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authors also reported an increase in incidence of cholangiomas, but these lesions were designated by
CDHS as benign, since no specific discussion of their malignancy was given.
Brunner et al. (1996) fed male and female Sprague-Dawley rats (50 animals/sex/Aroclor dose group)
diets containing 25, 50 or 100 ppm Aroclor 1260 or 1254; 50 or 100 ppm Aroclor 1242; or 50, 100
or 200 ppm Aroclor 1016 for 104 weeks. Control groups were also included (100 animals/sex).
Surviving animals were killed at 104 weeks. Statistically significant increases in liver adenoma or
carcinoma incidence were observed in female rats for all Aroclors tested, and in male rats for Aroclor
1260 (Table 1).
Table 1.
Liver tumor incidence in Sprague-Dawley rats exposed to PCBs (Brunner et al.,
1996; contained in US EPA, 1996a)
Mixture Exposure level Tumor incidence
(ppm) Females Males
Aroclor 1260 0
** 1/85 (1%)
** 7/98 (7%)
25 10/49 (20%) 3/50 (6%)
50 11/45 (24%) 6/49 (12%)
100 24/50 (48%) 10/49 (12%)
Aroclor 1254 0
** 1/85 (1%) 7/98 (7%)
25 19/45 (42%) 4/48 (8%)
50 28/49 (57%) 4/49 (8%)
100 28/49 (57%) 6/47 (13%)
Aroclor 1242 0
** 1/85 (1%) 7/98 (7%)
50 11/49 (24%) 1/50 (2%)
100 15/45 (33%) 4/46 (9%)
Aroclor 1016 0
** 1/85 (1%) 7/98 (7%)
50 1/48 (2%) 2/48 (4%)
100 6/45 (13%) 2/50 (4%)
200 5/50 (10%) 4/49 (8%)
** Statistically significant (p < 0.05) by Cochran-Armitage trend test.
In mice, two studies indicate that PCBs are carcinogenic, particularly with respect to hepatocarcinomas.
Kimbrough and Linder (1974) exposed groups of 50 male BALB/cj mice to Aroclor 1254 at 0 or 300
ppm in the diet for 11 months, or for 6 months with a 5 month recovery period. The incidences of
hepatoma were 0/34, and 0/24 for the 11- and 6-month exposure groups, respectively. The treated
animals had incidences of 9/22, and 1/24 for the 11- and 6-month groups, respectively.
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