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EWG's Tap Water Database — 2019 UPDATE

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Total trihalomethanes (TTHMs)

City of Sweetwater

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.

 

71

Samples

0

Samples exceeding legal limit (MCL)

54

Samples exceeding
health guidelines

Testing results - average by year

 
YearAverage resultSamples takenDetectionsRange of results
201213.2 ppb1113.2 ppb
201317.5 ppb65ND - 44.0 ppb
201420.0 ppb1614ND - 53.3 ppb
20153.76 ppb1610ND - 17.4 ppb
201612.8 ppb16165.33 ppb - 23.5 ppb
20177.54 ppb168ND - 22.2 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
2012-06-26AB9395513.2 ppb
2013-06-04Q130183300811.7 ppb
2013-09-23Q1308199002ND
2013-12-18Q131850100820.1 ppb
2013-12-18Q131850100744.0 ppb
2013-12-18Q131850100619.4 ppb
2013-12-18Q13185010059.51 ppb
2014-02-19Q14055680047.43 ppb
2014-02-19Q14055680011.27 ppb
2014-02-19Q14055680023.02 ppb
2014-02-19Q140556800351.7 ppb
2014-05-06Q141472700620.1 ppb
2014-05-06Q141472700534.0 ppb
2014-05-06Q141472700414.7 ppb
2014-05-06Q141472700311.3 ppb
2014-08-28Q144009300247.4 ppb
2014-08-28Q144009300131.5 ppb
2014-08-28Q144009300353.3 ppb
2014-08-28Q144009300441.7 ppb
2014-11-24Q1457322004ND
2014-11-24Q14573220031.30 ppb
2014-11-24Q1457322002ND
2014-11-24Q14573220011.20 ppb
2015-02-11Q15057780081.20 ppb
2015-02-11Q15057780071.30 ppb
2015-02-11Q15057780061.10 ppb
2015-02-11Q1505778005ND
2015-06-17Q1522698004ND
2015-06-17Q1522698003ND
2015-06-17Q1522698002ND
2015-06-17Q1522698001ND
2015-08-04Q15303200015.13 ppb
2015-08-04Q153032000215.1 ppb
2015-08-04Q15303200031.89 ppb
2015-08-04Q15303200041.06 ppb
2015-11-23Q154636800414.7 ppb
2015-11-23Q154636800317.4 ppb
2015-11-23Q15463680021.32 ppb
2015-11-23Q1546368001ND
2016-02-03Q16046960065.33 ppb
2016-02-03Q160469600512.2 ppb
2016-02-03Q16046960047.57 ppb
2016-02-03Q16046960037.00 ppb
2016-06-21Q162573800315.9 ppb
2016-06-21Q162573800115.2 ppb
2016-06-21Q162573800216.0 ppb
2016-06-21Q162573800413.9 ppb
2016-09-22Q163962900618.3 ppb
2016-09-22Q163962900521.4 ppb
2016-09-22Q163962900414.2 ppb
2016-09-22Q16396290039.02 ppb
2016-12-13Q165421900323.5 ppb
2016-12-13Q16542190017.76 ppb
2016-12-13Q16542190027.60 ppb
2016-12-13Q16542190049.18 ppb
2017-02-21Q1707286008ND
2017-02-21Q17072860079.29 ppb
2017-02-21Q1707286006ND
2017-02-21Q1707286005ND
2017-05-16Q1719907004ND
2017-05-16Q1719907001ND
2017-05-16Q1719907002ND
2017-05-16Q1719907003ND
2017-09-21Q174584300619.4 ppb
2017-09-21Q174584300518.4 ppb
2017-09-21Q174584300422.2 ppb
2017-09-21Q174584300312.9 ppb
2017-12-04Q1762012001ND
2017-12-04Q176201200414.6 ppb
2017-12-04Q176201200320.1 ppb
2017-12-04Q17620120023.70 ppb