Acute pulmonary toxicity of particulate matter filter extracts in rats: Coherence with epidemiologic studies in Utah Valley residents

Epidemiologic reports by C.A. Pope III et. al. demonstrated that in the Uta h Valley, closure of an open-hearth steel mill over the winter of 1987 was associated with reductions in respiratory disease and related hospital admi ssions in valley residents. To better examine the relationship between plan t-associated changes in ambient particulate matter (PM) and respiratory hea lth effects, we obtained total suspended particulate filters originally col lected near the steel mill during the winter of 1986 (before closure), 1987 (during closure), and 1988 (after plant reopening). PM subcomponents were water-extracted from these filters and Sprague-Dawley rats were intratrache ally instilled with equivalent masses of extract. Data indicated that 24 hr later, rats exposed to 1986 or 1988 extracts developed significant pulmona ry injury and neutrophilic inflammation. Additionally, 50% of rats exposed to 1986 or 1988 extracts had increased airway responsiveness to acetylcholi ne, compared to 17 and 25% of rats exposed to saline or the 1987 extract, r espectively. By 96 hr, these effects were largely resolved except for incre ases in lung lavage fluid neutrophils and lymphocytes in 1986 extract-expos ed rats. Analogous effects were observed with lung histologic assessment. E xtract analysis using inductively coupled plasma-mass spectroscopy demonstr ated in all three extracts nearly 70% of the mass appeared to be sodium-bas ed salts derived from the glass filter matrix. Interestingly, relative to t he 1987 extract, the 1986/1988 extracts contained more sulfate, cationic sa lts (i.e., calcium, potassium, magnesium), and certain metals (i.e., copper , zinc, iron, lead, strontium, arsenic, manganese, nickel). Although total metal content was less than or equal to 1% of the extracts by mass, the gre ater quantity detected in the 1986 and 1988 extracts suggests metals may be important determinants of the pulmonary toxicity observed. In conclusion, the pulmonary effects induced by exposure of rats to water-based extracts o f local ambient PM filters were in good accord with the cross-sectional epi demiologic reports of adverse respiratory health effects in Utah Valley res idents.