A recent study published in Environmental Health Journal assessed the risks to children from the cumulative exposure to chemicals and pesticides in a variety of foods. The study claims that cancer and non-cancer benchmarks were frequently exceeded by children for several food contaminants. Based on the study’s findings, the researchers suggested that new dietary guidelines be developed to minimize exposure to these contaminants.
The study generated some media attention, so we asked Carl Winter, PhD, Director, FoodSafe Program, Extension Food Toxicologist at the University of California-Davis, to provide some insights on the findings.
Best Food Facts: The study suggests that children could be negatively impacted by the cumulative risk of pesticide exposure from certain foods. How did the authors of the study determine the risk of pesticide exposure in children?
Dr. Winter: “The authors of the study relied upon results from government monitoring programs to estimate food contaminant levels, combined the results with food consumption estimates to estimate exposure, and then compared exposure levels with government-established health criteria to ascertain the health significance of the exposure levels.
“The unique contribution to this paper was the authors’ development of food consumption estimates based upon telephone surveys of northern and central California residents. The surveys did not attempt to establish total food consumption patterns, but focused upon consumption of 44 specific food items considered to represent the greatest sources of exposure to pesticides, metals, acrylamide, and persistent environmental pollutants.”
Best Food Facts: The study focused specifically on California. How do the food consumption estimates used in the study compare with national daily averages?
Dr. Winter: “When the food consumption estimates derived from the authors’ survey are compared with national daily averages, it appears as though the authors dramatically overestimate food consumption rates. In the case of children ages 2-6, for example, the authors’ estimates of consumption of the 20 most widely-consumed foods are greater than consumption rates from national surveys for all but one of the foods. Remarkably, on the average, food consumption estimates for these 20 foods were more than five times higher than estimates from national surveys.
“Some examples of consumption rates of specific foods from the survey data include the following:
Carrots – 12.7 times greater than the national average
Sweet Potatoes – 11.7 times greater
Tomatoes – 10.1 times greater
Strawberries – 9.8 times greater
Grapes – 8.9 times greater
Potatoes – 7.5 times greater
Pears – 5.6 times greater
Broccoli – 5.1 times greater
“In my opinion, this apparent large overestimation of food consumption patterns may significantly overestimate contaminant exposure levels and calls into question the validity of the authors’ findings and subsequent conclusions.”
Best Food Facts: The study found levels of arsenic and other chemicals in children to be above the safety consumption benchmark levels. What are the consumption benchmark levels for the chemicals mentioned in the study, and how do they compare with the study’s findings?
Dr. Winter: “The authors report that while the mean exposure of pre-school age children to arsenic is below the maximum acceptable oral dose as determined by the EPA, it is estimated that 18.36 percent of pre-school age children are exposed to levels exceeding this reference dose. This reference dose, however, is established for inorganic arsenic, while the contaminant monitoring data used to calculate exposure sampled total arsenic, which includes both inorganic arsenic and organic arsenic, a form of arsenic representing much lower toxicological concern.
“The authors do discuss the importance of this difference in types of arsenic and accurately indicate that inorganic arsenic usually represents less than half of the total arsenic. Such an important difference might not be noticed by the casual reader of this paper, however.
“The authors also concluded that “non-cancer benchmarks were exceeded for >95% of pre-school age children for acrylamide.” In reaching this conclusion, the authors relied upon an out-of-date estimate for the maximum acceptable oral dose of acrylamide (0.0002 mg/kg/day) that was established in 1988. This reference dose was adjusted by the U.S. Environmental Protection Agency in March 2010 to a level 10 times higher (0.002 mg/kg/day). Applying the more contemporary reference dose to the pre-school age median exposure estimates results in an exposure of less than half of the maximum acceptable oral dose.
"Where lead and DDE are concerned, the authors report that 100% of pre-school children exceeded the reference doses for both. Since no reference dose is established for either of these chemicals, this represents a curious interpretation. In essence, any miniscule exposure to either of these two chemicals would lead to a similar conclusion, thus ignoring the important dose/response relationship inherent in the risk assessment process.”
Best Food Facts: What did the study’s findings show relative to pesticide exposure?
Dr. Winter: “The study provided exposure estimates for six pesticides. Three of these (chlorpyrifos, permethrin, and endosulfan) were selected as examples of “current use pesticides,” while three others (chlordane, dieldrin, and the DDT breakdown product DDE) were selected to represent “persistent organic pollutants.” For the three current use pesticides, there was not a single participant in the pre-school aged group demonstrating an exposure in excess of the reference dose, and the median exposures were well below reference doses in all cases. Strategies to further reduce exposure to current use pesticides through increased purchasing of organic fruits and vegetables do not seem warranted by these findings.
“With respect to the three persistent organic pollutant pesticides, no participants in the pre-school aged group demonstrated exposures above the established reference dose level. However, the median exposures to dieldrin and DDE did exceed the cancer benchmark.”
Best Food Facts: The study recommends that the consumption of more organic fruits and vegetables would help minimize exposure to pesticides. Are organic fruits and vegetables safer than conventionally-grown fruits and vegetables where pesticides are concerned?
Dr. Winter:“Results from this study show and many others confirm that exposures to current use pesticides are at only a tiny fraction of levels considered to represent a “reasonable certainty of no harm,” so any further reduction in exposure to pesticides from consumption of organic fruits and vegetables is not likely to be of any appreciable health benefit. In terms of exposure to “persistent organic pollutant” pesticides,these pesticides may be present in small amounts in fields for which both organic and conventional agricultural techniques are practiced. Evidence supporting this hypothesis comes from the results of the California Department of Pesticide Regulation’s 2010 monitoring of organic and conventional fruit and vegetable samples analyzed for pesticide residues. These results showed that out of 137 organic fruits and vegetables sampled, four samples (2.9%) showed detectable residues of DDE, and 53 samples of conventional fruits and vegetables out of 2,883 (1.7%) showed detectable residues of DDE.”