(Beyond Pesticides, October 15, 2014) A new study published in Environmental Health Perspectives finds a strong relationship between the use of pesticides and depression in farmers. One specific class of pesticide, organochlorines, was associated with a 90% higher chance of being diagnosed with depression. For fumigants, the increased risk was up to 80 percent. This study echoes the conclusion from an earlier French study which also reported that farmers using pesticides face a greater risk of developing depression.
The study, Pesticide Exposure and Depression among Male Private Pesticide Applicators in the Agricultural Health Study, examines possible associations between pesticide exposure and depression among male private pesticide applicators in the Agricultural Health Study (AHS). Over 21,000 applicators who enrolled in the study in 1993—1997 were followed and examined. The applicators were asked about depression when enrolled in the study and then again around 2010. Previous work with this AHS sample found a higher prevalence of depression among male applicators who reported past pesticide poisoning or use of pesticides from several different classes. However, this study examines specific pesticides, and finds that two types of pesticides, fumigants and organochlorine insecticides are positively correlated with depression and cumulative days of use. Those exposed to organochlorine pesticides have a 90 percent risk of developing depression, while for fumigants the increased risk was up to 80 percent. Several individual pesticides, the fumigants aluminum phosphide and ethylene dibromide, the phenoxy herbicide (2,4,5-trichlorophenoxy)acetic acid (2,4,5-T), the organochlorine insecticide dieldrin, and the organophosphate insecticides diazinon, malathion, and parathion are also positively correlated. Of these, aluminum phosphide, diazinon, and malathion are still registered and in use in the U.S.
“I don’t think there’s any question that pesticides can affect the functions of the brain. There could also be indirect effects. Pesticides can promote other health problems, which could be related to depression,” said lead researcher Freya Kamel, PhD.
The authors report several strengths of their study, including its large size. Additionally, its prospective nature provided the opportunity to identify cases of depression diagnosed before and after the study period. Detailed information on applicators’ exposures, including general pesticide exposure, use of pesticide classes, and use of individual pesticides was also collected. The authors report similar results when they analyze the same group from 1993 to 1997. At that time, farmers with the highest cumulative exposure days to pesticides were 50 percent more likely to have a depression diagnosis. In 2013, a French study found that farmers using herbicides are nearly two and a half times as likely to be treated for depression as those who did not use herbicides, and that farmers who are exposed for greater periods of time are also afflicted with greater risk of developing depression.
Previous research has already suggested that pesticides, particularly organophosphates, cause a variety of serious neurological health problems, including Parkinson’s disease. This is not surprising, as organophosphates are known to be extremely toxic to nerve cells and deadly at large doses. However, risks from long-term low-dose exposure also exist. A 2012 study that sourced data from 14 studies over the past 20 years found that long-term, low-dose exposure to organophosphates can damage neurological and cognitive functions. Other studies have also connected low-dose exposure to organophosphates to ADHD, reduced IQs, and Alzheimers.
Organophosphates are a common class of chemicals used as insecticides. Several have already been banned or highly restricted in several European countries and in the U.S. In addition to being potent neurotoxins, organophosphates pesticides are extremely harmful to the nervous system, as they are cholinesterase inhibitors and bind irreversibly to the active site of an enzyme essential for normal nerve impulse transmission. Despite numerous organophosphate poisonings of farmworkers, homeowners, and children, the U.S. Environmental Protection Agency (EPA) has allowed the continued registration of many of these products. In the case of chlorpyrifos and diazinon, household uses of the products have been canceled because of the extreme health risks to children, but agricultural, golf course, and “public health” (mosquito control) uses remain on the market.
Through the Pesticide Induced Diseases Database (PIDD), Beyond Pesticides keeps track of the most recent studies related to pesticide exposure. For more information on the multiple harms of pesticides, see the PIDD pages on Alzheimer’s, Parkinson’s, cancer, and other diseases.
Studies such as these highlight the importance of buying, growing, and supporting organic. Consumer choices encourage the protection of the people who help put food on our table every day by purchasing organic. By buying organic, you support an agricultural system that does not rely on the widespread application of dangerous pesticides. For more information on how organic is the right choice for both consumers and the farmworkers that grow our food, see Beyond Pesticides webpage, Health Benefits of Organic Agriculture.
All unattributed positions and opinions in this piece are those of Beyond Pesticides.
Source: Environmental Health News