To Read Your Water Report

In the next few weeks and months, water agencies in California will be sending consumers annual water quality reports. At right is a portion of the 1996 report by the Metropolitan Water District. The full list includes average levels, if any, of contaminants found at various test sites. Agencies test for contamination throughout the year and are required to send separate notices when levels exceed safety standards.

The Measurements

Use the state maximum contaminant level (MCL) to determine if chemicals detected fall within state and federal safety standards. Most water agency brochures show amounts in milligrams per liter (mg/L). Many environmental experts say an easier way to understand the amounts is in parts per billion. To convert milligrams per liter to parts per billion, move the decimal point three places to the right. For example, the safety standard for trihalomethanes--a contaminant linked in one research report to an increase in miscarriages--would convert to 100 parts per billion.

Organic Chemicals

These chemicals are usually man-made contaminants. Most pesticides are given scientific names in the brochures but are more recognizable under a variety of brand names. Some examples: Alachor=Lasso; Chlordane=Futura; Glyphosate=Rodeo, Roundup; Picloram=Grazon, Tordon.

Volatile Organic Compounds

These may be of concern because they tend to evaporate and may expose consumers to health risks through contact with the skin or inhalation.

Inorganic Chemicals

These chemicals occur naturally in the earth and represent a fingerprint of the source water that comes out of your tap. Measureable chemicals may reflect traces of the rocks and minerals swished by your tapwater en route to filtration plants. Consumers may want to pay particular attention to levels of arsenic, lead and nitrates, which tend to be most commonly found at levels of concern.

Secondary Standards-Aesthetic Standards

Chemical levels in this category reflect the taste and odor of your water and are not usually considered health threats. But consumers may want to be alert to certain chemicals to which they they or their families may be particularly susceptible. Sulfates in tap water, for example, have been known to cause diarrhea in some infants. Those concerned about salt intake should watch out for sodium and chloride levels. Look at levels of calcium and magnesium to indicate hard water. High levels of iron and magnesium may explain clothing stains found after washing. Foaming agents refer to soap and other detergents.

More Information

For additional questions or concerns about the quality of your water, contact:

* California Dept. of Health Services (916) 445-4171 https://www.dhs.cahwnet.gov

* Metropolitan Water District of Southern California (213) 217-6485 https://www.mwd.dst.ca.us

* Assn. of California Water Agencies (916) 441-4545 https://www.acwanet.org

* U.S. Environmental Protection Agency, Office of Ground Water and Drinking Water Publications (800) 426-4791 https://www.epa.gov/ow/OGWDW/Pubs

* American Water Works Assn. (303) 794-7711 https://awwa.org