Neurobehavioral development of rats exposed to toluene through maternal milk

Organic solvents have been detected in the milk of workers in the rubber industry exposed during gestation to a mixture of solvents at average concentrations lower than the currently accepted occupational limit of exposure (100 ppm). The objective of the present study was to determine if exposure of rat offspring to toluene during lactation, through maternal milk, would affect the developing brain. Three month old, lactating Wistar rats were injected with toluene (1.2 g/kg, sc, N = 10) daily from lactation day 2 (day of delivery = day 1) to day 21. Controls (N = 9) were injected with the vehicle (corn oil). Offspring (7 pups per liter) were evaluated for neurosomatic development and exploratory behavior before weaning and behavior in the open field. A second group of toluene-treated rats (N = 6) and controls (N = 6) was used to evaluate behavior of the offspring in the open-field on day 35 and performance in a shuttle box in adulthood. Toluene levels in blood and milk after a single 1.2 g/kg sc injection were studied in a third group of rats on lactation day 10. Toluene levels in milk 4 h after a single injection (10.3 +/- 6.2) were 5 times higher than in blood (2.1 +/- 0.8). No effects of treatment on offspring development or on any of the behavioral tests were observed. Sex differences were observed in open-field behavior and performance in the shuttle box. The present results suggest that exposure of pups to high concentrations of toluene through maternal milk does not result in blood levels high enough to affect growth or development.