The Weed Killer Atrazine May Be Harming Your Health

Applying pesticides to a corn field in Utah | Photo: Aqua Mechanical, some rights reserved

If you’re worried about the increasing worldwide use of the weed-killer glyphosate, a.k.a. Roundup™, you’re not alone. The herbicide is getting increasing critical exposure in the news — and on social media — as we learn more about its potential effects on the environment and human health. And seeing as Roundup use is increasing exponentially, that concern is sensible.

But there are other commonly used pesticides that don’t get nearly as much public attention, despite the fact that pound for pound, they’re significantly more dangerous to people and the planet. In this short series, we'll discuss five very commonly used pesticides whose ill effects on human health and the environment are demonstrably worse than Roundup. 

In this article we look at atrazine, a weedkiller used mainly in agriculture that's been linked to monstrous deformities in wildlife, and to potential hormonal problems in human beings. 

If it wasn’t for Roundup, atrazine would probably be the most controversial herbicide on the planet. It’s the pesticide most commonly found as a runoff contaminant in rivers, streams, lakes, and wetlands. It can travel hundreds of miles on airborne dust from the farm fields where it’s applied in order to contaminate those wetlands, and can persist for decades once it gets there. It’s been linked to reproductive abnormalities in frogs, hormonal changes in alligators, and serious harm to other wildlife populations.

And it can even promote fungal diseases in the soil by killing off beneficial fungi while leaving the pathogens.

The jury’s out on whether atrazine causes cancer, but the EPA — long criticized as slow to cut into pesticide company profits by regulating their products effectively — agrees that the chemical is a likely endocrine disruptor. That would explain UC Berkeley biologist Tyrone Hayes’ findings that the herbicide caused serious reproductive abnormalities in frogs, including gender switching from male to female, along with extra legs and other deformities. The herbicide's manufacturer, Syngenta, originally hired Tyrone Hayes to investigate its product and, not entirely surprisingly, has repudiated his findings in a campaign that has attracted worldwide notoriety. 

Biologist Tyrone Hayes speaks to a group at King University in Tennessee.| Photo: Earl Neikirk, some rights reserved

We should note that it isn't all about the atrazine. Due to a loophole in U.S. pesticide regulations, manufacturers can add other substances to their pesticides to serve functions ranging from helping herbicides stick to waxy plant leaves to just acting as filler. Dubbed "inert ingredients," these substances can make up 99 percent of the contents of a pesticide container. Sometimes they're innocuous, like water or ethyl alcohol. But sometimes they can have their own significant negative effects on the environment and on public health. And pesticide companies aren't required to disclose which "inert ingredients" they use in their pesticides. Most companies refuse to disclose them publicly, calling the ingredients of their products trade secrets.

A number of studies have shown that atrazine combined with commonly used "inert ingredients" can do greater harm to living things than the chemical applied on its own.

For instance, independent studies have found ethoxylated nonyl phenols used as inerts in commercial atrazine formulations. Ethoxylated nonyl phenols act as "co-carcinogens," increasing the potency of chemicals that cause cancer. One 1996 study found that commercial formulations of atrazine caused twice as many mutations in wetland wildlife than atrazine applied by itself.

Almost all the atrazine used in the United States is applied to corn fields in the Midwest, though a fair bit is used on professionally maintained lawns such as golf courses. It’s used in these settings because it kills broad-leaved plants, while leaving grasses like corn and turf mostly undamaged. In 2014, the U.S. Department of Agriculture (USDA) estimated that just under 70 million pounds of atrazine was applied to agricultural fields, around 61 million pounds of it on cornfields.

How much is that in human health terms? Considering that the EPA’s safe standard for atrazine in drinking water is set at three micrograms per liter, 70 million pounds of atrazine is enough to make all the water in lakes Huron, Michigan, Erie, and Ontario officially unsafe to drink.

Like Roundup, atrazine has gotten itself a bit of negative publicity in social media, much of it concerning the manufacturer Syngenta’s campaign to undermine the research of UC Berkeley’s Hayes, as well as Hayes’ not entirely conciliatory responses.

It’s likely, for instance, that atrazine is the only herbicide that comes with its own cautionary rap:

Other governments have been quicker to respond to the herbicide’s perceived threat: the European Union banned atrazine in 2004 when it found groundwater contamination exceeding accepted safety standards. The EPA has been slower to act. An EPA review of the effects of atrazine ;is officially in progress; a 2016 draft assessment of the pesticide's environmental effects found that atrazine poses a significant risk to plant and animal biodiversity. A similar draft assessment of atrazine's effects on human health was due out in 2016, but seems to be unavailable online.

A decision on the environmental assessment is due sometime this year. Given the current leadership of the EPA, it is unlikely that restrictions in atrazine use will be the result.

The other pesticides we're covering in this series are the insecticide chlorpyrifos, the weedkiller 2,4-D, and the soil fumigants metam sodium and 1,3 dichloropropene.

Banner photo: A crop duster at work | Photo: Scott Butner, some rights reserved.