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© 1992 Oxford University Press

research-article

Pulmonary Bioavailability and Fine Particle Enrichment of 2,3,7,8-Tetrachlorodibenzo-p-dioxin in Respirable Soil Particles

CRAIG S. NESSEL*,1, MARIE A. AMORUSO{dagger}, THOMAS H. UMBREIT, ROBERT J. MEEKER and MICHAEL A. GALLO*,2

Department of Environmental and Community Medicine New Jersey 08854 *Gradilate Program in Public health. Environmental and Occupational Health Sciences Institute, University of Medicine and Dentistry of New Jersey-Robert Wood Johnson Medical School, Piscataway New Jersey 08854 {dagger}tExxon Biomedical Sciences, Inc. East Millstone. New Jersey 08875

Received September 9, 1991; accepted March 16, 1992

The pulmonary bioavailability of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and the enrichment of polychlorinated dioxins (PCDDs) and furans (PCDFs) in fine particles were evaluated to assess the implications that these factors have on risk and exposure assessments. Respirable subfractions of PCDD-contaminated soil from a former 2,4,5-trichlorophenoxyacetic acid manufacturing site were isolated by chemical dispersion and gravity sedimentation. Analysis of the subfractions revealed that there was a size-dependent enrichment of PCDDs and PCDFs, with smaller particles more highly contaminated. TCDD was enriched up to 33-fold as compared to unfractionated soil. Soil and laboratory-recontaminated gallium oxide, which served as the positive control, were administered by intratracheal instillation to female Sprague-Dawley rats. Animals were terminated up to 28 days following treatment and pulmonary bioavailability of TCDD was assessed by hepatic enzyme induction and TCDD concentration. Enzyme induction was dependent on the duration of exposure with up to 56 and 918% increases in cytochrome P450 and aryl hydrocarbon hydroxylase (AHH) activity, respectively, following exposure to PCDD-contaminated soil. There was no significant difference in AHH induction between animals which received contaminated soil and those treated with the positive control. Hepatic concentration of TCDD in soil-exposed rats was 115, 101, and 179% of positive controls at 1, 7, and 28 days post-treatment, suggesting that the soil or co-contaminants influenced retention of TCDD in the liver. These data indicate that the relative pulmonary bioavailability of TCDD on respirable soil particles is 100% as compared to laboratory-recontaminated gallium oxide and that PCDDs and PCDFs are highly enriched on respirable particles. Utilization of these results will reduce the uncertainty and improve the accuracy of envi ronmental risk assessments of PCDDs and PCDFs.


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