Pesticides

Here's a sneak peek into the February issue of Food, Nutrition & Science publishing this coming Monday. From our Health and Wellness section, this article addresses concerns about pesticides and their potential affect on health. To receive Monday's full issue, click here for a free subscription.

Pesticides are a broad class of crop-protection chemicals that include insecticides, which control insects, rodenticides, which control rodents, herbicides, which control weeds, and fungicides, which control fungi, mold and mildew. Some pesticides are naturally occurring chemicals, like sulfur, and others are synthetic. Both are used in modern agriculture and have led to dramatic increases in crop yields, according to the International Food Information Council (IFIC) Foundation.

Since pesticides are expensive, farmers have an incentive to use fewer and more carefully timed applications. The registration and use of pesticides are governed by the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA) and the Federal Food, Drug and Cosmetic Act (FFDCA). The FDA enforces pesticide tolerances for all domestically produced food shipped in interstate commerce and in imported foods. The USDA monitors meat, poultry and some egg products. And many states, like California and Florida, also conduct their own monitoring.

Pesticides have become a controversial topic over the years, and organophosphates (OP) are the major chemical class under scrutiny as a result of the Food Quality Protection Act (FQPA). The FQPA was unanimously passed in 1996 and directed the United States Environmental Protection Agency (EPA) to examine whether current standards protected children. OP’s are also one class of chemicals studied in a Cal Berkeley/Salinas Valley community research project released earlier this year. In that report, Dr. Brenda Eskenazi, the Maxwell Professor of Maternal and Child Health and Epidemiology, and her colleagues studied migrant workers in the area for 12 years, observing that children born to mothers with higher exposure to OP’s had poorer development. 

Observational studies such as this one, says Eskenazi, are the only way to examine toxic exposures in children, and they have been found to identify serious health consequences for exposures once thought to be safe, such as lead in children and cigarettes and cancer. She acknowledges that observational studies can have limitations, but points out that the study examines a priori hypotheses. In other words, it is based on prior knowledge about the toxicology of these chemicals and studies in animals.

Eskenazi says that the CHAMACOS (Center for the Health Assessment of Mothers and Children of Salinas) study is a longitudinal cohort study. In this well-accepted type of study design, there is not a "comparison" group but instead a population with a wide range of exposure, and the population studied here was relatively socioeconomically homogeneous.

“We are examining the relation of variability of exposure measures within this population with a health or developmental outcome,” says Eskenazi. “It is important to see whether our findings are replicated in other populations and in other studies. Consistency across studies helps to inform policy.”

Over the years, the majority of public concern has centered on pesticide residues and their potential affect on health – especially as it applies to children and agricultural workers. But Dr. Daniel Goldstein, Senior Science Fellow and Lead, Medical Sciences and Outreach, for Monsanto, says that there is no convincing data to suggest that pesticide residues on fruits and vegetables cause harm to health. In fact, the FDA’s regulatory monitoring program “Total Diet Study” indicates that the majority of analyzed domestic food samples contain very little or no pesticide residues, and those that do have detectable residues are usually below legally allowable limits. 

“Pesticides are certainly capable of causing harm at sufficiently high doses, but that is not the issue – the dose makes the poison – and dose matters. Pesticide residues (many of which are inactive metabolites) approved for, and typically found, in permitted levels have not been shown to cause harm,” says Goldstein.

Pesticide residues in food and water are expressed as parts per million (ppm), parts per billion (ppb), or parts per trillion (ppt). In other words, 1 ppm is equivalent to 1 gram (g) of residue in 1,000,000 g of food (or 1 cent in $10,000); 1 ppb is equivalent to 1 g of residue in 1,000,000,000 g of food (or 1 cent in $10 million). For each chemical approved for use on a particular crop, the EPA establishes a tolerance – the maximum residue level of a pesticide legally permitted in or on a food or feed.
 
Goldstein points out that while the risks may be low, efforts are nevertheless being made to reduce our reliance on pesticides. Integrated Pest Management (IPM) is a leading approach that balances pest control tactics to achieve results with the least disruption of the environment. The cultivation of pest-resistant plant varieties is an example of IPM. Genetic modification (GM) is another approach.
 
“With GM, there are good data to demonstrate that one can see very substantial reductions in insecticide use – particularly in organophosphates. This undoubtedly reduces field exposures, particularly to applicators on small-plot farms using relatively crude application techniques. Reduction on herbicides is less robust, but these are generally much less toxic to humans, though exceptions exist. It is clear though that GM allows better choices of herbicides. The use of Roundup Ready Corn, for example, allows us to reduce the use of pesticides that have been found in ground water monitoring programs,” says Goldstein.
 
Ultimately, Goldstein says that GM crops allow for better choices for the environment and for human health related to field applications in the developing world. Due to the limited number of crops, differences in application technology, and the fact that commodity crops are not picked by manual labor in the U.S., direct exposure reduction and health benefits for agricultural workers, he says, will most likely accrue to the developing world and will not be major in this country unless we see major growth of GM in table vegetable production.

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