From: Robina Suwol
Date: 18 Sep 2002
Time: 15:25:50
Remote Name: 24.28.136.94
LOS
ANGELES TIMES
http://www.latimes.com/news/science/la-na-weeds17sep17013053.story?coll=la%2
Dnews%2Dscience
THE NATION
Study Links Weed Killer to Reproductive Problems
Science: Tests on mice reveal an increase in failed pregnancies, researchers
report.
By EMILY GREEN
TIMES STAFF WRITER
September 17 2002
A cocktail of the three most common herbicides used by about 29 million American
households to kill dandelions may reduce fertility and cause miscarriages,
according to a study published today in the toxicology journal Environmental
Health Perspectives.
The results come as the Environmental Protection Agency prepares to review the
licensing of one of the chemicals, now used in more than 1,500 lawn-care and
agricultural products.
In the study, researchers at the University of Wisconsin-Madison and the
University of Valparaiso in Chile spiked the drinking water of laboratory mice
with weed killer, then charted the animals' reproductive rates. They found a 20%
increase in failed pregnancies at extremely low doses--seven times lower than
the maximum allowable rate for U.S. drinking water.
University of Wisconsin toxicologist Warren Porter said his group deliberately
selected the sort of weed killer most commonly employed by American homeowners
on their lawns. He would not name the brand, other than to say: "We bought
it in a hardware store."
He does, however, name the active ingredients: a mix of three "phenoxy
herbicides" called 2,4-D, dicamba and mecoprop. Typically blended together
into weed killers and "weed and feed" products, they kill broadleaf
plants such as dandelions while sparing grass.
They work by confounding the hormone system of the broadleaf plants, causing
them to choke their nutrient and water channels with their own growth.
The Scott and Dow Chemical Cos. were among the first to market 2,4-D in a host
of weed killers and weed-and-feed formulations immediately after World War II.
Since then, they have been formulated in more than 1,500 products made by scores
of companies. Most of these are over-the-counter products and will contain, in
addition to the herbicides, industrial soaps to help the chemical cling to and
then penetrate the plants.
Trials scrutinizing the safety of the products have typically only looked at the
herbicides singly and have shown the chemicals to have either low, or no,
toxicity. In the last 10 years, the pesticide industry has spent $30 million on
2,4-D toxicity trials.
North Carolina agronomist Don Page, who represents the leading suppliers of the
chemical in the U.S., has presented to the EPA 270 safety studies sponsored by
his clients. He believes the chemical and products containing it are safe.
"The only verified examples of 2,4-D poisoning in humans is in suicides. If
you drink enough of it, you can kill yourself," he said in June. He
declined to comment on the latest study.
However, since the late 1970s, independent studies of crop workers in Europe and
Kansas have suggested that pesticide applicators working heavily with products
containing 2,4-D had higher rates of non-Hodgkins lymphoma.
In the mid-1990s, University of Minnesota pathologist Vincent Garry conducted
studies in wheat, sugar beet and potato farming regions and found twice the rate
of birth defects among children of crop workers who conceived the children
during the months when the pesticide 2,4-D was sprayed.
Garry began to suspect that the reason the chemicals looked safe in trials
conducted for the government regulators is because the labs were using pure
2,4-D, while crop workers were handling an enhanced chemical blend. Porter
suspected the same thing. Designing the Wisconsin study, he set out to examine
the toxicity of the mix as sold over the counter, not the single herbicides
tested for the EPA.
"We have no idea what kind of reactions might be going on once these active
ingredients are formulated into products," he said. "You're talking
about putting a lot of very reactive chemicals together in a mix, and storing it
at room temperature."
From Minnesota, Garry praised the choice to use the commercial mix. "It
brings up the notion that it is the commercial-grade product that people are
exposed to, and these need to be studied," he said. He added that he would
like to see further tests to confirm the radical effects of such low doses.
Oakland research scientist Robert Gunier, an epidemiologist who has studied the
effects of pesticides for the California Department of Health Services, praised
the Wisconsin study for looking at such low doses. Most testing is done at
extremely high doses, he said. "I think it really raises some important
issues about how regulatory testing is done."
Spurred by the Kansas cancer study and Garry's work in Minnesota, the EPA is now
reviewing the safety literature of 2,4-D and expects a decision on the status of
the chemical in 2004.