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EWG's Tap Water Database — 2019 UPDATE

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Total trihalomethanes (TTHMs)

California Water Service Company-Lancaster

Trihalomethanes are cancer-causing contaminants that form during water treatment with chlorine and other disinfectants. The total trihalomethanes group includes four chemicals: chloroform, bromodichloromethane, dibromochloromethane and bromoform. Read More.

Studies conducted in the U.S. and Europe have found that drinking tap water that carries disinfection byproducts increases the risk of developing bladder cancer. In animal studies, all trihalomethanes cause liver, kidney and intestinal tumors. Some human epidemiological studies also reported an association between disinfection byproducts and an increased risk of problems during pregnancy, including spontaneous miscarriage, cardiovascular defects, neural tube defects and low birth weight.

The health guideline of 0.15 parts per billion, or ppb, for the group of four trihalomethanes, or THM4/TTHM, was defined in a peer-reviewed scientific study by EWG and represents a one-in-one-million lifetime cancer risk level.

Click here to read more about disinfection byproducts.

 

35

Samples

0

Samples exceeding legal limit (MCL)

21

Samples exceeding
health guidelines

Testing results - average by year

 
YearAverage resultSamples takenDetectionsRange of results
2012ND20ND
2013ND10ND
20140.833 ppb64ND - 1.50 ppb
20150.866 ppb107ND - 1.70 ppb
20164.80 ppb86ND - 33.1 ppb
20170.538 ppb84ND - 1.20 ppb

ppb = parts per billion

State and national drinking water standards and health guidelines

EWG Health Guideline 0.15 ppb

The health guideline of 0.15 parts per billion, or ppb, for the group of four trihalomethanes, or THM4/TTHM, was defined in a peer-reviewed scientific study by EWG and represents a one-in-one-million lifetime cancer risk level.

EPA Maximum Contaminant
Level (MCL) 80 ppb

The legal limit for the group of four trihalomethanes, established in 1998, was based on the need for residual disinfectant levels in water served to customers and the cost of treatment. This limit does not fully protect against the risk of cancer due to exposure to trihalomethanes.

ppb = parts per billion

All test results

Date Lab ID Result
2012-12-185810-005-1220ND
2012-12-185810-001-1230ND
2013-06-195701-005-1030ND
2014-05-135701-801-09421.40 ppb
2014-05-135701-800-10090.800 ppb
2014-05-205701-001-1000ND
2014-06-245701-005-1112ND
2014-07-235701-801-10111.30 ppb
2014-07-235701-800-09531.50 ppb
2015-02-035701-800-13071.50 ppb
2015-02-035701-801-12381.40 ppb
2015-05-125701-800-08080.800 ppb
2015-05-125701-801-08091.20 ppb
2015-05-195701-001-0937ND
2015-06-165701-005-1347ND
2015-08-115701-801-09501.70 ppb
2015-08-115701-800-09491.40 ppb
2015-11-095810-800-1650ND
2015-11-095810-801-16410.660 ppb
2016-02-095701-801-09081.50 ppb
2016-02-095701-800-09081.10 ppb
2016-05-105701-801-09190.900 ppb
2016-05-105701-800-0919ND
2016-08-095701-801-09450.800 ppb
2016-08-095701-800-0945ND
2016-11-155701-801-084433.1 ppb
2016-11-155701-800-08441.000 ppb
2017-02-145701-801-09411.20 ppb
2017-02-145701-800-09401.20 ppb
2017-05-095701-801-09560.900 ppb
2017-05-095701-800-0956ND
2017-08-155810-800-1423ND
2017-08-155810-801-1452ND
2017-11-135810-801-15001.000 ppb
2017-11-135810-800-1406ND