Atrazine: As bad for wildlife as it is for weeds?

Dec 14, 2009

Rohr JJ and KA McCoy. A qualitative meta-analysis reveals consistent effects of atrazine on freshwater fish and amphibians. Environmental Health Perspectives doi:10.1289/ehp.0901164s.

Synopsis by Heather Hamlin

The widely used herbicide atrazine may be responsible for a host of health problems seen in fresh water fish and amphibians, according to researchers who evaluated a group of published studies that examined the chemical's effects.

The weed-killer atrazine – in most cases – does not outright kill fish and amphibians in the wild, but it can routinely cause indirect health effects that can alter important life functions in the two groups. A new assessment of previous studies finds that some of the effects were permanent and not seen until months after the animals encountered the chemical.

Exposure to atrazine levels found in the environment reduced immune function, sex organ development and function, and the production of steroid hormones in both groups of animals. The oft-times slight changes to these important body systems can affect the timing of metamorphosis in amphibians and behavior in amphibians and fish – changes that could affect an animal's survival.

The study also found that atrazine’s affects are often non-monotonic, meaning that lower doses could in fact be more harmful than higher doses. For example, atrazine affected how fish swam in all the studies analyzed. The exposures increased hyperactivity at the lower concentrations reported but not at higher levels.

Atrazine is the second most common herbicide in the US and is used heavily for the production of corn, sugarcane and other crops. The safety of atrazine is currently being re-evaluated by the US EPA because of a growing body of scientific literature that raises concerns about the chemical’s safety.

This study, called a meta-analysis, is the first to be conducted by a group that is not funded by the corporation that manufactures atrazine and highlights a growing concern about the heavy use of atrazine in the production of food crops.

A meta-analysis combines data from similar types of studies to look for similarities and general impacts to exposures. In this case, researchers used the approach to identify related effects in wildlife from exposure to atrazine levels that are found in the environment. 

The authors focused on effects to behavior; metamorphic traits; and immune, endocrine, and reproductive systems in amphibians and fish. Specifically, atazine consistently increased hyperactivity and slowed escape behavior in both groups, decreased smelling in fish,  increased parasite and viral infections in both amphibians and fish and altered development of male sex organs in both groups.