Frequent Questions

4. What are EPA's drinking water regulations for cis-1,2-dichloroethylene?


The MCLG for cis-1,2-dichloroethylene is 0.07 mg/L or 70 ppb. EPA has set this level of protection based on the best available science to prevent potential health problems. EPA has set an enforceable regulation for cis-1,2-dichloroethylene, called a maximum contaminant level (MCL), at 0.07 mg/L or 70 ppb. 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. In this case, the MCL equals the MCLG, because analytical methods or treatment technology do not pose any limitation.

The Phase II Rule, the regulation for cis-1,2-dichloroethylene, became effective in 1992. 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. EPA reviewed cis-1,2-dichloroethylene as part of the Six Year Review and determined that the 0.07 mg/L or 70 ppb MCLG and 0.07 mg/L or 70 ppb MCL for cis-1,2-dichloroethylene are still protective of human health.

States may set more stringent drinking water MCLGs and MCLs for cis-1,2-dichloroethylene than EPA.

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