Abstract
Despite observed geographic and temporal variation in particulate matter (PM)-related health morbidities, only a small number of epidemiologic studies have evaluated the relation between PM2.5 chemical constituents and respiratory disease. Most assessments are limited by inadequate spatial and temporal resolution of ambient PM measurements and/or by their approaches to examine the role of specific PM components on health outcomes. In a case-crossover analysis using daily average ambient PM2.5 total mass and species estimates derived from the Community Multiscale Air Quality (CMAQ) model and available observations, we examined the association between the chemical components of PM (including elemental and organic carbon, sulfate, nitrate, ammonium, and other remaining) and respiratory hospitalizations in New York State. We evaluated relationships between levels (low, medium, high) of PM constituent mass fractions, and assessed modification of the PM2.5–hospitalization association via models stratified by mass fractions of both primary and secondary PM components. In our results, average daily PM2.5 concentrations in New York State were generally lower than the 24-hr average National Ambient Air Quality Standard (NAAQS). Year-round analyses showed statistically significant positive associations between respiratory hospitalizations and PM2.5 total mass, sulfate, nitrate, and ammonium concentrations at multiple exposure lags (0.5–2.0% per interquartile range [IQR] increase). Primarily in the summer months, the greatest associations with respiratory hospitalizations were observed per IQR increase in the secondary species sulfate and ammonium concentrations at lags of 1–4 days (1.0–2.0%). Although there were subtle differences in associations observed between mass fraction tertiles, there was no strong evidence to support modification of the PM2.5-respiratory disease association by a particular constituent. We conclude that ambient concentrations of PM2.5 and secondary aerosols including sulfate, ammonium, and nitrate were positively associated with respiratory hospitalizations, although patterns varied by season. Exposure to specific fine PM constituents is a plausible risk factor for respiratory hospitalization in New York State.Implications: The association between ambient concentrations of PM2.5 components has been evaluated in only a small number of epidemiologic studies with refined spatial and temporal scale data. In New York State, fine PM and several of its constituents, including sulfate, ammonium, and nitrate, were positively associated with respiratory hospitalizations. Results suggest that PM species relationships and their influence on respiratory endpoints are complex and season dependent. Additional work is needed to better understand the relative toxicity of PM species, and to further explore the role of co-pollutant relationships and exposure prediction error on observed PM–respiratory disease associations.
Highlights
Fine particles less than 2.5 μm in diameter (PM2.5) are emitted directly from sources or are formed in the atmosphere through gas- and/or aqueous-phase reactions of primary pollutants such as NOx and SO2
This study investigated the association between daily ambient PM2.5 species concentrations and respiratory hospitalizations in New York State (NYS) using 24-hr average particulate matter (PM) constituent concentrations estimated by combining Community Multiscale Air Quality (CMAQ) outputs with available observations
Exceedance of the 24-hr National Ambient Air Quality Standard (NAAQS) for PM2.5 (35 μg/m3) occurred on roughly 9% of days across the 6-year study period; 60% of these exceedances occurred in New York City (NYC)
Summary
Fine particles less than 2.5 μm in diameter (PM2.5) are emitted directly from sources or are formed in the atmosphere through gas- and/or aqueous-phase reactions of primary pollutants such as NOx and SO2. A substantial body of epidemiologic evidence exists in support of the association between short-term exposure to ambient fine particles and respiratory morbidity, including hospitalizations and emergency department (ED) visits, increased medication use, symptoms, and infections (Dominici et al, 2006; Host et al, 2008; Karakatsani et al, 2003; Tecer et al, 2008; von Klot et al, 2002) Most of these studies have quantified health burdens in relation to PM2.5 total mass only, examination of relationships with the components of PM2.5 could potentially explain observed geographic variation in particulate matter (PM)-related health risk (Atkinson et al, 2015). Few existing studies have examined PM constituents using a casecrossover design, this method is increasingly common in the epidemiologic air quality literature and provides advantages for confounding adjustment over traditional timeseries analysis
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