CHRONIC INHALATION TOXICITY AND ONCOGENICITY OF METHYL-METHACRYLATE IN RATS AND HAMSTERS

Male and female Fischer 344 rats were exposed to methyl methacrylate ( MMA) monomer vapours at 0, 25, 100 and 400 ppm, 6 hr/day, 5 days/wk fo r 24 months and male and female Golden hamsters were exposed to simila r vapour concentrations of MMA for 18 months. Parameters monitored thr oughout the study included clinical signs, individual body weights, ha ematology, clinical chemistry (rats only) and urinalyses (rats only). 10 rats per sex per exposure group were killed after 13 and 52 wk of e xposure and all surviving rats were killed during wk 104-106. All surv iving hamsters were killed at wk 78. Mortality and haematological, cli nical chemistry and urinalyses parameters were not affected by MMA exp osure. Body weights of male rats were not affected by exposure to MMA while body weights of female rats exposed to 400 ppm were lower than c ontrol values after wk 52. Male and female hamsters exposed to 400 ppm had body weight decreases ranging from 9 to 12% after wk 48. The nasa l cavity was identified as the target organ for chronic toxicity in ma le and female rats exposed to 100 or 400 ppm. The microscopic nasal ca vity changes occurred primarily in olfactory epithelium lining the dor sal meatus and consisted of degeneration of neuroepithelium, basal cel l hyperplasia and atrophy of Bowman's glands. Hamsters did not have de monstrable nasal cavity microscopic changes. Chronic exposure to MMA v apour did not cause tumours in either rats or hamsters. (C) 1997 Elsev ier Science Ltd.