Atrazine, Making Babies & Timing

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Not to get too personal, but if you’re thinking of making a baby anytime soon, you might not want to wait until spring. That’s the conclusion one could draw from a recent analysis that correlates atrazine contamination spikes, time of year a baby is conceived and increased rates of birth defects. This is just the latest in a long line of studies indicating that the popular corn herbicide’s negatives outweigh its positives. The EPA announced last month that it is going to reconsider whether atrazine is safe enough to be used on this country’s crop fields. Let’s hope research like the birth defects study is on top of the agency’s review pile.

The study was published in Acta Paediatrica, an international scientific journal that focuses on the latest research in pediatric health. It found that levels of atrazine, nitrates and other agrichemicals in surface water were usually highest in the period from April to July. No  surprise there, since that’s when crop farmers are applying chemicals to get the growing season started.

But what concerned the researchers, who are based out of Indiana University and the University of Cincinnati, is that if a baby was conceived during that particular stretch of months, it was significantly more likely to have a birth defect. How much more likely? Babies conceived in any period other than April to July had birth defect rates of 1,573 per 100,000. But when conception took place between April and July, the birth defect rate jumped to 1,621 per 100,000. The increase was significant for 11 of the 22 categories of birth defects reported in the Centers for Disease Control’s natality database.

This study has significant statistical heft to it: it’s based on 30.11 million births that occurred in the U.S. between 1996 and 2002. The agrichemical data is based on the U.S. Geological Survey’s National Water-Quality Assessment study, which accounts for 70 percent of total water use and 50 percent of the country’s drinking water. The Geological Survey’s testing showed that between 1991 and 2002 pesticides were present in most stream water samples and over half of groundwater samples. Atrazine was found in 87 percent of the drinking water samples taken in 12 Corn Belt states.

The Acta Paediatrica paper concludes that in general individual agrichemical contaminants could not be associated with specific birth defects. But there is one big exception: in the case of atrazine, exposure to the pesticide increased the odds of nine of the 11 birth defect categories.

The authors of the study say while their research doesn’t provide a direct causal link between chemicals like atrazine and birth defects, the correlation is “statistically significant.”

It’s especially significant in light of a 2005 University of Missouri study which found that high levels of atrazine and other pesticides in the urine of men were associated with abnormal sperm. Spring or summer samples were more likely to be abnormal than winter ones.

This kind of research points to the reality that in the case of chemicals like atrazine, dose doesn’t necessarily make the poison. It’s the timing of that dose that can do the real harm.

“There are short, critical times—like when a fetus’s brain is developing—when chemicals can have disastrous impacts, even in very small concentrations,” atrazine researcher Deborah Cory-Slechta told the New York Times recently.

I was first introduced to this concept over a decade ago while interviewing scientists like Warren Porter and Vincent Garry, who at the time were doing cutting-edge research on how exposures to low, “pulse” doses of chemicals could cause major problems if they came along at critical times in a human’s development.

Garry and others at the University of Minnesota did extensive research on the incidence of birth defects among licensed pesticide applicators in western Minnesota’s Red River Valley. He and his team found a correlation between higher birth defect rates, spring applications of agrichemicals and the times of year babies were conceived. You guessed it: spring-conceived babies were much more likely to have problems, according to their research.

This is why people are so concerned about the research being done by scientists like Tyrone Hayes. He has found that frogs can be turned into hermaphrodites when exposed to levels of atrazine that are 30 times below the federal drinking water standard (three parts per billion) for the chemical.

It’s also why we should take seriously Paul Wotzka’s research in southeast Minnesota showing significant seasonal spikes in atrazine levels on the Whitewater River (as much as 30 parts per billion after storm events).

And it’s why assurances from the pesticide industry, USDA and state agencies like the Minnesota Department of Agriculture that a lot less atrazine is applied per acre than in the old days don’t lay the issue to rest. Granted, the federal atrazine limit of 1.5 pounds per acre is well less than half what farmers used to apply (it should also be pointed out that a lot of corn farmers use less than 1.5 pounds per acre as they target weed infestations). But in Minnesota, about 45 percent of the 7.3 million acres of corn planted in 2005 (the latest year for which USDA data are available) were sprayed with atrazine. In Iowa, 60 percent of the corn acreage was treated with the herbicide that year. An Iowa Department of Natural Resources official told the Des Moines Register on Oct. 8 that in that state the herbicide is used in smaller amounts, but on more acreage than it used to be.

In other words, as corn acres expand, more of our landscape is being exposed to this chemical during the spring, albeit in smaller per-acre dosages. That means more of the people living on that landscape are being exposed as well.

In a world where it may be the timing, and not necessarily the dose, that’s the problem, that’s a scary thought.

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