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EWG's Tap Water Database — 2019 UPDATE

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Total trihalomethanes (TTHMs)

Garden City Water and Sewer System

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
20120.313 ppb81ND - 2.50 ppb
20130.400 ppb81ND - 3.20 ppb
20143.15 ppb222.50 ppb - 3.80 ppb
20152.05 ppb21ND - 4.10 ppb
2016ND20ND
20172.14 ppb21ND - 4.27 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
2012-07-12D1221131ND
2012-07-12D1221130ND
2012-07-12D1221129ND
2012-07-12D1221128ND
2012-07-12D1221127ND
2012-07-12D1221126ND
2012-07-12D12211332.50 ppb
2012-07-12D1221132ND
2013-07-10D1329615ND
2013-07-10D1329616ND
2013-07-10D13296173.20 ppb
2013-07-10D1329618ND
2013-07-10D1329619ND
2013-07-10D1329620ND
2013-07-10D1329621ND
2013-07-10D1329622ND
2014-07-01D14245673.80 ppb
2014-07-01D14245662.50 ppb
2015-07-16D15289214.10 ppb
2015-07-16D1528920ND
2016-07-18D1631710ND
2016-07-18D1631709ND
2017-07-12D1730457ND
2017-07-12D17304564.27 ppb