Of great concern has been the potential association between cancer incidence and exposure to DDT, especially via an environmental route. Studies of the mutagenicity of DDT and its significance in human beings have not yielded clear results. Although DDT acts as a hepatocarcinogen at high doses in some strains of mice, there is no convincing evidence for this effect in human beings. No case studies or epidemiological investigations concerning the carcinogenic effects in humans after dermal exposure exclusively to DDT, DDE, or DDD were located. Data collected during DDT skin painting of mice did not showed a significant increase in tumor incidence.
Occupational exposure to DDT in a case control study of the Uruguayan work force was associated with increased lung cancer. Elevated, but not statistically significant, odds ratios for any type of lung cancer were observed in workers who had been exposed for 120 years. Significantly elevated odds ratios were reported in a subset of DDTexposed lung cancer patients with small cell cancer or in patients with adenocarcinoma. Analyses were adjusted for age, residence, education, tobacco smoking, and alcohol consumption.
No studies were located regarding cancer in animals after inhalation exposure to DDT, DDE, or DDD. EPA (IRIS 2001a, 2001b, 2001c) calculated an inhalation unit risk of 9.7x105 per μg/m3 for DDT from oral data in animals.
Many epidemiological studies have investigated the association between breast cancer and levels of DDT and DDTderived compounds in blood or adipose tissue from humans. Some studies have suggested a positive association, while others do not support such an association.
The Department of Health and Human Services (DHHS) determined that DDT may reasonable be anticipated to be a human carcinogen. The International Agency for Research on Cancer (IARC) determined that DDT may possibly cause cancer in humans. According to the U.S. EPA Carcinogen List there is a sufficient evidence of DDT carcinogenicity from animal studies with inadequate or no data from epidemiologic studies in humans, there for it is classified as a Category B2, Probable human carcinogen.