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EWG's Tap Water Database — 2021 UPDATE

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Total trihalomethanes (TTHMs)

Port Washington 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.

MORE ABOUT THIS CONTAMINANT

 

121

Samples

0

Samples exceeding legal limit (MCL)

26

Samples exceeding
health guidelines

Testing results - average by year

 
YearAverage resultSamples takenDetectionsRange of results
2013N/A00N/A
2014N/A00N/A
20156.95 ppb11ND - 12.0 ppb
20166.95 ppb11ND - 12.0 ppb
20179.70 ppb11ND - 12.4 ppb
20180.181 ppb6013ND - 1.70 ppb
20190.140 ppb5810ND - 1.10 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
2015-06-016.95 ppb*
2016-06-016.95 ppb*
2017-06-019.70 ppb*
2018-01-027039454001ND
2018-01-0270394480010.540 ppb
2018-01-087039795001ND
2018-01-167040529001ND
2018-02-0570420140010.910 ppb
2018-02-1270426610010.600 ppb
2018-02-127044444001ND
2018-02-127042660001ND
2018-02-127042666001ND
2018-03-0570444460010.600 ppb
2018-03-1270450630010.610 ppb
2018-03-127045064001ND
2018-04-037046952001ND
2018-04-0370469470010.590 ppb
2018-04-037046957001ND
2018-04-0970477150010.620 ppb
2018-04-177048617001ND
2018-05-017050056001ND
2018-05-017050054001ND
2018-05-0170500570010.910 ppb
2018-05-027050234001ND
2018-05-0770507230030.710 ppb
2018-05-077050720001ND
2018-06-047053565001ND
2018-06-047053566001ND
2018-06-047053564001ND
2018-06-0570536940030.760 ppb
2018-06-057053695001ND
2018-07-027056887001ND
2018-07-027056888001ND
2018-07-0270568790010.820 ppb
2018-07-107057562001ND
2018-08-067060517002ND
2018-08-067060517001ND
2018-08-067060517005ND
2018-08-067060517006ND
2018-08-147061475004ND
2018-08-147061475008ND
2018-09-047063537001ND
2018-09-047063532001ND
2018-09-047063539001ND
2018-09-107064201002ND
2018-09-107064201003ND
2018-09-107064201001ND
2018-10-017066393013ND
2018-10-017066393002ND
2018-10-097067296013ND
2018-10-097067296011ND
2018-10-097067296014ND
2018-10-157068010001ND
2018-11-057070049001ND
2018-11-057070047001ND
2018-11-147071068001ND
2018-11-1470710560011.70 ppb
2018-11-147071061001ND
2018-12-177074163001ND
2018-12-177074163003ND
2018-12-177074163005ND
2018-12-1770741630009ND
2018-12-1770741630021.50 ppb
2019-01-0770757570021.000 ppb
2019-01-077075754001ND
2019-01-077075760002ND
2019-01-147076492005ND
2019-01-147076492009ND
2019-02-047078270001ND
2019-02-047078269002ND
2019-02-0470782710010.630 ppb
2019-02-197080027001ND
2019-03-057081319004ND
2019-03-057081321003ND
2019-03-057081319003ND
2019-03-057081319002ND
2019-04-107085264001ND
2019-04-117085526004ND
2019-04-117085526010ND
2019-04-127085694006ND
2019-04-257087268002ND
2019-05-207090159001ND
2019-05-217090306002ND
2019-05-217090306001ND
2019-05-227090505002ND
2019-05-227090505003ND
2019-06-107092896001ND
2019-06-1070928960040.590 ppb
2019-06-107092896002ND
2019-06-127093301001ND
2019-07-0970967170040.640 ppb
2019-07-097096717013ND
2019-07-1570975140060.880 ppb
2019-07-157097514003ND
2019-07-227098451004ND
2019-07-297099249002ND
2019-08-057099946001ND
2019-08-057099947001ND
2019-08-057099945001ND
2019-08-0570999480020.770 ppb
2019-09-0970104217006ND
2019-09-0970104215002ND
2019-09-0970104217003ND
2019-09-0970104215001ND
2019-09-09701042170021.000 ppb
2019-10-16701086370050.870 ppb
2019-10-1670108637007ND
2019-10-16701086370020.660 ppb
2019-10-2170109179002ND
2019-10-2570109763003ND
2019-10-2970109987001ND
2019-11-0470110559001ND
2019-11-0470110559003ND
2019-11-0470110559002ND
2019-11-12701115540011.10 ppb
2019-11-1270111554010ND
2019-12-1370115286001ND
2019-12-1370115289001ND
2019-12-1370115292001ND
2019-12-1670115580001ND
2019-12-2370116328002ND

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