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EWG's Tap Water Database — 2019 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.

 

180

Samples

0

Samples exceeding legal limit (MCL)

2

Samples exceeding
health guidelines

Testing results - average by year

 
YearAverage resultSamples takenDetectionsRange of results
2012ND320ND
2013ND320ND
2014ND300ND
2015ND160ND
20160.0257 ppb301ND - 0.770 ppb
20170.0215 ppb401ND - 0.860 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
2012-01-041201060-001A-POCND
2012-02-071202239-001A-POCND
2012-02-291202982-001-POCSND
2012-02-291202982-005-POCSND
2012-02-291202982-002-POCSND
2012-02-291202982-004-POCSND
2012-02-291202982-003-POCSND
2012-03-061203167-001A-POCND
2012-04-10104385-001A-POCSND
2012-05-011205064-001A-POCND
2012-05-291205B26-001-POCSND
2012-05-291205B26-002-POCSND
2012-05-291205B26-005-POCSND
2012-05-291205B26-004-POCSND
2012-05-291205B26-003-POCSND
2012-06-201206845-001A-POCND
2012-07-241207B14-001A-POCND
2012-08-141208853-001A-POCND
2012-09-111209462-001A-POCND
2012-09-171209795-003-POCSND
2012-09-171209795-004-POCSND
2012-09-171209795-005-POCSND
2012-09-171209795-002-POCSND
2012-09-171209795-001-POCSND
2012-10-091210463-001A-POCND
2012-11-141211578-001A-POCND
2012-11-271211B12-004-POCSND
2012-11-271211B12-002-POCSND
2012-11-271211B12-005-POCSND
2012-11-271211B12-001-POCSND
2012-11-271211B12-003-POCSND
2012-12-171212866-001A-POCND
2013-01-151301650-001A-POCND
2013-02-121302408-001A-POCND
2013-03-051303134-004-POCSND
2013-03-051303134-005-POCSND
2013-03-051303134-001-POCSND
2013-03-051303134-002-POCSND
2013-03-051303134-003-POCSND
2013-03-271303D04-001A-POCND
2013-04-161304942-001A-POCND
2013-05-081305379-001A-POCND
2013-06-071306365-001-POCSND
2013-06-191306A33-002-POCSND
2013-06-191306A33-003-POCSND
2013-06-191306A33-004-POCSND
2013-06-191306A33-001-POCSND
2013-06-191306A33-005-POCSND
2013-07-101307477-001-POCSND
2013-08-271308E22-001-POCSND
2013-09-111309562-004-POCSND
2013-09-111309562-003-POCSND
2013-09-111309562-005-POCSND
2013-09-111309562-001-POCSND
2013-09-111309562-002-POCSND
2013-09-171309958-001-POCSND
2013-10-141310777-001-POCSND
2013-11-131311601-001-POCSND
2013-12-041312158-001-POCSND
2013-12-181312990-004-POCSND
2013-12-181312990-002-POCSND
2013-12-181312990-003-POCSND
2013-12-181312990-001-POCSND
2013-12-301312E04-001-POCSND
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