Here's a compelling reason to consider organic gardening and landscaping at home: low-dose exposure to lawn care pesticides my cause injury to developing embryos before pregnancy is even noticed.

That's according to a new study recently released by researchers at the Marshfield Clinic Research Foundation (MCRF) in Marshfield, WI, a system of 40 patient care and research and education facilities in Wisconsin.

MCRF conducted the study because little is known about residential use of pesticides and their possible effects on embryonic development during the first few days of pregnancy.

The study's general use of the term "pesticides" refers to a host of herbicides (weed killers), insecticides (insect killers), fungicides (fungus/mold killers) and fertilizers.

The active ingredients studied include six herbicides (atrazine, dicamba, metolachlor, 2,4-D, pendimethalin, MCPP); three insecticides (chlorpyrifos, terbufos, permethrin); two fungicides (chlorothalonil, mancozeb); one drying agent (diquat) and one fertilizer (ammonium nitrate).

The chemicals are typical of those used in the upper Midwest. Lawn pesticides studied are typical of those used throughout the United States.

Within hours of MCRF publishing "Low-dose Agrochemicals and Lawn Care Pesticides Induce Developmental Toxicity in Murine Preimplantation Embryos" on the Internet (in Environmental Health Perspectives, the journal of the National Institute of Environmental Health Sciences, National Institutes of Health), the Environmental Protection Agency (EPA) asked to review the data for possible inclusion in the re-registration decision process for 2,4-D.

Re-registration is required for pesticides initially registered before November 1984. These pesticides must undergo a complete review as part of compliance with the Food Quality Protection Act (FQPA). Many commonly used pesticides fall into this group, the clinic said.

Since Rachel Carson's "Silent Spring" in 1962 exposed the deadly toxic dangers of DDT (dichloro-diphenyl-trichloroethane, also known as "drop dead twice") numerous studies have suggested that exposure to high doses of other pesticides, such as those experienced by pesticide applicators, may be associated with adverse reproductive outcomes, including spontaneous abortion, birth defects and parental risk of infertility.

"In research conducted with mouse embryos, injury was observed during laboratory studies with a variety of agrochemicals and lawn care products, such as weed and insect killers and fertilizers, at concentrations previously assumed to be without adverse health consequences for humans," said Anne Greenlee, Ph.D., lead author of the article and a scientist at MCRF's National Farm Medicine Center.

The study was funded by the Wisconsin Department of Agriculture, Trade and Consumer Protection (DATCP) and MCRF's disease-specific research funds.

Greenlee's study used mouse embryos to model possible human effects because embryos of different animal species react similarly at this early stage of development.

Researchers examined agrochemicals and lawn care herbicides for their effects on embryo development during the preimplantation period. The preimplantation period corresponds to the first to seventh day of pregnancy, when an embryo is rapidly dividing and before implantation occurs in the mother.

The types of injury observed included slowed embryonic development and reductions in the number of cells comprising the embryo, both of which may contribute to implantation failures and lengthening in time needed to achieve pregnancy.

Greenlee says additional research is needed to validate her findings to better access human risk, but it may be impossible to specifically define the amount or mixture of chemicals dangerous to human reproductive health.

For those who choose not to go the organic route to landscaping and gardening, extreme caution is the alternative.

"Women considering or trying to conceive should make every effort to minimize their exposure to lawn care and agrochemical products," Greenlee said. "Applying these products according to label guidelines and wearing protective gear, such as masks or gloves, can help reduce exposure. It's also important to adhere to the length of time manufacturers recommend you remain off your lawn or field after using pesticides, herbicides and fertilizers," she added.

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