DDT exposure linked to liver cancer in humans

NEW YORK (Reuters Health) - High blood levels of the pesticide DDT are associated with an elevated risk of liver cancer, according to the results of a study conducted in China.

Previous reports have linked DDT and its breakdown product DDE with liver tumors in laboratory animals. Whether exposure to this pesticide is associated with liver cancer in humans, however, has been less clear.

To investigate, Dr. Katherine A. McGlynn, from the National Cancer Institute in Rockville, Maryland, and colleagues analyzed data from 168 "case" patients with liver cancer and 385 age- and sex-matched healthy controls who participated in the Nutritional Intervention Trials in Linxian. DDT and DDE serum levels were measured using gas chromatography-mass spectrometry.

The risk of liver cancer was directly related to the DDT serum level, McGlynn's group reports in the current Journal of the National Cancer Institute. Subjects in the highest DDT quintile were nearly four times more likely to develop liver cancer than those in the lowest quintile.

The DDE level alone was not significantly associated with liver cancer risk. However, in conjunction with a high DDT level, a low DDE level appeared to increase the risk further.

In terms of absolute risk, the highest DDT quintile was tied to a liver cancer rate of 46 cases per 100,000 persons per year compared with a rate of 26 cases per 100,000 persons per year for the lowest quintile.

The results suggest that DDT exposure may be a risk factor for the development of liver cancer in humans, "especially in populations that are directly exposed to DDT, rather than just exposed to its metabolites," the authors conclude.

SOURCE: Journal of the National Cancer Institute, July 19, 2006.