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EWG's Tap Water Database — 2021 UPDATE

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Total trihalomethanes (TTHMs)

California American Water Company - Suburban

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

 

102

Samples

0

Samples exceeding legal limit (MCL)

6

Samples exceeding
health guidelines

Testing results - average by year

 
YearAverage resultSamples takenDetectionsRange of results
201419.0 ppb11ND - 2.00 ppb
201510.00 ppb11ND - 38.0 ppb
201610.00 ppb11ND - 8.00 ppb
20171.000 ppb291ND - 1.000 ppb
201811.0 ppb491ND - 24.0 ppb
201924.0 ppb211ND - 62.0 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
2014-06-0119.0 ppb*
2015-06-0110.00 ppb*
2016-06-0110.00 ppb*
2017-06-011.000 ppb*
2017-09-195810-064-1520ND
2017-09-195810-066-1520ND
2017-09-205810-064-1112ND
2017-09-205810-066-1118ND
2017-09-215810-064-1319ND
2017-09-215810-066-1324ND
2017-09-225810-064-1158ND
2017-09-225810-066-1203ND
2017-09-235810-064-1143ND
2017-09-235810-066-1248ND
2017-09-265810-064-1343ND
2017-09-265810-066-1348ND
2017-10-035810-064-0745ND
2017-10-035810-066-0750ND
2017-10-105810-064-1500ND
2017-10-105810-066-1505ND
2017-10-245810-064-1405ND
2017-10-245810-066-1410ND
2017-10-315810-064-1243ND
2017-10-315810-066-1248ND
2017-11-075810-064-0930ND
2017-11-075810-066-0935ND
2017-11-145810-064-1241ND
2017-11-145810-066-1246ND
2017-11-215810-064-1133ND
2017-11-215810-066-1138ND
2017-11-285810-064-1352ND
2017-11-285810-066-1357ND
2018-01-025810-063-1215ND
2018-01-025810-064-1220ND
2018-01-025810-065-1225ND
2018-01-025810-066-1230ND
2018-02-205810-063-1045ND
2018-02-205810-064-1050ND
2018-02-205810-065-1055ND
2018-02-205810-066-1100ND
2018-03-125810-063-0950ND
2018-03-125810-064-0955ND
2018-03-125810-065-1000ND
2018-03-125810-066-1005ND
2018-04-035810-063-1415ND
2018-04-035810-064-1420ND
2018-04-035810-065-1425ND
2018-04-035810-066-1430ND
2018-05-015810-063-1200ND
2018-05-015810-064-1205ND
2018-05-015810-065-1210ND
2018-05-015810-066-1215ND
2018-06-0111.0 ppb*
2018-06-135810-063-1110ND
2018-06-135810-064-1115ND
2018-06-135810-065-1120ND
2018-06-135810-066-1125ND
2018-07-115810-063-1140ND
2018-07-115810-064-1145ND
2018-07-115810-065-1150ND
2018-07-115810-066-1155ND
2018-08-145810-063-1425ND
2018-08-145810-064-1430ND
2018-08-145810-065-1435ND
2018-08-145810-066-1440ND
2018-09-115810-063-1040ND
2018-09-115810-064-1045ND
2018-09-115810-065-1050ND
2018-09-115810-066-1055ND
2018-10-165810-063-1005ND
2018-10-165810-064-1010ND
2018-10-165810-065-1015ND
2018-10-165810-066-1020ND
2018-11-065810-063-1035ND
2018-11-065810-064-1040ND
2018-11-065810-065-1045ND
2018-11-065810-066-1050ND
2018-12-125810-063-1130ND
2018-12-125810-064-1135ND
2018-12-125810-065-1140ND
2018-12-125810-066-1145ND
2019-01-085810-063-1205ND
2019-01-085810-064-1210ND
2019-01-085810-065-1215ND
2019-01-085810-066-1220ND
2019-02-125810-063-1105ND
2019-02-125810-064-1110ND
2019-02-125810-065-1115ND
2019-02-125810-066-1120ND
2019-03-195810-063-1035ND
2019-03-195810-064-1040ND
2019-03-195810-065-1045ND
2019-03-195810-066-1050ND
2019-04-175810-063-1005ND
2019-04-175810-064-1010ND
2019-04-175810-065-1015ND
2019-04-175810-066-1020ND
2019-05-145810-063-0945ND
2019-05-145810-064-0950ND
2019-05-145810-065-0955ND
2019-05-145810-066-1000ND
2019-06-0124.0 ppb*

* Sample result is taken from the system's CCR report.