chemicals may affect male fertility,
MU researcher says
A pretty darn good reason to
lay off the ag chemicals, don't you think?
By Lynn Franey, Kansas City Star
Monday, Nov. 11, 2002, Kansas City Star via CropChoice
news: Men living in agricultural mid-Missouri
are markedly less fertile than men living in New York,
Minneapolis and Los Angeles, researchers at the University
of Missouri-Columbia have found.
The researchers suspect that runoff from farm chemicals
may be to blame.
The results "are important to couples that are trying
to conceive. If we can find out what specific exposures
were related to this reduced semen quality, we might be
able to prevent delays in conception in the future,"
said Shanna Swan, the MU professor who led the study.
Swan said she hopes the study prompts further inquiry
into how agricultural chemicals negatively affect people's
The study, conducted between 1999 and 2001, found that,
on average, fertile men in Columbia produced 58.7 million
sperm per milliliter of semen, compared with 80.8 million
for men in Los Angeles, 98.6 million for men in Minneapolis
and 102.9 million for men in New York City.
On another important measure, sperm mobility, fertile
men in Columbia also lagged behind their urban counterparts.
On average, fertile men in Columbia produced just 113
million mobile sperm per sample, compared with 162 million
in New York, 196 million in Los Angeles and 201 million
in Minneapolis. Swan measured mobile sperm by the sample,
not by the milliliter, as was used to measure the number
of all sperm.
The mobility measure is important because so few sperm
make it to the woman's fallopian tubes. After sperm has
been deposited in the vagina, only a small percentage
find their way into the cervix and then begin their journey
though the uterus and into the fallopian tubes. That journey
must occur to fertilize the woman's egg. Only 1,000 or
2,000 sperm usually make it.
"While it's true that it only takes one sperm to
conceive a pregnancy, the length of time that it takes
a couple to conceive is related to the sperm quality --
how fast and directly the sperm swim, and how they are
shaped," Swan said. "If you follow couples trying
to become pregnant, those that have better semen quality
do conceive more quickly."
Swan's research corroborates an earlier study that found
lower sperm counts among men in Iowa City, Iowa, the only
other semiagricultural region used in a U.S. semen-quality
That 1974 study found the sperm concentration of Iowa
City men was 48 million per milliliter of semen.
The MU study will be published in today's edition of Environmental
Health Perspectives, the scientific journal of the National
Institute of Environmental Health Sciences. The unit of
the National Institutes of Health provided Swan a $2.8
million grant to conduct the research.
Swan did not connect lower sperm counts and quality to
particular agricultural chemicals. But the study does
highlight the significant difference in land use among
the other sites studied.
According to the U.S. Department of Agriculture, Swan
wrote, about 57 percent of the land surrounding Boone
County, where Columbia is located, was used for agriculture,
compared with 19 percent in Minneapolis, 5 percent in
Los Angeles and 0 percent in New York.
The study recruited 512 men whose pregnant partners were
visiting hospitals for prenatal care in Columbia and the
three other cities.
Researchers noted where the men had lived before moving
to Boone County, if they were not Boone County natives.
Swan said even very recent exposure to farm chemicals,
not just long-term exposure, could affect one's health.
Swan, who has been a professor at the MU School of Medicine
for four years, said she plans to publish a research article
also based on the study's data that deals with specific
Swan said she also would like to follow the children delivered
by the women whose partners participated in the study
to see whether where they were conceived -- an agricultural
or urban area -- affected their future health.
"Semen quality doesn't get affected in a vacuum,"
Swan said. "We might call it the canary in the mine
shaft. It indicates other potential reproductive problems
because it relates to testicular function. There may also
be problems in the woman's reproductive function. And
there may be indications in other health areas, perhaps
links to cancer down the line."
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