Here's a compelling reason to consider organic gardening and landscaping: low-dose exposure to lawn-care pesticides may cause injury to developing embryos before pregnancy is even noticed. That's according to a new study report released last week by researchers at the Marshfield Clinic Research Foundation in Marshfield, Wis., 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 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 asked to review the data for possible inclusion in the re-registration­decision 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. Many commonly used pesticides fall into this group, the clinic said.

"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 effects on human embryos 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 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 constituting the embryo, both of which may contribute to implantation failures and longer times required to conceive.

Greenlee says additional research is necessary to validate her findings, and she concedes it may be impossible to specifically define the amount or mixture of chemicals dangerous to human reproductive health.

Since Rachel Carson's Silent Spring in 1962 exposed the deadly toxic dangers of DDT (dichloro-diphenyl-trichloroethane, also known as "drop dead twice"), studies have suggested that exposures 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.

For those who choose not to go the organic route when landscaping and gardening, extreme caution is the alternative. "Women considering conception 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.

The full report, "Low-dose Agrochemicals and Lawn Care Pesticides Induce Developmental Toxicity in Murine Preimplantation Embryos," is online at http://ehp.niehs.nih.gov/docs/2004/6774/abstract.html. Background on the historic Silent Spring is also available online at http://www.nrdc.org/health/pesticides/hcarson.asp.

Real estate writer Broderick Perkins, executive editor of San Jose-based DeadlineNews.Com, writes regularly for
Los Gatos Weekly-Times.