Author: Winston Craig, MPH, PhD, RD.
Fruits and vegetables are known to protect against heart disease and cancer. They are rich in vitamins, minerals, fiber, and health-promoting phytochemicals. However, many fruits and vegetables test positive for pesticide residues, with about one-third of them showing up with multiple residues. Research reveals that prolonged exposure to pesticide residues may increase the risk of various cancers and neurological problems (such as Parkinson’s disease), and impair the immune system. Almost 40% of the fruit and 12% ofthe vegetables consumed by Americans last year were imported. With an increasing amount of fresh produce being imported, the pesticide picture is not improving. Imported produce contains, on average, about three times the pesticide residue level found on domestically produced food. Only about 1% of imported foods from Asia and Latin America gets tested by the FDA. A number of recent food-borne illness outbreaks have also been associated with imported produce, such as hepatitis A from strawberries, Cyclospora from raspberries, andE. coli– infection from alfalfa sprouts and lettuce.
About 1.3 million tons of pesticides are used in the U.S. each year, giving an average of 6 pounds of pesticides for every acre planted. Safety tests are required to determine the potential of a pesticide to cause chronic illness in humans. Unfortunately, sufficient data on the reproductive effects and other chronic effects are lacking for most pesticides. Less than 21% of all pesticides sold in U.S. have been adequately tested for carcinogenicity. Less than 10% have been adequately tested for their ability to cause genetic mutations, and less than 40% have been adequately tested for their potential to cause birth defects. In 1978 Congress mandated the EPA to begin reassessing the safety of some 35,000 registered pesticide products, but a lack of funds has seriously delayed the process so that many of the registered pesticides remain unevaluated. At present, there are forty-five pesticides approved for food use that are known or suspected to cause cancer in animals, but it is uncertain at this time whether they are harmful to humans. For the average consumer there is little data available on dietary exposure to a particular pesticide over a period of time, making it very difficult to link pesticide exposure with a specific health problem.
There are a number of reports of adverse reproductive and developmental effects in wildlife resulting from heavy exposure to pesticides, PCBs, dioxins and other environmental contaminants. What evidence is there that pesticides cause harm to human health? We know that those who are exposed through their work, such as farm workers and other persons handling pesticides and herbicides, face the greatest risk. For example, leukemia and cancers of the lymphatic system are more common among workers who for many years have applied phenoxyherbicides along railroads, electrical lines or in agricultural settings. Lung cancer rates are elevated among pesticide applicators while liver cancer and leukemia rates are elevated among farm workers. The incidence of lymphatic, genital and digestive tract cancers correlates with a higher than average herbicide use.
Recent studies in Germany show a link between heavy pesticide use in rural areas and incidence of childhood leukemia. Pesticides, along with PCBs, dioxin and other environmental contaminants may act as endocrine disrupters– interfering with hormonal action and body functions. This makes them possible risk factors for hormone-related cancers such as prostate and breast cancer. Recent studies by the National Cancer Institute in Hawaii suggest that repeated exposure to the endocrine-disrupting chemicals, chlordane/heptachlor and 1,2-dibromo-3-chloropropane, may play a role in the development of breast cancer.
On average, which foods are noted for being the most heavily contaminated with pesticides? Strawberries, cherries, apples, Mexican cantaloupe, Chilean grapes, raspberries, apricots, peas, peaches, nectarines, and spinach. The least contaminated with pesticides include avocados, onions, scallions, corn, cauliflower, cabbage, broccoli, green peas, carrots, sweet potatoes, and blueberries. Pesticides tend to accumulate in fatty material. Hence fatty meats, fish, and dairy products will have higher pesticide residue than the low-fat products. The wax coating on cucumbers facilitates the retention of the fungicides used on cucumbers.
What About Canned And Frozen Foods?
The washing and treatment process to prepare fruits and vegetables for canning or freezing removes or destroys most of the pesticide residues. For example, 80-90% of the benomyl residue (the fungicide suspected of causing birth defects) is removed when apples are made into applesauce and when tomatoes are converted into tomato juice.
There are a number of ways that we can minimize our individual exposure to pesticides. Firstly, eat a variety of foods. This will lessen our exposure to any one pesticide. Secondly, fruits and vegetables should be properly washed or peeled before eating. Fruits and vegetables with edible peels can be cleaned by scrubbing with a brush. Researchers in Texas substantially reduced the pesticide residues on 17 popular fruits and vegetables by washing in a dilute solution of dish detergent (1 tsp. per gallon of water), then rinsing in slightly warm water. The outer leaves of vegetables (lettuce and cabbage) should be discarded since these are the ones most contaminated. Thirdly, one can buy organically grown produce, usually at a higher price. However, an organic label does not guarantee the produce is truly organic. The federal government is working towards developing universal standards for what constitutes an organic food.
Today there are over 5,000 certified organic growers in the US. About one percent of the total U.S. fruit and vegetable acreage is organic. In California, about 2% of the state’s farmers are organic farmers, while Texas reports more than 10% of its vegetable-crops are organically grown. Sales of organic foods reached $3.5 billion in 1996, and continue to increase 20% each year. More and more farmers are reducing reliance on pesticides by adopting integrated pest management.
Overall, the consumption of low-fiber, fat-rich and calorie-rich diets, along with the use of alcohol, pose a much, much greater threat to human health than chemical residues on our food.