Are common herbicides safe to use?
July 17th, 2015
Farmers count on chemical herbicides to keep their fields weed-free. But exposure to weed-killing chemicals could come at a cost. Scientists recently looked at two of the most heavily used farm chemical to determine whether they could cause cancer.
In the last few months scientists brought together by theÂ International Agency for Research on Cancer, or IARC, considered glyphosate and 2,4-D.[audio:https://kvnonews.com/wp-content/uploads/2015/07/888_HERBICIDE_KVNO.mp3]
IARC is part of the World Health Organization. The agency assembles scientific panels to evaluate data on different chemicals and decide if there is evidence they could cause cancer. ItÂ has reviewed nearly 1,000 chemicalsÂ over the last 50 years andÂ categorized themÂ as causes cancer, probably causes cancer, possibly causes cancer, not classifiable, or non-carcinogenic.
TheyÂ looked at glyphosate, the active ingredient in Monsantoâ€™s Roundup, and determined it probably could cause cancer.Â For 2,4-D, which has been on the market since the 1940s, the group said it was possible the chemical could cause cancer.
Environmental groups want regulators in the U.S. to take notice of IARCâ€™s findings. IARC doesnâ€™t regulate herbicides itself, but the agencyâ€™s decisions do carry weight.Â BrazilÂ is taking another look at glyphosate. Glyphosate was already under review by theÂ Environmental Protection Agency.
â€œIARC is the decision-making body to which every regulator around the world looks to,â€ said Scott Faber, vice president of government affairs for theÂ Environmental Working Group.
Farmers fighting herbicide resistant weedsÂ will likely look to spray more chemicals not less. Thatâ€™s why Faber says the EPA needs to take IARCâ€™s conclusions into account when deciding how much is safe, both for farmers and their neighbors.
Hazard versus risk
But the EPA doesnâ€™t look at herbicides the same way as IARC. Take the case of 2,4-D. Anneclaire De Roos, an epidemiologist at Drexler University and a member of the 2,4-D group at IARC, says the scientistsâ€™ taskÂ was only to ask whether a chemical is a potential hazard.
â€œIs there enough evidence to say that this agent or chemical causes cancer, and if so what types of cancer is there sufficient evidence for,â€ De Roos said.
At the end of that hazard assessment, scientists concluded 2,4-D isÂ a possible carcinogen. But so are coffee and aloe vera, according to IARC. The EPAâ€™s job is to go beyond that toÂ assess risk, that is, whether it is likely to cause cancer or if there is a safe way to use it in the real world.
â€œThey also try to characterize what is the dose response,â€ De Roos said. â€œHow much exposure do you need to develop cancer?â€
Julie Goodman is a toxicologist and consultant who works with theÂ Industry Task Force on 2,4-D, which is supported by chemical manufacturers. She says 90 government agencies around the world have conducted risk assessments on 2,4-D and found itâ€™s safe to use.
â€œFarmers or anyone else using or potentially exposed to 2,4-D should really rely on the results of the risk assessments,â€ Goodman said. â€œAnd these risk assessments demonstrate that 2,4-d does not increase cancer risk.â€
The herbicide industry is also pushing back againstÂ IARCâ€™s classification of glyphosate as a probableÂ carcinogen, Monsanto saysÂ it will convene its own panel of scientistsÂ to review the science on the chemical.
Farmers and weeds
Dorn farms with his family in southeast Nebraska. On a warm summer morning he walks down a strip of grass between a field of corn and a field of soybeans. He bends down to pull up a green, leafy stalk of pigweed by its roots. He snaps the stalk like celery.
â€œWhat do you see there,â€ Dorn asked squeezing water out of the weed. â€œThatâ€™s moisture this plant is using to grow thatâ€™s not in there for my corn, not in there for my soybeans.â€
Thatâ€™s why, before he plants his crop, Dorn sprays the field with a herbicide cocktail. Each acre is sprayed twice, some three times, to wipe out weeds.
â€œYou want to make sure you have crops in your fields and not weeds because weeds donâ€™t end up in the combine bin. Weeds donâ€™t pay the bills,â€ Dorn said.
Any major changes from the EPA would affect how Dorn earns his livelihood. In the end, the real risk from any chemical is tied to the dose and thatâ€™s up to the EPA
Dorn is comfortable following EPA guidelines, and right now that means heâ€™ll keep using chemicals like glyphosate and 2,4-D as long as they keep killing weeds.
â€œItâ€™s effective and you know what youâ€™re going to get,â€ Dorn said. â€œRight or wrong it works.â€
Those tools will stay in his toolbox, at least until the EPA releases its review of glyphosate. Thatâ€™s expected to come out this summer.
But this is not likely to be the last farmers hear about IARC.Â In October, the agency will gather scientists to evaluate the cancer causing potential of red meat.
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