Michelle Hammond and Jeremiah Holland were intrigued when a friend at the Oakland Tribune asked them and their two young children to take part in a cutting-edge study to measure the industrial chemicals in their bodies.

Tests showed that Rowan, at 18 months, had high levels of a chemical in his bloodstream that can cause thyroid dysfunction in rats.
1 of 3 "In the beginning, I wasn't worried at all; I was fascinated," Hammond, 37, recalled.
But that fascination soon changed to fear, as tests revealed that their children -- Rowan, then 18 months, and Mikaela, then 5 -- had chemical exposure levels up to seven times those of their parents.