Know Your Environment. Protect Your Health.

Total trihalomethanes (TTHMs)

City of Pocatello

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.

 

156

Samples

0

Samples exceeding legal limit (MCL)

94

Samples exceeding
health guidelines

Testing results - average by year

 
YearAverage resultSamples takenDetectionsRange of results
20187.93 ppb2516ND - 19.8 ppb
20195.47 ppb3217ND - 21.7 ppb
20206.96 ppb2416ND - 25.8 ppb
20215.98 ppb2416ND - 16.0 ppb
20223.87 ppb2712ND - 12.8 ppb
20237.83 ppb2417ND - 17.8 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
2018-01-23DI8011270114.1 ppb
2018-01-23DI8011270213.7 ppb
2018-01-23DI8011270312.7 ppb
2018-01-23DI801127047.52 ppb
2018-04-25DI8042250114.4 ppb
2018-04-25DI8042250213.7 ppb
2018-04-25DI804225036.80 ppb
2018-04-25DI8042250415.7 ppb
2018-05-02VI80502301ND
2018-07-16DI807196017.85 ppb
2018-07-16DI807196029.31 ppb
2018-07-16DI807196039.24 ppb
2018-07-16DI807196046.32 ppb
2018-09-26VI80927601ND
2018-09-26VI80927602ND
2018-09-26VI80927603ND
2018-09-26VI80927604ND
2018-09-26VI80927605ND
2018-09-26VI80927606ND
2018-09-26VI80927607ND
2018-09-26VI80927608ND
2018-12-04DI8120280113.0 ppb
2018-12-04DI8120280218.9 ppb
2018-12-04DI8120280315.3 ppb
2018-12-04DI8120280419.8 ppb
2019-01-08DI9010430112.9 ppb
2019-01-08DI9010430214.5 ppb
2019-01-08DI9010430314.8 ppb
2019-01-08DI9010430418.6 ppb
2019-06-24DI906316018.67 ppb
2019-06-24DI906316027.89 ppb
2019-06-24DI906316038.57 ppb
2019-06-24DI906316040.910 ppb
2019-07-31DI907412019.42 ppb
2019-07-31DI907412027.60 ppb
2019-07-31DI907412039.97 ppb
2019-07-31DI907412046.80 ppb
2019-10-08VI91008801ND
2019-10-08VI91008802ND
2019-10-08VI91008803ND
2019-10-08VI91008804ND
2019-10-08VI91008805ND
2019-10-08VI91008806ND
2019-10-08VI91008807ND
2019-10-08VI91008808ND
2019-10-08VI910092010.800 ppb
2019-10-08VI91009202ND
2019-10-08VI91009203ND
2019-10-08VI91009204ND
2019-10-08VI910092053.25 ppb
2019-10-08VI91009206ND
2019-10-08VI91009207ND
2019-10-08VI91009208ND
2019-10-21DI9101930121.7 ppb
2019-10-21DI9101940117.2 ppb
2019-10-21DI91019501ND
2019-10-21DI9101960111.6 ppb
2020-03-10DI003073019.03 ppb
2020-03-10DI0030730214.2 ppb
2020-03-10DI0030730316.1 ppb
2020-03-10DI0030730425.8 ppb
2020-05-11VI00507303ND
2020-05-11VI00507304ND
2020-05-11VI00507306ND
2020-05-11VI00507308ND
2020-05-11VI00507309ND
2020-05-11VI00507313ND
2020-05-11VI00507314ND
2020-05-11VI00507315ND
2020-06-22DI006279019.04 ppb
2020-06-22DI006279029.49 ppb
2020-06-22DI006279048.69 ppb
2020-06-22DI006279032.32 ppb
2020-08-24DI008229012.93 ppb
2020-08-24DI008229028.53 ppb
2020-08-24DI008229037.29 ppb
2020-08-24DI0082290413.6 ppb
2020-10-13DI0101390111.2 ppb
2020-10-13DI0101390212.5 ppb
2020-10-13DI0101390313.5 ppb
2020-10-13DI010139042.77 ppb
2021-03-02DI1030230412.6 ppb
2021-03-02DI103023016.51 ppb
2021-03-02DI1030230311.3 ppb
2021-03-02DI1030230212.0 ppb
2021-06-09DI106153037.43 ppb
2021-06-09DI106153047.83 ppb
2021-06-09DI106153015.94 ppb
2021-06-09DI106153022.33 ppb
2021-08-10DI108124041.45 ppb
2021-08-10VI10813508ND
2021-08-10DI108124027.22 ppb
2021-08-10VI10813506ND
2021-08-10DI108124016.31 ppb
2021-08-10VI10813503ND
2021-08-10VI10813502ND
2021-08-10VI10813501ND
2021-08-10DI108124037.35 ppb
2021-08-10VI10813505ND
2021-08-10VI10813507ND
2021-08-10VI10813504ND
2021-11-05DI1110580214.4 ppb
2021-11-05DI1110580110.2 ppb
2021-11-05DI1110580316.0 ppb
2021-11-05DI1110580414.7 ppb
2022-02-22DI202179049.69 ppb
2022-02-22DI202179036.66 ppb
2022-02-22DI2021790211.1 ppb
2022-02-22DI2021790111.9 ppb
2022-09-13DI209121019.19 ppb
2022-09-13DI209121026.51 ppb
2022-09-13DI209121035.72 ppb
2022-09-13DI209121042.02 ppb
2022-10-10DI2100960111.8 ppb
2022-10-10DI2100960210.5 ppb
2022-10-10DI2100960312.8 ppb
2022-10-10DI210096046.73 ppb
2022-10-12VI21012901ND
2022-10-12VI21012902ND
2022-10-12VI21012903ND
2022-10-12VI21012904ND
2022-10-12VI21012905ND
2022-10-12VI21012906ND
2022-10-12VI21012907ND
2022-10-12VI21012908ND
2022-10-12VI21012909ND
2022-10-12VI21012910ND
2022-10-12VI21012911ND
2022-10-12VI21012912ND
2022-10-12VI21012801ND
2022-10-12VI21012802ND
2022-10-12VI21013001ND
2023-03-21DI303199017.96 ppb
2023-03-21DI3031990213.9 ppb
2023-03-21DI3031990314.9 ppb
2023-03-21DI3031990415.5 ppb
2023-06-22DI3063900111.7 ppb
2023-06-22DI3063900210.9 ppb
2023-06-22DI3063900313.8 ppb
2023-06-22DI306390042.11 ppb
2023-08-10DI3081740111.5 ppb
2023-08-10DI3081740212.5 ppb
2023-08-10DI3081740311.5 ppb
2023-08-10DI308174044.38 ppb
2023-10-11VI31012801ND
2023-10-11VI31012802ND
2023-10-11VI310128030.630 ppb
2023-10-11VI31012805ND
2023-10-11VI31012806ND
2023-10-11VI31012807ND
2023-10-11VI31012808ND
2023-10-11VI31012809ND
2023-12-27DI3122280117.8 ppb
2023-12-27DI3122280215.5 ppb
2023-12-27DI3122280316.0 ppb
2023-12-27DI312228047.22 ppb