Exposure to the pesticide DDT, which has been linked to a raft of diseases, has now been shown to lower body heat in the female offspring of mice later in their lives. Slower metabolic rate raised the likelihood of obesity, diabetes, and high cholesterol in the mice and could suggest cause for concern in U.S. populations of women in their 50s, researchers at the University of California, Davis, said Wednesday.
"As mammals, we have to regulate our body temperature in order to live," said lead author Michele La Merrill, an environmental toxicologist, in a news release. "We found that DDT reduced female mice's ability to generate heat. If you're not generating as much heat as the next guy, instead of burning calories, you're storing them." (In another recent study, scientists said sleeping in the cold causes the body to work harder to maintain warmth, raising metabolism.)
DDT has been outlawed in the United States since 1972 when the newly formed Environmental Protection Agency concluded its use was a danger to wildlife and human health. Many countries, however, still use it to battle mosquitoes carrying malaria. Over the years, scientists have conducted numerous studies mainly focused on possible links to cancer. To date, the EPA says, DDT is generally considered a "probable" carcinogen based on animal studies. It has also been associated with premature births, low birth weight, and developmental problems.
The UC Davis study, which appears in the journal PLOS ONE, is the first to link in utero DDT exposure to metabolic syndrome later in life. "The women and men this study is most applicable to in the United States are currently at the age when they're more likely to develop metabolic syndrome, because these are diseases of middle to late adulthood," La Merrill said. For example, the child of a pregnant woman exposed in 1959 would now be in her mid-50s, the age of peak risk even without DDT exposure.
Curiously, male mice in the study did not show any increased risks. According to the news release, "Females were at higher risk of obesity, type 2 diabetes, and cholesterol, but in males, DDT exposure did not affect obesity or cholesterol levels." At worst, males experienced slightly higher glucose levels. The scientists say future studies will have to probe the sex differences.
Source: La Merrill M, et al. PLOS ONE. 2014.