Dr. Chensheng "Alex" Lu of Emory University and colleagues tested the urine of 23 Seattle-area children over a 15-day period in order to measure their exposure to malathion and chlorpyrifos, organophosphorus pesticides (OP) which often are used in US agricultural production. Previous research has linked OPs to causes of neurological effects in animals and humans.

Same Food, But Organic

The participants, who ranged from three to 11 years of age, were monitored for three days on their conventional diets. Then they were switched to a mostly organic diet. After five days of testing, the children once again were given their normal foods and monitored for an additional seven days.

To ensure that any detectable change in dietary pesticide exposure would be attributable to the organic food rather than the change in diet, the researchers substituted organic versions of items the children normally eaten would have as part of their conventional diet, including fresh fruits and vegetables, juices, processed fruits or vegetables (e.g. salsa), and such wheat-based or corn-based products as pasta, cereal, popcorn or chips.

Non-Detectable Levels

"Immediately after substituting organic food items for the children's normal diets, the concentration of the organophosphorus pesticides found in their bodies decreased substantially to non-detectable levels until the conventional diets were re-introduced," says Dr. Lu, an assistant professor in the department of environmental and occupational health, Rollins School of Public Health, Emory University.

Most of the children's urine samples contained zero concentration for the malathion metabolite during the days when they ate organic foods. After they returned to their regular diets, the average malathion metabolite concentration increased to 1.6 parts per billion with a concentration range from 5 to 263 parts per billion, Dr. Lu explains.

A similar trend was observed for chlorpyrifos. The average chlorpyrifos metabolite concentration increased from one part per billion during the organic diet days to six parts per billion when children consumed conventional food.

Fewer Restrictions in Agriculture

"Recent regulatory changes aiming to minimize children's exposures to pesticides have either banned or restricted the use of many organophosphorus pesticides in the residential environment. However, fewer restrictions have been imposed in agriculture," Dr. Lu says.

Organophosphorus pesticide residues are found routinely in food items that young children commonly consume, according to the annual survey by the US Department of Agriculture Pesticide Data Program.