Michigan Food Monitoring Program
1991
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. Eight raw agricultural commodities were identified for analysis in 1991. The commodities were chosen according to consumption levels or production volume in Michigan and complement the food monitoring program of the US Department of Agriculture (USDA). The pesticides to be analyzed were chosen because of the volume of use, availability of methodology, and the need for more exposure data.

MDA Sampling

Samples were collected at random by Michigan Department of Agriculture (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 on 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 phosphorus, 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 to 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 ensured 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 for some representative compounds.

Analytical Results

All but one of the pesticide residues detected were below FDA tolerances; however, the frequencies of detection were higher than expected given previous MDA monitoring programs. Table 2 summarizes the pesticides detected in each commodity, the frequency of the detection and the range of detectable levels. For example, carbaryl was found in 18 out of 50 sample apples (36%) analyzed. The residue levels of carbaryl in apples ranged between 0.01 to 0.76 ppm.

Other Food Monitoring Programs

FDA

The FDA program is perhaps the largest program and has several components. The first component is regulatory monitoring which enforces tolerance levels set by the Environmental Protection Agency (EPA). Regulatory monitoring involves surveillance and compliance monitoring. In surveillance monitoring, samples are collected and tested for chemical tolerances. Compliance monitoring is used when a chemical is found on a particular crop above the tolerance level. FDA monitors the growers or importers until they are in compliance with the regulation.

The second component is the Total Diet Study or Market Basket Study. It is designed to estimate the dietary intake of pesticide residues of eight age/sex groups ranging from infants to senior citizens. 19,962 food samples were tested by FDA. 19,146 of these were surveillance samples. No residues were found in 60% of domestic samples or 64% of imported samples. 2.8% of the surveillance samples were found to be above the tolerance level.

The 1990 Total Dietary Study demonstrated that dietary intake of pesticides are below the standards established by the World Health Organization and EPA. These results are similar to those found in previous years and continue to demonstrate that levels of pesticide residues in the food supply are low.

As with FDA, MDA also performed a Market Basket Survey to determine the dietary exposure of chemicals to Michigan residents and found that vegetables and fruits accounted for the majority of exposure. Therefore, MDA concentrated its resources to examine exposures from fruits and vegetables. MDA and FDA sampling protocol and screening methods are similar, although the MDA sampling is more random. MDA modified the methods to lower the limit of detection.

USDA

The USDA Pesticide Data Collection program objectives are to:

1.	Collect comprehensive, statistically valid, and scientifically based pesticide usage and residue data; and
2.	Provide EPA with pesticide residue data that it could use in making pesticide re-registration decisions.

Michigan is one of six states that participate in the USDA program. Currently, the Food Division collects seven randomly selected samples of ten agricultural commodities per month. The Laboratory Division analyzes the samples, targeting specific compounds. MDA's data are then combined with the other states. The results of the USDA program and the Michigan Food Safety program indicate that the levels of pesticides were low, but the frequency was high.

A total of 1,901 samples were analyzed of which 422 samples (22%) had detectable residues. Most of the residues were detected at levels substantially below the tolerance levels. The percentage of positive samples varied by commodity as follows: apples (38%), grapes (34%), potatoes (27%), oranges (19%), lettuce (17%), grapefruit (16%), and none in bananas.

Five hundred and eleven pesticide residues were detected in the 1,901 samples including: Iprodione/grapes (15.2%), dicloran/grapes (14.6%), cloropyrifos/apples (15.7%), permethrins/lettuce (9.4%), clorophropham/potatoes (17.9%), azinphos-methyl/apples (15.6%), captan/apples (8.%), and thiabenzadone/citrus (60%).