Michigan Food Monitoring Program
1993
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 third 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.  

In 1992, the commodities tested were canola, celery, cucumbers, sugar beets, black turtle beans, cranberry beans, navy beans, and red kidney beans. A total of 200 samples were analyzed of which 41 samples (21%) had detectable residues. The concentrations of all pesticides detected were all below the established tolerances and therefore of insignificant risk.  

Twelve raw commodities were selected for analysis in 1993. The commodities included apples, asparagus, blueberries, cauliflower, corn, grapes, mint, onions, peaches, pears, plums, and potatoes. A total of 225 samples were analyzed.  

MDA Sampling  

Samples were collected at random by Michigan Department of Agriculture (MDA) inspectors. Samples were collected from various post harvest locations including the producer, distributor, and in a few cases, the retailer.  

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, pesticides detected in each commodity, the frequency of the detection, the range of detectable levels and the corresponding food tolerance.  

Conclusions

A total of 225 samples were analyzed of which 109 samples (48%) had detectable residues. However, several commodities had detectable levels of pesticides for which no tolerances exist. This included atrazine in asparagus, diphenylamine and esfenvalerate in peaches, and oxamyl and methomyl in plums. In addition, two of the peach samples showed concentrations of chloropyrifos in excess of the tolerance (0.05 ppm). Table 3 shows the number and percent of samples having one or more pesticides detected for each commodity. For example, nineteen of twenty apple samples (95%) showed the presence of one or more pesticides as did 19% of asparagus, 100% of blueberries, 0% of cauliflower, etc.

The concentrations of most of the pesticides detected were below the established tolerances and therefore of insignificant risk. Those pesticides that were found above tolerance were at levels of no toxicological significance. however, all commodities that had residues above tolerance were resampled and seized if necessary. Planned use investigations either have been or will be conducted by MDA regional staff at all grower locations where these commodities were produced.