What Is Atrazine?

Exposure has serious health consequences for animals and humans

Pesticide warning sign on fertile farm land
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Atrazine is an agricultural herbicide that is widely used by farmers to control broadleaf weeds and grasses that interfere with the growth of corn, sorghum, sugar cane, and other crops. Atrazine is also used as a weed killer on golf courses as well as a variety of commercial and residential lawns.

Atrazine, which is produced by the Swiss agrochemical company Syngenta, was first registered for use in the United States in 1959. The herbicide has been banned in the European Union since 2004—individual countries in Europe banned Atrazine as early as 1991—but 80 million pounds of the stuff is used each year in the United States - it is now the second most used herbicide in the US after glyphosate (Roundup).

Atrazine Threatens Amphibians

Atrazine may protect crops and lawns from certain types of weeds, but it is a real problem for other species. The chemical is a potent endocrine disruptor that causes immunosuppression, hermaphroditism and even complete sex reversal in male frogs at concentrations as low as 2.5 parts per billion (ppb)—well below the 3.0 ppb that the U.S. Environmental Protection Agency (EPA) says is safe.

This problem is particularly acute because amphibian populations worldwide have been declining at such unprecedented rates that, today, nearly one-third of the world's amphibian species are threatened with extinction (though in large due to the chytrid fungus). In addition, atrazine has been linked to reproductive defects in fish and prostate and breast cancer in laboratory rodents. Epidemiological studies also suggest that atrazine is a human carcinogen and leads to other human health issues.

Atrazine Is a Growing Health Problem for Humans

Researchers are finding an increasing number of links between atrazine and poor birth outcomes in humans. A 2009 study, for example, found a significant correlation between prenatal atrazine exposure (primarily from the drinking water consumed by pregnant women) and reduced body weight in newborns. Low birth weight is associated with an increased risk of illness in infants and conditions such as cardiovascular disease and diabetes.

The public health issue is a growing concern because atrazine is also the most commonly detected pesticide in American groundwater. An extensive U.S. Geological Survey study found atrazine in approximately 75 percent of stream water and about 40 percent of groundwater samples in the agricultural areas tested. More recent data showed atrazine present in 80 percent of drinking water samples taken from 153 public water systems.

Atrazine is not only widely present in the environment, but it is also unusually persistent. Fifteen years after France stopped using atrazine, the chemical can still be detected there. Every year, more than half a million pounds of atrazine drift off during spraying and falls back to Earth in rain and snow, eventually seeping into streams and groundwater and contributing to chemical water pollution.

The EPA re-registered atrazine in 2006 and deemed it safe, saying that it posed no health risks for humans. The NRDC and other environmental organizations question that conclusion, pointing out that the EPA's inadequate monitoring systems and weak regulations have allowed atrazine levels in watersheds and drinking water to reach extremely high concentrations, which certainly puts public health in question and possibly at serious risk.

In June 2016 the EPA released a draft ecological assessment of atrazine, which recognized negative consequences of the pesticide on aquatic communities, including their plant, fish, amphibian, and invertebrate populations. Additional concerns extend to terrestrial ecological communities. These findings concern the pesticide industry, of course, but also many farmers who rely on atrazine to control hardy weeds.

Many Farmers Like Atrazine

It’s easy to see why a lot of farmers like Atrazine. It’s relatively cheap, it doesn’t harm crops, it increases yields, and it saves them money. According to one study, farmers growing corn and using Atrazine over a 20-year period (1986-2005) saw average yields of 5.7 bushels more per acre, an increase of more than 5 percent.

The same study found that Atrazine’s lower costs and higher yields added an estimated $25.74 per acre to farmers’ income in 2005, which added up to a total benefit to U.S. farmers of $1.39 billion. A different study by the EPA estimated the increased income for farmers at $28 per acre, for a total benefit of more than $1.5 billion to U.S. farmers.

Banning Atrazine Would Not Hurt Farmers

On the other hand, a study by the U.S. Department of Agriculture (USDA) suggests that if atrazine were banned in the United States, the drop in corn yields would be only about 1.19 percent, and the corn acreage would be reduced by only 2.35 percent. Dr. Frank Ackerman, an economist at Tufts University, concluded that estimates of higher corn losses were flawed due to problems in methodology. Ackerman found that despite a 1991 ban on atrazine in both Italy and Germany, neither country has recorded significant adverse economic effects.

In his report, Ackerman wrote there was “no sign of yields dropping in Germany or Italy after 1991, relative to the U.S. yield—as would be the case if atrazine were essential. Far from showing any slowdown after 1991, both Italy and (especially) German show faster growth in harvested areas after banning atrazine than before.”

Based on this analysis, Ackerman concluded that if “the yield impact is on the order of 1%, as USDA estimated, or close to zero, as suggested by the newer evidence discussed here, then the economic consequences [of phasing out atrazine] become minimal.”

Conversely, the economic costs of continuing to use atrazine—both in water treatment and public health costs—could be significant when compared to the relatively small economic losses of banning the chemical.

Edited by Frederic Beaudry.