Excerpts from an interview with Dr. Charles Benbrook
Nutrition Action Healthletter
Q: Should we be concerned about pesticide residues?
A: Yes. We know that prolonged exposure to pesticides raises the risk of some cancers, neurological problems like Alzheimers and Parkinsons diseases, and developmental problems. It can also weaken the immune system, which leaves us more vulnerable to disease.
Those exposed through their work -- farmworkers, pesticide applicators, people who work in manufacturing plants -- face the greatest risk.
However, there is rarely, if ever, solid information available on the levels of pesticide exposure a person has experienced. And that makes it difficult for scientists to definitely link pesticide exposures that might have happened years ago -- even prior to birth -- to specific health problems. [for more information see: Pesticides and Human Health]
Q: What's the evidence that pesticides cause cancer in humans?
A: The most thoroughly researched examples are the so-called phenoxyherbicides, which raise the risk of leukemia and cancers of the lymphatic system. These cancers are more common among workers who have applied those herbicides along railroads or electrical lines, or in agricultural settings or forestry, for many years.
Evidence is not nearly so clear in the case of other cancers and other pesticides, But we know that many cancers are not cause d by one thing or exposure to a single carcinogen. Sometimes it takes 20 or 30 years for a tumor to form. If pesticides impair the immune system over such a long period, they might be one reason why a person gets cancer, or whether he or she gets it at age 40 instead of age 60.
Q: How do pesticides affect the immune system?
A: Humans are blessed with a phenomenally complex and effective immune system when it's working well. Everyone is exposed to the flu bug many times during the winter, but most of us only get one bout of the flu, and some don't even get it once.
But pesticide exposure can impair or block or disrupt both the development and the normal triggering of the immune system.
For example, in the late 1980s and early 1990s, the highly toxic insecticide aldicarb was widely present in the drinking water in central Wisconsin. Researchers at the University of Wisconsin documented an impaired immune response in women living in houses with high aldicarb levels in the drinking water.
Q: Have researchers found more evidence since then?
A: Several other studies have since documented at least a short-term impact on the normal functioning of the immune system. It is enormously important that we find out how pesticides and other pollutants interfere with the treatment and prevention of hepatitis, AIDS, cancer, and a range of opportunistic infections, from pneumonia to ear infections in children.
There is also suggestive evidence from lawsuits in which doctors have documented neurological symptoms in families that have gone back into homes that had recently been treated for termites or other insects.
Q: What about neurological problems in children?
A: There are some. FOr example, Japanese scientists recently linked a cluster of nearsightedness in school-children that occurred in the 1950s and 1960s to exposure to organophosphate insecticides. And scientists at the Environmental Protection Agency's Research Triangle Park Laboratory in North Carolina have recently demonstrated that, in chickens, exposure to these pesticides changes the shape and development of the eyeball, which can lead to nearsightedness.
Studies are under way to see if endocrine disruptors increase the risk of hormone-related cancers like breast and prostate and whether they cause reproductive problems like lower sperm counts. Endocrine disruptors may also impair the nervous and immune systems.
Q: Are all endocrine disruptors pesticides?
A: No. We're exposed to many others -- including PCBs and dioxin -- through the air, water, and the products that we purchase, like buying a car that's got that "new car smell." People can also be exposed when they bring into their homes furnishings that have been treated with fire-retardants or fabric-guards.
Still, pesticides are likely a significant source of exposure to endocrine disruptors for many, if not most, people. Nearly 40 percent of the pesticides applied in agriculture are known or suspected endocrine disruptors.
Q: Do grains have fewer residues?
A: Yes. Wheat and bread and other grain products tend not to have residues. That's because milling often removes them. Plus, most grains are treated predominantly with herbicides that are sprayed before or very soon after planting, long before the harvested edible part of the plant ever forms.
But there clearly are exceptions. Rice grown in the Southeastern U.S., for example, is often treated with fungicides before it's harvested. So it sometimes contains residues.
Q: How can you urge people to eat more fruits and vegetables when pesticides may cause diseases like cancer or
A: Many non-organic fruits and vegetables don't contain detectable levels of pesticide residues. Fruits and vegetables have high levels of fiber, vitamins, minerals and phytochemicals. There's strong evidence that they help protect against heart disease and some forms of cancer. I am a strong supporter of the National Cancer Institute's 5-a-Day program, which encourages people to eat more fruits and vegetables. And I believe that progress on the farm in adopting Integrated pest management (IPM) will steadily reduce reliance on pesticides and residue levels. IPM uses pesticides only as a last resort.
Q: How else can people avoid pesticides?
A: They can buy fresh and processed organic foods, and they can support stores and growers that offer organic. People can also look for produce that's been okayed by the NutriClean program, which some supermarkets use to certify that their produce contains no detectable pesticide residues. And shoppers can buy food that's been grown under biologically based IPM programs.
While there isn't much IPM produce in supermarkets yet, more is on its way, perhaps this year.
Consumers Union is going to assess the IPM programs used by major food companies. A few are making significant progress. We're interested in tomato products, peanut butter, fruit juices, and other foods that may contain significant residues. We'll rate companies IPM programs and tell the world what we find.