Exposure of pregnant mice to the pesticide DDT is linked to an increased risk of obesity, diabetes, high cholesterol and related conditions in female offspring later in life, according to a study led by the University of California, Davis.
The study, published online July 30 in the journal PLOS ONE, is the first to show that developmental exposure to DDT increases the risk of females later developing metabolic syndrome — a cluster of conditions that include increased body fat, blood glucose and cholesterol.
DDT was banned in the United States in the 1970s but continues to be used for malaria control in countries including India and South Africa.
Scientists gave mice doses of DDT comparable to exposures of people living in malaria-infested regions where it is regularly sprayed, as well as of pregnant mothers of U.S. adults who are now in their 50s.
“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,” said lead author Michele La Merrill, assistant professor of environmental toxicology at UC Davis.
The scientists found that exposure to DDT before birth slowed the metabolism of female mice and lowered their tolerance of cold temperature. This increased their likelihood of developing metabolic syndrome and its host of related conditions.
“As mammals, we have to regulate our body temperature in order to live,” La Merrill said. “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.”
The study found stark gender differences in the mice’s response to DDT. Females were at higher risk of obesity, Type 2 diabetes and cholesterol, but in males, DDT exposure did not affect obesity or cholesterol levels and caused only a minor increase in glucose levels.
A high fat diet also caused female mice to have more problems with glucose, insulin and cholesterol but was not a risk factor for males. The sex differences require further research, the authors said.
The study was funded by the National Institute of Environmental Health Sciences.
Co-authors include Emma Karey and Michael La Frano of UC Davis; John Newman of UC Davis and the U.S. Department of Agriculture; and Erin Moshier, Claudia Lindtner, and Christoph Buettner of Mount Sinai School of Medicine.
About UC Davis
UC Davis is a global community of individuals united to better humanity and our natural world while seeking solutions to some of our most pressing challenges. Located near the California state capital, UC Davis has more than 34,000 students, and the full-time equivalent of 4,100 faculty and other academics and 17,400 staff. The campus has an annual research budget of over $750 million, a comprehensive health system and about two dozen specialized research centers. The university offers interdisciplinary graduate study and 99 undergraduate majors in four colleges and six professional schools.
In the past five decades, the case that DDT and its daughter metabolites damage human health in subtle but extremely destructive ways constantly mounted. Perhaps Rachel Carson was right to urge much more study of the stuff, in Silent Spring. Perhaps the National Academy of Sciences was right when it called for a rapid phasing out of DDT use in 1970, after noting it had been one of the greatest lifesaving pesticides ever known.
In 1972 the U.S. Environmental Protection Agency prohibited use of DDT in agriculture. Use in day-to-day indoor extermination had ended earlier; bedbugs had become almost wholly immune to DDT by 1960. The U.S. ban was predicated on damage to wildlife, not human health. The order allowed U.S. DDT manufacturers to continue to make the stuff for export to other nations. Exports continued from 1972 to 1984, when the Superfund required manufacturers to clean up any pollution they may have caused.