As part of a comparative chronic toxicity/oncogenicity study of different
Aroclors (1016, 1242, 1254, and 1260), neurotoxicity was assessed in male and female Sprague-Dawley rats using functional observational battery (FOB) and motor activity tests, and histopathologic evaluation of selected nervous system tissues. Doses varied by
Aroclor and ranged from 25 to 200 ppm in the diet. Animals were evaluated prior to initiation of dosing and at 13, 26, 39, and 52 weeks of exposure. Clinical signs,
body weights, and feed consumption were evaluated weekly. Data analysis of FOB and motor activity results revealed several instances where
Aroclor-treated groups were different from control. However, these were considered incidental, as they lacked any consistent dose- or time-related pattern that would suggest
Aroclor-induced neurotoxicity. The nonremarkable findings during each of the four assessments were supported by the absence of any treatment-related clinical signs or mortality. Decreased
body weight gain was evident in the male 100 ppm
Aroclor 1254 dose group and in all female
Aroclor 1254 dose groups late in the study (when a linear relationship was assumed between
body weight and time), correlating with decreased feed consumption. Although a variety of incidental, spontaneous, degenerative changes were found in nervous tissue evaluated histopathologically, these changes were seen with similar incidence and severity in treated and control groups. No lesions were found that could be attributed to
Aroclor-related neurotoxicity. In summary, 52 weeks of exposure to
Aroclors 1016, 1242, 1254, or 1260 mixed in the diet did not yield any functional or morphologic changes indicative of PCB-induced neurotoxicity.