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Following an earlier study
that found that men in rural mid-Missouri had lower sperm counts and lower sperm
quality than men in urban centers, a University of Missouri-Columbia researcher
has identified and linked three agricultural chemicals to the problem.
In November 2002, Shanna Swan, a professor of family and community medicine
at the university, announced findings indicating that men in rural areas have
lower sperm counts and less vigorous sperm than men in urban areas. Through her
most recent study, published today in the journal Environmental Health
Perspectives (EHP), Swan confirmed that men with lower sperm counts and
quality had higher concentrations of alachlor, diazinon, and atrazine
metabolites in their urine than men with higher-quality sperm. These three
chemicals are commonly used in agriculture throughout the Midwest.
Swan's study compared pesticide exposure in two groups: men with low sperm
concentration and quality, and men with better semen quality. Although men were
drawn from both mid-Missouri (a mostly rural area) and Minneapolis, Minnesota (a
highly urban setting), links between pesticides and semen quality were detected
only in Missouri men. Swan obtained urine samples from both groups and tested
them for 15 currently used pesticides. Samples from Missouri men with poor semen
quality contained significantly higher concentrations of alachlor, atrazine, and
diazinon metabolites than samples from men with higher-quality sperm. For
example, men with high levels of alachlor were 30 times more likely to have poor
semen quality than men with low levels. Swan found no correlation between semen
quality and pesticides used primarily in the home, such as DEET.
"This is the first study that shows a link between elevated levels of these
pesticides in the human body and potential reproductive problems," Swan said.
"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."
According to a 1995 survey by the U.S. Geological Survey, these pesticides
were found in groundwater supplies in rural areas in the Midwest at
concentrations exceeding federal reporting levels. In addition, the agency
stated that conventional water treatment is ineffective in removing herbicides
such as alachlor and atrazine from finished drinking water. Unlike many other
contaminants, those herbicides remain in the water following conventional
treatment processes such as coagulation and sand filtration.
"We think it is likely that men are ingesting these chemicals through their
drinking water," Swan said. "Some water filters do claim to rid the system of
these chemicals. We need to analyze men's home tap water and examine alternative
water treatment methods to determine levels of these chemicals currently in the
water supply and to find effective ways to remove them."
Swan also said that although researchers should examine the water supply and
seek methods of removing the pesticides, safer alternatives to these chemicals
need to be found. Because women and children are likely to be exposed to these
pesticides as well, additional studies examining the impact of these pesticides
on the health of the entire family are needed, Swan said.
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