Test kitchen.

On 16 Friday mornings each year, 10-12 volunteers-mostly women in their 70s and 80s-gather in the kitchen of the United Methodist Church of Belton, Missouri. title first to arrive is Faye Wallace, a retired bookkeeper who wipes down the counters, turns on the ovens and starts making ]rot wrier at 7:30.

In the modest church kitchen, Wallace and other volunteers cook hundreds of pounds of meats and vegetables--and as many as 250 other recipe items--until they are table-ready. The resulting feast would be suitable for any church function, but no one ever has the pleasure of eating it. By about 10:30 a.m., the food finds a temporary home in the bellies of gallon-sized glass jars on their way to a nearby US Food and Drug Administration (FDA) lab in Lenexa, Kansas. At the lab, giant blenders grind the food into testing consistency as part of the Total Diet Study, a 42-year-old FDA program that monitors contaminant and nutrient levels in the typical American diet.

The testing, which is performed for 4-5 weeks four times a year, can reveal the presence of more than 300 different pesticides and industrial chemicals and 15 elements. The foods are brought to Belton from different cities in each of the four geographic regions of the country (West, North Central, South and Northeast). Wallace's involvement with the program began in the mid-1980s, when the FDA needed a new food preparation site close to its Lenexa lab. Willing to lend a hand, she and other members of her church volunteered.

Lacking professional culinary and scientific training, the Belton women were perfect cooks for the study. "The program is really ...