Basic Information on the Chemical Contaminant Rules

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EPA established Maximum Contaminant Levels (MCLs), Maximum Contaminant Level Goals (MCLGs), monitoring requirements and best available technologies for removal for 65 chemical contaminants over a five year period as EPA gathered and analyzed occurrence and health effects data. This series of rules are known as the Chemical Phase Rules and they define regulations for three contaminant groups:

• Inorganic Chemicals (IOCs),
• Synthetic Organic Chemicals (SOCs), and
• Volatile Organic Chemicals (VOCs).

The Chemical Phase rules provide public health protection through the reduction of chronic risks from:

• cancer;
• organ damage; and
• circulatory,
• nervous, and
• reproductive system disorders.

They also help to reduce the occurrence of Methemoglobinemia or "blue baby syndrome" from ingestion of elevated levels of nitrate or nitrite. All public water systems must monitor for Nitrate and Nitrite. Community water systems and Non-transient non-community water systems must also monitor for IOCs, SOCs, and VOCs.

• List of established Maximum Contaminant Levels (MCLs) and their Maximum Contaminant Level Goals (MCLGs)

Regulated Chemical Contaminants

For more information on each of these contaminants, click on the links in the table below.

¹Aldicarb, aldicarb sulfone, and aldicarb sulfoxide are considered regulated chemicals although their MCLs are stayed. Therefore PWS are not required to meet an MCL.

For each contaminant, EPA set a health goal, or Maximum Contaminant Level Goal (MCLG). This is the level at which a person could drink two liters of water containing the contaminant every day for 70 years without suffering any ill effects. This goal is not a legal limit with which water systems must comply; it is based solely on human health. For known cancer-causing agents (carcinogens), EPA set the health goal at zero, under the assumption that any exposure to the chemical could present a cancer risk.

The rules also set a legal limit, or Maximum Contaminant Level (MCL), for each contaminant. EPA sets legal limits as close to the health goal as possible, keeping in mind the technical and financial barriers that exist. Except for contaminants regulated as carcinogens, most legal limits and health goals are the same. Even when they are less strict than the health goals, the legal limits provide substantial public health protection.

Federal Register Notices for the Chemical Phase Rules

You will need the free Adobe Reader to view some of the files on this page. See EPA's PDF page to learn more. If you need help accessing these PDF documents below, please contact EPA's Safe Drinking Water Hotline at 1-800-426-4791.

• Drinking, Water, Synthetic, Inorganic, Chemicals, Unregulated, Contaminants, Implementation, Secondary National Primary Drinking Water Regulations; Synthetic Organic Chemicals; Monitoring for Unregulated Contaminants
  July 8, 1987
  Copy of Federal Register Notice for Drinking, Water, Synthetic, Inorganic, Chemicals, Unregulated, Contaminants, Implementation, Secondary National Primary Drinking Water Regulations; Synthetic Organic Chemicals; Monitoring for Unregulated Contaminants (PDF) (27 pp, 12MB)
• National Primary Drinking Water Regulations; Synthetic Organic Chemicals; Monitoring for Unregulated Contaminants; Correction
  July 1, 1988
  Copy of Federal Register Notice for National Primary Drinking Water Regulations; Synthetic Organic Chemicals; Monitoring for Unregulated Contaminants; Correction (PDF) (5 pp, 1MB)
• National Primary Drinking Water Regulations - Synthetic Organic Chemicals and Inorganic Chemicals; Monitoring for Unregulated Contaminants; National Primary Drinking Water Regulations Implementation; National Secondary Drinking Water Regulations
  January 30, 1991
  Copy of Federal Register Notice for National Primary Drinking Water Regulations - Synthetic Organic Chemicals and Inorganic Chemicals; Monitoring for Unregulated Contaminants; National Primary Drinking Water Regulations Implementation; National Secondary Drinking Water Regulations (PDF) (73 pp, 11MB)
• Drinking Water; National Primary Drinking Water Regulations; Monitoring for Volatile Organic Chemicals; MCLGs and MCLs for Aldicarb, Aldicarb Suffoxide, Aldicarb Sulfone, Pentachchlorophenol, and Barium
  July 1, 1991
  Copy of Federal Register Notice for Drinking Water; National Primary Drinking Water Regulations; Monitoring for Volatile Organic Chemicals; MCLGs and MCLs for Aldicarb, Aldicarb Suffoxide, Aldicarb Sulfone, Pentachchlorophenol, and Barium (PDF) (18 pp, 7MB)
• National Primary Drinking Water Regulations; Synthetic Organic Chemicals and Inorganic Chemicals; Final Rule
  July 17, 1992
  Copy of Federal Register Notice for National Primary Drinking Water Regulations; Synthetic Organic Chemicals and Inorganic Chemicals; Final Rule (PDF) (75 pp, 28MB)

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The Standardized Monitoring Framework

The Standardized Monitoring Framework (SMF), promulgated in the Phase II rule on January 30, 1991 and revised under Phases IIB and V, includes contaminants regulated under Phases I, II, IIB, V, the revised Arsenic Rule, and the Radionuclides Rule. Monitoring under the SMF began in 1993. The goal of the Standardized Monitoring Framework is to standardize, simplify, and consolidate drinking water monitoring requirements across contaminant groups. In order to do this, EPA has established nine-year compliance cycles. Each nine-year compliance cycle is divided into 3 three-year compliance periods, which may be further subdivided into annual and quarterly periods. Compliance periods run on a calendar year basis, from January 1 through December 31. Compliance cycle 1 began January 1, 1993 and ended December 31, 2001; the second compliance cycle began January 1, 2002 and ends December 31, 2010; the third compliance cycle begins January 1, 2011 and ends December 31, 2019. Monitoring schedules and sample requirements are standardized for each compliance cycle for each contaminant group.

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Monitoring Waivers

The SMF allows States to grant waivers to water systems to reduce the sampling frequencies to once every 3, 6 or 9 years for inorganic compounds, synthetic organic compounds, and volatile organic compound. Waivers of sampling requirements are granted for specified contaminants based on both a vulnerability assessment and the analytical results of previous sampling. The vulnerability assessment may be based on a determination that either the contaminant has not been used in the area or that the system is not susceptible to contamination.

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