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EWG's Tap Water Database — 2019 UPDATE

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Total trihalomethanes (TTHMs)

Lafayette

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.

 

120

Samples

0

Samples exceeding legal limit (MCL)

94

Samples exceeding
health guidelines

Testing results - average by year

 
YearAverage resultSamples takenDetectionsRange of results
20123.11 ppb3222ND - 14.1 ppb
20133.76 ppb2420ND - 9.60 ppb
20143.39 ppb1613ND - 7.70 ppb
20153.26 ppb1614ND - 5.80 ppb
20163.16 ppb1612ND - 5.70 ppb
20173.79 ppb1613ND - 8.70 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
2012-02-15AH53445ND
2012-02-15AH534464.80 ppb
2012-02-15AH534471.20 ppb
2012-02-15AH534487.40 ppb
2012-02-15AH534492.70 ppb
2012-02-15AH534503.70 ppb
2012-02-15AH534511.70 ppb
2012-02-15AH534522.80 ppb
2012-05-30AH65611ND
2012-05-30AH6561210.3 ppb
2012-05-30AH65613ND
2012-05-30AH656144.60 ppb
2012-05-30AH65615ND
2012-05-30AH656165.20 ppb
2012-05-30AH65617ND
2012-05-30AH65618ND
2012-08-27AH75892ND
2012-08-27AH758933.00 ppb
2012-08-27AH758947.00 ppb
2012-08-27AH758955.90 ppb
2012-08-27AH75896ND
2012-08-27AH7589710.1 ppb
2012-08-27AH75898ND
2012-08-27AH758991.20 ppb
2012-11-15AH842032.00 ppb
2012-11-15AH842041.30 ppb
2012-11-15AH842052.50 ppb
2012-11-15AH842064.40 ppb
2012-11-15AH84207ND
2012-11-15AH8420814.1 ppb
2012-11-15AH842092.30 ppb
2012-11-15AH842101.20 ppb
2013-03-12AH907372.60 ppb
2013-03-12AH907382.50 ppb
2013-03-12AH907391.10 ppb
2013-03-12AH907405.20 ppb
2013-03-12AH90741ND
2013-03-12AH907427.40 ppb
2013-03-12AH90743ND
2013-03-12AH907441.30 ppb
2013-05-14AI01532ND
2013-05-14AI015335.80 ppb
2013-05-14AI015341.20 ppb
2013-05-14AI015357.80 ppb
2013-05-14AI015363.00 ppb
2013-05-14AI015379.60 ppb
2013-05-14AI015382.90 ppb
2013-05-14AI015395.50 ppb
2013-09-18AI16140ND
2013-09-18AI161414.90 ppb
2013-09-18AI161425.10 ppb
2013-09-18AI161435.60 ppb
2013-12-19AI254677.50 ppb
2013-12-19AI254683.80 ppb
2013-12-19AI254693.60 ppb
2013-12-19AI254703.80 ppb
2014-03-20AI364854.50 ppb
2014-03-20AI364865.40 ppb
2014-03-20AI364872.60 ppb
2014-03-20AI364882.50 ppb
2014-06-16AI433207.30 ppb
2014-06-16AI433214.80 ppb
2014-06-16AI433223.00 ppb
2014-06-16AI433231.40 ppb
2014-09-16AI540377.70 ppb
2014-09-16AI540382.50 ppb
2014-09-16AI540394.90 ppb
2014-09-16AI540405.30 ppb
2014-12-17AI617322.30 ppb
2014-12-17AI61733ND
2014-12-17AI61734ND
2014-12-17AI61735ND
2015-03-18AI69326ND
2015-03-18AI693272.50 ppb
2015-03-18AI693283.00 ppb
2015-03-18AI693292.40 ppb
2015-06-16AI799195.30 ppb
2015-06-16AI799203.00 ppb
2015-06-16AI799214.80 ppb
2015-06-16AI799223.50 ppb
2015-09-15AI898114.90 ppb
2015-09-15AI89812ND
2015-09-15AI898133.60 ppb
2015-09-15AI898144.30 ppb
2015-12-15AJ029452.40 ppb
2015-12-15AJ029464.10 ppb
2015-12-15AJ029475.80 ppb
2015-12-15AJ029482.60 ppb
2016-03-15AJ082003.90 ppb
2016-03-15AJ082015.70 ppb
2016-03-15AJ082025.50 ppb
2016-03-15AJ082034.00 ppb
2016-06-14AJ141465.70 ppb
2016-06-14AJ141473.30 ppb
2016-06-14AJ141483.30 ppb
2016-06-14AJ141493.10 ppb
2016-09-21AJ284813.80 ppb
2016-09-21AJ284822.90 ppb
2016-09-21AJ284834.20 ppb
2016-09-21AJ28484ND
2016-12-20AJ372445.20 ppb
2016-12-20AJ37245ND
2016-12-20AJ37246ND
2016-12-20AJ37247ND
2017-03-20AJ483475.20 ppb
2017-03-20AJ483483.70 ppb
2017-03-20AJ483494.00 ppb
2017-03-20AJ483502.20 ppb
2017-06-21AJ582138.70 ppb
2017-06-21AJ582146.70 ppb
2017-06-21AJ582155.00 ppb
2017-06-21AJ582163.80 ppb
2017-09-18AJ682946.90 ppb
2017-09-18AJ682955.00 ppb
2017-09-18AJ682965.20 ppb
2017-09-18AJ682973.00 ppb
2017-12-18AJ75637ND
2017-12-18AJ756381.20 ppb
2017-12-18AJ75639ND
2017-12-18AJ75640ND