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Table 1: Tumor incidence data in rats and mice exposed to ethylene dichloride (NCI, 1978).
Tumor Type
Male rats
Squamous cell carcinoma
(forestomach)
Exposure Concentration (mg/kg-day)
0 47 95
0/60 3/50 9/50*
Hemangiosarcoma 1/60 9/50* 7/50*
Female rats
Hemangiosarcoma 0/59 4/50* 4/50*
Mammary adenomas 1/59 1/50 18/50*
Male mice
Exposure Concentration (mg/kg-day)
0 97 195
Hepatocellular carcinomas 4/59 6/47 12/48*
Alveolar/bronchiolar
adenomas
Female mice
Alveolar/bronchiolar
adenomas
0/59 1/47 15/48*
Exposure Concentration (mg/kg-day)
0 149 299
2/60 7/50* 15/48*
Mammary adenocarcinoma 0/60 9/50* 7/48*
Endometrial polyp or
stromal sarcomas
0/60 5/49* 5/47*
*Significantly increased incidence in treated animals compared with pooled vehicle controls; significance
calculated using Fisher Exact Test (one-tailed); p ≤ 0.05.
Maltoni et al. (1980) conducted extensive inhalation carcinogenicity studies in Sprague-Dawley rats and
Swiss mice. Four groups, each consisting of 180 rats or mice of both sexes, were exposed to EDC
concentrations of 5, 10, 50, or 150-250 ppm, respectively, seven hours/day, five days/week, for 78
weeks. Two groups of 180 rats per sex, or one group of 249 mice, served as controls. Although all
animals received a lifetime exposure and extensive histopathology was performed on each animal, no
significant increased in tumor incidences were seen (Maltoni et al., 1980).
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