New research that has come to light shows a strong relationship between the use of pesticides and depression in farmers. In particular, farmers were substantially more likely to kill themselves as a result of their depression.
One woman from Iowa in the US, the wife of a farmer, spoke to Scientific American about how her husband’s depression set in suddenly, and drastically. He told her he felt paralysed and he could no longer sleep. Not longer afterwards, he killed himself.
Several studies have been done into the association between pesticide use and depression amongst farmers. A recent large-scale study involved 19 000 farmers and specifically focused on the relationship between their job and health.
The researchers found that subjects who used certain types of pesticide were at an increased risk of depression. One specific class of pesticide, organochorines, was associated with a 90% higher chance of being diagnosed with depression, according to the report, which was published in Environmental Health Sciences.
A similar study in France found similar results, with pesticide-using farmers twice as likely to be diagnosed with depression as those who didn’t. This effect was multiplied in farmers who had been using pesticides for many years.
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When it comes to suicide, there are further studies supporting the association. A World Health Organisation study conducted in China found that people who stored pesticides in their home were at twice the risk of having suicidal thoughts.
A US study conducted in Iowa discovered that farmers as a whole were 3.6 times more likely to die from suicide than other jobs, though the cause of the suicide was not recorded.
While the causal link between pesticides and depression has not been discovered, there are clear reasons why the correlation seems believable.
Many commercial pesticides work by targeting the nervous systems of invasive organisms, such as the pests that invade crops.
Similarly, tests in rats have shown that pesticides can actually alter the structure of brain cells, according to a study in Ecotoxicology and Environmental Safety.
Perhaps more important, though, is a study in Toxicology and Applied Pharmacology which observed the effect of pesticides on neurotransmitters in rats' brains. The study found that receptors became less sensitive following pesticide exposure, severely so in the long term.
Impaired neurotransmitter functioning is one of the primary causes of depression, and any tampering with this delicate system is likely to lead to mental issues. Farmers are, by the nature of their job, exposed to varying levels of pesticides for long periods of time.
Farmers aside, these results also raise concerns for those living near pesticide-using farms. Winds could easily below substantial quantities of pesticides into homes, exposing unsuspecting people to potentially hazardous chemicals.
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Any chemical used on farms undergoes rigorous testing to ensure that it doesn’t have any serious health consequences. However, less tangible conditions like depression are often neglected, despite having a clear physiological basis.
The pesticides used in the study were: the fumigants aluminum phosphide and ethylene dibromide; the phenoxy pesticide 2,4,5-trichlorophenoxyacetic acid (2,4,5-T); the organochlorine insecticide dieldrin; and the organophosphate insecticides diazinon, malathion and parathion, according to Scientific American.
Most organochlorine pesticides are now banned in the US and many other countries. However, their use is still prevalent in South Africa. A 2008 study in Science of the Total Environment found high levels of organochlorine pesticides in the air in Durban, and another study concluded that the Jukskei River is “definitely polluted” by organochlorine pesticides.
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Image credit: Sad Farmer from Shutterstock