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EWG's Tap Water Database — 2019 UPDATE

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Total trihalomethanes (TTHMs)

Averydale Mutual Water Company

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.

 

24

Samples

0

Samples exceeding legal limit (MCL)

6

Samples exceeding
health guidelines

Testing results - average by year

 
YearAverage resultSamples takenDetectionsRange of results
2012ND20ND
2013ND70ND
20140.980 ppb51ND - 4.90 ppb
20152.98 ppb62ND - 15.0 ppb
20160.500 ppb21ND - 1.000 ppb
20171.75 ppb221.20 ppb - 2.30 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
2012-07-103761-004-0936ND
2012-07-103761-003-0925ND
2013-05-143761-006-1314ND
2013-05-143761-004-1232ND
2013-05-143761-001-1300ND
2013-08-133761-006-1127ND
2013-08-133761-004-1013ND
2013-08-133761-001-1121ND
2013-08-133761-003-1022ND
2014-08-053761-801-1350ND
2014-08-053761-800-14074.90 ppb
2014-08-193761-006-1320ND
2014-08-193761-003-1346ND
2014-09-093761-001-0918ND
2015-02-173761-004-141415.0 ppb
2015-10-133761-001-1515ND
2015-10-133761-801-14552.90 ppb
2015-10-133761-800-1505ND
2015-10-133761-006-1532ND
2015-10-133761-003-1442ND
2016-08-233761-801-1353ND
2016-08-233761-800-14171.000 ppb
2017-08-223761-801-14072.30 ppb
2017-08-223761-800-14171.20 ppb