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EWG's Tap Water Database — 2021 UPDATE

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Total trihalomethanes (TTHMs)

City of Salisbury

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

 

68

Samples

0

Samples exceeding legal limit (MCL)

47

Samples exceeding
health guidelines

Testing results - average by year

 
YearAverage resultSamples takenDetectionsRange of results
2013N/A00N/A
20140.750 ppb21ND - 1.50 ppb
2015ND10ND
20162.08 ppb1611ND - 14.7 ppb
20171.72 ppb1715ND - 3.19 ppb
20182.76 ppb1611ND - 22.4 ppb
20192.24 ppb169ND - 6.70 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
2014-07-171.50 ppb
2014-09-18ND
2015-07-09ND
2016-02-23L6088959-30.500 ppb
2016-02-23L6088959-41.10 ppb
2016-02-23L6088959-51.70 ppb
2016-02-23L6088959-6ND
2016-05-12L6248152-31.20 ppb
2016-05-12L6248152-42.60 ppb
2016-05-12L6248152-61.80 ppb
2016-05-12L6248152-52.80 ppb
2016-08-08216558400314.7 ppb
2016-08-0821655840011.23 ppb
2016-08-0821655840022.79 ppb
2016-08-0821655840042.86 ppb
2016-11-172190463004ND
2016-11-172190463006ND
2016-11-172190463005ND
2016-11-172190463003ND
2017-02-1422085680041.14 ppb
2017-02-1422085680031.97 ppb
2017-02-1422085680061.85 ppb
2017-02-1422085680051.50 ppb
2017-05-172231145003ND
2017-05-1722311450052.80 ppb
2017-05-172231145004ND
2017-05-1722311450061.20 ppb
2017-08-1622550570051.28 ppb
2017-08-1622550570063.19 ppb
2017-08-1622550570033.15 ppb
2017-08-1622550571.82 ppb
2017-11-090.630 ppb
2017-11-1622776310031.99 ppb
2017-11-1622776310062.65 ppb
2017-11-1622776310052.65 ppb
2017-11-1622776310041.50 ppb
2018-02-2122971670031.51 ppb
2018-02-2122971670050.530 ppb
2018-02-2122971670061.66 ppb
2018-02-2122971670041.10 ppb
2018-05-172316033003ND
2018-05-1723160330051.10 ppb
2018-05-1723160330064.60 ppb
2018-05-1723160330041.20 ppb
2018-08-14233252400322.4 ppb
2018-08-142332524005ND
2018-08-1423325240042.50 ppb
2018-08-1423325240062.10 ppb
2018-11-1430008670045.50 ppb
2018-11-143000867003ND
2018-11-143000867005ND
2018-11-143000867006ND
2019-02-1130160920041.10 ppb
2019-02-113016092003ND
2019-02-113016092005ND
2019-02-113016092006ND
2019-05-1430339280043.70 ppb
2019-05-1430339280056.20 ppb
2019-05-143033928003ND
2019-05-1430339280064.60 ppb
2019-08-213053458004ND
2019-08-2130534580052.40 ppb
2019-08-2130534580066.70 ppb
2019-08-2130534580032.90 ppb
2019-11-253072163004ND
2019-11-2530721630034.80 ppb
2019-11-253072163005ND
2019-11-2530721630063.40 ppb