Perchlorates in water can pose a health hazard—one reason the CDC wants to quantify the problem.

The CDC is carrying out a National Health and Nutrition Examination Survey (NHANES).  It’s a comprehensive series of studies, including both interviews and physical examinations.  The survey is designed to provide a snapshot of “the health and nutritional status of adults and children in the United States.”  The full survey is composed of subsets focussing on specific issues, like this one looking at volatile organic compounds and perchlorates.  After asking a series of questions, the protocol directs the field investigators to sample water from each household and immediately store it in the laboratory refrigerator.