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Common herbicide atrazine emasculates male frogs in study

March 3rd, 2010

From Green Right Now Reports

Blame lawns. And Big Ag. A new study looking at the effects of the common pesticide atrazine has found that it emasculated three-quarters of the male frogs exposed to the chemical.

It turned one in ten of the male frogs into females.

African clawed frog (Photo: Columbia University)

African clawed frog (Photo: Columbia University)

The study suggests that a key reason for the vast worldwide decline of frogs could be their exposure to atrazine and similar pesticides. “The 75 percent that are chemically castrated are essentially ‘dead’ because of their inability to reproduce in the wild,” says Dr. Tyrone B. Hayes, a University of California-Berkeley professor and lead researcher of the study.

“These male frogs are missing testosterone and all the things that testosterone controls, including sperm….” Hayes says in a UC Berkeley news report.

The peer-reviewed study, published by the Proceedings of the National Academy of Sciences, was released Monday.

Hayes’ earlier work with frogs and atrazine had shown that the chemical disrupted the development of both male and female frogs, creating hermaphrodites that had features of both sexes.

The new study of 40 African clawed frogs, which were housed in water contaminated with atrazine, shows that the hormonal imbalance can be even more extreme.

The frogs were exposed to a level of the chemical (2.5 parts per billion) below the level deemed safe by the EPA (3.0 ppb).

Syngenta AG, the large manufacturer of atrazine,  responded by calling Hayes’ work, past and present, flawed.

“For 50 years, atrazine has been used safely in agriculture with no effect to amphibians, fish, birds and other wildlife at concentrations found in the environment,’’ the company said in a statement. Syngenta maintains that independent research in labs has shown “no association between atrazine and declines in frog numbers.”

The European Union banned atrazine in 2004 over health concerns. The EPA is reviewing its use in the United States, and some states are suing over the use of the chemical, which leaches into groundwater and has been found above safe levels in drinking water supplies.

The Center for Biological Diversity has called for a U.S. ban on atrazine.

“It’s time to ban atrazine to protect our drinking water and our most imperiled wildlife,” said Jeff Miller, a conservation advocate with the Center for Biological Diversity, in August, 2009. “There is no reason to continue use of this poisonous contaminant given the building evidence of harm to humans and endangered species.”

The chemical is used on corn and soybeans in the United States to control weeds and increase crop yields. Its tendency to contaminate streams and ground water caused the EPA to set a maximum level (3 parts per billion, ppb) for its presence in water. Water departments are required to test for atrazine at regular intervals and take action if levels rise above that.

The EPA reports that short-term exposure to atrazine can cause heart, lung and kidney problems; longterm exposure can cause cancer and other health effects.

Atrazine was the second most common pesticide found in well water by EPA researchers. It can break down in water and soil, but sunlight does not “reduce its presence,” according to the federal agency. (See the EPA fact sheet.)

Contamination is the Midwest is high, because of the proximity to agricultural use. Studies of atrazine and frogs in the Midwest have found eggs in the testes of native leopard frogs taken from atrazine-contaminated streams.

However, the chemical has been shown to travel hundreds of miles, with the EPA detecting unsafe levels in wells in New York and Delaware, as well as Illinois, Indiana, Iowa, Kansas, Michigan, Minnesota, Missouri and Nebraska.

Atrazine also is found in many common products for home weed control. The EPA has put out a list of trade names of products that contain atrazine.

Other studies show that atrazine also acts as an endocrine disruptor in fish, birds, reptiles, laboratory rats and in human cells. Recent studies hint that is could produce human birth defects, according to the UC Berkeley news report.

Syngenta and others advocating conventional chemical farming argue that strong weed killers are needed to produce high crop yields and make U.S. farms more productive.

Recent research on soils and organic production has been challenging those assumptions. Studies on soil conditions in the US have found that the use of synthetic fertilizers and herbicides is depleting soils. Organic organizations, like the Organic Consumers Association, maintain that small, organic farms can produce enough to feed the world, without degrading soil or groundwater.

For more information on the dwindling world populations of frogs, see our previous story.


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