common pesticide may be infertility culprit in women: Yale Medicine

Common Pesticide May be Infertility Culprit in Women

by John C. Martin

A common pesticide used on crops may lead to reduced fertility in
women, says a new study from Yale University.1

The research team, at the Yale School of Medicine, found that the
pesticide known as methoxychlor (MXC) may reduce female fertility by
interfering with proper development and function of the reproductive
tract.

Chemical Found in Food, Water: Government MXC is a man-made pesticide
manufactured as a safer replacement for the now-banned DDT. It is used
to kill flies, mosquitoes, cockroaches, and other insects, and is
applied directly to food crops, livestock, home gardens, and pets. MXC
is included in a class of chemicals that mimic the action of hormones,
and in some cases, it can interfere with hormonal function.

According to the government, MXC may also be found in drinking water,
and may cause health problems if found in quantities higher than those
set by the Environmental Protection Agency (EPA). However, according to
the EPA, production of MXC in the United States has plunged from about
3.7 million pounds in 1978 to 700,000 pounds, starting in 1982. While
the chemical can be released into the environment due to its use as a
pesticide, and also during the manufacture, packaging, and disposal of
the chemical, such releases totaled only about 2000 pounds over the
entire period between 1987 and 1993.2

MXC also degrades rapidly in drinking water, within days, compared to
within months in soil, the EPA states.2

You can be exposed to the chemical through breathing contaminated air
or eating contaminated food, but it leaves your body rather quickly,
experts point out. Once in the body, methoxychlor can change into other
chemicals, which are then released by the body. Sometimes, low doses of
MXC can be found in food from when it was applied to crops. If you work
in a factory that produces the chemical, you risk breathing it in, or
getting it on your skin. If you work on a farm using the chemical,
exposure is also more likely, as in cases in which gardening products
or pet sprays that contain MXC are used.3

How MXC May Affect Fertility The research team led by Hugh Taylor, MD,
an associate professor in the Division of Reproductive Endocrinology
and Infertility at Yale, found that MXC alters the function of a gene
that regulates estrogen in the reproductive tract and reduces the
ability of the uterus to support embryo implantation. They used mice
and samples of human cells in reaching their findings.

"MXC has an adverse effect on these mice similar to that of DES, a
synthetic estrogen," Taylor explained. "Female offspring of women
exposed to DES were more likely to have an abnormally shaped cervix,
and were more prone to cancer of the vagina, early labor and other
complications."

Effect on the Uterus The gene focused on in this study is known as
Hoxa10. It regulates the events that lead to preparation of the uterus
to receive an embryo after fertilization, just before it implants
there. In the study, Taylor and his colleagues found that MXC disrupts
the function of the Hoxa10 gene, making the uterine environment more
hostile for the inbound embryo. This was seen after mice in the study
were given doses of the chemical.

In a lab experiment using human cell lines, Taylor's team found that
treating the cells with estradiol-a form of estrogen-mediated the
interaction between the Hoxa10 gene and estrogen, as it's supposed to.
However, when MXC was introduced, the pesticide disrupted the gene's
ability to regulate the hormone.

In mice, MXC blocked the effect of estradiol on the function of the
Hoxa10 gene, as well.

"One common mechanism by which endocrine [hormonal]-disrupting
chemicals produce lasting reproductive tract defects is through
alteration of developmental gene _expression," the research team wrote.

But limiting your exposure to the chemical isn't likely to be harmful,
the government stresses. The EPA has established a so-called "Reference
Dose" for metholxychor at 0.005 milligrams per day. The agency says
people exposed to MXC at this level will not experience any harmful
effects. It adds that consuming this amount of the chemical over a
lifetime will not cause chronic health effects, as well.3

1. Fei X, Chung H, Taylor HS. Methoxychlor disrupts uterine Hoxa10 gene
_expression. Endocrinology 2005 Aug;146(8):3445-51. Epub 2005 May 12.
2. U.S. Environmental Protection Agency. Consumer Factsheet on
Methoxychlor. Available at:
http://www.epa.gov/safewater/contami.../methoxyc.html.
Accessed September 27, 2005. 3. U.S. Environmental Protection Agency.
Methoxychlor. Available at:
http://www.epa.gov/epaoswer/hazwaste...s/methoxch.pdf.
Accessed September 27, 2005.



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