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Photochemical Conversion of Surrogate Emissions for Use in Toxicological Studies: Role of Particulate- and Gas-Phase Products
Krug, J., M. Lewandowski, J. Offenberg, J. Turlington, W. Lonneman, N. Modak, Todd Krantz, C. King, S. Gavett, Ian Gilmour, D. DeMarini, AND Tad Kleindienst. Photochemical Conversion of Surrogate Emissions for Use in Toxicological Studies: Role of Particulate- and Gas-Phase Products. International Journal of Environmental Science and Technology. Springer, Heidelburg, Germany, 52(5):3037-3044, (2018).
It is well recognized that exposure to specific criteria air pollutants including O3, PM2.5, and NO2 results in a broad array of adverse health outcomes such as reduced lung function, cardiopulmonary inflammation, increased risk or severity of respiratory and cardiovascular disease, cancer, and in some instances (e.g. PM) increased mortality.1,2,3 Ascribing causality between common regional complex multipollutant mixtures in epidemiology studies, however, is challenging because the aforementioned criteria pollutants often track together. Thus, it is not always clear whether the resulting health effects are consequence of additive, antagonistic, or synergistic interactions of the components of air pollution.
The production of photochemical atmospheres under controlled conditions in an irradiated chamber permits the manipulation of a variety of parameters that influences resulting air pollutant chemistry and potential biological effects. To date no studies have examined how contrasting atmospheres with a similar calculated air quality health index (AQHI), but with differing ratios of criteria air pollutants, might differentially affect health endpoints. Here we produced two distinct, stable atmospheres with equivalent AQHIs based on the final concentrations of ozone, nitrogen dioxide, and particulate matter (PM2.5). One simulated atmosphere (SA-PM) generated from irradiation of ~23 ppmC gasoline, ~5 ppmC of α-pinene, 529 ppb NO, and 3 μg/m3 of (NH4)2SO4 as a seed and resulted in ~976 μg/m3 PM2.5, 326 ppb NO2, and 141 ppb O3 (AQHI 97.7). The other atmosphere (SA-O3) generated from ~8 ppmC gasoline, 5 ppmC isoprene, 874 ppb NO, 2 μg/m3 of (NH4)2SO4 and resulted in ~55 μg/m3 PM2.5, 643 ppb NO2, and 430 ppb O3 (AQHI of 99.8). In addition to the criteria pollutants, detailed chemical speciation by gas chromatography showed that photo-oxidation by the UV light degraded the organic precursors and promoted the de novo formation of secondary reaction products such as formaldehyde and acrolein. Further work in accompanying papers describe toxicological outcomes from the two distinct photochemical atmospheres.
Record Details:Record Type: DOCUMENT (JOURNAL/PEER REVIEWED JOURNAL)
Organization:U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF RESEARCH AND DEVELOPMENT
NATIONAL EXPOSURE RESEARCH LABORATORY
EXPOSURE METHODS & MEASUREMENT DIVISION