Poisoned Waterways: Atrazine

Timber companies often use atrazine in clear-cut areas, such as this one in Korbel, in order to kill the plants that compete with conifer seedlings. Photo: Jennifer Kalt

An estimated 12 tons of atrazine – an herbicide known to cause cancer, low birth weights, and hermaphroditic frogs – was used in our local forests in the last six years, raising questions about contamination of our local water sources.

A new report from the Natural Resources Defense Council has found that an alarming number of streams and drinking water sources in the Midwestern and Southern United States contain atrazine.

The report, “Atrazine: Poisoning the Well,” notes that many Americans drink contaminated water without even realizing it could be harming their health. This is because the EPA does not consider daily intake of atrazine at levels well above legal limits to be unsafe.

Under the Safe Drinking Water Act, the EPA has determined that no more than three parts per billion (ppb) of atrazine as an annual average may be present in drinking water. As long as the annual average is within those limits, springtime spikes of nearly 10 times the maximum allowable levels in drinking water are not considered in violation of the standard.

Researchers examined biweekly data from 139 municipal water systems, mostly in the Midwestern corn belt, and found that atrazine was present in drinking water 90 percent of the time, and is deposited in rainfall and fog throughout the Midwest.

Banned in the European Union and Israel, atrazine is one of the most frequently used pesticides in the U.S. where it is sprayed on corn, soybeans, and other crops. It has been clearly linked to  harmful impacts to wildlife and human health. Reproductive damage has been documented in amphibians, mammals, and humans, even at very low levels of exposure. Concentrations as low as 0.1 ppb have been shown to alter the development of sex organs in male frogs.

In this bioregion, atrazine is often used by timber companies after clear-cutting, to kill native and non-native plants that compete with conifer seedlings.
According to the Dept. of Pesticide Regulation’s Pesticide Use Reporting data, nearly 25,000 lbs. of atrazine were applied to private timberlands in Humboldt County from 2001 to 2007.

Though it is a known groundwater contaminant and is extremely toxic to aquatic species, its use is not prohibited in the Mad River watershed, where the drinking water originates for the communities in the Humboldt Bay area.

The Mad River drinking water wells are deep in the gravel riverbed, but it is unknown whether atrazine is adequately filtered out in the treatment process. Municipal water supply companies were required to test for atrazine and other contaminants when the Safe Drinking Water Act first went into effect, but only are required to continue regular testing if contaminants are detected.

The Humboldt Bay Municipal Water District (HBMWD)—which delivers drinking water to local suppliers in Eureka, Cutten, Arcata, McKinleyville, Fieldbrook/Glendale, Blue Lake, and Manila— has not detected atrazine in the several samplings that have been conducted since 2001. (detection level = 1.7 ppb).

Tera Prucha, HBMWD Division 2 Director, thinks that water from the Mad River wells is safe. “I am a fan of the philosophy ‘err on the side of caution’ and do my best to balance exposure to possible health risks,” she said.

“That being said, I drink Mad River water straight from the tap,” she added. It is true that the quality of our local drinking water is well above average, and – per a June 2009 report – more regulated than bottled water.

Buying bottled water is not a solution for avoiding contaminated water. The bottled water industry consumes huge amounts of fossil fuels for transport, relies on non-reusable plastic bottles that mostly end up in the landfill (or worse, in the ocean), and depletes groundwater in areas where the residents have little control over local water supplies. Furthermore, bottled water is not routinely tested for contaminants, and is likely to contain toxic leachates from cheap plastic containers.

So what is the solution? “Protecting local waters, especially those that provide drinking water,” says Pete Nichols of Humboldt Baykeeper. Strengthening pesticide regulation and revising drinking water public health goals to reflect up-to-date scientific information would also help protect human health while protecting salmon, frogs, and other species that rely on clean water even more than we do.

For information about past herbicide and pesticide use, visit the California Department of Pesticide Regulation’s website. For information on local pesticide issues and safer alternatives, contact Californians for Alternatives to Toxics at 445-5151.


Jennifer Kalt works for California Indian Basketweavers Association. She is a botanist working to protect plants of importance to California Indian basketweavers by reducing pesticide use in gathering areas, promoting the use of fire to restore and enhance native plant populations, and preserving free access to gathering areas.

Minimizing your exposure to atrazine and other contaminants in tap water is best done with a water filter that can reduce the levels of  “Volatile Organic Compounds” (VOCs).

Filters certified by NSF International to meet American National Standards Institute (ANSI) Standard 53 for VOC reduction are capable of significantly reducing atrazine and other pesticides from drinking water. Learn more about choosing the right water filter here.