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Fact Sheet: Preliminary Regulatory Determinations for 

the Second Drinking Water Contaminant Candidate List 

(CCL 2) 

EPA has drinking water regulations for more than 90 contaminants. To assess and address risks 

posed by unregulated contaminants, EPA, in accordance with the Safe Drinking Water Act 

(SDWA), identifies a list of contaminants which may require regulation in the future, and every 

five years, EPA determines whether we should regulate at least five contaminants in drinking 

water. 

In February 2005, EPA published the second CCL of 51 contaminants. EPA has evaluated 

available occurrence, exposure, and health effects information for CCL 2 contaminants. EPA is 

announcing preliminary determinations for 11 of these 51 contaminants. EPA is requesting 

comment on its preliminary determination that none of these 11 contaminants need to be 

regulated in drinking water and is requesting comment from the public. 

 

Questions and Answers

 

What is the drinking water CCL?

The drinking water CCL is the primary source of priority contaminants for conducting research 

and making decisions about whether drinking water regulations are needed. The contaminants 

on the list are known or anticipated to occur in public water systems. However, they are 

currently unregulated with a national primary drinking water regulation. 

How often is the CCL published?

The Safe Drinking Water Act directs EPA to publish a CCL every five years. We published the 

first CCL of 60 contaminants in March 1998. We published the second CCL (CCL 2) in 

February 2005. The second CCL carried forward 51 (of the original 60) unregulated 

contaminants from the first CCL, including nine microbiological contaminants and 42 chemical 

contaminants or contaminant groups (see Table 1). 

What is a regulatory determination?

A regulatory determination is a formal decision on whether EPA should initiate a rulemaking 

process to develop a national primary drinking water regulation for a specific contaminant. The 

law requires that we make regulatory determinations for at least five contaminants from the most 

recent CCL every five years. 

In this notice, EPA announced its preliminary determinations for 11 contaminants listed on the 

second CCL. EPA had sufficient health and occurrence information to make the determination 

not to regulate boron, the dacthal mono- and di-acid degradates, 1,1-dichloro-2,2-bis(p-
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chlorophenyl)ethylene (DDE), 1,3-dichloropropene (Telone), 2,4-dinitrotoluene, 2,6-

dinitrotoluene, s-ethyl propylthiocarbamate (EPTC), fonofos, terbacil, or 1,1,2,2-

tetrachloroethane. 

Occurrence information indicates that these 11 contaminants either appear to be nonexistent or 

have low levels of occurrence at health levels of concern in public water systems and regulating 

these contaminants does not present a meaningful opportunity for health risk reduction. In those 

cases where low levels of occurrence exist, we are recommending that the Agency update the 

current health advisories to reflect new information or to include the potential degradates. These 

determinations are preliminary and the public can comment on the Agency’s decisions during the 

60-day public comment period. We plan to notify the public of the final regulatory 

determinations in 2008. 

It is important to note that we are not limited to making regulatory determinations for only those 

contaminants on the CCL. We can also decide to regulate other unregulated contaminants if 

information becomes available, showing that a specific contaminant presents a public health risk. 

What criteria does EPA consider in making regulatory determinations?

When making a determination to regulate, the law requires consideration of three areas: 

• the potential adverse effects of the contaminant on the health of humans, 

• the extent of contaminant occurrence in public drinking water, and 

• whether regulation of the contaminant presents a meaningful opportunity for reducing 

public health risks. 

What is the Agency doing about perchlorate and methyl tertiary butyl ether (MTBE)?

The Agency continues to use the best available science on perchlorate to protect public health 

and the environment. EPA has already developed a reference dose for perchlorate based on the 

2005 recommendations by the National Academy of Sciences. EPA has also issued updated 

guidance on how to use the reference dose in source water cleanup decisions. The Agency 

believes additional information may be needed to more fully characterize perchlorate exposure 

and determine whether it is appropriate to regulate perchlorate in drinking water (i.e., whether 

setting a national primary drinking water standard would provide a meaningful opportunity to 

reduce risk for people served by public water systems). The notice describes how the Agency is 

considering FDA food data and CDC human exposure data to see if it can help us determine 

whether it is appropriate to regulate perchlorate. 

EPA is not making a regulatory determination for MTBE at this time because the Agency’s 

health risk assessment has not been finalized. However, the notice summarizes some of the 

available and relevant occurrence information for MTBE and provides an opportunity for states 

to voluntarily submit finished drinking water occurrence data, information on the potential 

impacts of MTBE contamination on public water systems, and any treatment information as 

well. 
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Do these Regulatory Determinations impose any requirements on public water systems?

No. The regulatory determinations on the CCL alone do not impose any requirements on public 

water systems. However, if EPA decided to regulate a contaminant on the list in the future, then 

public water systems would have to comply with the regulation. 

Where can I find more information about this notice and the CCL 2 Regulatory 

Determinations?

For information on the regulatory determinations for the second CCL, please visit 

http://www.epa.gov/safewater/ccl/reg_determine2.html. For general information on drinking 

water, please visit the EPA Safewater Web site at www.epa.gov/safewater or contact the Safe 

Drinking Water Hotline at 1-800-426-4791. The Safe Drinking Water Hotline is open Monday 

through Friday, excluding legal holidays, from 10:00 a.m. to 4:00 p.m., Eastern time. 
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Table 1 - Drinking Water Contaminant Candidate List 2 (CCL 2) 

Microbial Contaminant Candidates

Adenoviruses 

Aeromonas hydrophila 

Caliciviruses 

Coxsackieviruses 

Cyanobacteria (blue-green algae), other freshwater algae, and their toxins 

Echoviruses 

Helicobacter pylori 

Microsporidia (Enterocytozoon & Septata) 

Mycobacterium avium intracellulare (MAC) 

Chemical Contaminant Candidates CASRN

1,1,2,2-tetrachloroethane 79-34-5 

1,2,4-trimethylbenzene 95-63-6 

1,1-dichloroethane 75-34-3 

1,1-dichloropropene 563-58-6 

1,2-diphenylhydrazine 122-66-7 

1,3-dichloropropane 142-28-9 

1,3-dichloropropene 542-75-6 

2,4,6-trichlorophenol 88-06-2 

2,2-dichloropropane 594-20-7 

2,4-dichlorophenol 120-83-2 

2,4-dinitrophenol 51-28-5 

2,4-dinitrotoluene 121-14-2 

2,6-dinitrotoluene 606-20-2 

2-methyl-Phenol (o-cresol) 95-48-7 

Acetochlor 34256-82-1 
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Chemical Contaminant Candidates CASRN

Alachlor ESA & other acetanilide pesticide 

degradation products 

N/A 

Aluminum 7429-90-5 

Boron 7440-42-8 

Bromobenzene 108-86-1 

DCPA mono-acid degradate 887-54-7 

DCPA di-acid degradate 2136-79-0 

DDE 72-55-9 

Diazinon 333-41-5 

Disulfoton 298-04-4 

Diuron 330-54-1 

EPTC (s-ethyl-dipropylthiocarbamate) 759-94-4 

Fonofos 944-22-9 

p-Isopropyltoluene (p-cymene) 99-87-6 

Linuron 330-55-2 

Methyl bromide 74-83-9 

Methyl-t-butyl ether (MTBE) 1634-04-4 

Metolachlor 51218-45-2 

Molinate 2212-67-1 

Nitrobenzene 98-95-3 

Organotins N/A 

Perchlorate 14797-73-0 

Prometon 1610-18-0 

RDX 121-82-4 

Terbacil 5902-51-2 

Terbufos 13071-79-9 
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Chemical Contaminant Candidates CASRN

Triazines & degradation products of triazines including, but not limited to Cyanazine 

21725-46-2 and atrazine-desethyl 6190-65-4 

Vanadium 7440-62-2