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Gender-Bending Herbicide Contaminates Lakes Far from Use Sites

(Beyond Pesticides, September 23, 2008) According to the Minnesota Department of Agriculture’s 2007 Water Quality Monitoring Report, released in August 2008, the endocrine disrupting herbicide atrazine is detected in pristine lakes in northern Minnesota far from the agricultural fields where it is applied. Metolachlor, acetochlor and dimethenamid are also frequent contaminants, according to the statewide sampling.

The report, which uses data collected by a collaborative program between the U.S. Environmental Protection Agency, the Minnesota Department of Agriculture and the Minnesota Pollution Control Agency, analyzed samples from 55 of the state’s lakes. Atrazine was detected in approximately 87% of the 2007 samples, an increase from 2006. The presence of atrazine in such a large percentage of the lakes, many of which are located in non-agricultural areas of northern Minnesota, suggests widespread atmospheric deposition of this chemical (movement through wind and rain).

“To some people, it is a bit of a surprise, but the concentrations are low, very low,” Steven Heiskary, a research scientist with the Minnesota Pollution Control Agency (MPCA) told the Star Tribune.

Unfortunately, this is not very reassuring, given the fact that many of the developmental impacts linked to atrazine are seen at very low levels, sometimes at just a fraction of a part per billion. Research by Tyrone Hayes, Ph.D., has shown that 0.1 parts per billion of atrazine in the water where a frog develops can hermaphrodize the animal (having both male and female gonads). Even concentrations of a few parts per trillion can seriously impact the way an animal develops.

A recent study has linked the common herbicide atrazine with endocrine disruption in both fish and human cells. The University of Califonia, San Francisco (UCSF) research examines the reaction of zebrafish to environmentally relevant levels of atrazine, and mirrors the study in human placental cells.

It is the ubiquitous nature of the contamination rather than the concentration of the herbicides that worries Samuel Yamin, a public health scientist for the environmental group, the Minnesota Center for Environmental Advocacy. “The fact that these chemicals are basically everywhere in the water resources is itself a concern even if the levels in each one are not pushing the health benchmarks,” Mr. Yamin told the Star Tribune.

Atrazine is the second most commonly used agricultural pesticide in the U.S., and the most commonly detected pesticide in rivers, streams and wells. It is linked to endocrine disruption, neuropathy and cancer. An estimated 76.4 million pounds of atrazine are applied in the U.S. annually. Atrazine has a tendency to persist in soils and move with water, making it a very common water contaminant.

Bill VanRyswyk, an Agriculture Department hydrologist who worked on the lake study, explained to the Star Tribune that some of the tested lakes probably became contaminated with herbicides from runoff. Yet the northern lakes that tested positive for atrazine are nowhere near farms. The likely explanation is that atrazine and other herbicides are spread through the atmosphere.

According to Mr. VanRyswyk, pesticides get into the air when they are applied or when wind blows dust from treated fields. Studies by other researchers suggest the chemicals can be transported long distances and fall to earth as dust or in rain. “So it may well be coming in from out of state for those northern lakes,” Mr. VanRyswyk said. He said additional lakes are being tested this year, and state agencies hope to test the original 53 lakes every few years to measure trends in concentrations.

According to the Star Tribune, six of the 46 lakes containing atrazine are in or near the Boundary Waters Canoe Area Wilderness, including two trout lakes in St. Louis and Cook counties. Trout lakes are among the state’s highest-quality waters. The only urban lake tested, Nokomis in Minneapolis, also had trace amounts of atrazine.

Water is the most basic building block of life. Clean water is essential for human health, wildlife, and a balanced environment. According to a Beyond Pesticides report, Threatened Waters: Turning the Tide on Pesticide Contamination, over 50% of the U.S. population draws its drinking water supply from ground water, which includes sources below the earth’s surface, including springs, wells, and aquifers. Once groundwater has been contaminated, it takes many years or even decades to recover, while streams and shallow water sources can recover much more rapidly. Herbicides are found more often in ground water than insecticides, but insecticides in ground water exceed drinking water standards more often than herbicides.


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