Review of recent toxicology studies on p-dichlorobenzene.

Results from recent long-term inhalation, mutagenicity, embryotoxicity and metabolism studies on p-dichlorobenzene (p-DCB) are reviewed. Groups of male and female rats and female mice were exposed for 5 hr/day on 5 days/wk to p-DCB at concentrations of 0, 75 or 500 ppm for a total period of c. 76 wk (rats) or 57 wk (female mice) followed by 36 wk (rats) or 19 wk (female mice) without p-DCB exposure. No overt signs of toxicity were apparent at any exposure level nor were there treatment-related effects on the biochemical determinations, urine analyses or haematological parameters. Slightly elevated urinary coproporphyrin excretion and increased liver and kidney weights were regarded as treatment-related effects in the 500-ppm exposure group of the rats. The non-tumour and tumour pathology did not indicate any treatment-related effect in any group of either species. An embryotoxicity and teratology study on rats exposed to 0, 75, 200 or 500 ppm p-DCB vapour in air during the period of organogenesis did not demonstrate any signs of embryo- or foetotoxicity or teratogenicity at any exposure level. In a series of mutagenicity tests including the Salmonella typhimurium, dominant lethal and cytogenetic assays, p-DCB did not produce a mutagenic response. Studies using oral or inhalation routes of exposure demonstrated rapid metabolic transformation of p-DCB and excretion of the products, even after long-term exposure.