part one of a two-part series, PBS NewsHour Science Correspondent Miles O'Brien travels to Hinkley, Calif. -- the town whose multi-million dollar settlement for groundwater contamination was featured in the movie "Erin Brockovich." Now, almost 30 years later, O'Brien explores the reasons why the groundwater in Hinkley still has dangerous levels of the chemical chromium and its link to cancer.

More than 80,000 chemicals are on the market in the United States, with hundreds added each year. The Environmental Protection Agency and other regulators are supposed to protect the public from contaminants in air, water and consumer products that can cause cancer and other illnesses. But the chemical industry's sway over science and policy is powerful. Toxic Clout explores how the industry's actions create uncertainty and delay, threatening public health.