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National Drinking Water Database


Chloromethane in California


Chloromethane is a naturally occuring chemical that forms during combustion of plant material; it may be released from the manufacture of silicone, rubber and pesticides, and also forms as a byproduct of water disinfection.

The Most Polluted Communities in California

77 water utilities reported detecting Chloromethane in tap water since 2004, according to EWG's analysis of water quality data supplied by state water agencies

Ranked by highest average Chloromethane level

RankSystem Population Served Positive test results of total reported tests Average Level
(Range)
1Bella Vista Mutual Water Company
Weldon, CA
681 of 15.4 ppb
(5.4 ppb)
2Town & Country Water Company
Bakersfield, CA
1001 of 23.4 ppb
(0 to 6.8 ppb)
3Mission Springs Conference Center
Scotts Valley, CA
5641 of 11.9 ppb
(1.9 ppb)
4H2O, Inc
Arroyo Grande, CA
601 of 51.7 ppb
(0 to 8.5 ppb)
5Holly Ranch Village
Fort Bragg, CA
781 of 11.7 ppb
(1.7 ppb)
6Lake County Csa 22 - Mt. Hannah
Kelseyville, CA
1001 of 11.4 ppb
(1.4 ppb)
7Spindrift Marina
Isleton, CA
1001 of 11.4 ppb
(1.4 ppb)
8Squaw Valley Mutual Water Comp
Olympic Valley, CA
5001 of 21.35 ppb
(0 to 2.7 ppb)
9Ridge Mutual Water Company
Los Gatos, CA
2401 of 11.15 ppb
(1.15 ppb)
10Rancho Sespe Workers Imp Assoc
Ventura, CA
4001 of 21.15 ppb
(0 to 2.3 ppb)

Health Based Limits for Chloromethane

StandardDescriptionLevel
Lifetime health-based limit, non-cancer riskConcentration of a chemical in drinking water that is not expected to cause any adverse, noncarcinogenic health effects for a lifetime of exposure. The Lifetime health-based limit (or Health Advisory, HA) is based on exposure for a a 70-kg adult consuming 2 liters of water per day. Source: U.S. Environmental Protection Agency.30 ppb
Health-Based Screening LevelA benchmark concentration of contaminants in water that may be of potential concern for human health, if exceeded. For noncarcinogens, the HBSL represents the contaminant concentration in drinking water that is not expected to cause any adverse effects over a lifetime of exposure. For carcinogens, the HBSL range represents the contaminant concentration in drinking water that corresponds to an excess estimated lifetime cancer risk of 1 chance in 1 million to 1 chance in 10 thousand. Source: U.S. Geological Survey.30 ppb
Drinking Water Equivalent LevelA lifetime exposure concentration protective of adverse, noncarcinogenic health effects, that assumes all of the exposure to a contaminant is from drinking water. Source: U.S. Environmental Protection Agency.100 ppb
Children's health-based limit for 10-day exposureConcentration of a chemical in drinking water that is not expected to cause any adverse, noncarcinogenic effects for up to ten days of exposure. The Ten-Day health-based limit (or Health Advisory, HA) is typically set to protect a 10-kg child consuming 1 liter of water per day. Source: U.S. Environmental Protection Agency.400 ppb
Children's health-based limit for 1-day exposureConcentration of a chemical in drinking water that is not expected to cause any adverse, noncarcinogenic health effects for up to one day of exposure. The One-Day health-based limit (or Health Advisory, HA) is typically set to protect a 10-kg child consuming 1 liter of water per day. Source: U.S. Environmental Protection Agency.9000 ppb

Violation Summary for Chloromethane in California

There are no violations reported for this contaminant in California