METAL AND SULFATE COMPOSITION OF RESIDUAL OIL FLY-ASH DETERMINES AIRWAY HYPERREACTIVITY AND LUNG INJURY IN RATS

The biological effects of particulate matter (PM) deposition in the ai rways may depend on aqueous-leachable chemical constituents of the par ticles. The effects of two residual oil fly ash (ROFA) PM samples of e quivalent diameters but different metal and sulfate contents on pulmon ary responses in Sprague-Dawley rats were investigated. ROFA sample 1 (R1) had approximately twice as much saline-leachable sulfate, nickel, and vanadium, and 40 times as much iron as ROFA sample 2 (R2), while R2 had a 31-fold higher zinc content. Four groups of rats were intratr acheally instilled with a suspension of 2.5 mg R2 in 0.3 ml saline (R2 ), the supernatant of R2 (R2s), the supernatant of 2.5 mg R1 (R1s), or saline only. By 4 days after instillation, 4 of 24 rats treated with R2s or R2 had died, compared with none treated with R1s or saline, and pathological indices were greater in both R2 groups compared with the R1s group. In surviving rats, baseline pulmonary function parameters and airway hyperreactivity to acetylcholine challenge were significant ly worse in R2 and R2s groups than in the R1s group. Numbers of bronch oalveolar lavage neutrophils, but not other inflammatory cells or bioc hemical parameters of lung injury, were greater in both R2 groups comp ared with the R1s group. These results reinforce the hypothesis that t he composition of soluble metals and sulfate leached from ROFA, an emi ssion source particle, is critical in the development of airway hyperr eactivity and lung injury.