A
carcinogenesis bioassay of
1,2-dibromoethane, a widely used nematocide and leaded
gasoline additive, was conducted by exposing groups of 50 F344 rats and B6C3F1 mice of each sex by inhalation to concentrations of 10 or 40 ppm of the
1,2-dibromoethane for 78-103 weeks. Untreated controls consisted of 50 rats and 50 mice of each sex exposed in chambers to ambient air. Throughout the study, mean
body weights of high-dose rats and high-dose mice of either sex were lower than those of the corresponding untreated controls. Survival of the high-dose rats of either sex and of the low- and high-dose female mice was significantly shorter than that in the corresponding controls. The principal cause of early death in control and dosed male mice was ascending, suppurative
urinary tract infection that resulted in necrotic, ulcerative lesions around the urethral opening, chronic or suppurative
cystitis (often with urinary tract obstruction), and ascending suppurative
pyelonephritis.
Carcinomas and
adenocarcinomas of the nasal cavity were observed with significantly increased incidences (P<0.001) in high-dose rats of either sex relative to controls. The incidences of
adenocarcinomas and
adenomas of the nasal cavity were also significantly increased (P<0.001) in low-dose rats of either sex.
Adenomatous polyps of the nasal cavity showed significantly increased incidence (P<0.001) in low-dose male rats. The combined incidence of alveolar/bronchiolar
adenomas and
carcinomas was statistically significant (P=0.024) for high-dose female rats.
Hemangiosarcomas of the circulatory system (mainly spleen) and
mesotheliomas of the tunica vaginalis occurred in high-dose male rats with significantly increased incidences (P<0.001) relative to controls. The incidence of
fibroadenomas of the mammary gland was significantly elevated (P<0.001) in dosed female rats relative to controls. The incidences of alveolar/
bronchiolar carcinoma and alveolar/bronchiolar
adenoma were significantly increased(P<0.001) in high-dose male mice relative to controls. These
tumors were also increased in high-dose female mice (P=0.007 for
adenomas and P<0.001 for
carcinomas).
Hemangiosarcomas occurred in low- and high dose female mice at incidences significantly greater (P<0.001) than the incidence in the controls (0/50). High-dose female mice also had significantly increased incidences of subcutaneous
fibrosarcomas (P<0.001) and of nasal cavity
carcinomas (P=0.013). Low-dose female mice also showed a significantly increased incidence (P<0.001) of mammary gland
adenocarcinomas. Exposure to
1,2-dibromoethane was also associated with hepatic
necrosis and toxic nephropathy in rats of either sex, testicular degeneration in male rats,
retinal degeneration in female rats, and epithelial
hyperplasia of the respiratory system in mice. Under the conditions of this bioassay,
1,2-dibromoethane was carcinogenic for F344 rats, causing increased incidences of
carcinomas,
adenocarcinomas,
adenomas of the nasal cavity, and
hemangiosarcomas of the circulatory system in males and females;
mesotheliomas of the tunica vaginalis and
adenomatous polyps of the nasal cavity in males; and
fibroadenomas of the mammary gland and alveolar/bronchiolar
adenomas and
carcinomas (combined) in females.
1,2-Dibromoethane was carcinogenic for B6C3F1 mice, causing alveolar/
bronchiolar carcinomas and alveolar/bronchiolar
adenomas in males and females; and
hemangiosarcomas of the circulatory system,
fibrosarcomas in the subcutaneous tissue,
carcinomas of the nasal cavity, and
adenocarcinomas of the mammary gland in females. Levels of Evidence of Carcinogenicity: Male Rats: Positive Female Rats: Positive Male Mice: Positive Female Mice: Positive Synonyms:
ethylene dibromide; EDB;
ethylene bromide