Textbook Problem

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 did the children's urine contain the lowest level of the malathion metabolite?

Summary Introduction

To determine: The phase of the experiment in which children’s urine contains the lowest level of the malathion metabolite.

Concept introduction: Conventionally, the fruits, vegetables, and grains are produced in which pesticides are used. Pesticides such as malathion and chlorpyrifos are neurotoxicant. At the high level, it works by inhibiting acetylcholinesterase.  This can lead to paralysis, breathing problem, and even death. Due to its toxic effect, the fruits and vegetable are produced through organic farming without the use of pesticides and gain the label of USDA’s organic label.

Explanation of Solution

The study was performed to assess the effect of eating organic food on the level of pesticides in children’s bodies. The urine samples were collected over the course of 15 days from 23 children aged between 3 to 11years. The samples were tested for the breakdown products of two synthetic pesticides malathion and chlorpyrifos. The study was conducted in three phases. In first phase conventional food was given for 3 days, then the organic food for 5 days, and again conventional food for one week.

Refer to Fig. 40.11 “concentration of metabolites of two pesticides in children’s urine” in the question; the second (organic) phase of the experiment contains mean malathion value of 0.3 µg/liter which is lower than the first phase (conventional phase, 2.9 µg/liter) and the third phase (conventional phase, 4.4 µg/liter) of the mean value. Therefore, in the second phase of the experiment, children’s urine contains the lowest level of the malathion metabolite.

Conclusion

The urine during phase two, when ingesting an organic diet, contained the lowest level of metabolite.