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EWG's Tap Water Database — 2021 UPDATE

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Total trihalomethanes (TTHMs)

Golden State Water Company (GSWC) - South Arcadia

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.

MORE ABOUT THIS CONTAMINANT

 

96

Samples

0

Samples exceeding legal limit (MCL)

62

Samples exceeding
health guidelines

Testing results - average by year

 
YearAverage resultSamples takenDetectionsRange of results
2013N/A00N/A
20142.63 ppb1611ND - 9.60 ppb
20152.87 ppb1612ND - 8.40 ppb
20162.81 ppb1612ND - 6.90 ppb
20171.36 ppb168ND - 4.40 ppb
20181.85 ppb169ND - 7.40 ppb
20192.15 ppb1610ND - 7.00 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
2014-01-239588-802-08005.00 ppb
2014-01-239588-800-0835ND
2014-01-239588-801-0810ND
2014-01-239588-803-08203.50 ppb
2014-04-229588-803-08009.60 ppb
2014-04-229588-802-07404.00 ppb
2014-04-229588-801-07503.40 ppb
2014-04-229588-800-08151.10 ppb
2014-07-239588-803-07353.70 ppb
2014-07-239588-802-07052.20 ppb
2014-07-239588-801-0720ND
2014-07-239588-800-0750ND
2014-10-239588-802-08002.00 ppb
2014-10-239588-801-08101.50 ppb
2014-10-239588-803-08206.00 ppb
2014-10-239588-800-0835ND
2015-01-239588-803-07503.60 ppb
2015-01-239588-802-07302.40 ppb
2015-01-239588-801-07400.520 ppb
2015-01-239588-800-0805ND
2015-04-229588-803-07505.00 ppb
2015-04-229588-802-07304.10 ppb
2015-04-229588-800-0800ND
2015-04-229588-801-07401.10 ppb
2015-07-239588-800-08051.30 ppb
2015-07-239588-803-07558.40 ppb
2015-07-239588-802-07357.00 ppb
2015-07-239588-801-07450.530 ppb
2015-10-269588-801-0740ND
2015-10-269588-800-0805ND
2015-10-269588-803-07508.20 ppb
2015-10-269588-802-07303.70 ppb
2016-01-269588-801-08000.510 ppb
2016-01-269588-800-0825ND
2016-01-269588-803-08104.80 ppb
2016-01-269588-802-07505.60 ppb
2016-04-229588-801-0740ND
2016-04-229588-800-08051.70 ppb
2016-04-229588-803-07506.90 ppb
2016-04-229588-802-07303.40 ppb
2016-07-269588-803-07555.70 ppb
2016-07-269588-801-07401.50 ppb
2016-07-269588-800-0810ND
2016-07-269588-802-07301.90 ppb
2016-10-269588-803-08204.60 ppb
2016-10-269588-801-08102.60 ppb
2016-10-269588-802-08005.80 ppb
2016-10-269588-800-0830ND
2017-01-249588-802-07404.40 ppb
2017-01-249588-803-08003.30 ppb
2017-01-249588-801-0750ND
2017-01-249588-800-0815ND
2017-04-249588-802-08552.00 ppb
2017-04-249588-800-0940ND
2017-04-249588-801-0905ND
2017-04-249588-803-09253.20 ppb
2017-07-279588-800-1435ND
2017-07-279588-801-1515ND
2017-07-279588-803-14502.30 ppb
2017-07-279588-802-15301.20 ppb
2017-10-249588-803-07552.80 ppb
2017-10-249588-800-0810ND
2017-10-249588-802-07302.60 ppb
2017-10-249588-801-0740ND
2018-01-249588-803-08151.90 ppb
2018-01-249588-800-0830ND
2018-01-249588-801-08051.20 ppb
2018-01-249588-802-07553.60 ppb
2018-04-249588-801-0740ND
2018-04-249588-802-07302.30 ppb
2018-04-249588-803-07504.00 ppb
2018-04-249588-800-0810ND
2018-07-249588-801-0725ND
2018-07-249588-803-07354.00 ppb
2018-07-249588-802-07153.00 ppb
2018-07-249588-800-0750ND
2018-10-239588-801-0740ND
2018-10-239588-803-07507.40 ppb
2018-10-239588-802-07302.20 ppb
2018-10-239588-800-0805ND
2019-01-249588-800-0850ND
2019-01-249588-802-0810ND
2019-01-249588-801-0820ND
2019-01-249588-803-08304.50 ppb
2019-04-239588-800-08000.540 ppb
2019-04-239588-802-07252.70 ppb
2019-04-239588-803-07456.80 ppb
2019-04-239588-801-07351.20 ppb
2019-07-239588-803-07255.70 ppb
2019-07-239588-802-07051.70 ppb
2019-07-239588-800-0740ND
2019-07-239588-801-07152.40 ppb
2019-10-239588-803-07407.00 ppb
2019-10-239588-802-07201.90 ppb
2019-10-239588-800-0755ND
2019-10-239588-801-0730ND