Chapter 40, Problem 2DAA

Pesticide Residues in Urine To carry the USDA’s organic label (right), food must be produced without synthetic pesticides that farmers often use on conventionally grown, fruits, vegetables, and many grains.

Chensheng Lu of Emory University used urine testing to see whether eating organic food has a significant effect on the levels of pesticides in children's bodies (FIGURE 40.11). Over the course of 15 days, Lu and his colleagues collected the urine of 23 children (aged 3 to 11) and tested it for breakdown products of two synthetic pesticides. The children ate their normal diet of conventionally grown foods for three days, switched to organic versions of the same foods and drinks for five days, then returned to their convention.al diet for a week

FIGURE 40.11 Concentrations of metabolites of two pesticides (malathion and chlorpyrifos) in children’s urine during the three different phases of the study. The difference in the mean level of metabolites between the organic and conventional phases of the study was statistically significant.

During which phase of the experiment was the maximum level of the chlorpyrifos metabolite detected?