Published By: Water Quality
Chemical Risk Overview:
The SFPUC drinking water does not contain any contaminants that pose a health hazard. However, many consumers are interested in learning more about how drinking water contamination may occur and how this could affect health. The purpose of these pages is to provide this information for interested people.
Drinking water may become contaminated through naturally occurring processes or human activity. Getting water from its source, purifying it at a treatment facility and distributing it to users may introduce contaminants. Sources of chemical pollutants can be classified into the following categories:
Source Water: Source water, which is untreated water from streams, rivers, lakes, or underground aquifers, may become contaminated through naturally occurring processes. Common natural source water contaminants include radon, arsenic, cadmium, chromium, lead, and selenium, however none of these are present at levels of concern in the SFPUC drinking water sources.
Source Water Contamination: Source waters may become contaminated by accident. Two examples of events potentially leading to source water contamination are: surface spills and leaking underground tanks.
Chemical Addition to Drinking Water: Not all chemicals in water are accidental or undesired. Chemical disinfectants such as chlorine and chloramine are commonly added to drinking water to destroy microorganisms which are hazardous to human health. Also, in many U.S. cities, fluoride is added to prevent and control tooth decay among water consumers.
Disinfection By-Products: Chemicals which are added to kill microorganisms in drinking water may form disinfection by-products when they come into contact with other substances found in water. An example of this is the formation of trihalomethanes, which occurs when chlorine is used to disinfect water containing organic substances.
Distribution System Contamination: Pollutants may be introduced into drinking water as it travels through the distribution pipes to people’s homes. Metals such as lead and copper may be leached from the pipes themselves or contaminants may enter from outside sources through cracked piping.
Chemicals that may exist in drinking water vary in potential risk to consumer’s health. For example, while trace amounts of some elements, like calcium or magnesium, can be beneficial to one’s health, others, such as lead or arsenic, are detrimental in any quantity. To protect consumers, water quality regulations have been set-up at the state and federal levels. Locally, the San Francisco Public Utilities Commission(SFPUC) monitors water quality at the source and in treated water supplies. Yearly, the SFPUC publishes a water quality report listing the chemical content of its water. Furthermore, general information and health effects of sixteen chemical compounds potentially in drinking water are found in the following fact sheets:
Bromate
Chlorate/Chlorite
N-nitrosodimethylamine
Haloacetic Acids
Haloacetonitriles
Halopicrins
Trihalomethanes
