continued-
Contaminants sneak into food
Finding those traces is painstaking.
Donning safety goggles, Sack picks up a flask filled with smushed yellow cake. He adds in alcohols, solvents and salts -- "pesticides hate salt" -- and boils and siphons the now-watery mixture to leach out everything but the pesticide-containing fat.

A faintly yellow, oily skin rises to the top -- those few bites of cake were 15 percent fat, thanks to the icing. A sophisticated machine then isolates chemical molecules, separating pesticide residue from fat and identifying it.

The cake harbored traces of methyl chlorpyrifos, a widely used insecticide found in virtually any wheat-containing product "unless it's organic, and then there's no guarantee," Sack says.

Down the hall, FDA metals specialist Duane Hughes burns chocolate cake, hunting traces of lead. Metals such as brain-harming lead and mercury can sneak into food through polluted soil or water. Finding them requires destroying all of a food's organic compounds, using acid and temperatures up to 880 degrees. A machine that measures the light absorption of atoms in the remaining ash tallies any metal.

Contaminant traces are mostly what the Total Diet Study records, levels usually far below federal safety limits -- on the order of a part per billion, the equivalent of a kernel of corn in a silo 45 feet tall.

As long as they're legal, why bother counting so low?

"We learn every day that levels once thought safe are in question," responds Hughes, the metals specialist. He notes that the government is about to lower by more than three-quarters the amount of arsenic allowed in drinking water.

And as levels of well-known pollutants like DDT and PCBs have plummeted in recent years, concern shifts to newer contaminants like volatile organic compounds -- industrial chemicals such as the solvent benzene or petroleum byproduct toluene -- found in more and more food.

Even traces add up over time, warns Richard Wiles of the Environmental Working Group, a consumer advocacy organization.

Using FDA's findings, the environmental group is about to urge grocery stores to sell brands of peanut butter and other child-friendly foods that contain the fewest chemicals. Some brands contain 30 different contaminants, admittedly legal traces, Wiles says -- but he contends parents would prefer peanut butter without any benzene or toluene.

"Can we clean up the production processes to get rid of them?" he asks. "It's always better to reduce your exposure to these synthetic chemical contaminants when you can."

'Cooking for the federal government'

The Total Diet Study doesn't hunt every threat. Food-poisoning bacteria, for instance, aren't on the list -- the government tries to tackle those bugs through a mix of different programs. That's where FDA should put more focus, contends Caroline Smith DeWaal of the advocacy Center for Science in the Public Interest.

Another weakness: The program can trace the source of most foods if contamination is found, but can't always track fresh produce -- so finding which farmers used illegal pesticides this year is unlikely.

Still, "it's an early warning system ... because they look at foods in a way nobody else does and find things nobody else finds," Wiles says.

FDA's church ladies must cook carefully to avoid altering the findings.

They use steel utensils that won't leach metal into food, and a specially cleansed water supply to avoid contaminants from the local tap. They can't just wipe off a dropped biscuit -- it could have picked up lead from dust tracked in on the women's shoes.

They shrug off the national importance of the sweaty work. When asked, they just say, "We're cooking for the federal government."

"It's wonderful fellowship," says Martha McKarnin as she fries pork chops.

And it earns the church $2,000 a year, more than traditional bake sales.

"You go home and have to take a shower -- you smell," McKarnin says, waving aside the smoke. But, "I'm an old farm gal, I'm used to hard work."