Water Contaminant FAQ

What about Cryptosporidium?

Fortunately, the general public is at very low risk; there have never been any cases of cryptosporidiosis attributed to the public water supply in our service area. However, because the disease is potentially very serious for people with compromised immune systems-such as chemotherapy patients, organ, and bone marrow recipients or people infected with HIV or AIDS, the California Department of Public Health (CDPH) has issued guidance for preventing exposure to cryptosporidium. The guidance recommends that people with such conditions consult with their doctor or health care provider about preventing infection from all potential sources of cryptosporidium and may choose to boil their drinking water for one minute as an extra precaution.

For more information about cryptosporidiosis or a copy of the Fact Sheet, contact CDPH’s Division of Communicable Disease Control at (916) 552-9700. Or contact the Santa Clara County Department of Environmental Health at (408) 885-4214.

What About MTBE?

In 1996, the California Air Resources Board mandated that all gasoline sold in California be reformulated to contain 11 percent oxygenates, most commonly methyl tertiary butyl ether (MTBE), in order to reduce levels of automobile exhaust emissions. While air quality in California has improved since the gasoline was reformulated, MTBE has been found in some drinking water supplies in California. MTBE is particularly problematic because it causes taste and odor concerns even in trace concentrations, and it is highly mobile in water and difficult to remove.

We are monitoring all of our wells and local surface supply for MTBE, and to date it has not been detected. We draw our groundwater from very deep aquifers that are protected by impermeable confining layers of soil. Our local mountain surface water supplies originate from a very pristine and well protected watershed, that allows very little opportunity for pollution. We are also working very closely with the Santa Clara Valley Water District (SCVWD), a wholesale water agency that supplies treated surface water to San Jose Water and seven other water retailers in the county, to monitor the occurrence of MTBE in our imported water sources. SCVWD has previously detected trace levels of MTBE in Calero and Anderson Reservoirs and in water from the State Water Project supplying their three water treatment plants. The levels found in SCVWD's treated drinking water are extremely minute, approximately 1 part per billion (1 microgram per liter) and do not represent a public health risk. This is well below the Health-based Primary Maximum Contaminant Level of 13 ppb as well as the aesthetic-based Secondary Maximum Contaminant Level of 5 parts per billion. The California Division of Drinking Water considers levels below 3 parts per billion to be non-detectable for reporting purposes.

The use of MTBE as a gasoline additive was completely phased out in California at the end of 2002. San Jose Water and SCVWD will continue to monitor our supplies and pursue long-term solutions to this potential problem. For more information about MTBE and other drinking water issues check the homepage of the California Division of Drinking Water.

What is Perchlorate?

Recently, the California Department of Public Health (CDPH) found perchlorate in a number of drinking water sources in California. Perchlorate is an inorganic chemical derived from ammonium perchlorate, which is used in the manufacture of solid rocket propellants and explosives.

Because perchlorate historically has not been considered a common contaminant, no federal or state drinking water standards exist. However, the CDPH has adopted a provisional action level for perchlorate in drinking water of 18 micrograms per liter, or parts per billion (ppb). The primary human health concern related to perchlorate is that it can interfere with the thyroid gland's ability to utilize iodine to produce thyroid hormones. Perchlorate in very high doses has been used in medicine in the treatment of Graves' disease, a condition in which excessive amounts of thyroid hormone are produced.

Although perchlorate contamination of local water supply sources is not considered likely, factors such as the widespread use of the material in defense/aerospace activities and the detection of perchlorate in other areas of California prompted San Jose Water to conduct additional monitoring in our service area. Monitoring completed in January 1998 confirmed that perchlorate is not present in any of our water supplies.

Additional information on perchlorate >>

What are trihalomethanes (THMs)?

Trihalomethanes, also known as THMs, are formed along with other disinfection byproducts when chlorine is added to drinking water during the water treatment process. Chlorine, in addition to destroying disease-causing organisms, reacts with naturally occurring organic matter (dissolved leaves and other vegetation) to produce THMs. THMs include the compounds Chloroform, Bromodichloromethane, Dibromochloromethane and Bromoform.

In our local water supplies, individual THMs are formed at low levels, generally in the range of a few parts per billion (ppb) up to 40 ppb. The total of all THMs may not exceed 80 ppb in accordance with USEPA and State Drinking Water Standards. The current drinking water standard for THMs was developed in response to studies indicating that certain THMs cause cancer in laboratory animals and may pose a similar risk in humans.