EPA indicated that the group rule would contain as many as 16 compounds, including eight currently regulated cVOCs and up to eight from the third Contaminant Candidate List. These 16 cVOCs include:
Currently regulated cVOCs
- Carbon tetrachloride
- Trichloroethylene (TCE)
- Vinyl chloride
- Tetrachloroethylene (PCE)
- Benzyl chloride
- Oxirane methyl
EPA has also indicated that four additional cVOCs are being considered as potential substitutes of one or more of 16 listed above:
- 1,2-Dibromo-3-chloropropane (DBCP)
- 1,2-Dibromoethane (EDB)
This may not be the final list of chemicals to be included in the cVOCs group rule. As new information on health effects, occurrence and treatment become available, EPA may add, drop or substitute some other contaminants into the rule.
It should also be noted that 1,1-dichloroethane; 1,3-butadiene; and 1,2,3-trichloropropane from the above CCL3 list are included in monitoring under the Third Unregulated Contaminant Monitoring Rule (UCMR3).
Clearly, the cVOC Group Rule as announced is using similar health effects (carcinogenicity) as the primary method way to choose the contaminants for consideration.
Another possible classification framework would be common analytical method(s) for the group. But there now is no single analytical method for all 16 cVOCs (and the possible substitutes) being considered. Depending on the composition of the final group, several different analytical methods may be required to test for the contaminants.
Common treatment is another potential group classification. For cVOCs, the physical and chemical characteristics are critical in order to evaluate whether a common treatment is practical and feasible. Likely cVOC treatment technologies include aeration and granular activated carbon, although the expense and efficacy of treatment for some of the currently unregulated cVOCs is not yet well understood.
There are a number of different ways in which a group cVOC rule could function.
It is likely that all of the currently regulated cVOCs will maintain their current MCLs (due to the anti-backsliding provisions in the Safe Drinking Water Act). It is unclear whether an MCL will be set individually for each currently unregulated cVOC included in the group or whether there will be some type of pooled or group MCL across all of the contaminants in the group.
Given differences in health effects among cVOCs, it is also unclear whether a group MCL would require some type of weighting and how compliance with the rule’s requirements would be determined.