Know Your Environment. Protect Your Health.

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.

 

48

Samples

0

Samples exceeding legal limit (MCL)

22

Samples exceeding
health guidelines

Testing results - average by year

 
YearAverage resultSamples takenDetectionsRange of results
201821.4 ppb880.700 ppb - 70.0 ppb
20190.989 ppb84ND - 2.80 ppb
20200.253 ppb82ND - 1.02 ppb
202111.5 ppb84ND - 46.0 ppb
20226.63 ppb82ND - 38.0 ppb
202312.3 ppb82ND - 50.0 ppb

ppb = parts per billion

State, National, and Health Guidelines for Drinking Water

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
2018-02-13CA1910010_DST_800-20180213155770.0 ppb
2018-02-13CA1910010_DST_801-20180213154855.0 ppb
2018-05-15CA1910010_DST_801-20180515094518.7 ppb
2018-05-15CA1910010_DST_800-20180515094523.4 ppb
2018-08-14CA1910010_DST_800-2018081410020.700 ppb
2018-08-14CA1910010_DST_801-2018081410021.20 ppb
2018-11-13CA1910010_DST_800-2018111310040.900 ppb
2018-11-13CA1910010_DST_801-2018111310051.60 ppb
2019-02-12CA1910010_DST_801-2019021215472.80 ppb
2019-02-12CA1910010_DST_800-2019021215171.50 ppb
2019-05-14CA1910010_DST_800-201905141014ND
2019-05-14CA1910010_DST_801-2019051410142.33 ppb
2019-08-13CA1910010_DST_800-201908131449ND
2019-08-13CA1910010_DST_801-2019081315131.28 ppb
2019-11-12CA1910010_DST_800-201911121058ND
2019-11-12CA1910010_DST_801-201911121040ND
2020-02-11CA1910010_DST_800-202002110954ND
2020-02-11CA1910010_DST_801-2020021109291.02 ppb
2020-05-12CA1910010_DST_800-202005121222ND
2020-05-12CA1910010_DST_801-202005121235ND
2020-08-18CA1910010_DST_801-202008181455ND
2020-08-18CA1910010_DST_800-202008181430ND
2020-11-09CA1910010_DST_800-202011091521ND
2020-11-09CA1910010_DST_801-2020110915011.000 ppb
2021-02-08CA1910010_DST_800-202102081201ND
2021-02-08CA1910010_DST_801-20210208115215.0 ppb
2021-05-11CA1910010_DST_800-202105111405ND
2021-05-11CA1910010_DST_801-20210511144046.0 ppb
2021-08-10CA1910010_DST_801-2021081015037.70 ppb
2021-08-10CA1910010_DST_800-202108101432ND
2021-11-08CA1910010_DST_801-20211108103323.0 ppb
2021-11-08CA1910010_DST_800-202111081141ND
2022-02-15CA1910010_DST_800-202202151408ND
2022-02-15CA1910010_DST_800-20220215141815.0 ppb
2022-05-10CA1910010_DST_800-202205101318ND
2022-05-10CA1910010_DST_801-202205101413ND
2022-08-09CA1910010_DST_800-202208091541ND
2022-08-09CA1910010_DST_801-20220809152238.0 ppb
2022-11-15CA1910010_DST_800-202211150956ND
2022-11-15CA1910010_DST_801-202211150935ND
2023-02-14CA1910010_DST_800-202302141031ND
2023-02-14CA1910010_DST_801-202302140925ND
2023-05-09CA1910010_DST_801-20230509143650.0 ppb
2023-05-09CA1910010_DST_800-202305091343ND
2023-08-15CA1910010_DST_801-20230815121048.0 ppb
2023-08-15CA1910010_DST_800-202308151156ND
2023-11-14CA1910010_DST_800-202311141052ND
2023-11-14CA1910010_DST_801-202311141231ND