Menu

EWG's Tap Water Database — 2019 UPDATE

Donate

Total trihalomethanes (TTHMs)

City of Ripon

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.

 

65

Samples

0

Samples exceeding legal limit (MCL)

30

Samples exceeding
health guidelines

Testing results - average by year

 
YearAverage resultSamples takenDetectionsRange of results
2012N/A00N/A
20130.900 ppb42ND - 2.00 ppb
20141.12 ppb126ND - 3.60 ppb
20150.322 ppb174ND - 2.60 ppb
20160.994 ppb166ND - 3.90 ppb
20172.57 ppb1612ND - 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
2013-11-052625-901-09382.00 ppb
2013-11-052625-900-0850ND
2013-11-052625-902-09501.60 ppb
2013-11-052625-903-1050ND
2014-02-052625-901-11153.60 ppb
2014-02-052625-900-10062.80 ppb
2014-02-052625-902-11402.20 ppb
2014-02-052625-903-10272.60 ppb
2014-05-072625-902-1408ND
2014-05-072625-900-1334ND
2014-05-072625-903-1311ND
2014-05-072625-901-13521.50 ppb
2014-08-112625-903-0916ND
2014-08-112625-902-1100ND
2014-08-112625-901-10470.700 ppb
2014-08-112625-900-0951ND
2015-02-182625-902-1047ND
2015-02-182625-903-0958ND
2015-02-182625-900-1017ND
2015-02-182625-901-1035ND
2015-05-052625-900-0910ND
2015-05-052625-901-09450.400 ppb
2015-05-052625-903-0925ND
2015-05-052625-902-1000ND
2015-08-055810-902-10000.670 ppb
2015-08-055810-900-09001.80 ppb
2015-08-055810-903-0915ND
2015-08-055810-901-09352.60 ppb
2015-11-032625-903-0920ND
2015-11-032625-903-0945ND
2015-11-032625-901-1015ND
2015-11-032625-902-1045ND
2015-11-032625-900-0945ND
2016-02-112625-901-1020ND
2016-02-112625-903-1055ND
2016-02-112625-902-0910ND
2016-02-112625-900-1035ND
2016-05-032625-901-14153.40 ppb
2016-05-032625-900-14453.00 ppb
2016-05-032625-902-14003.90 ppb
2016-05-032625-903-14303.60 ppb
2016-08-032625-901-1400ND
2016-08-032625-903-1410ND
2016-08-032625-902-1345ND
2016-08-032625-900-1420ND
2016-11-022625-902-0845ND
2016-11-022625-901-08300.900 ppb
2016-11-022625-900-08151.10 ppb
2016-11-022625-903-0900ND
2017-02-022625-901-11202.90 ppb
2017-02-022625-903-1110ND
2017-02-022625-900-10473.10 ppb
2017-02-022625-902-11343.20 ppb
2017-05-182625-901-0825ND
2017-05-182625-903-09342.60 ppb
2017-05-182625-902-09107.00 ppb
2017-05-182625-900-07574.00 ppb
2017-08-012625-900-08352.60 ppb
2017-08-012625-903-0905ND
2017-08-012625-901-10222.80 ppb
2017-08-012625-902-09583.60 ppb
2017-11-152625-900-13053.20 ppb
2017-11-152625-901-1410ND
2017-11-152625-902-13505.60 ppb
2017-11-152625-903-13250.500 ppb