June 17, 2003
Study links pesticide exposure to low sperm counts and quality.
A new study by researchers at the University of Missouri-Columbia (UM-C) published in the scientific journal Environmental Health Perspectives (published by the U.S. National Institute of Environmental Health Sciences) has found a high correlation between low sperm counts and less vigorous sperm in men in rural Missouri and the presence in their semen of the herbicides alachlor and atrazine and the pesticide diazinon, all commonly used in agricultural operations in the U.S. Midwest. The study found that men with high levels of alachlor in their urine were 30 times more likely to have poor quality or lower semen counts than men with low levels of the herbicide. Men with high levels of diazinon were 16.7 times more likely to show such effects, and men with high levels of atrazine 11 times more likely.
"This is the first study that shows a link between elevated levels of these pesticides in the human body and potential reproductive problems," said Shanna Swan, the lead author of the study and a professor of family and community medicine at UM-C. "Since our subjects include a cross-section of men in mid-Missouri, rather than mostly farmers, the pesticide levels we found probably represent the exposure of the general population."
The scientists studied 50 men in rural Missouri and 36 men in Minneapolis. Based on semen samples, the men were divided into two groups: those with low sperm counts and quality and those with better semen quality. A Centers for Disease Control and Prevention lab measured levels of the byproducts of 15 different pesticides in urine samples from the men. Men with higher levels of alachlor, atrazine and diazinon were significantly more likely to have poorer sperm quality. All three pesticides were more likely to be found in high levels in the Missouri men than in the Minneapolis men. The study also found a correlation between sperm problems and the herbicides 2,4-D and metolachlor.
Only two of the Missouri men were farmers, and Swan and her coauthors suspect that the men were exposed to the pesticides through drinking water. "We think it is likely that (the Missouri men) are ingesting these chemicals through their drinking water," Swan said. "Regulators should be re-evaluating permissible levels of these pesticides in our drinking water. As long as we're seeing effects at permissible levels, they're too high. These are not small effects. This is affecting a lot of people."
To Swan, the latest findings underscore the need for the federal government to reduce the level of the chemicals it allows in the nation's drinking water. "We're looking at the canary in the mine. You don't change one system of the body, like the testes, in a vacuum," she noted.
A 1995 study by the U.S. Geological Survey (USGS) found atrazine, alachlor and diazinon in groundwater drinking-water supplies throughout North America, including the Northeast, but the greatest contamination levels tended to be in farm belt states like Missouri. The USGS also found that conventional water treatment does not remove herbicides like alachlor and atrazine from drinking before water reaches consumers. However, charcoal filters that consumers can attach to sink faucets can remove the herbicides. Removing the herbicides from shower and bath water is more problematic because of the larger volume of water involved.
The U.S. Environmental Protection Agency has banned diazinon for indoor and garden use because of evidence that it can damage the nervous systems of children even at low doses, but agricultural use is still permitted. Until the EPA ordered it phased out in 1990, diazinon was the nation's top lawn pesticide. Studies have also tied atrazine to prostate cancer in men, and a study published in 2002 found that atrazine is making male frogs in the Midwest grow female gonads
Other researchers said the new study's results are powerful. "You just don't see [effects] this large in environmental epidemiology very often. This is interesting and intriguing," said Dr. Russ Hauser of the Harvard School of Public Health.
Rex Hess, a reproductive toxicologist at the University of Illinois-Urbana, praised the design and execution of Swan's study. The logical next step will be to test drinking water in Missouri for the pesticides, Hess says.
Swan is plowing new ground with this study, and her results are extraordinary, said J. Peterson Myers, a biologist who co-wrote the ground-breaking book, Our Stolen Future, an investigation of endocrine-disrupting chemicals. "Epidemiologists get very excited about a risk factor of two or three. She's got a risk factor for alachlor of 30. That is extremely significant statistically. The risk factors for atrazine and diazinon are also off the charts."
The new study follows a study published in November 2002, in which Swan's research group found that fertile men from mid-Missouri's Boone County have a mean sperm count of only about 59 million per milliliter, compared to 103 million for men in New York, 99 million in Minnesota and 81 million in Los Angeles. The Boone County sperm also tended to be less vigorous, the study in 2002 found. Farms make up more than half of Boone County, and most use chemical fertilizers, herbicides or pesticides. In contrast, 0 to 19 percent of the urban areas studied were devoted to farming.
This latest study adds new fuel to a decade-long controversy over whether toxic chemicals are responsible for the fact that male fertility is decreasing in some parts of the world, including portions of Northern Europe, which has become a hotbed of research into the trend. Evidence in a number of studies in the last ten years or so have found that pesticides in the environment can trigger damaging increases in the female sex hormone estrogen. For example, in 2002, researchers found direct evidence that chemicals in the environment mimic the effect of estrogen on the ability of sperm to fertilize eggs. Such chemicals, they said, might make sperm burn out before reaching the egg.
Swan plans to replicate this latest study, looking not only at men from mid-Missouri but men from Iowa as well. She also plans to apply for funds to test sperm samples from men with high pesticide levels to look for DNA damage to try to determine how pesticides can cause reproductive havoc.
The scientists involved in this study were from the Department of Family and Community Medicine, University of Missouri - Columbia School Of Medicine; the Department of Obstetrics and Gynecology, University Of Missouri-Columbia; University of California, Davis; Harbor-UCLA; Departments of Medicine and Urologic Surgery, University Of Minnesota; and the U.S. Centers for Disease Control and Prevention (CDC).
Posted by Oneida in categories: [ Life Disintegrating (Earth Crash) | Life Out of Balance ]
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