An airplane spraying DDT over Baker County, Oregon as part of a spruce budworm control project, 1955. Credit: USDA Forest Service
Key points:
- Exposure to DDT can trigger changes to the heritable sperm epigenome and may raise risk of birth defects and disease.
- Men in South Africa are exposed to the banned toxin as the country has special permission to use it in the fight against malaria.
- The number of people and animals exposed to DDT is reportedly increasing due to climate change.
A decade-long research project has found that fathers exposed to environmental toxins—notably DDT—may produce sperm with health consequences for their children.
The study examined the impact of DDT on the sperm epigenome of South African Vhavenda and Greenlandic Inuit men, some of whom live in Canada’s North. Despite a global ban on DDT, the South African government has special permission to use it as an insecticide to control malaria.
Published in the journal Environmental Health Perspectives, the study demonstrates a link between long-term exposure to DDT and changes in the sperm epigenome. These changes, particularly in genes vital for fertility, embryo development, neurodevelopment, and hormone regulation, correspond to increased rates of birth defects and diseases, including neurodevelopmental and metabolic disorders.
In some areas of South Africa, home interiors are coated with the toxin to help prevent malaria, which is still an epidemic. Thus, families cannot afford to refuse spraying their houses—though the side effects are clearly undesirable as well.
“We identified regions of the sperm epigenome that are associated with the serum levels of DDE (chemicals that form when DDT breaks down) and this association follows a dose-response trend. I think that's quite striking, in that the more DDE you’re exposed to, the higher the chromatin, or DNA methylation defects are in the sperm,” said Ariane Lismer, the study’s lead author, who completed the work while pursuing her PhD at the University of McGill.
What’s more, the number of people and animals exposed to DDT is reportedly increasing due to climate change. DDT can travel vast distances through what is known as the “grasshopper effect,” evaporating with warm air and returning to Earth with rain and snow in colder regions, where it persists in the Arctic food chain.
“We demonstrate the sperm epigenome’s response to toxin exposures may be linked with disease in the next generation,” said Sarah Kimmins, who led the research as a professor of pharmacology at McGill. “This is a critical new step for the field because while there are many studies of animals demonstrating toxin effects on the sperm epigenome, studies in humans have not comprehensively demonstrated this.”
Although the study focuses on DDT exposures, the researchers say it is not a leap to suggest that exposures to more common household endocrine disruptors such as those found in cosmetics and personal care items may act similarly.