Citation:

Hargrove, M., S. Snow, R. Luebke, C. Wood, J. Krug, Todd Krantz, C. King, C. Copeland, S. McCullough, K. Gowdy, U. Kodavanti, Ian Gilmour, AND S. Gavett. Effects of Simulated Smog Atmospheres in Rodent Models of Metabolic and Immunologic Dysfunction. ENVIRONMENTAL SCIENCE & TECHNOLOGY. American Chemical Society, Washington, DC, 52(5):3062-3070, (2018). https://doi.org/10.1021/acs.est.7b06534

Impact/Purpose:

Assessment of complex multipollutant mixtures is needed to better characterize health impacts of real-world exposures, identify sources for the most harmful pollution emissions, and enable more effective management of air quality. The principal constituents of smog such as O3, NO2, and SOA particulate matter (PM) may exist in differing relative concentrations as a result of regional-specific geographic and urban environment characteristics. We generated simulated smog atmospheres (SAs) in a photochemical reaction chamber, which allows precise control of atmospheric conditions. Our objective was to study the health effects of the SA mixtures with different criteria pollutants. Simulated SAs with different compositions were compared: low O3/high PM (SA-PM) and high O3/low PM (SA-O3). These acute inhalation exposure studies were designed to investigate which dominant source profile has the greatest impact in animal models representing metabolic impairment, allergic asthma, response to immunization, or resistance to infection. Pulmonary and systemic health effects were examined in a metabolically-impaired, Type II diabetic rat model. Effects on allergic responses to house dust mite (HDM), the humoral response to immunization with heat-killed Streptococcus pneumoniae (HKSP), and resistance to influenza A (H1N1) infection were examined in mice. We hypothesized that exposure to simulated SAs would exacerbate health outcomes in these models of disease which would vary depending on the source profile. These atmospheres produced few short-term health effects in animal models of metabolic and immune diseases, although greater responses were found with SA-O3, suggesting that gas-phase components in these photochemically-derived multipollutant air pollution mixtures may be of greater concern than secondary organic aerosol PM.

Description:

Air pollution is a diverse and dynamic mixture of gaseous and particulate matter. This complexity has limited our understanding of adverse health outcomes resulting from common types of air contaminants. The biological effects of two simulated smog atmospheres (SA) generated in a photochemical reaction chamber with different compositions but similar air quality health indexes were compared in rodent models of different susceptible populations: a non-obese diabetic rat model (Goto-Kakizaki, GK) and three mouse immune models (house dust mite (HDM) allergy, antibody response to heat-killed pneumococcus, and resistance to influenza A infection). In GK rats, both SA-PM (high particulate matter) and SA-O3 (high ozone) decreased HDL and LDL cholesterol immediately after a 4-hour exposure, whereas only SA-O3 decreased ventilatory relaxation time and increased an index of airflow limitation. Airway responsiveness to methacholine was increased in HDM-allergic mice compared with non-allergic mice, but 1 or 5 days of exposure to SA-PM or SA-O3 did not significantly alter responsiveness. A 5-day exposure to SA-O3 produced mild lung injury in HDM-allergic mice as demonstrated by increased bronchoalveolar lavage fluid protein. Seven days of exposure to SA-PM did not affect the T-independent IgM response to pneumococcus, and SA-O3 did not affect virus titers, although inflammatory cytokine levels were decreased in mice infected at the end of the SA-O3 exposure. Collectively, acute SA exposures produced limited health effects in animal models of metabolic and immune diseases. Effects of SA-O3 tended to be greater than those of SA-PM, suggesting that gas-phase components in these photochemically-derived multipollutant air pollution mixtures may be of greater concern than secondary organic aerosol PM.

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