Michigan Food Monitoring Program
1992
Michigan Department of Agriculture

The goal of the Michigan Food Monitoring Program is to characterize and assess potential pesticide exposure through the food chain in Michigan and to make appropriate recommendations to state and federal agencies for proactive risk management. Now in its second year, the Food Monitoring Program continues to analyze raw agricultural commodities for the presence of pesticides. First year samples included apples, asparagus, carrots, cherries (sweet and tart), grapes, lettuce, potatoes, and tomatoes. While a number of pesticides were detected on each of these commodities, all but one were significantly below the tolerance.

Tolerance is the maximum concentration of a pesticide that can be present in a food product allowed for sale. Tolerances are determined by the Environmental Protection Agency (EPA) and enforced by the Food and Drug Administration (FDA) and the Michigan Department of Agriculture (MDA).

Eight raw agricultural commodities were identified for analysis in 1992. The commodities were canola, celery, cucumbers, sugar beets, black turtle beans, cranberry beans, navy beans, and red kidney beans.

MDA Sampling

Samples were collected at random by MDA inspectors and included commodities grown in the state as well as those produced by other states.

The collection schedule and sample sizes are shown in table 1.

Analytical Methodology

Two multi-residue methods were chosen. One referred to as the "Luke" procedure was used to determine a wide range of pesticides that contain phosphorous, chlorine, or nitrogen. The second method was capable of detecting N-methyl carbamates such as carbaryl, methomyl, etc. Both methods were used in the screening mode. A screening analysis for pesticides refers to the extraction and analysis of a commodity to determine the presence of any compound which is known to be recovered by the method. The screening analysis  included a matrix spike containing representative compounds of the classes of recovered compounds. This insured method performance throughout the analysis process. To prevent false positives, every compound detected by screening was confirmed by a second method. The majority were confirmed by mass spectroscopy.

However, in a screening method, the statistical variability of the amount present is not determined for every compound and may be determined only for some representative compounds.

Analytical Results

Table 2 summarizes the number of samples collected, pesticides detected in each commodity, the frequency of the detection, the range of detectable levels and the corresponding food tolerance. No pesticides were detected in any of the four kinds of dry beans: black turtle, cranberry, navy, and red kidney. Twenty-six percent of the celery samples had detectable levels of the fungicide chlorothalonil (Bravo) ranging from 0.1 to 0.8 ppm. The insecticide permethrin was also found in about 30 percent of samples at levels of 0.05 to 0.9 ppm. three pesticides were detected in cucumbers including carbofuran (insecticide), dieldrin (insecticide), and chlorothalonil (fungicide). Carbofuran (Furadan) was detected in 14 percent of samples, chlorothalonil in 24 percent and dieldrin in 19 percent. The insecticide DDT was found at a concentration of 0.03 ppm in one of the 36 (2%) sugar beet samples analyzed. The canola samples analyzed showed no detectable levels of pesticides.

Conclusions

A total of 200 samples were analyzed of which 41 samples (21%) had detectable residues. All pesticides detected are currently approved for use on these commodities or, and in the case of DDT and dieldrin, have had all uses cancelled yet have existing tolerances due to environmental persistence. It is believed that the DDt and dieldrin residues found were associated with soil particles on the surface of the cucumbers and sugar beets. The concentrations of pesticides detected were all below the established tolerances and therefore of insignificant risk. Table 3 shows the percent of tolerance for the highest concentration of a specific pesticide found per commodity.