INHALATION TOXICITY STUDIES OF AQUEOUS DISPERSION RESIN

Abstract

Aqueous dispersion resin (ADR) is a water-based acrylate copolymer designed to allow a range of ethanol concentrations for hair-spray formulations. A series of inhalation (whole-body) aerosol toxicity studies, including acute, 9-day, and 90-day exposures, was conducted to determine any toxicological effects for ADR. An acute study of ADR was conducted for 4 h with a 14-day observation period. The maximum ADR aerosol concentration was 1.07 (+/- 0.04) mg/L with a mass medium aerodynamic diameter (MMAD) value of 1.46 mu m and a geometric mean (sigma_g) of 1.42. No deaths or exposure-related lesions were observed. Thus, the LC50 value was greater than 1.07 mg/L. For the 9-day study, each group contained 10 animals/sex and was exposed for 2 h/day. The mean exposure concentrations (+/- standard deviation) were 244 (+/- 39.6), 543 (+/- 71.9), and 843 (+/- 186.2) mg/m³ for the 250-, 500-, and 1000-mg/m³ groups, respectively. The mean MMADs were 2.83, 2.90, and 4.09 mu m for the 250-, 500-, and 1000-mg/m³ groups, respectively, with sigma g values ranging from 3.15 to 6.22. Unkempt fur and alopecia in the males and females from the 1000-mg/m³ group at sacrifice were the only exposure-related clinical signs observed. Increased lung weights in the 500- and 1000-mg/m³ exposure groups were found. Histopathological effects, such as alveolar histiocytosis and interstitial pneumonitis, were also noted in these two exposure groups. For the 90-day study, 10 animals per sex were included in each group with a 6-wk recovery group of 5 female rats/group. Exposures were conducted for 2 h/day. The mean exposure concentrations were 30.4 (+/- 2.3), 102 (+/- 11.6), and 308 (+/- 19.3) mg/m³ with mean MMADs of 3.09, 2.64, and 2.67 mu m and sigma_g values ranging from 3.54 to 3.90 for exposure concentrations of 30, 100, and 300 mg/m³, respectively. The only findings at the 90-day sacrifice were increased lung weights for the males and females in the 300-mg/m³ group and males in the 100-mg/m³ group. For the 6- wk recovery sacrifice of the females, the lung weights for the 300- and 100-mg/m³ groups were increased. Histopathological effects at the 90-day sacrifice included alveolar histiocytosis and lymphadenitis in the mediastinal lymph nodes in the 100- and 300-mg/m³ exposure groups for males and females, while alveolar histiocytosis, intraalveolar cellular debris, lymphadenitis in the mediastinal lymph nodes, and/or interstitial pneumonitis were noted in these 2 exposure groups of the females after the 6-wk recovery period. Animals exposed for 90 days to 100 and 300 mg/m³ for 2 h had increased lung weights. However, no effects were observed in the 30-mg/m³ exposure group. Thus, under the conditions of the present 90-day study, a no-observable-effect level (NOEL) was found to be 30 mg/m³.