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EWG's Tap Water Database — 2021 UPDATE

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Total trihalomethanes (TTHMs)

Oyster Bay Water District

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

 

178

Samples

0

Samples exceeding legal limit (MCL)

6

Samples exceeding
health guidelines

Testing results - average by year

 
YearAverage resultSamples takenDetectionsRange of results
2014ND300ND
2015ND160ND
20160.0257 ppb301ND - 0.770 ppb
20170.0215 ppb401ND - 0.860 ppb
20180.0172 ppb361ND - 0.620 ppb
20190.0735 ppb263ND - 0.790 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
2014-01-211401843-001-POCSND
2014-02-111402492-001-POCSND
2014-03-051403199-001-POCSND
2014-03-181403C52-001-POCSND
2014-03-181403C52-004-POCSND
2014-03-1803C52-005-POCSND
2014-03-181403C52-003-POCSND
2014-03-181403C52-002-POCSND
2014-04-081404646-001-POCSND
2014-04-221404F72-004-POCSND
2014-04-221404F65-001ND
2014-04-221404F65-001-POCSND
2014-04-221404F72-001-POCSND
2014-04-221404F72-002-POCSND
2014-04-221404F72-003-POCSND
2014-05-271405J26-001-POCSND
2014-06-171406B90-001-POCSND
2014-08-181408B68-007-POCSND
2014-09-101409716-001-POCSND
2014-09-231409H36-004-POCSND
2014-09-231409H36-003-POCSND
2014-09-231409H36-005-POCSND
2014-09-231409H36-001-POCSND
2014-09-231409H36-002-POCSND
2014-10-301410J92-001-POCSND
2014-12-031412213-001-POCSND
2014-12-031412213-005-POCSND
2014-12-031412213-002-POCSND
2014-12-031412213-004-POCSND
2014-12-161412B34-001-POCSND
2015-01-201501A62-001-POCSND
2015-02-111502655-001-POCSND
2015-03-041503213-001-POCSND
2015-03-041503213-003-POCSND
2015-03-041503213-002-POCSND
2015-03-041503213-004-POCSND
2015-03-041503213-005-POCSND
2015-03-091503478-001-POCSND
2015-04-011504003-001-POCSND
2015-05-181505C34-001-POCSND
2015-05-201505E59-002-POCSND
2015-05-201505E59-001-POCSND
2015-05-201505E59-003-POCSND
2015-05-201505E59-004-POCSND
2015-05-201505E59-005-POCSND
2015-06-031506225-001-POCSND
2016-01-271601H95-001ND
2016-02-241502E28-001ND
2016-03-151603B65-001ND
2016-03-301603O03-002ND
2016-03-301603O03-001ND
2016-03-301603O03-004ND
2016-03-301603O03-003ND
2016-03-301603O03-005ND
2016-04-191604G74-001ND
2016-06-151606E92-005ND
2016-06-151606E92-001ND
2016-06-151606E92-002ND
2016-06-151606E92-003ND
2016-06-151606E92-004ND
2016-06-241605L69-001ND
2016-07-191607E62-001ND
2016-08-241608N05-001ND
2016-09-131609895-001-POCND
2016-09-261609L71-005-POCND
2016-09-261609L71-003-POCND
2016-09-291609L71-002-POCND
2016-09-291609L71-001-POCND
2016-10-24702735006ND
2016-11-07703821001-POCND
2016-11-217050540010.770 ppb
2016-11-21705054004ND
2016-11-21705054003ND
2016-11-21705054005ND
2016-11-21705054002ND
2016-12-19707151001ND
2017-01-18709324001-POCND
2017-02-13701114001-POCND
2017-03-207013675001-POCND
2017-03-297014366004ND
2017-03-297014366002-POCND
2017-03-297014366005-POCND
2017-03-297014366001-POCND
2017-03-297014366003-POCND
2017-04-177015995001ND
2017-06-207021777001-POCSND
2017-06-217021951002-POCND
2017-06-217021951008-POCND
2017-06-217021951004-POCND
2017-06-217021951006-POCND
2017-06-217021951010-POCND
2017-06-277022475002-POCS0.860 ppb
2017-06-277022475001-POCSND
2017-06-277022475003-POCSND
2017-06-277022475005-POCSND
2017-06-277022475004-POCSND
2017-07-252902844-POCSND
2017-08-227027829001-POCND
2017-09-197030333001-POCND
2017-09-277031121003-POCND
2017-09-277031121004-POCND
2017-09-277031121005-POCND
2017-09-277031121001-POCSND
2017-09-277031121002-POCND
2017-10-117032516001-POCND
2017-11-287036579001-POCND
2017-12-207038629001-POCND
2017-12-277039161003-POCND
2017-12-277039108001-POCND
2017-12-277039161004-POCND
2017-12-277039108003-POCND
2017-12-277039108004-POCND
2017-12-277039108005-POCND
2017-12-277039108002-POCND
2017-12-277039161001-POCND
2017-12-277039161005-POCND
2018-01-237041065001-POCND
2018-02-207043329001ND
2018-03-057044397002-POCND
2018-03-057044397005-POCND
2018-03-057044397003-POCND
2018-03-057044397003ND
2018-03-057044397004-POCND
2018-03-057044397002ND
2018-03-057044397005ND
2018-03-057044397004ND
2018-03-0570443970010.620 ppb
2018-03-057044397001-POCND
2018-03-127045041001ND
2018-04-167048487001ND
2018-05-227019203001-POCND
2018-06-187055214001ND
2018-06-197055367005-POCND
2018-06-197055367001-POCND
2018-06-197055367002-POCND
2018-06-197055367003-POCND
2018-06-197055367004-POCND
2018-07-107057586001-POCND
2018-09-047063482001ND
2018-09-107064169005ND
2018-09-107064169001ND
2018-09-107064169003ND
2018-09-107064169004ND
2018-09-107064169002ND
2018-10-027066425001ND
2018-11-057069977001ND
2018-12-117073536001ND
2018-12-187074229002ND
2018-12-187074229001ND
2018-12-187074229003ND
2018-12-187074229004ND
2018-12-187074229005ND
2019-01-157076659001ND
2019-02-257080524001ND
2019-03-057081264001ND
2019-03-067081538005ND
2019-03-067081538003ND
2019-03-0670815380010.590 ppb
2019-03-067081538004ND
2019-03-067081538002ND
2019-04-087084888001ND
2019-05-217090317001ND
2019-06-177093915002ND
2019-06-1770939150050.530 ppb
2019-06-177093915003ND
2019-06-1770939150010.790 ppb
2019-06-177093915004ND
2019-06-187094101001ND
2019-07-167097674001ND
2019-08-2070101965001ND
2019-09-1770105249001ND
2019-09-1870105360004ND
2019-09-1870105360001ND
2019-09-1870105360002ND
2019-09-1870105360003ND
2019-09-1870105360005ND
2019-10-1570108433001ND
2019-11-1470111424001ND