Farm 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
The researchers suspect that runoff from farm chemicals may be to
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 bodies.
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
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 study.
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
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 agricultural chemicals.
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."