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EWG's Tap Water Database — 2021 UPDATE

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Total trihalomethanes (TTHMs)

Roslyn WD

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.

 

113

Samples

0

Samples exceeding legal limit (MCL)

0

Samples exceeding
health guidelines

Testing results - average by year

 
YearAverage resultSamples takenDetectionsRange of results
2014ND290ND
2015ND80ND
2016ND140ND
2017ND160ND
2018ND250ND
2019ND210ND

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
2014-01-081401261-002-POCSND
2014-02-111402494-002-POCSND
2014-03-271403J26-002-POCSND
2014-04-141404A24-002-POCSND
2014-05-081405607-002-POCSND
2014-05-161405C18-002-POCSND
2014-05-161405C18-003-POCSND
2014-05-161405C18-005-POCSND
2014-05-161405C18-004-POCSND
2014-06-051406390-002-POCSND
2014-06-121406931-002-POCSND
2014-06-171406B96-002-POCSND
2014-07-081407453-002-POCSND
2014-07-211407E33-002-POCSND
2014-07-231407G36-002-POCSND
2014-07-301407L12-002-POCSND
2014-08-051408195-002-POCSND
2014-08-121408739-002-POCSND
2014-08-131408868-002-POCSND
2014-08-211408F37-002-POCSND
2014-08-251408H19-002-POCSND
2014-09-041409267-002-POCSND
2014-09-111409890-002-POCSND
2014-09-181409E16-001-POCSND
2014-10-091410647-002-POCSND
2014-10-221410E31-002-POCSND
2014-11-101411665-002-POCSND
2014-11-211411E96-002-POCSND
2014-12-051412410-002-POCSND
2015-01-151501871-002-POCSND
2015-02-101502633-001-POCSND
2015-04-161504C10-002-POCSND
2015-04-231504I52-001-POCSND
2015-04-231504I52-002-POCSND
2015-05-011505031-002-POCSND
2015-05-281505K32-002-POCSND
2015-06-091506722-002-POCSND
2016-01-131604L15-001ND
2016-02-111602918-002ND
2016-02-111602918-001ND
2016-05-031605147-001ND
2016-06-221606L82-001ND
2016-07-181607D67-002ND
2016-07-191607E94-002ND
2016-08-161608E60-002ND
2016-08-231608L92-002ND
2016-09-201609F92-001ND
2016-09-291609P72-001ND
2016-10-11701661001ND
2016-11-15704522005-POCND
2016-12-14706837002ND
2017-01-04708255003-POCND
2017-02-157011343003ND
2017-04-067015144002ND
2017-04-197016340004ND
2017-04-197016340004-POCND
2017-05-107018231002ND
2017-05-127018516002-POCND
2017-06-067020424002-POCND
2017-07-217024907002-POCND
2017-08-167027363002-POCND
2017-08-287028346002-POCND
2017-09-287031248001-POCND
2017-11-137035525002-POCND
2017-11-167035924002-POCND
2017-12-017036961002-POCND
2017-12-017036957002-POCND
2018-01-117040222002-POCND
2018-01-197040884002-POCND
2018-02-087042437002ND
2018-02-277043967002-POCND
2018-03-087044819001ND
2018-03-137045126002ND
2018-04-057047399001-POCND
2018-05-077050698002ND
2018-05-307053122001ND
2018-06-127054579002ND
2018-06-277056403002ND
2018-07-177058450002ND
2018-07-197058782002-POCND
2018-07-267059540002-POCND
2018-08-037060299002-POCND
2018-08-077060662002-POCND
2018-08-097060947002-POCND
2018-09-177065090001ND
2018-09-197065305001ND
2018-10-177068227002ND
2018-10-257069045002ND
2018-11-157071210002ND
2018-11-287072146002ND
2018-12-047072741002ND
2018-12-127073713001ND
2019-01-087075818002ND
2019-01-237077366001ND
2019-02-147079548002ND
2019-02-157079807002ND
2019-03-047081159002ND
2019-04-117085552002ND
2019-04-257087227002ND
2019-05-077088362002ND
2019-06-047092008002ND
2019-06-137093546002ND
2019-06-147093737003ND
2019-07-117097203001ND
2019-07-257098830002-POCND
2019-08-0670100015002-POCND
2019-08-1470101279002ND
2019-09-1070104226002ND
2019-09-1270104647001ND
2019-09-2470106023002ND
2019-10-1670108611002ND
2019-11-1370111657002ND
2019-11-1470111831002ND