No such thing as "safe" levels of contamination

Cross-disciplinary research reveals low-level pesticide exposure linked to myriad of learning, behavioral and medical problems.

By Amanda Kimble-Evans

editor's NOTE Rodale Institute’s researchers continue to work with a range of soil and crop scientists to evaluate the dynamics and benefits of regenerative organic farming. To extend our understanding of the benefits of organics for human health, we’re looking at the work of Dr. Warren P. Porter. Officially, Dr. Porter is professor of zoology and environmental toxicology at the University of Wisconsin, Madison. But the scope of his expertise includes environmental and molecular toxicology, conservation biology and engineering physics. Through a series of life events, a gift of intense curiosity and a willingness to follow the scientific evidence where it leads, he’s discovered disturbing scientific evidence of unacknowledged risks from non-organic farming products and techniques. His research interests include: impacts on organisms subjected to simultaneous changes in climate, topography and vegetation (as is happening due to global warming phenomena); impact of low-level contaminant/pesticide mixtures on organisms and biological communities in terms of reproduction, food-web interaction, developmental processes, neurological function (learning abilities and aggression levels), immune function and endocrine function. He addressed Rodale Institute staff and local health care professionals this week, laying out key research findings pointing to the need for a radical reconsideration of the impact of pesticides on human and wildlife populations. Here’s a bit of background and some of his major talking points.

In 1995, Warren P. Porter, Ph.D., read an article in the Wisconsin State Journal that reported skyrocketing remedial education costs due to an increase in children with disabilities in the Madison school district. The numbers were surprising: an 87-percent jump in children with emotional disturbances, a 70-percent increase in children with learning disabilities and 83 percent more children with physical disabilities between 1990 and 1995.

What Dr. Porter noticed as he began to look at other communities, was that there was an epidemic change in these levels worldwide. "My children are everything to me," said Dr. Porter. And so he began to ask "Why?"

Because he is a professor of zoology and environmental toxicology at the University of Wisconsin, Madison, Dr. Porter attacked this nagging question scientifically. Because he is Dr. Warren Porter, he began to look into the advanced academic research from several disciplines to find the answer.

In 1998, Elizabeth Guillette published her finding on the affects of agrichemicals on preschool children in the Yaqui Valley of Sonora, Mexico, the source of much of the U.S. supply of winter fruits and vegetables. Children regularly exposed to pesticides on the farms in the valley displayed classic signs of severe neurological devastation. They also expressed poor coordination, low stamina, poor memory and heightened aggression when compared to the children who lived just a few miles away in the mountains and were not exposed.

In the 10 years since Dr. Guillette published her shocking findings, Dr. Porter and a number of other researchers have begun to take a cross-disciplinary look at the effects common pesticides have on the health and well-being of our communities at levels considered "safe" by the current regulatory bodies in the U.S. According to Dr. Porter, "normal" exposures in food, water and air may be creating many of the serious long-term health problems emerging in humans and wildlife.

National and international research projects show that pesticides contribute to an increase in aggressive behavior, birth defects, developmental roadblocks, failing immune function and sexual disorders. And evidence is just surfacing that our fundamental genetic constitution could be in jeopardy.

There are no straight lines in nature

Dr. Porter cites a number of problems with how the wider scientific community and the Environmental Protection Agency have underestimated the risks associated with pesticides, including herbicides and fungicides.

"They assume a linear dose response. In toxicology the size of the dose is what is considered important in determining how poisonous something will be." Meaning, the more to which you are exposed, the worse the effect.

But, says Dr. Porter, a bell-shaped dose response is much more common in real life. "Physiologically, the timing of the dose is often more important than size." Meaning, it is possible that a very low-level exposure during a particular period of development can have a dramatic affect, whereas the same exposure before or after that period may have no affect at all.

A study by Levin, et al. in 2002 found the learning ability of female rats was affected the most when exposed to the lowest dose of a pesticide called chlorpyrifos during in-utero development. Higher-dose exposure showed much less of a negative response. Another study by Agoos, et al. in 2007 found the very same "inverse dose response" in female mice. As mice are very different than rats physiologically, it was surprising to see a consistent response.

The same inverse dose response pattern was seen in a 2002 study by Cavieres, et al. where researchers dosed the drinking water of pregnant mice with a common herbicide at high, intermediate, low and very low levels. The highest degree of fetal losses was at the very low level.

And, again, in a 2005 study on another common pesticide's ability to affect brain function, the inverse dose response appeared. Rodriguez, et al. found 5 mg of atrazine had more of an effect on neurotransmitters in the brain than 10 mg of the very same chemical.

"It should be noted that the EPA only tests the effects of intermediate concentrations," says Dr. Porter, "since the assumption is that there will be less of an effect the smaller the concentration."

Porter also points to studies by Richard, et al. (2005) and Fan, et al. (2007) that show how two common herbicides effect the levels of testosterone and estrogen in the system at "environmentally relevant levels," or levels currently found in the environment. They found that atrazine increases the levels of estrogen in the system and glyphosate increases the levels of testosterone. Changes in the levels of these sex hormones feed back to the brain and immune systems leading to other systemic problems, says Porter. "It's like ripping up telephone cables. The signals get mixed and broken. You end up with serious long-term consequences that are very difficult to diagnose."

Creating a successful poison

When confronted with these studies, Porter asked himself, "Why do pesticides and herbicides at low-levels have such devastating systemic affects on animals, including humans?" This lead him to the second assumption in our regulatory process that has created a toxic loophole.

"It all goes back to the principles of creating a poison that effectively kills," says Porter. "You want something that is quickly and easily absorbed through the 'skin' or outer defense system and something that is water- and fat-soluble which gives it a 'master entry key' to every cell in the body, brain and/or fetus."

Solvents (organic soaps) and surfactants (that diminish the surface tension of water) are added to pesticide and herbicide formulations to create a product that encourages effective uptake and allows access to all cells of the targeted organism. The problem is that they are also absorbed through our skin and lungs more effectively and they have a master entry key to our cells, says Porter.

Dr. Porter cites two independent studies that determined the "inactive" ingredients in Round-up make it twice as biologically active and, therefore, twice as potentially toxic as the potential of it's "active" chemical parts. Unfortunately, solvents and surfactants are not tested as part of the EPA registration process. "For example," says Porter, "the EPA registers glyphosate, the chemical considered an active ingredient in Round-up, not Round-up itself."

Passing the damage on

Researchers at Washington State University studied DNA of male rats and discovered DNA sequences were altered through methylation (changes in the epigenic pattern) by exposure to the fungicide vinclozolin. "Methylation patterns reflect our environmental history," says Dr. Porter. "It's our genetic response to environmental insults." Porter points out that early-immune insults have also been linked to asthma, allergies, autoimmune diseases, cancer, cerebral palsy and male sterility.

The expression of the NCAM1 gene, specifically, was blocked by exposure to the fungicide. Diseases related to this gene include Alzheimer's, schizophrenia, neural tube defects and various tumors, says Porter.

The revealing piece of the Washington State University study was the fact that the DNA alterations caused by exposure to the fungicide were actually passed down four generations.
"The evidence is strong," says Dr. Porter. "We are compromising our children and our children's children."

The extent of our exposure

Recent studies have begun to capture the true extent of our low-level exposure to pesticides that could be quietly causing serious health problems in our population. The toxins are nearly inescapable in the water we drink, the food we eat and the air we breathe.

Lu, et al. (2006) measured organophosphates in the urine of Seattle children and discovered levels of chemical indicators up to 14 parts per billion "Organophosphates are neurotoxins by design and we're capable of responding to neurotoxins in the parts per trillion level," says Porter, "especially during [fetal] development."

And new work by Paul Winchester, et al. is taking a look at the correlation between the amount of atrazine in the water at the time of conception to the math and reading skills of Indiana children.

"The public has been slow awakening to the danger of low-level pesticide exposure," said Porter. "And the EPA regulatory process doesn't capture the full and devastating risk of these chemical cocktails."

Dr. Porter suggests we rework the way chemical products are registered to reflect discoveries related to non-linear dose responses, the effects of solvents and surfactants, the compound and synergistic affects of chemical mixtures, and the differences in hormonal and developmental responses between males and females.

In the meantime, the study by Lu, et al. offers a path to reducing our exposure. When the Seattle children were put on an organic food diet, concentrations of the chemical indicators in their urine were undetectable within five days.

Porter agrees: "Buy organic or grow your own, and get a really good water filter for your drinking and washing water. It won't eliminate all your exposure, but it will dramatically reduce your risk."

Amanda Kimble-Evans is an editor at the Rodale Institute. She specializes in nutrition issues and recently became a mom. Growing up surrounded by small farms and large gardens in northeast Pennsylvania, Amanda was raised to have a close relationship with the food on her plate. She continues to cultivate that relationship in her home, in her garden, and through her work at the Institute.

Key citations:

1. Elizabeth A. Guillette, et al. An Anthropological Approach to the Evaluation of Preschool Children Exposed to Pesticides in Mexico. Environmental Health Perspectives, June 1998 (v.106, n.6). 
   
   Comparative study of children in the Yaqui Valley of northwestern Mexico, evaluating growth, development and abilities. Some of the children were exposed to high levels of multiple pesticides while children from the same genetic group and families living nearby were not exposed. Significant functional differences were noted. Full study