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Pesticide DDT linked to heightened Alzheimer's risk

The pesticide DDT, banned in the United States since 1972 because of its toxic effects on wildlife and potential to harm human health, may increase the risk for Alzheimer's disease, a new study finds.

People with the disease had about four times the level of a DDT byproduct in their blood, compared with those who didn't have dementia, according to the research published Monday in the journal JAMA Neurology.

DDT, or dichlorodiphenyltrichloroethane, is still found in blood samples because it can take decades for chemicals to break down. The pesticide is used in other countries, and U.S. residents can ingest it by eating fruits, vegetables and grains that are grown in those areas, researchers said.

The study points to the need for more analysis about how environmental factors may interact with genes to boost Alzheimer's risk, said Jason Richardson of the Robert Wood Johnson Medical School at Rutgers University, lead author of the study.

"The prevailing thought has always been it's a genetic disease. Unfortunately, that hasn't panned out," he said.

Just how DDT and its byproduct, DDE, are linked to Alzheimer's disease remains unclear. The pesticide may affect levels of proteins in the brain that are associated with the plaque that leads to the disease, Richardson said.

More than 5 million people in the United States have Alzheimer's, a number projected to triple by 2050, according to the Alzheimer's Association.