Chronic Exposure to PM Nitrate, Sulfate, and Ammonium Causes Respiratory System Impairments in Mice.

Water-soluble inorganic (WSI) ions are major components of ambient air PM (particulate matter of diameter ≤2.5 μm); however, their potential health effects are understudied. On C57BL/6 mice, we quantified the effect of three major PM WSIs (NO, SO, and NH) on respiratory systems. Exposure scenarios include different WSI types, concentrations, animal development stages (young vs adult), and sex. The exposure effects were comprehensively assessed, with special focus on the respiratory function and tissue/cell level changes. Chronic PM NO exposure produced significant respiratory function decline, mainly presented as airflow obstruction. The decline was more profound in young mice than in adult mice. In young mice, exposure to 22 μg/m PM NO reduced FEV (forced expiratory volume in 0.05 s) by 11.3% ( = 9.6 × 10) and increased pulmonary neutrophil infiltration by 7.9% ( = 7.1 × 10). Causality tests identified that neutrophil infiltration was involved in the biological mechanism underlying PM NO toxicity. In contrast, the effects of PM SO were considerably weaker than NO. PM NO exposure was 3.4 times more potent than PM SO in causing reduction of the peak expiratory flow. PM NH exposure had no statistically significant effects on the respiratory function. In summary, this study provided strong evidence on the adverse impacts of PM WSIs, where the impacts were most profound in young mice exposed to PM NO. If confirmed in humans, toxicity of PM WSI will have broad implications in environment health and policy making.