The U.S. Environmental Protection Agency has begun a major new risk assessment of 20 flame-retardant chemicals. These compounds have been widely used for decades in many consumer products, from furniture to sleepwear. But the chemicals are toxic. And although they are being phased out, they have become a worldwide pollutant -- and a threat to human health. Measuring their presence in our water, soil, and air has been a major challenge. But as Erika Celeste reports, a new technique promises to make it easier.