In 1974, Congress passed the Safe Drinking Water Act. This law requires EPA to determine the level of contaminants in drinking water at which no adverse health effects are likely to occur. These non-enforceable health goals, based solely on possible health risks and exposure over a lifetime, with an adequate margin of safety, are called maximum contaminant level goals (MCLG). Contaminants are any physical, chemical, biological or radiological substances or matter in water. EPA sets MCLGs based on the best available science to prevent potential health problems.
Based on the MCLG, EPA sets an enforceable regulation called a maximum contaminant level (MCL). MCLs are set as close to the health goals as possible, considering cost, benefits and the ability of public water systems to detect and remove contaminants using suitable treatment technologies. MCLs for disinfection byproducts are set at the following levels:
|Levels for Total Trihalomethanes|
|Bromodichloromethane||Zero||0.080 mg/L or 80 ppb
(Sum of the concentrations of all four trihalomethanes) as an annual average
|Dibromochloromethane||0.06 mg/L or 60 ppb|
|Chloroform||0.07 mg/L or 70 ppb|
|Levels for Haloacetic acids|
|Dichloroacetic acid||Zero||0.060 mg/L or 60 ppb
(Sum of the concentrations of all five haloacetic acids) as an annual average
|Trichloroacetic acid||0.02 mg/L or 20 ppb|
|Monochloroacetic acid||0.07 mg/L or 70 ppb|
|Bromoacetic acid||Regulated with this group but has no MCLG|
|Dibromoacetic acid||Regulated with this group but has no MCLG|
|Bromate||Zero||0.010 mg/L or 10 ppb as an annual average|
|Chlorite||0.80 mg/L or 800 ppb||1.0 mg/L or 1 part per million (ppm)|
MCLs are set as close to the health goals as possible, considering cost, benefits and the ability of public water systems to detect and remove contaminants using suitable treatment technologies. States may set more stringent drinking water MCLGs and MCLs for disinfection byproducts than EPA.
The following drinking water regulations apply to disinfectants and disinfection byproducts:
- Stage 1 Disinfectants and Disinfection Byproducts Rule (Stage 1 DBP) (December 16, 1998)
The Stage 1 Disinfectants and Disinfection Byproducts Rule reduces exposure to disinfection byproducts for customers of community water systems and non-transient non-community systems, including those serving fewer than 10,000 people, that add a disinfectant to the drinking water during any part of the treatment process.
- Stage 2 Disinfectants and Disinfection Byproducts Rule (Stage 2 DBP) (December 15, 2005)
Stage 2 DBP rule builds upon earlier rules that addressed disinfection byproducts to improve your drinking water quality and provide additional public health protection from disinfection byproducts.
The Safe Drinking Water Act requires EPA to periodically review the national primary drinking water regulation for each contaminant and revise the regulation, if appropriate, based on new scientific data. EPA will include the Disinfectants and Disinfection Byproducts rules in a future review cycle.