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Getting to the Bottom of Perchlorate

California is fighting a costly battle against the chemical perchlorate, a component of fuel for rockets and missiles. The state's aerospace and defense companies, as well as the military, have used large amounts of the chemical since World War II.

But in recent years, perchlorate has been discovered in California's water supplies. The state has suggested that even tiny amounts are worrisome. So communities have shut down wells, filed lawsuits and started costly clean-up efforts. Remarkably, all of this has taken place without any solid evidence that even the most contaminated water has made anyone sick. NPR's Jon Hamilton reports in a two-part series.

Part 1: The Health Risks

If there's any place in California where perchlorate might have been expected to hurt people, it's Rancho Cordova. The city lies just east of Sacramento and right next to one of the nation's worst perchlorate spills. Hamilton reports on attempts to link the contamination to health problems.

Part 2: The Cost of Clean-Up

Billions of gallons of potential drinking water in California are going unused because of fears about over perchlorate. Studies show that small amounts don't cause any health problems. But California is encouraging cities to shut down wells rather than serve water with more than a trace of the chemical. That's causing problems in a state where water is scarce. Hamilton reports on one city's struggle -- Rialto -- to keep its water pure without sacrificing its future.

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Jon Hamilton is a correspondent for NPR's Science Desk. Currently he focuses on neuroscience and health risks.