Multi-pollutant exposures in an asthmatic cohort

An investigation of personal fine and coarse particulate matter (PM2.5, PM10–2.5), nitrogen dioxide (NO2), and ozone (O3) exposures was conducted with an adult asthmatic cohort as part of the U.S. Environmental Protection Agency's Moderate and Severe Asthmatics and their Environment Study (MASAES). The overall goal of the MASAES was to determine the association of particulate matter on the degree of resulting lung inflammation, with those having severe asthma hypothesized to be more highly susceptible to such outcomes. The primary exposure objective was to determine the spatial (personal versus ambient) and temporal relationships associated with the aforementioned air pollutants and establish the precision of a new dual PM2.5, PM10–2.5 monitor (CPEM) for personal exposure monitoring. A total of 16 non-smoking adults of various asthma severities were monitored over the course of a 14 month period during 2008–2009. Participants were monitored for 24 continuous hours each monitoring day with a maximum of five events per participant. Median personal PM2.5 and PM10–2.5 exposures were 16.5 and 10.1 μg m−3, respectively. Daily ambient mass concentrations accounted for less than 1% of the observed variability in personal PM2.5 or PM10–2.5 exposures. Duplicate personal measures yielded R2 values of 0.92 PM2.5 and 0.77 PM10–2.5, respectively. Maximum daily personal exposures of 17.0 ppb NO2 and 21.7 ppb O3 occurred with respective mean exposures of 5.8 and 3.4 ppb. Ambient NO2 and O3 measures were observed to be poorly associated with personal exposures (R2 < 0.08) when viewed independent of the participant. The poor correlation between personal and ambient concentrations of PM as well as the various gaseous copollutants indicates the complexity of the multi-pollutant environment and the impact of non-ambient sources on these pollutants relative to total personal exposures.