Impact/Purpose:

Project I, an inhalation toxicological animal exposure study, will investigate the relative toxicity of different component concentration combinations of air pollution mixtures. These components include both particles and gases that are emitted directly from sources (primary species) or are formed in the atmosphere through a series of reactions that are predominantly photochemical (secondary species) Using a novel integration of our ambient particle concentrator and photochemical chamber technologies to generate realistic mixtures, we will test these specific hypotheses: (i) secondary gaseous pollutants formed from the photochemical oxidation of Boston ambient gases can induce biological responses; (ii) aging Boston concentrated ambient particles (CAPs) in the photochemical chamber enhances their toxicity; (iii) toxicological effects of photochemically aged CAPs are exacerbated by coexposure to ozone and other secondary gases; and (iv) mixture composition and toxicity exhibit inter- and intra-seasonal variability due to changes in source emissions and weather conditions.

Description:

The proposed study will differentiate the health effects of components of multi-pollutant exposure mixtures. We expect to add to our understanding of the exposure- response relationship, the interaction between particulate matter and photochemical gases, and the extent to which the resultant products exert toxicity. The biological outcomes assessed in this Project focus on responses important in oxidant initiation of pulmonary inflammation, and important functional measures of vascular and cardiovascular health.

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Toxicity will be assessed in Sprague-Dawley rats by changes in 1) in vivo oxidant response, 2) blood pressure, 3) measures of inflammation, and 4) vascular blood flow/resistance. Three concurrent exposures groups (Sham, Control Exposure and Exposure) will allow us to control for the variability in CAPs composition. With this design, there can always be a direct comparison between two exposure mixtures on every exposure day, making it possible to determine which mixture is more toxic. In studies of vascular blood flow/resistance using a crossover design, each animal will have multiple exposures that will include each of the three types, including baseline measurements. This will permit for control of inter-subject variability in the biological response. Exposure atmospheres will be chemically and physically characterized using a broad array of measurement techniques for CO. NOx, 03, PM, BC, particle count and size distribution, EC/OC, elemental composition, sulfate, formaldehyde, acetaldehyde and VOCs. For the biological effects observed during each exposure, inter-group differences will be assessed using multi-way analysis of variance. To determine the effect of PM composition on biological response, linear regression models containing exposure concentrations as predictors will be fitted to each response outcome measure. Multiple pollutant linear regressions will be used to assess the independent effects of multiple pollution components on biological response.

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