Know Your Environment. Protect Your Health.

Total trihalomethanes (TTHMs)

Waialua

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.

 

17

Samples

0

Samples exceeding legal limit (MCL)

8

Samples exceeding
health guidelines

Testing results - average by year

 
YearAverage resultSamples takenDetectionsRange of results
20180.437 ppb32ND - 0.760 ppb
20190.170 ppb31ND - 0.510 ppb
20200.670 ppb330.500 ppb - 0.960 ppb
20210.453 ppb32ND - 0.770 ppb
2022ND30ND
2023ND20ND

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
2018-01-29201801300813ND
2018-10-032018100505630.550 ppb
2018-10-152018101704970.760 ppb
2019-01-312019020102450.510 ppb
2019-10-04201910080583ND
2019-10-04201910080584ND
2020-03-040.500 ppb
2020-10-070.960 ppb
2020-10-070.550 ppb
2021-02-10ND
2021-10-040.770 ppb
2021-10-040.590 ppb
2022-10-14ND
2022-10-14ND
2022-10-19ND
2023-10-04ND
2023-10-06ND