Pulmonary and Systemic Inflammatory Response to Ambient Particulate Matter in the San Joaquin Valley of California

Strong evidence exists for associations between exposure to ambient particulate matter (PM) and adverse cardiopulmonary health effects. Numerous epidemiological studies have correlated increases in ambient PM mass concentration with increased incidence of emergency room visits, hospital admissions and mortality for cardiopulmonary conditions. However, these findings have been difficult to reproduce in experimental studies, suggesting that mass alone does not explain observed health effects. Current national ambient air quality standards are based on particle mass with no consideration for chemical composition. Thus, improved understanding of the relationship between PM exposure and cardiopulmonary health effects can support regulation for improved protection of human health. We have conducted numerous experimental studies in the San Joaquin Valley of California, a region that regularly exceeds the current mass-based standards for PM pollution. Studies were conducted both in the field using inhaled concentrated ambient particles (CAPs) and in the laboratory to study PM-induced pulmonary and systemic inflammatory responses, a hallmark of adverse cardiopulmonary conditions. Our objective was to investigate these responses in the context of season, location, PM mass and chemical composition. Inhalation studies indicated that chemical composition arising from differences in location and season were critical factors influencing PM toxicity. Further, associations between health effects and PM mass and chemical composition demonstrated that short-term changes in ambient PM concentrations may provide improved interpretation of experimental results. Associations between biological responses and specific chemical components suggest that different sources may have different toxicity. Potential source-specific regulation of the source emitting the most toxic PM components or precursors may have substantial human health benefit. Together, these findings provide biological plausibility for the epidemiological associations between PM exposure and adverse health effects.