Clearance of /sup 59/Fe/sub 3/O/sub 4/ particles from the lung of rats during exposure to coal mine dust and diesel exhaust

Experiments in rats were performed to investigate the influence of diesel/coal dust exposure on lung clearance of inert tracer particles. Four groups of 80 rats each were exposed as follows: (1) Coal mine dust, 2 mg/m/sup 3/; (2) Diesel exhaust, 2 mg/m/sup 3/); (3) Coal mine dust (1 mg/m/sup 3/) plus diesel exhaust (1 mg/m/sup 3/); (4) Filtered air (control). The exposure was for 7 hours per day, 5 days per week for a period of 6 months. Two months after commencement of the study, all animals were exposed in nose only exposure units to /sup 59/Fe/sub 3/O/sub 4/ dust for 2 hours. Lungs of serially killed animals were excised and their /sup 59/Fe activity measured. Biological half lives of long term clearance of Fe/sub 3/O/sub 4/ from the lung were 47 days (controls), 42 days (coal), 43 days (coal/diesel) and 37 days (diesel). /sup 59/Fe/sub 3/O/sub 4/ retention on day 120 was significantly lower in all exposure groups as compared to controls, with the diesel group showing the lowest retention (< 50% of controls). Short term clearance determined from Fe/sub 3/O/sub 4/ retention of day 1 was not significantly different between the groups. 11 references.