Toxic groundwater: Even "safe" pesticide levels may be harmful
Common farm chemicals that reach ponds and groundwater may be damaging wildlife and humans in previously unknown ways.

By Greg Bowman, New Farm® editor

Organic systems utilize water much more effectively

“The organic soils at our farm soak up precipitation much more effectively,” says Bill Liebhardt, Research Director at The Rodale Institute. “This means less erosion of soil, less silting of streams, less flooding and no new pesticide residue moving into surface waters.

“At the same time, our non-conventionally farmed soils that are rich in organic matter absorb water much better, storing it longer in dry seasons and allowing less agricultural water to move downward into the groundwater,” he said. “Again, these fields have no herbicide (weed killing chemicals) applied, so no residue flows into the groundwater that provides drinking water for so many millions of Americans.”

Liebhardt is completing a two-year analysis comparing water quality in side-by-side, long-term trials of conventional and organic grain production. Technicians at The Institute are gathering data from the 21-year-old Farm Systems Trial (FST) and the 10-year-old Compost Utilization Trial (CUT).

The comparison shows that herbicides give more consistent weed control in the conventional plots, but over the trial period, did not deliver greater yields. The pesticide-free organic field plots had more weeds, but end up yielding as well as the conventional areas. And with potential price we pay in human health for pesticide pollution, that equality of yield may be very significant.

OCT. 15, 2002, KUTZTOWN, PA: At much lower levels than previously thought, common agricultural pesticides in groundwater can harm frogs, mice and possibly humans, especially during early development in utero. Organic farming, however, creates water-absorbent soil and does not add to this pesticide residue in groundwater, according to Dr. William Liebhardt, research director at The Rodale Institute.

New data from The Institute's long term Farm Systems Trial (comparing conventional and organic systems) show atrazine levels in water from conventionally farmed soil that exceed concentrations now shown to harm organisms. Further, this documented injury comes at concentrations lower than the US-EPA safe drinking water standard.

Dr. Liebhardt said a report from Rodale Institute, due out next spring for farmers, landowners and policy makers, will detail the significant differences seen in organically farmed soils at the farm, located in Kutztown, Pa. Further, the report will highlight the health implications of how agricultural pesticides are used by farmers across North America.

More than 60 million pounds of the herbicide were applied last year in the United States alone. Manufacturer Syngenta estimates that farmers use the herbicide to control weeds on about two-thirds of all U.S. corn and sorghum acreage. On average, it improves corn yield by slightly more than 4 percent. The compound has generally been considered safe because it quickly decomposes in the environment and, being water soluble, is quickly excreted from the body. However, new research identifies unexpected effects that are not so benign.

Most significantly, two recent studies indicate that Atrazine residue in groundwater and surface waters has harmful effects in combinations that it does not have on its own. This indirect effect reveals a weakness in current safety testing on ecological and health impacts of herbicides prior to release of new materials.

Liebhardt cites three researchers who have found that herbicides in groundwater have a detrimental impact on animals and possibly humans. They lend some urgency to The Institute's research documenting that organic production prevents herbicide and pesticide pollution of groundwater.

  • Warren P. Porter, of the University of Wisconsin, and others reported in 1999 that common ag chemicals in a groundwater mixture with each other and nitrates had detrimental impacts together that they did not have individually. The mixtures, including herbicides, had negative effects on the nervous, immune and endocrine (hormone) systems of mice in a five-year study.

    Impacts showed up as suppressed immune function, altered thyroid levels hormone levels and behavior (increased aggression) changes. Other studies show other chemical contaminants induce similar health risks, and that these together may contribute to human developmental injury prior to birth. Results could include attention deficit and/or hyperactivity disorders, autism syndromes, multiple chemical sensitivity, elevated irritability, and aggressive behavior.

    See, an Interview with helpful explanations of human risks

  • Tyrone B. Hayes, of the University of California at Berkeley, and others, reported in April that Atrazine disrupts the sexual development of frogs at concentrations 30 times lower than levels allowed by the US-EPA. At frequently occurring environmental levels, the pesticide demasculinizes tadpoles, turning them into hermaphrodites with male and female sexual characteristics. Atrazine lowered levels of the male hormone testosterone in adult male frogs by a factor of 10, according to a report from the National Science Foundation.

    In the NSF story, Hayes said “The use of atrazine in the environment is basically an uncontrolled experiment – there seems to be no atrazine-free environment.” He doubts that atrazine’s impact on humans is as severe, because of all the time frogs spend in direct contact with contaminated water. However, the low-dose impact on frogs may indicate risk to the development of human sex hormones and characteristics, as well.
  • Joseph M. Kiesecker, a biologist at Penn State University, and other reported in July that deformities in frogs were increased when the amphibians suffered damaged immune systems caused by pesticide exposure. Tested were atrazine, malathion (used in households and on farms) and Esfenvalerate, a synthetic pyrethroid appreciated because it is thought be to fairly safe for birds and mammals. The latter material class is highly toxic to many other kinds of organisms, including the frogs he tested.

    He conducted studies in the field where the frogs were living, at times with deformity occurrence levels of 20 to 30 percent. While a parasitic infection caused the deformities, the impact was heightened by even very low levels of atrazine and the synthetic pyrethroid.
    For details:

Also troubling for Liebhardt, who serves as research director at The Institute, is a 1998 report that has brought many more researchers to look at human developmental effects of pesticides. Anthropologist E.A. Guillete of the University of Arizona found profound and pervasive differences in two groups of Mexican children with similar genetics and culture, but different exposure to pesticides. She documented dramatic differences in short-term memory, hand-eye coordination and stamina, as well as a striking difference in the ability to draw a person.

Her work, its impact in the scientific community and action it spawned in a Canadian municipality, can be seen in the new video release “Playing with Poison.”

Liebhardt is overseeing final data collection and analysis of the Rodale soil water study.

Watch here for news of The Institute’s report in spring 2003, with recommendations on practical ways that farmers and policy makers can significantly reduce agricultural pesticide pollution. “It’s like driving while intoxicated – we just can’t afford it,” says Liebhardt of continued casual acceptance of pesticide use now shown to harm wildlife and, quite probably, developing babies as well.