: Building on the Worcester Heart Attack Study, an ongoing community-wide investigation examining changes over time in myocardial infarction incidence in greater Worcester, Massachusetts, we conducted a case–control study of 4,467 confirmed cases of AMI diagnosed between 1995 and 2003 and 9,072 matched controls selected from Massachusetts resident lists. We used a prediction model based on satellite aerosol optical depth (AOD) measurements to generate both exposure to particulate matter ≤ 2.5 μm in diameter (PM_2.5) at the area level (10 × 10 km) and the local level (100 m) based on local land use variables. We then examined the association between area and local particulate pollution and occurrence of AMI.Results: An interquartile range (IQR) increase in area PM_2.5 (0.59 μg/m³) was associated with a 16% increase in the odds of AMI (95% CI: 1.04, 1.29). An IQR increase in total PM_2.5 (area + local, 1.05 μg/m³) was weakly associated with a 4% increase in the odds of AMI (95% CI: 0.96, 1.11).Conclusions: Residential exposure to PM_2.5 may best be represented by a combination of area and local PM_2.5, and it is important to consider spatial gradients within a single metropolitan area when examining the relationship between particulate matter exposure and cardiovascular events.     

Risk of nonaccidental and cardiovascular mortality in relation to long-term exposure to low concentrations of fine particulate matter: a Canadian national-level cohort study

Background: Few cohort studies have evaluated the risk of mortality associated with long-term exposure to fine particulate matter [≤ 2.5 μm in aerodynamic diameter (PM_2.5)]. This is the first national-level cohort study to investigate these risks in Canada.Objective: We investigated the association between long-term exposure to ambient PM_2.5 and cardiovascular mortality in nonimmigrant Canadian adults.Methods: We assigned estimates of exposure to ambient PM_2.5 derived from satellite observations to a cohort of 2.1 million Canadian adults who in 1991 were among the 20% of the population mandated to provide detailed census data. We identified deaths occurring between 1991 and 2001 through record linkage. We calculated hazard ratios (HRs) and 95% confidence intervals (CIs) adjusted for available individual-level and contextual covariates using both standard Cox proportional survival models and nested, spatial random-effects survival models.Results: Using standard Cox models, we calculated HRs of 1.15 (95% CI: 1.13, 1.16) from nonaccidental causes and 1.31 (95% CI: 1.27, 1.35) from ischemic heart disease for each 10-μg/m³ increase in concentrations of PM_2.5. Using spatial random-effects models controlling for the same variables, we calculated HRs of 1.10 (95% CI: 1.05, 1.15) and 1.30 (95% CI: 1.18, 1.43), respectively. We found similar associations between nonaccidental mortality and PM_2.5 based on satellite-derived estimates and ground-based measurements in a subanalysis of subjects in 11 cities.Conclusions: In this large national cohort of nonimmigrant Canadians, mortality was associated with long-term exposure to PM_2.5. Associations were observed with exposures to PM_2.5 at concentrations that were predominantly lower (mean, 8.7 μg/m³; interquartile range, 6.2 μg/m³) than those reported previously.     

Maternal Exposure to Particulate Air Pollution and Term Birth Weight: A Multi-Country Evaluation of Effect and Heterogeneity

Background: A growing body of evidence has associated maternal exposure to air pollution with adverse effects on fetal growth; however, the existing literature is inconsistent.Objectives: We aimed to quantify the association between maternal exposure to particulate air pollution and term birth weight and low birth weight (LBW) across 14 centers from 9 countries, and to explore the influence of site characteristics and exposure assessment methods on between-center heterogeneity in this association.Methods: Using a common analytical protocol, International Collaboration on Air Pollution and Pregnancy Outcomes (ICAPPO) centers generated effect estimates for term LBW and continuous birth weight associated with PM₁₀ and PM_2.5 (particulate matter ≤ 10 and 2.5 µm). We used meta-analysis to combine the estimates of effect across centers (~ 3 million births) and used meta-regression to evaluate the influence of center characteristics and exposure assessment methods on between-center heterogeneity in reported effect estimates.Results: In random-effects meta-analyses, term LBW was positively associated with a 10-μg/m³ increase in PM₁₀ [odds ratio (OR) = 1.03; 95% CI: 1.01, 1.05] and PM_2.5 (OR = 1.10; 95% CI: 1.03, 1.18) exposure during the entire pregnancy, adjusted for maternal socioeconomic status. A 10-μg/m³ increase in PM₁₀ exposure was also negatively associated with term birth weight as a continuous outcome in the fully adjusted random-effects meta-analyses (–8.9 g; 95% CI: –13.2, –4.6 g). Meta-regressions revealed that centers with higher median PM_2.5 levels and PM_2.5:PM₁₀ ratios, and centers that used a temporal exposure assessment (compared with spatiotemporal), tended to report stronger associations.Conclusion: Maternal exposure to particulate pollution was associated with LBW at term across study populations. We detected three site characteristics and aspects of exposure assessment methodology that appeared to contribute to the variation in associations reported by centers.     

Estimated global mortality attributable to smoke from landscape fires

Background: Forest, grass, and peat fires release approximately 2 petagrams of carbon into the atmosphere each year, influencing weather, climate, and air quality.Objective: We estimated the annual global mortality attributable to landscape fire smoke (LFS).Methods: Daily and annual exposure to particulate matter ≤ 2.5 μm in aerodynamic diameter (PM_2.5) from fire emissions was estimated globally for 1997 through 2006 by combining outputs from a chemical transport model with satellite-based observations of aerosol optical depth. In World Health Organization (WHO) subregions classified as sporadically affected, the daily burden of mortality was estimated using previously published concentration–response coefficients for the association between short-term elevations in PM_2.5 from LFS (contrasted with 0 μg/m³ from LFS) and all-cause mortality. In subregions classified as chronically affected, the annual burden of mortality was estimated using the American Cancer Society study coefficient for the association between long-term PM_2.5 exposure and all-cause mortality. The annual average PM_2.5 estimates were contrasted with theoretical minimum (counterfactual) concentrations in each chronically affected subregion. Sensitivity of mortality estimates to different exposure assessments, counterfactual estimates, and concentration–response functions was evaluated. Strong La Niña and El Niño years were compared to assess the influence of interannual climatic variability.Results: Our principal estimate for the average mortality attributable to LFS exposure was 339,000 deaths annually. In sensitivity analyses the interquartile range of all tested estimates was 260,000–600,000. The regions most affected were sub-Saharan Africa (157,000) and Southeast Asia (110,000). Estimated annual mortality during La Niña was 262,000, compared with 532,000 during El Niño.Conclusions: Fire emissions are an important contributor to global mortality. Adverse health outcomes associated with LFS could be substantially reduced by curtailing burning of tropical rainforests, which rarely burn naturally. The large estimated influence of El Niño suggests a relationship between climate and the burden of mortality attributable to LFS.     

Effects of coarse particulate matter on emergency hospital admissions for respiratory diseases: a time-series analysis in Hong Kong

Background: Many epidemiological studies have linked daily counts of hospital admissions to particulate matter (PM) with an aerodynamic diameter ≤ 10 μm (PM₁₀) and ≤ 2.5 μm (PM_2.5), but relatively few have investigated the relationship of hospital admissions with coarse PM (PM_c; 2.5–10 μm aerodynamic diameter).Objectives: We conducted this study to estimate the health effects of PM_c on emergency hospital admissions for respiratory diseases in Hong Kong after controlling for PM_2.5 and gaseous pollutants.Methods: We conducted a time-series analysis of associations between daily emergency hospital admissions for respiratory diseases in Hong Kong from January 2000 to December 2005 and daily PM_2.5 and PM_c concentrations. We estimated PM_c concentrations by subtracting PM_2.5 from PM₁₀ measurements. We used generalized additive models to examine the relationship between PM_c (single- and multiday lagged exposures) and hospital admissions adjusted for time trends, weather conditions, influenza outbreaks, PM_2.5, and gaseous pollutants (nitrogen dioxide, sulfur dioxide, and ozone).Results: A 10.9-μg/m³ (interquartile range) increase in the 4-day moving average concentration of PM_c was associated with a 1.94% (95% confidence interval: 1.24%, 2.64%) increase in emergency hospital admissions for respiratory diseases that was attenuated but still significant after controlling for PM_2.5. Adjusting for gaseous pollutants and altering models assumptions had little influence on PM_c effect estimates.Conclusion: PM_c was associated with emergency hospital admissions for respiratory diseases in Hong Kong independent of PM_2.5 and gaseous pollutants. Further research is needed to evaluate health effects of different components of PM_c.     

Estimated short-term effects of coarse particles on daily mortality in Stockholm, Sweden

Background: Although serious health effects associated with particulate matter (PM) with aerodynamic diameter ≤ 10 μm (PM₁₀) and ≤ 2.5 μm (PM_2.5; fine fraction) are documented in many studies, the effects of coarse PM (PM_2.5–10) are still under debate.Objective: In this study, we estimated the effects of short-term exposure of PM_2.5–10 on daily mortality in Stockholm, Sweden.Method: We collected data on daily mortality for the years 2000 through 2008. Concentrations of PM₁₀, PM_2.5, ozone, and carbon monoxide were measured simultaneously in central Stockholm. We used additive Poisson regression models to examine the association between daily mortality and PM_2.5–10 on the day of death and the day before. Effect estimates were adjusted for other pollutants (two-pollutant models) during different seasons.Results: We estimated a 1.68% increase [95% confidence interval (CI): 0.20%, 3.15%] in daily mortality per 10-μg/m³ increase in PM_2.5–10 (single-pollutant model). The association with PM_2.5–10 was stronger for November through May, when road dust is most important (1.69% increase; 95% CI: 0.21%, 3.17%), compared with the rest of the year (1.31% increase; 95% CI: –2.08%, 4.70%), although the difference was not statistically significant. When adjusted for other pollutants, particularly PM_2.5, the effect estimates per 10 μg/m³ for PM_2.5–10 decreased slightly but were still higher than corresponding effect estimates for PM_2.5.Conclusions: Our analysis shows an increase in daily mortality associated with elevated urban background levels of PM_2.5–10. Regulation of PM_2.5–10 should be considered, along with actions to specifically reduce PM_2.5–10 emissions, especially road dust suspension, in cities.     

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     

Acute respiratory inflammation in children and black carbon in ambient air before and during the 2008 Beijing Olympics

Background: Epidemiologic evidence for a causative association between black carbon (BC) and health outcomes is limited.Objectives: We estimated associations and exposure–response relationships between acute respiratory inflammation in schoolchildren and concentrations of BC and particulate matter with an aerodynamic diameter of ≤ 2.5 μm (PM_2.5) in ambient air before and during the air pollution intervention for the 2008 Beijing Olympics.Methods: We measured exhaled nitric oxide (eNO) as an acute respiratory inflammation biomarker and hourly mean air pollutant concentrations to estimate BC and PM_2.5 exposure. We used 1,581 valid observations of 36 subjects over five visits in 2 years to estimate associations of eNO with BC and PM_2.5 according to generalized estimating equations with polynomial distributed-lag models, controlling for body mass index, asthma, temperature, and relative humidity. We also assessed the relative importance of BC and PM_2.5 with two-pollutant models.Results: Air pollution concentrations and eNO were clearly lower during the 2008 Olympics. BC and PM_2.5 concentrations averaged over 0–24 hr were strongly associated with eNO, which increased by 16.6% [95% confidence interval (CI), 14.1–19.2%] and 18.7% (95% CI, 15.0–22.5%) per interquartile range (IQR) increase in BC (4.0 μg/m³) and PM_2.5 (149 μg/m³), respectively. In the two-pollutant model, estimated effects of BC were robust, but associations between PM_2.5 and eNO decreased with adjustment for BC. We found that eNO was associated with IQR increases in hourly BC concentrations up to 10 hr after exposure, consistent with effects primarily in the first hours after exposure.Conclusions: Recent exposure to BC was associated with acute respiratory inflammation in schoolchildren in Beijing. Lower air pollution levels during the 2008 Olympics also were associated with reduced eNO.     

Chronic exposure to fine particles and mortality: an extended follow-up of the Harvard Six Cities study from 1974 to 2009

Background: Epidemiologic studies have reported associations between fine particles (aerodynamic diameter ≤ 2.5 µm; PM_2.5) and mortality. However, concerns have been raised regarding the sensitivity of the results to model specifications, lower exposures, and averaging time.Objective: We addressed these issues using 11 additional years of follow-up of the Harvard Six Cities study, incorporating recent lower exposures.Methods: We replicated the previously applied Cox regression, and examined different time lags, the shape of the concentration–response relationship using penalized splines, and changes in the slope of the relation over time. We then conducted Poisson survival analysis with time-varying effects for smoking, sex, and education.Results: Since 2001, average PM_2.5 levels, for all six cities, were < 18 µg/m³. Each increase in PM_2.5 (10 µg/m³) was associated with an adjusted increased risk of all-cause mortality (PM_2.5 average on previous year) of 14% [95% confidence interval (CI): 7, 22], and with 26% (95% CI: 14, 40) and 37% (95% CI: 7, 75) increases in cardiovascular and lung-cancer mortality (PM_2.5 average of three previous years), respectively. The concentration–response relationship was linear down to PM_2.5 concentrations of 8 µg/m³. Mortality rate ratios for PM_2.5 fluctuated over time, but without clear trends despite a substantial drop in the sulfate fraction. Poisson models produced similar results.Conclusions: These results suggest that further public policy efforts that reduce fine particulate matter air pollution are likely to have continuing public health benefits.     

Does Air Pollution Trigger Infant Mortality in Western Europe? A Case-Crossover Study

Background: Numerous studies show associations between fine particulate air pollutants [particulate matter with an aerodynamic diameter ≤ 10 μm (PM₁₀)] and mortality in adults.Objectives: We investigated short-term effects of elevated PM₁₀ levels on infant mortality in Flanders, Belgium, and studied whether the European Union (EU) limit value protects infants from the air pollution trigger.Methods: In a case-crossover analysis, we estimated the risk of dying from nontraumatic causes before 1 year of age in relation to outdoor PM₁₀ concentrations on the day of death. We matched control days on temperature to exclude confounding by variations in daily temperature.Results: During the study period (1998–2006), PM₁₀ concentration averaged 31.9 ± 13.8 μg/m³. In the entire study population (n = 2,382), the risk of death increased by 4% [95% confidence interval (CI), 0–8%; p = 0.045] for a 10-μg/m³ increase in daily mean PM₁₀. However, this association was significant only for late neonates (2–4 weeks of age; n = 372), in whom the risk of death increased by 11% (95% CI, 1–22%; p = 0.028) per 10-μg/m³ increase in PM₁₀. In this age class, infants were 1.74 (95% CI, 1.18–2.58; p = 0.006) times more likely to die on days with a mean PM₁₀ above the EU limit value of 50 μg/m³ than on days below this cutoff.Conclusions: Even in an affluent region in Western Europe, where infant mortality is low, days with higher PM air pollution are associated with an increased risk of infant mortality. Assuming causality, the current EU limit value for PM₁₀, which may be exceeded on 35 days/year, does not prevent PM₁₀ from triggering mortality in late neonates.     

Long-Term Exposure to Urban Air Pollution and Mortality in a Cohort of More than a Million Adults in Rome

Background: Few European studies have investigated the effects of long-term exposure to both fine particulate matter (≤ 2.5 µm; PM_2.5) and nitrogen dioxide (NO₂) on mortality.Objectives: We studied the association of exposure to NO₂, PM_2.5, and traffic indicators on cause-specific mortality to evaluate the form of the concentration–response relationship.Methods: We analyzed a population-based cohort enrolled at the 2001 Italian census with 9 years of follow-up. We selected all 1,265,058 subjects ≥ 30 years of age who had been living in Rome for at least 5 years at baseline. Residential exposures included annual NO₂ (from a land use regression model) and annual PM_2.5 (from a Eulerian dispersion model), as well as distance to roads with > 10,000 vehicles/day and traffic intensity. We used Cox regression models to estimate associations with cause-specific mortality adjusted for individual (sex, age, place of birth, residential history, marital status, education, occupation) and area (socioeconomic status, clustering) characteristics.Results: Long-term exposures to both NO₂ and PM_2.5 were associated with an increase in nonaccidental mortality [hazard ratio (HR) = 1.03 (95% CI: 1.02, 1.03) per 10-µg/m³ NO₂; HR = 1.04 (95% CI: 1.03, 1.05) per 10-µg/m³ PM_2.5]. The strongest association was found for ischemic heart diseases (IHD) [HR = 1.10 (95% CI: 1.06, 1.13) per 10-µg/m³ PM_2.5], followed by cardiovascular diseases and lung cancer. The only association showing some deviation from linearity was that between NO₂ and IHD. In a bi-pollutant model, the estimated effect of NO₂ on mortality was independent of PM_2.5.Conclusions: This large study strongly supports an effect of long-term exposure to NO₂ and PM_2.5 on mortality, especially from cardiovascular causes. The results are relevant for the next European policy decisions regarding air quality.     

Saharan dust and associations between particulate matter and daily mortality in Rome, Italy

Background: Outbreaks of Saharan-Sahel dust over Euro-Mediterranean areas frequently induce exceedances of the Europen Union''s 24-hr standard of 50 μg/m³ for particulate matter (PM) with aerodynamic diameter ≤ than 10 μm (PM₁₀).Objectives: We evaluated the effect of Saharan dust on the association between different PM fractions and daily mortality in Rome, Italy.Methods: In a study of 80,423 adult residents who died in Rome between 2001 and 2004, we performed a time-series analysis to explore the effects of PM_2.5, PM_2.5–10, and PM₁₀ on natural, cardiac, cerebrovascular, and respiratory mortality. We defined Saharan dust days by combining light detection and ranging (LIDAR) observations and analyses from operational models. We tested a Saharan dust–PM interaction term to evaluate the hypothesis that the effects of PM, especially coarse PM (PM_2.5–10), on mortality would be enhanced on dust days.Results: Interquartile range increases in PM_2.5–10 (10.8 μg/m³) and PM₁₀ (19.8 μg/m³) were associated with increased mortality due to natural, cardiac, cerebrovascular, and respiratory causes, with estimated effects ranging from 2.64% to 12.65% [95% confidence interval (CI), 1.18–25.42%] for the association between PM_2.5–10 and respiratory mortality (0- to 5-day lag). Associations of PM_2.5–10 with cardiac mortality were stronger on Saharan dust days (9.73%; 95% CI, 4.25–15.49%) than on dust-free days (0.86%; 95% CI, –2.47% to 4.31%; p = 0.005). Saharan dust days also modified associations between PM₁₀ and cardiac mortality (9.55% increase; 95% CI, 3.81–15.61%; vs. dust-free days: 2.09%; 95% CI, –0.76% to 5.02%; p = 0.02).Conclusions: We found evidence of effects of PM_2.5–10 and PM₁₀ on natural and cause-specific mortality, with stronger estimated effects on cardiac mortality during Saharan dust outbreaks. Toxicological and biological effects of particles from desert sources need to be further investigated and taken into account in air quality standards.     

Modeling the residential infiltration of outdoor PM(2.5) in the Multi-Ethnic Study of Atherosclerosis and Air Pollution (MESA Air)

Background: Epidemiologic studies of fine particulate matter [aerodynamic diameter ≤ 2.5 μm (PM_2.5)] typically use outdoor concentrations as exposure surrogates. Failure to account for variation in residential infiltration efficiencies (F_inf) will affect epidemiologic study results.Objective: We aimed to develop models to predict F_inf for > 6,000 homes in the Multi-Ethnic Study of Atherosclerosis and Air Pollution (MESA Air), a prospective cohort study of PM_2.5 exposure, subclinical cardiovascular disease, and clinical outcomes.Methods: We collected 526 two-week, paired indoor–outdoor PM_2.5 filter samples from a subset of study homes. PM_2.5 elemental composition was measured by X-ray fluorescence, and F_inf was estimated as the indoor/outdoor sulfur ratio. We regressed F_inf on meteorologic variables and questionnaire-based predictors in season-specific models. Models were evaluated using the R² and root mean square error (RMSE) from a 10-fold cross-validation.Results: The mean ± SD F_inf across all communities and seasons was 0.62 ± 0.21, and community-specific means ranged from 0.47 ± 0.15 in Winston-Salem, North Carolina, to 0.82 ± 0.14 in New York, New York. F_inf was generally greater during the warm (> 18°C) season. Central air conditioning (AC) use, frequency of AC use, and window opening frequency were the most important predictors during the warm season; outdoor temperature and forced-air heat were the best cold-season predictors. The models predicted 60% of the variance in 2-week F_inf, with an RMSE of 0.13.Conclusions: We developed intuitive models that can predict F_inf using easily obtained variables. Using these models, MESA Air will be the first large epidemiologic study to incorporate variation in residential F_inf into an exposure assessment.     

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

Background: Current air quality standards for particulate matter (PM) use the PM mass concentration [PM with aerodynamic diameters ≤ 10 μm (PM₁₀) or ≤ 2.5 μm (PM_2.5)] as a metric. It has been suggested that particles from combustion sources are more relevant to human health than are particles from other sources, but the impact of policies directed at reducing PM from combustion processes is usually relatively small when effects are estimated for a reduction in the total mass concentration.Objectives: We evaluated the value of black carbon particles (BCP) as an additional indicator in air quality management.Methods: We performed a systematic review and meta-analysis of health effects of BCP compared with PM mass based on data from time-series studies and cohort studies that measured both exposures. We compared the potential health benefits of a hypothetical traffic abatement measure, using near-roadway concentration increments of BCP and PM_2.5 based on data from prior studies.Results: Estimated health effects of a 1-μg/m³ increase in exposure were greater for BCP than for PM₁₀ or PM_2.5, but estimated effects of an interquartile range increase were similar. Two-pollutant models in time-series studies suggested that the effect of BCP was more robust than the effect of PM mass. The estimated increase in life expectancy associated with a hypothetical traffic abatement measure was four to nine times higher when expressed in BCP compared with an equivalent change in PM_2.5 mass.Conclusion: BCP is a valuable additional air quality indicator to evaluate the health risks of air quality dominated by primary combustion particles.     

Fine particulate matter constituents and cardiopulmonary mortality in a heavily polluted Chinese city

Background: Although ambient fine particulate matter (PM_2.5; particulate matter ≤ 2.5 µm in aerodynamic diameter) has been linked to adverse human health effects, the chemical constituents that cause harm are unknown. To our knowledge, the health effects of PM_2.5 constituents have not been reported for a developing country.Objectives: We examined the short-term association between PM_2.5 constituents and daily mortality in Xi’an, a heavily polluted Chinese city.Methods: We obtained daily mortality data and daily concentrations of PM_2.5, organic carbon (OC), elemental carbon (EC), and 10 water-soluble ions for 1 January 2004 through 31 December 2008. We also measured concentrations of fifteen elements 1 January 2006 through 31 December 2008. We analyzed the data using over-dispersed generalized linear Poisson models.Results: During the study period, the mean daily average concentration of PM_2.5 in Xi’an was 182.2 µg/m³. Major contributors to PM_2.5 mass included OC, EC, sulfate, nitrate, and ammonium. After adjustment for PM_2.5 mass, we found significant positive associations of total, cardiovascular, or respiratory mortality with OC, EC, ammonium, nitrate, chlorine ion, chlorine, and nickel for at least 1 lag day. Nitrate demonstrated stronger associations with total and cardiovascular mortality than PM_2.5 mass. For a 1-day lag, interquartile range increases in PM_2.5 mass and nitrate (114.9 and 15.4 µg/m³, respectively) were associated with 1.8% [95% confidence interval (CI): 0.8%, 2.8%] and 3.8% (95% CI: 1.7%, 5.9%) increases in total mortality.Conclusions: Our findings suggest that PM_2.5 constituents from the combustion of fossil fuel may have an appreciable influence on the health effects attributable to PM_2.5 in Xi’an.