In January storage tanks owned by Freedom Industries spilled 10,000 gallons of industrial chemicals into the Elk River in West Virginia. The toxic liquids washed a short distance downstream into the region's largest drinking-water treatment plant. About 500 residents checked into local hospitals; 300,000 people could not use tap water for weeks on end; and businesses closed, leaving employees without a paycheck.

Similar stories abound. In February failed pipes at a Duke Energy dump sent tens of thousands of tons of hazardous coal ash into the Dan River in Eden, N.C., which supplies the drinking water for communities in both North Carolina and Virginia. Industrial and agricultural chemicals show up repeatedly in groundwater that serves millions of Californians. Nationwide, 19 million Americans become sick every year from viruses, bacteria and parasites that sneak through ineffective municipal drinking-water treatment plants, according to a New York Times investigation.

Contamination of water supplies occurs for many reasons. Chemical storage tanks, often poorly built and monitored, can leak and foul drinking water. Inspectors in many (if not most) states do not even know where all those states' chemical storage facilities are located. And the Environmental Protection Agency has placed significant restrictions on only five of the tens of thousands of chemicals used commercially.

It is time for state and federal legislators to strengthen regulations that protect U.S. drinking-water supplies and for government agencies to aggressively enforce the rules. Regulation-averse West Virginia passed its own bill after the Elk River spill. Congress should follow its lead and pass the Chemical Safety and Drinking Water Protection Act. The law would require states or the epa to inventory chemical storage facilities and to examine them annually. Storage tanks would also have to meet minimum standards for construction and leak detection. The Senate Committee on Environment and Public Works approved the legislation in April, but as of early May, the bill had not been scheduled for a full Senate debate. Opposition to the bill is being led by energy, utility and industrial companies that would be forced to upgrade their infrastructure.

A thorny question is where states would get the money to enforce the rules. One place is the Drinking Water State Revolving Fund, which provides federal aid for such purposes. The Obama administration and some members of Congress, however, want to cut $100 million from the $900-million fund. Those cuts should not go through.

Wider measures should also be taken to safeguard drinking water. The Toxic Substances Control Act, last updated in 1976, allows industry to use new chemicals without first demonstrating that they are safe. Instead it places the burden of proof on the epa. Yet of the more than 50,000 chemicals used commercially, the epa has tested just 300.

The epa can more effectively tackle those 50,000 chemicals by improving and expanding the experimental Tox21 and ToxCast systems it has developed with the National Institutes of Health. These systems rely on automated, robotic laboratories that can examine the effects of hundreds of chemicals at a time on human cells and proteins. Those that react should be put on a short list for thorough toxicity testing.

One welcome development is that municipal treatment plants have started to go beyond basic filtering and disinfecting, which can allow chemicals, bacteria and pharmaceuticals to remain in the water supply. Cincinnati and Louisville use activated carbon filters and ultraviolet light disinfection to make water cleaner. San Diego has built a pilot plant that can turn wastewater directly into superclean drinking water [see “Bottoms Up,” on page 68]. Regulators should allow municipalities to bring such plants online.

Unfortunately, there is no single solution to our water woes. Clean water requires keeping water sources pristine and then scrubbing the water further at advanced treatment plants. It requires coordinated actions from federal, state and municipal governments—actions that may lead to increased costs for industries and perhaps even consumers as well. But as residents of West Virginia and North Carolina have recently learned, there is perhaps no more vital resource than the one we count on to flow out of our taps.