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Although numerous studies have demonstrated links between particulate matter (PM) and adverse health effects, the chemical components of the PM mixture that cause injury are unknown. Objectives: This work characterizes spatial and temporal variability of PM2.5 (PM with aerodynamic diameter < 2.5 μm) components in the United States; our objective is to identify components for assessment in epidemiologic studies. Methods: We constructed a database of 52 PM2.5 component concentrations for 187 U.S. counties for 2000-2005. First, we describe the challenges inherent to analysis of a national PM2.5 chemical composition database. Second, we identify components that contribute substantially to and/or co-vary with PM2.5 total mass. Third, we characterize the seasonal and regional variability of targeted components. Results: Strong seasonal and geographic variations in PM2.5 chemical composition are identified. Only seven of the 52 components contributed ≥ 1% to total mass for yearly or seasonal averages [ammonium (NH4+), elemental carbon (EC), organic carbon matter (OCM), nitrate (NO3-), silicon, sodium (Na+), and sulfate (SO42-)]. Strongest correlations with PM2.5 total mass were with NH4+ (yearly), OCM (especially winter), NO3- (winter), and SO42- (yearly, spring, autumn, and summer), with particularly strong correlations for NH4+ and SO42- in summer. Components that co-varied with PM2.5 total mass, based on daily detrended data, were NH4+, SO42-, OCM, NO3-, bromine, and EC. Conclusions: The subset of identified PM2.5 components should be investigated further to determine whether their daily variation is associated with daily variation of health indicators, and whether their seasonal and regional patterns can explain the seasonal and regional heterogeneity in PM10 (PM with aerodynamic diameter < 10 μm) and PM2.5 health risks.

Published Jul 1, 2017

Bell, M. L., Dominici, F., Ebisu, K., Zeger, S. L., & Samet, J. M. (2007). Spatial and temporal variation in PM2.5 chemical composition in the United States for health effects studies. In Environmental Health Perspectives (Vol. 115, Issue 7, pp. 989–995). https://doi.org/10.1289/ehp.9621

Reports the results of a large study, including more than 60 million Medicare beneficiaries from the years 2000 through 2012, that addresses the association between annual average levels of PM2.5 and ozone,9 as measured at the ZIP Code level, and mortality. For every increase of 10 μg per cubic meter in PM2.5, there was an associated 7.3% increase in all-cause mortality (95% confidence interval [CI], 7.1 to 7.5), after adjustment for demographic characteristics, Medicaid eligibility, and area-level covariates. Below the current NAAQS for PM2.5 of 12 μg per cubic meter, the data showed that each increase in PM2.5 of 10 μg per cubic meter was associated with an even greater increase (13.6%) in mortality (95% CI, 13.1 to 14.1). There was no appreciable level below which the risk of death tapered off — and thus no “safe” level of PM2.5. Owing to the large size of the cohort, Di et al. were able to perform robust subgroup analyses and identified greater risks of death associated with air pollutants among blacks and Medicaid-eligible populations; moreover, these groups were more likely to be exposed to higher pollutant levels.

Published Jun 29, 2017

Berger, R. E., Ramaswami, R., Solomon, C. G., & Drazen, J. M. (2017). Air pollution still kills. New England Journal of Medicine, 376(26), 2591–2592. https://doi.org/10.1056/NEJMe1706865

Studies have shown that long-term exposure to air pollution increases mortality. However, evidence is limited for air-pollution levels below the most recent National Ambient Air Quality Standards. Previous studies involved predominantly urban populations and did not have the statistical power to estimate the health effects in underrepresented groups. METHODS We constructed an open cohort of all Medicare beneficiaries (60,925,443 persons) in the continental United States from the years 2000 through 2012, with 460,310,521 person-years of follow-up. Annual averages of fine particulate matter (particles with a mass median aerodynamic diameter of less than 2.5 μm [PM2.5]) and ozone were estimated according to the ZIP Code of residence for each enrollee with the use of previously validated prediction models. We estimated the risk of death associated with exposure to increases of 10 μg per cubic meter for PM2.5 and 10 parts per billion (ppb) for ozone using a two-pollutant Cox proportionalhazards model that controlled for demographic characteristics, Medicaid eligibility, and area-level covariates. RESULTS Increases of 10 μg per cubic meter in PM2.5 and of 10 ppb in ozone were associated with increases in all-cause mortality of 7.3% (95% confidence interval [CI], 7.1 to 7.5) and 1.1% (95% CI, 1.0 to 1.2), respectively. When the analysis was restricted to person-years with exposure to PM2.5 of less than 12 μg per cubic meter and ozone of less than 50 ppb, the same increases in PM2.5 and ozone were associated with increases in the risk of death of 13.6% (95% CI, 13.1 to 14.1) and 1.0% (95% CI, 0.9 to 1.1), respectively. For PM2.5, the risk of death among men, blacks, and people with Medicaid eligibility was higher than that in the rest of the population. CONCLUSIONS In the entire Medicare population, there was significant evidence of adverse effects related to exposure to PM2.5 and ozone at concentrations below current national standards. This effect was most pronounced among self-identified racial minorities and people with low income. (Supported by the Health Effects Institute and others.)

Published Jun 29, 2017

Di, Q., Wang, Y., Zanobetti, A., Wang, Y., Koutrakis, P., Choirat, C., Dominici, F., & Schwartz, J. D. (2017). Air pollution and mortality in the medicare population. New England Journal of Medicine, 376(26), 2513–2522. https://doi.org/10.1056/NEJMoa1702747

BACKGROUND: Daily changes in ambient concentrations of particulate matter, nitrogen oxides and ozone are associated with increased cardiopulmonary morbidity and mortality, with the lungs and their function being a vulnerable target. METHODS: To evaluate the association between daily changes in air pollution and lung function in healthy adults we obtained annual lung function measurements from a routine worker health surveillance program not designed for research purposes. Forced Vital Capacity (FVC), Forced Expiratory Volume in the first second (FEV1), FEV1/FVC and Peak Expiratory flow (PEF) from a cohort of 2449 employees were associated with daily measurements of PM10, NO2 and ozone at a nearby monitoring station in the North of Belgium. Repeated measures were available for the period 2011-2015. RESULTS: The mean (SD) PM10 concentration on the day of the lung function test was 24.9 (15.5) μg/m3. A 10 μg PM10/m3 increase on the day of the clinical examination was associated with a 18.9 ml lower FVC (95% CI: -27.5 to -10.3, p < 0.0001), 12.8 ml lower FEV1 (-19.1 to -6.5; p < 0.0001), and a 51.4 ml/s lower PEF (-75.0 to -27.0; p < 0.0001). The FEV1/FVC-ratio showed no associations. An increase of 10 μgNO2/m3 was associated with a reduction in PEF (-66.1 ml/s (-106.6 to -25.6; p < 0.001)) on the day of the examination. CONCLUSIONS: We found negative associations between daily variations in ambient air pollution and FVC, FEV1 and PEF in healthy adults.

Published Jun 14, 2017

Int Panis, L., Provost, E. B., Cox, B., Louwies, T., Laeremans, M., Standaert, A., Dons, E., Holmstock, L., Nawrot, T., & De Boever, P. (2017). Short-term air pollution exposure decreases lung function: a repeated measures study in healthy adults. Environmental Health : A Global Access Science Source, 16(1), 60. https://doi.org/10.1186/s12940-017-0271-z

How school location impacts children’s air pollution exposure and their ability to walk and bike to school has been a growing policy issue. Smart growth advocates encourage districts to locate schools in “walkable” locations, often near high-volume roadways while health professionals emphasize the importance of minimizing exposure to high levels of air pollution and distance schools from major roads. As states consider or implement laws to site schools away from high-volume roadways, such policies can lead to school locations disconnected from neighborhoods and accessible only by motorized transport modes. This study analyzes children’s air pollution exposure across an average school day, analyzing variation across roadway characteristics, local school and home environment, and mode choice for school commute. This research compares daily average exposures for children walking to a local school in a high-traffic area versus exposures if they were required to be bussed or driven to a distant, “greener” school located in a low-traffic environment. Daily average exposures to air pollution were estimated across an average school day (AM Commute, Unload, School Day, Load, PM Commute). The analysis also assesses how pollution exposure can be mitigated through clean school bus technology, improved HVAC systems, and no-idling policies. Bussing children from a high-traffic neighborhood to a distant school in a low-traffic environment resulted in average daily exposures from 2 to 4 times higher than children walking to their local school. The authors' simulated school siting policy assessment found that bussing children to a distant school in a “cleaner” air quality school site did not reduce average daily personal exposure of children who would otherwise walk or be driven/bussed to their local school in a “dirtier” air quality site. Mitigation measures like a clean bus fleet greatly reduce exposures for children bussing longer distances to a distant school while school HVAC improvements in a heavy-diesel/heavy-traffic school environment yield more conservative reductions.

Published Jun 1, 2017

Wolfe, M., McDonald, N., Arunachalam, S., & Valencia, A. (2017). Air Pollution Exposure during School Commutes. Journal of Transport & Health, 5, S48–S49. https://doi.org/10.1016/j.jth.2017.05.339

Although exposure to traffic emissions is frequently associated with negative health impacts, few studies have measured air pollution directly in-vehicle, and limited measurements of daily commuter exposure exist. This research, part of the Atlanta Commuter Exposures (ACE) Study, assesses on-roadway in-cabin particulate pollution (PM 2.5 ) collected from scripted rush hour commutes on highways and on non-highway side streets. Water-soluble extracts from PM 2.5 filters were analyzed for oxidative potential of water-soluble species using the dithiothreitol (DTT) assay, and results suggest that there may be substantial gas-phase DTT activity in fresh emissions. We measured DTTv activities (i.e., DTT activity normalized to the sampled air volume) that were on average two times higher than comparable measurements collected by stationary roadside monitoring sites. Although some of this difference may be attributable to positive artifacts due to relatively brief (2-h) quartz filter sampling durations, the current findings provide some indication that commuters encounter notably higher exposure to redox-active PM 2.5 in the on-road environment. Strong correlations are observed between water-soluble DTT activity and water-soluble organic carbon (WSOC), specifically for the ‘semivolatile’ WSOC component (measured as the difference between denuded and non-denuded filters). Although potential for artifacts when measuring DTT activity of fresh emissions using filter-based methods is considerable, these results suggest that semivolatile organic species are important contributors to DTT activity, at least in environments where ambient PM 2.5 is dominated by vehicular sources.

Published Jun 1, 2017

Vreeland, H., Weber, R., Bergin, M., Greenwald, R., Golan, R., Russell, A. G., Verma, V., & Sarnat, J. A. (2017). Oxidative potential of PM 2.5 during Atlanta rush hour: Measurements of in-vehicle dithiothreitol (DTT) activity. Atmospheric Environment, 165, 169–178. https://doi.org/10.1016/j.atmosenv.2017.06.044

Lung function in early life has been shown to be an important predictor for peak lung function in adults and later decline. Reduced lung function per se is associated with increased morbidity and mortality. With this review, we aim to summarize the current epidemiological evidence on the effect of traffic-related air pollution on lung function in children and adolescents. We focus in particular on time windows of exposure, small airway involvement, and vulnerable sub-groups in the population. Findings from studies published to date support the notion that exposure over the entire childhood age range seems to be of importance for lung function development. We could not find any conclusive data to support evidence of sup-group effects considering gender, sensitization status, and asthma status, although a possibly stronger effect may be present for children with asthma. The long-term effects into adulthood of exposure to air pollution during childhood remains unknown, but current studies suggest that these deficits may be propagated into later life. In addition, further research on the effect of exposure on small airway function is warranted.

Published May 27, 2017

Schultz, E.S., Litonjua, A.A. & Melén, E. Effects of Long-Term Exposure to Traffic-Related Air Pollution on Lung Function in Children. Curr Allergy Asthma Rep 17, 41 (2017). https://doi.org/10.1007/s11882-017-0709-y

Background Exposure to ambient air pollution increases morbidity and mortality, and is a leading contributor to global disease burden. We explored spatial and temporal trends in mortality and burden of disease attributable to ambient air pollution from 1990 to 2015 at global, regional, and country levels. Methods We estimated global population-weighted mean concentrations of particle mass with aerodynamic diameter less than 2·5 μm (PM2·5) and ozone at an approximate 11 km × 11 km resolution with satellite-based estimates, chemical transport models, and ground-level measurements. Using integrated exposure–response functions for each cause of death, we estimated the relative risk of mortality from ischaemic heart disease, cerebrovascular disease, chronic obstructive pulmonary disease, lung cancer, and lower respiratory infections from epidemiological studies using non-linear exposure–response functions spanning the global range of exposure. Findings Ambient PM2·5 was the fifth-ranking mortality risk factor in 2015. Exposure to PM2·5 caused 4·2 million (95% uncertainty interval [UI] 3·7 million to 4·8 million) deaths and 103·1 million (90·8 million 115·1 million) disability-adjusted life-years (DALYs) in 2015, representing 7·6% of total global deaths and 4·2% of global DALYs, 59% of these in east and south Asia. Deaths attributable to ambient PM2·5 increased from 3·5 million (95% UI 3·0 million to 4·0 million) in 1990 to 4·2 million (3·7 million to 4·8 million) in 2015. Exposure to ozone caused an additional 254 000 (95% UI 97 000–422 000) deaths and a loss of 4·1 million (1·6 million to 6·8 million) DALYs from chronic obstructive pulmonary disease in 2015. Interpretation Ambient air pollution contributed substantially to the global burden of disease in 2015, which increased over the past 25 years, due to population ageing, changes in non-communicable disease rates, and increasing air pollution in low-income and middle-income countries. Modest reductions in burden will occur in the most polluted countries unless PM2·5 values are decreased substantially, but there is potential for substantial health benefits from exposure reduction. Funding Bill & Melinda Gates Foundation and Health Effects Institute.

Published Apr 10, 2017

Cohen, Aaron J, et al. “Estimates and 25-Year Trends of the Global Burden of Disease Attributable to Ambient Air Pollution: an Analysis of Data from the Global Burden of Diseases Study 2015.” The Lancet, vol. 389, no. 10082, 10 Apr. 2017, pp. 1907–1918., doi:10.1016/s0140-6736(17)30505-6.

Anthropogenic ambient fine particulate matter less than 2.5 µm (PM2.5) air pollution from fossil fuel combustion (eg, coal-fired power plants and traffic) ranks among the leading causes of worldwide morbidity and mortality.1 In agreement with figures from the World Health Organization (http://www.who.int/topics/global_burden_of_disease/en/), estimations indicate that approximately 3.15 million deaths per year are attributable to PM2.5. This alarming figure exceeds that of many more widely recognized risk factors (eg, hypercholesterolemia) and unfortunately is estimated to double by 2050.1 However, perhaps underappreciated by health care professionals and the general populace alike is that the largest portion of ambient PM2.5–induced health effects are owing to cardiovascular events. Short-term elevations in PM2.5 increase the risk for myocardial infarctions, strokes, heart failure, arrhythmias, and cardiac death.2,3 Longer-term exposures synergistically increase this acute risk and can even potentiate the development of chronic cardiometabolic conditions including diabetes and hypertension. As such, both the American Heart Association and European Society of Cardiology have formally recognized ambient PM2.5 as a major cardiovascular risk factor.2,3

Published Apr 1, 2017

Brook, R. D., Newby, D. E., & Rajagopalan, S. (2017). The global threat of outdoor ambient air pollution to cardiovascular health: Time for intervention. JAMA Cardiology, 2(4), 353–354. https://doi.org/10.1001/jamacardio.2017.0032

Background: Approaches to estimating and addressing the risk to children from fossil fuel combustion have been fragmented, tending to focus either on the toxic air emissions or on climate change. Yet developing children, and especially poor children, now bear a disproportionate burden of disease from both environmental pollution and climate change due to fossil fuel combustion. Objective: This commentary summarizes the robust scientific evidence regarding the multiple current and projected health impacts of fossil fuel combustion on the young to make the case for a holistic, child-centered energy and climate policy that addresses the full array of physical and psychosocial stressors resulting from fossil fuel pollution. Discussion: The data summarized here show that by sharply reducing our dependence on fossil fuels we would achieve highly significant health and economic benefits for our children and their future. These benefits would occur immediately and also play out over the life course and potentially across generations. Conclusion: Going beyond the powerful scientific and economic arguments for urgent action to reduce the burning of fossil fuels is the strong moral imperative to protect our most vulnerable populations.

Published Feb 1, 2017

Perera, F. P. (2017). Multiple threats to child health from fossil fuel combustion: Impacts of air pollution and climate change. Environmental Health Perspectives, 125(2), 141–148. https://doi.org/10.1289/EHP299