In the U.S., farmers dependent on genetically engineered (GE) Roundup Ready soybean crops are increasingly running into a problem. Weeds are quickly becoming resistant to Roundup herbicide, leaving the farmers desperate for an effective chemical alternative.
Paraquat is being marketed as one such alternative, but this pesticide is highly toxic to humans, according to the U.S. Environmental Protection Agency (EPA), to the extent that just one sip can be fatal.1
Sadly, it's become an herbicide commonly used for suicide attempts,2 but in countries that have banned its use, such as South Korea, suicide rates dropped significantly.
The association was so strong that researchers wrote in 2015, "Paraquat prohibition should be considered as a national suicide prevention strategy in developing and developed countries."3
Europe is ahead of the game, as they've already prohibited the use of paraquat. In all, 32 countries have banned the chemical.4
In Switzerland, paraquat has been banned since 1989, but the country still allows it to be produced, as long as it's shipped for use elsewhere, like in the U.S., where use is actually growing dramatically.
Despite Parkinson's Concerns, Use of Paraquat in US Increases
Paraquat is banned in Europe not only because of its highly lethal nature but also because it's linked to Parkinson's disease. The EPA is aware of the issue, and reported "a large body of epidemiology data on paraquat dichloride use and Parkinson's disease."5
They're currently reviewing whether to allow continued use in the U.S., but not with the urgency one would expect; a decision isn't even expected until 2018. In the meantime, its connection to Parkinson's disease grows.
"Paraquat causes tissue damage by setting off a redox cycle that generates toxic superoxide free radicals," researchers wrote in the International Journal of Environmental Research and Public Health.6
In acute exposures, it typically kills by damaging lung tissue, as one biochemist and toxicologist explained in a warning about paraquat:7
"I should warn you that it probably has killed more people than all other pesticides combined. It is taken up by a transport system in the lung where it generates a variety of reactive oxygen species and burns the lungs; people normally drown several weeks later of pneumonia.
There is no antidote. Most deaths now are suicides and murders, with a few accidents thrown in."
Chronic exposures, however, are known to damage the nervous system. Paraquat is often applied in the same areas as another pesticide, maneb, and it's believed the two have synergistic effects.
One study published in the American Journal of Epidemiology revealed that exposure to both pesticides within 500 meters of the home increased the risk of Parkinson's disease by 75 percent.8
Even the EPA noted that paraquat may be a causative agent or contributor to the development of Parkinson's disease,9 and in 2011 a National Institutes of Health study found people who used paraquat were 2.5 times more likely to develop Parkinson's than non-users.10
A meta-analysis of more than 100 studies similarly found a two-fold increased risk of Parkinson's with paraquat exposure,11 while those with a certain genetic variant (individuals lacking glutathione S-transferase T1, or GSTT1) may face a particularly increased Parkinson's risk — by 11-fold — with paraquat exposure.12
In the U.S., the use of paraquat has increased four-fold in the last 10 years. In 2015 alone, 7 million pounds of the herbicide were sprayed on close to 15 million U.S. acres.13
EPA Proposes Label Changes Due to Paraquat Poisonings
The EPA reported a "large number of human incidents" involving accidental and intentional consumption of paraquat that have been reported to U.S. poison control centers.
"There is a disproportionately high number of deaths resulting from accidental ingestion of paraquat compared to similar pesticides," they noted, which led to so-called "safening" agents being added to the chemical in the 1980s.14
The pesticide was dyed blue and now includes a special addition to make it smell terrible. It's also formulated to solidify when it contacts stomach acid and an emetic was added to induce vomiting should it be ingested.
Accidental poisonings have occurred nonetheless, particularly when farmers transfer the chemical into beverage containers for storage or sharing, despite warnings against doing so on the label.
The EPA therefore proposed a new set of changes they believe will make paraquat safer to use while again avoiding the burning question, which is why paraquat is still allowed in the U.S. at all.
Paraquat is already a restricted-use product in California, but EPA proposals would restrict its use nationally. Their proposed changes include:15
• New closed-system packaging that make it impossible to transfer the pesticide into other packaging
• Special training for applicators, emphasizing the importance of not transferring it to improper containers
• Warnings added to labels to highlight risks and toxicity
• Prohibiting application from hand-held and backpack equipment
• Restricting use to certified pesticide applicators only