Measuring Contaminants in the Food Supply. (Behind the Lab Door)

Article excerpt

Since the early 1960s, the Food and Drug Administration has been conducting a "market basket" study of average American food-consumption patterns for different age/gender groups. This "market basket"--a selection of foods eaten in the typical diet--is analyzed for chemical contaminants. The results are used to estimate the average intake of contaminants. The information obtained is used to formulate regulations and to track the impact of regulations. Several government agencies use the findings.

Market-basket studies, officially designated as the Total Diet Study (TDS) program, grew out of the concerns of many scientists in the late 1950s regarding nuclear-weapons testing and the potential contamination of food by radioactive fallout. The isotopes strontium 90 and cesium 137 were of special concern. It was thought that milk was the most likely food to be contaminated. Because milk was consumed by all segments of the population and especially by vulnerable groups such as infants, young children, and the elderly, this food needed to be monitored.

The U.S. Public Health Service, the U.S. Atomic Energy Commission, and their counterpart agencies in the United Kingdom, Germany, and Japan, all began to test milk for possible radionuclide residues. At the same time, home economists at 25 American colleges and universities, in collaboration with a consumer organization, tested a wider variety of foods for possible residues of radionuclides.

In 1961, the FDA began its TDS monitoring program, and focused on residues of organophosphate and organochlorine pesticides, industrial chemicals, toxic trace elements, and radionuclides. At first, the foods chosen were based on a typical 16- to 19-year-old boy's food intake. This age/gender group was known to consume the greatest quantity of foods of any group, and therefore would be at highest risk for dietary exposure to contaminants.

The first study was conducted in 1961 in Washington, D.C. Investigators purchased samples of 82 commonly consumed food items every three months at four different supermarkets, over one year. They analyzed the samples in laboratories.

The following year, the study was expanded to include sample foods collected from different areas of the country. The foods, from San Francisco, St. Louis, Minneapolis, and Atlanta, were prepared by dietitians at hospitals and universities, and sent to Washington, D.C. for analysis by FDA laboratory technicians.

Later, the program was expanded. Many more typically eaten foods were added for analyses. Also, the FDA added more pesticides, industrial chemicals, and toxic trace elements for testing.

Until the early 1980s, the laboratory analyses consisted of several foods, combined as they might be present in a meal of meat, eggs, grains, and fruits. Later, the foods were combined in a dozen different types of meals before they underwent analysis.

In 1982, the TDS program was reorganized. The laboratory analysis was expanded to include 234 individual "core foods." representing those foods consumed by Americans most commonly and in the greatest quantities. The selection of some foods was based on findings from consumption surveys conducted by the U.S. Department of Agriculture. This revision of the TDS Program yielded more information about the levels of contaminants in specific foods, rather than in food-group combinations. The revision increased the numbers and types of contaminants analyzed.

At an earlier stage, in 1973, the FDA had begun to test some food nutrients in the TDS program. By 1983, in the expanded program. FDA laboratory technicians were analyzing food for 11 nutrients. In the early 1990s, vitamins [B.sub.6] and folate were added to the list of nutrient analyses.

Currently, the TDS program continues, collaboratively, with the central and regional offices of the FDA. The Agency's Center for Food Safety and Applied Nutrition (CFSAN) controls the contents and focus of the program. …