Scientific studies on atrazine indicate that this widely used herbicide in the U.S. has the ability to feminize male frogs as well as some other animals. Results from limited research on this controversial pesticide that has been conducted on humans, however, remains inconclusive. A few studies indicate that atrazine may be linked to some birth defects and poor semen quality in men.
According to Suzanne Fenton of the National Institute of Environmental Health Sciences, atrazine has a short half-life in animals making it difficult to measure accurately. This creates problems for conducting proper scientific studies, so essentially all studies that have been conducted to date are questionable.
According to researchers at the University of Texas, atrazine has the ability to disrupt hormones, thereby altering male reproductive tissues when an animal is exposed during development. Their studies published back in 2005 and 2008 also indicate a reduction in birth size in amphibians and fish. A recent analysis (2013) of birth defect records in Texas found a moderate, however consistent link between boys’ genital defects and their mothers who live near areas that contain atrazine.
Syngenta, a Switzerland-based pesticide company and manufacturer of atrazine, believes this chemical to be safe for animals and humans at the concentrations found in the environment. The U.S. uses more than 80 million pounds annually and has been doing so for more than 50 years, particularly on corn crops.
Some ten years ago, researchers at UC Berkeley found that low concentrations of atrazine caused male tadpoles to develop into female frogs. The amounts involved in this lab experiment were comparable to what one would expect around farm lands that use atrazine. Research done by Tyrone Hayes, (UC Berkeley biology professor), found male tadpoles in the wild were either turned into females or demasculinized. The males actually had eggs growing in their testes, which of course makes them unable to reproduce. More recent research has found that atrazine has similar hormone effects on salmon, caimans and lab rats. Hayes also reports that fish and frogs exposed to atrazine have abnormal swimming patterns which would make it difficult for them to escape predators and catch food.
Syngenta is attempting to dispute scientific reports indicating that atrazine can disrupt hormonal processes, and evidently the company has gone as far as to commission a psychological profile of UC Berkeley’s Tyrone Hayes. The controversy, however, doesn’t stop there: Syngenta has also launched a multi-million dollar campaign in hopes of protecting profits threatened by a lawsuit over this controversial herbicide. This includes hiring a detective agency to investigate scientists and looking into the personal life of a judge. Moreover, it is reported that Syngenta has paid “third-party allies” presenting themselves as independent supporters of atrazine. In fact, they have a list of some 130 individuals and various groups that they can call on as expert witnesses without disclosing any ties to Syngenta.
At this point, Syngenta denies there is anything unsafe about atrazine. Back in 2003, the US Environmental Protection Agency asked Syngenta to conduct at least two labs testing the effect of atrazine on frogs. The follow-up studies were unable to replicate Hayes’ research and they concluded that there was no feminizing effects on frogs. These findings were peer-reviewed and published.
Dr. Hayes retaliated Syngenta’s claims in an article he wrote back in 2004, discrediting the company’s research. According to Hayes, Syngenta’s studies had a high frog mortality rate, as well as inappropriate measurements of hormone levels. Therefore, their research could not be compared to his. So far. all studies on atrazine coming from academia demonstrate an issue, whereas industry studies demonstrate no effect.
According to Krista McCoy (biology professor) at East Carolina University, the field studies that Syngenta performed that couldn’t replicate Hayes’ findings used different methods of measurement. Apparently, an assumption was made about some ponds used in the study: some were considered clean and could be used as a reference site. To further complicate the issue, if they found similar frog abnormalities in these so-called clean ponds and polluted ponds, they concluded there was no link to atrazine.
As McCoy points out, “there’s no such thing as a clean control site where there’s no man-made chemicals. If you collect samples from a pond in an agricultural area and then go across the street to someone’s yard, well, the animals [in the non-agricultural pond] are probably exposed to the same chemicals due to runoff.”
McCoy has analyzed previous research and found that atrazine consistently affected male frog development. What she’s uncertain about is whether this has affected the animal population in terms of decreasing population size and how that relates to humans.
Yet another scientist, Jason Rohr (biology professor) at the University of South Florida, has concerns about atrazine research. He feels there are problems with Hayes’ work due to less accurate measuring techniques. He also feels that Syngenta-funded research may have skewed results.
Back in 2007, atrazine was reviewed again and the EPA decided to renew its registration. The EPA concluded that atrazine was not harming frogs or wild life at levels found in the environment based on Syngenta’s results. By Federal law, “a pesticide must be found not to cause unreasonable risks to people or the environment” in order for the EPA to allow continued use. But the law also allows the EPA to take into “account the economic, social, and environmental costs and benefits of the use of the pesticide” when assessing “unreasonable risks.” The EPA has established that water containing atrazine is safe to drink at concentrations of 3 parts per billion. Keep in mind that pesticides are reviewed every 15 years.
Interestingly, Europe banned atrazine back in 2003. Atrazine was found widespread in their water supplies.