SECONDARY STANDARDS: Even if tap water meets the EPA's basic requirement for safe drinking water, some people still object to its taste, smell or appearance. These are aesthetic concerns, however, and therefore fall under the EPA's voluntary secondary standards. Some tap water is drinkable, but may be temporarily clouded because of air bubbles or have a chlorine taste. A bleach-like taste can be improved by letting the water stand exposed to the air for a while.
HOW MERCURY GETS INTO WATER: Mercury is found in many rocks including coal, which when burned, releases mercury into the environment. Coal-burning power plants are the largest human-caused source of mercury emissions to the air in the United States, accounting for over 40 percent of all domestic human-caused mercury emissions. The EPA has estimated that about one quarter of U.S. emissions from coal-burning power plants are deposited within the U.S. Burning hazardous wastes, producing chlorine, mercury spills or leaks, as well as the improper treatment and disposal of products or wastes containing mercury can also release it into the environment. Current estimates are that less than half of all mercury within the U.S. comes from U.S. sources. Mercury in the air eventually settles into water or onto land where it can be washed into water.
The American Geophysical Union contributed to the information contained in the TV portion of this report.