Behind The Numbers: Regulating Water Contaminants a Lengthy Process

There are around 100,000 potential drinking-water contaminants, but the U.S. Environmental Protection Agency regulates only about 90 of them. The selections are based on risk, how often the contaminants occur in water supplies, and the feasibility and cost of detecting and removing them—but even when the agency decides to regulate a contaminant, the process can take years.