Coarse particulate matter: Characterization of pulmonary effects using a mouse bioassay

Particulate matter (PM) elicits inflammatory and toxic responses in the lung specific to its constituents. Concentrations and chemical properties of PM vary with time, season, climate, and size range, as well as by point and non-point sources. To identify the mechanism of toxicity of coarse PM (2.5--10 mum diameter [PM10--2.5]), we collected particles from rural areas in the San Joaquin Valley of Central California and parts of Northern California. A proposed explanation for reported adverse effects elicited by PM is its content of primary emissions and secondary air pollutants, but it still remains elusive which specific component or combinations of coarse PM components are responsible for the observed inflammatory and toxic effects in the respiratory system. Potential pro-inflammatory and toxic effects of both coarse and fine PM in the lung were investigated using intratracheally instilled mice. Total and differential cell profiles and inflammatory chemoattractants in lung lavage fluid were used as biomarkers of toxicity resulting from PM exposure. Responses of the mice were readily observed with doses ranging from 1--100 mug of PM per mouse. Complex particulate mixtures were analyzed by fractionation techniques (solubility, heat treatment, solvent extraction) based on the physical chemical properties of the constituents making up the whole mixture to identify fractions of PM that elicited increased or decreased pro-inflammatory activity in the lung. The results described should have broad applications for the investigation of the pro-inflammatory and toxic potential of specific constituents of coarse PM mixtures from collected from California's Central Valley.