Exposure to the toxic pesticide DDT has another potentially harmful side effect: increasing the risk of Alzheimer's disease, a new study from Rutgers University finds. The study is the first time a link has been shown between DDT and Alzheimer's disease. DDT, a synthetic pesticide that was banned in the U.S. in 1972, has well-documented health risks, including liver cancer and damage to the nervous system, and was also linked to premature birth and fetal health defects in 2001.

The study discovered that late-onset Alzheimer's patients showed higher levels of DDE, the chemical left over after the breakdown of DDT, in their blood compared to those who did not have the disease. Over 5 million Americans have Alzheimer's disease, according to the Alzheimer's Association, a number which is expected to rise over the next few years. The cost of caring for Alzheimer's cost the U.S. $203 billion in 2013, and is expected to reach $1.2 trillion by 2050, the association said.

Researchers found that 74 out of the 86 Alzheimer's patients they looked at had DDE blood levels nearly four times higher than the 79 people in the group who didn't have Alzheimer's. DDE and DDT levels take decades to break down in the environment, which may explain their presence in the blood of Alzheimer's patients. The study also found that patients with a variation of the ApoE gene, which increases the risk of developing Alzheimer's, combined with high DDE blood levels, showed much worse brain deterioration than those without the gene.

"This study demonstrates that there are additional contributors to Alzheimer's disease that must be examined and that may help identify those at risk of developing Alzheimer's," said Jason R. Richardson, associate professor in the Department of Environmental and Occupational Medicine at Robert Wood Johnson Medical School at Rutgers University. "It is important because when it comes to diagnosing and treating this and other neurodegenerative diseases, the earlier someone is diagnosed, the more options there may be available."

Recent studies have discovered ways to potentially prevent developing Alzheimer's, suggesting that improving your diet can protect against the disease. Alzheimer's may also be worsened by stress and exposure to copper.

DDT was introduced as a pesticide during World War II and was used for insect control in crops and to combat insect-carried diseases like malaria. The Pesticide Action Network, a group that looks into pesticide alternatives, says that Americans are still living with the effects of DDT today, over 40 years since it was banned. Products from the breakdown of DDT can still be found in 60 percent of heavy cream samples and 42 percent of kale greens. Yikes.