Know Your Environment. Protect Your Health.

Total trihalomethanes (TTHMs)

Avon 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.

 

97

Samples

0

Samples exceeding legal limit (MCL)

95

Samples exceeding
health guidelines

Testing results - average by year

 
YearAverage resultSamples takenDetectionsRange of results
20186.43 ppb1716ND - 12.0 ppb
20197.84 ppb1615ND - 18.0 ppb
20209.08 ppb16162.40 ppb - 18.6 ppb
20219.84 ppb16161.70 ppb - 22.8 ppb
20228.89 ppb16160.650 ppb - 21.3 ppb
202310.3 ppb16161.57 ppb - 19.1 ppb

ppb = parts per billion

State, National, and Health Guidelines for Drinking Water

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
2018-01-24D8A1669-02VOC5.50 ppb
2018-01-24D8A1669-03VOC7.20 ppb
2018-01-24D8A1669-04VOC3.50 ppb
2018-01-24D8A1669-01VOC6.00 ppb
2018-04-25D8D2151-08VOC0.800 ppb
2018-04-25D8D2151-09VOC12.0 ppb
2018-04-25D8D2151-10VOC7.10 ppb
2018-04-25D8D2151-11VOC9.90 ppb
2018-07-26CA9874610.7 ppb
2018-07-26CA987455.03 ppb
2018-07-26CA9874410.6 ppb
2018-07-26CA987430.630 ppb
2018-10-09DBP 2005086646.60 ppb
2018-10-09DBP 2005086656.10 ppb
2018-10-09DBP 2005086767.80 ppb
2018-10-09DBP 2005086789.90 ppb
2018-10-09VOC1 200508699ND
2019-01-08DBP 2005181314.90 ppb
2019-01-08DBP 200518132ND
2019-01-08DBP 2005181334.40 ppb
2019-01-08DBP 2005181353.60 ppb
2019-04-11DBP 2005282697.70 ppb
2019-04-11DBP 2005282708.00 ppb
2019-04-11DBP 20052826812.2 ppb
2019-04-11DBP 2005282675.80 ppb
2019-07-02DBP 2005389922.70 ppb
2019-07-02DBP 20053899315.0 ppb
2019-07-02DBP 2005389958.50 ppb
2019-07-02DBP 20053899611.9 ppb
2019-10-03DBP 2005514292.60 ppb
2019-10-03DBP 20055143018.0 ppb
2019-10-03DBP 2005514318.40 ppb
2019-10-03DBP 20055143211.7 ppb
2020-01-09DBP 2005627576.90 ppb
2020-01-09DBP 2005627586.20 ppb
2020-01-09DBP 2005627565.40 ppb
2020-01-09DBP 2005627552.40 ppb
2020-04-16DBP 2005729264.40 ppb
2020-04-16DBP 2005729278.90 ppb
2020-04-16DBP 2005729288.20 ppb
2020-04-16DBP 20057292916.1 ppb
2020-07-20DBP 2005834132.60 ppb
2020-07-20DBP 20058341412.9 ppb
2020-07-20DBP 2005834156.70 ppb
2020-07-20DBP 20058341615.6 ppb
2020-10-21DBP 20059504718.6 ppb
2020-10-21DBP 20059504618.2 ppb
2020-10-21DBP 2005950442.50 ppb
2020-10-21DBP 2005950459.70 ppb
2021-01-07DBP 2006034026.10 ppb
2021-01-07DBP 2006034045.90 ppb
2021-01-07DBP 20060340515.9 ppb
2021-01-07DBP 20060340616.4 ppb
2021-04-15DBP 2006136524.20 ppb
2021-04-15DBP 2006136538.00 ppb
2021-04-15DBP 2006136549.80 ppb
2021-04-15DBP 20061365510.2 ppb
2021-07-01DBP 20062333621.7 ppb
2021-07-01DBP 20062333822.8 ppb
2021-07-01DBP 2006233353.80 ppb
2021-07-01DBP 2006233341.70 ppb
2021-10-12H300079406 3000794107.20 ppb
2021-10-12H300079407 30007941211.3 ppb
2021-10-12H300079408 30007941410.7 ppb
2021-10-12H300079409 3000794161.70 ppb
2022-01-14CK177793.22 ppb
2022-01-14CK177805.21 ppb
2022-01-14CK177816.85 ppb
2022-01-18CK177741.31 ppb
2022-04-15CL1116914.3 ppb
2022-04-15CL111688.60 ppb
2022-04-15CL111666.76 ppb
2022-04-15CL111678.10 ppb
2022-07-08CL753090.650 ppb
2022-07-08CL7531021.3 ppb
2022-07-08CL7531110.5 ppb
2022-07-08CL753129.80 ppb
2022-10-21CM692488.00 ppb
2022-10-21CM6924910.5 ppb
2022-10-21CM6925013.1 ppb
2022-10-21CM6925114.0 ppb
2023-01-11CN219644.30 ppb
2023-01-12CN2419012.7 ppb
2023-01-12CN2418912.9 ppb
2023-01-12CN241889.80 ppb
2023-04-14CN858625.85 ppb
2023-04-14CN858638.20 ppb
2023-04-14CN858648.30 ppb
2023-04-14CN858657.80 ppb
2023-07-13CO530411.57 ppb
2023-07-13CO530428.50 ppb
2023-07-13CO5304312.0 ppb
2023-07-25CO5885514.6 ppb
2023-10-04CP178075.48 ppb
2023-10-04CP1780819.1 ppb
2023-10-04CP1780917.7 ppb
2023-10-04CP1781015.9 ppb