A new study suggests that moderate exposure to pesticides could yield long-term negative results to the people exposed to them. These findings should serve as warning to those who indiscriminately spray pesticides around the house, exposing their children, pets and other loved ones.

This new research shows that farmers who used agricultural insecticides experienced increased neurological symptoms, even when they were no longer using the products. Data from 18,782 North Carolina and Iowa farmers linked use of insecticides, including organophosphates and organochlorines, to reports of reoccurring headaches, fatigue, insomnia, dizziness, nausea, hand tremors, numbness and other neurological symptoms. Some of the insecticides addressed by the study are still on the market, but some, including DDT, have been banned or restricted.

These findings will be available online in April, and published in the June issue of Environmental Health Perspectives. The research is part of the ongoing Agricultural Health Study funded by the National Institute of Environmental Health Sciences and the National Cancer Institute, two of the National Institutes of Health, and the Environmental Protection Agency.

"This research is really important because it evaluated the health effects of agricultural chemicals as they were commonly used by farmers. It's different from previous studies that focused on pesticide poisoning or high dose exposures, for example when large amounts of a chemical were accidentally spilled on the skin," said Freya Kamel, Ph.D., a researcher for the National Institute of Environmental Health Sciences (NIEHS).

Researchers found that nearly 3,000 participants had a high lifetime exposure to insecticides--that is, they used insecticides more than 500 days in their lifetime. Nearly 800 of these farmers reported more than 10 neurological symptoms compared to those using insecticides fewer than 50 days. The researchers found no significant association between neurological symptoms and other chemicals, including herbicides or fungicides, and only a weak association between fumigant exposure and neurological symptoms.

Researchers found that nearly 3,000 participants had a high lifetime exposure to insecticides--that is, they used insecticides more than 500 days in their lifetime. Nearly 800 of these farmers reported more than 10 neurological symptoms compared to those using insecticides fewer than 50 days. The researchers found no significant association between neurological symptoms and other chemicals, including herbicides or fungicides, and only a weak association between fumigant exposure and neurological symptoms.

Some of the insecticides used by the licensed farmers over the past 25 years are no longer available commercially. DDT, a well known example of an organochlorine, has been banned for use in the US since 1972. Organophosphates, such as malathion, chlorypyrifos, and diazinon, have been banned or restricted for home and garden use in the US. However, some of the pesticides examined, including carbaryl and some pyrethroids, are available to home gardeners, although in different formulations and in lower concentrations, which may make them less hazardous.

"Because the participants in this study are telling us they have never been previously diagnosed with pesticide poisoning or medically treated for any exposure to any pesticide, we are led to conclude that their symptoms are related to moderate lifetime exposure," said Dr. Kamel.

Organophosphate insecticides, such as diazinon, disulfoton, azinphos-methyl, and fonofos, are used widely in agriculture and around the house. With over 25,000 brands of pesticides available in the United States, the use of organophosphates is probably more common than most people suspect. Many toxic nerve agents, used in milary applications are also also organophosphates.

Organochlorines are named as organic molecules bound with chlorine atoms. These include PCBs and DDT. Some organochlorines are also known as xenoestrogens because of their ability to mimic estrogen in the body. These compounds have been theorized to be at the root of a variety of estrogen-dominate illnesses in woman, like endometriosis and in wide spread genetic defects in wildlife like the three-legged frogs reported in Florida.

While this report does focus on farmers whose "moderate exposure" is likely higher than most people in the home, this report should serve as a caution to indiscriminate use of such products in the house and especially in the presence of children and those with weakened immune systems. Many of these compounds were initially popular because of their hardiness in the environment, meaning the compounds last longer to provide more killing effectiveness. This may be a good feature for the economics of agriculture and warfare, but at what consequence?