Safe Drinking Water Program

How the Federal Government, Other States, and the European Union Address Unregulated Contaminants in Drinking Water

1. USEPA

For Public Comment -- Deadline April 2, 2004

The following descriptions are presented for illustrative purposes only. This section is not meant as an exhaustive assessment of all activities of other agencies in this area.

It has already been stated that currently, before a chemical can be considered for federal or state regulation, toxicity information that shows adverse or potentially adverse health effects is needed. However, there are a number of other strategies that USEPA is using in order to address the risk of unregulated chemicals to human health. The federal programs are generally information-based (such as the Right-To-Know program), incentive-based (such as providing companies with fiscal or regulatory incentives to using non-toxic chemicals in their manufacturing processes), or monitoring-based (such as the research studies being conducted in the Great Lakes region on persistent bioaccumulative toxics).

The regulators mechanism that most clearly addresses unregulated contaminants in drinking water is the Unregulated Contaminant Monitoring Rule.

Unregulated Contaminant Monitoring Rule The 1996 Amendments to the Safe Drinking Water Act requires the USEPA to establish criteria for a monitoring program for unregulated contaminants and to publish a list of contaminants to be monitored. The rule was published on September 17, 1999, and supplemented on March 2, 2000 and January 11, 2001. The data generated by the Unregulated Contaminant Monitoring Rule is be used to evaluate and prioritize contaminants on the Drinking Water Contaminant Candidate List (Table 4), a list of contaminants USEPA is considering for possible new drinking water standards.

Contaminants on the Contaminant Candidate List (Table 4) are divided into three groups based on priorities for regulation, need for further health research, and need for further occurrence data collection. The Unregulated Contaminant Monitoring Regulation requires USEPA to establish monitoring requirements for 30 contaminants in any 5-year cycle. Since many of the contaminants still have analytical methods under development, the success of the methods development efforts will dictate which contaminants will be monitored in the 5-year cycle. Currently, most of the unregulated contaminants with potential of occurring in drinking water are pesticides and microbes. In addition, every six years, USEPA will re-evaluate existing regulations to determine if modifications are necessary. In 2003, USEPA reported the results of its evaluation on the first five-year cycle. The agency finalized regulators determinations for nine contaminants on the Contaminant Candidate List. The Agency determined that at this time it is not appropriate to develop regulations for acanthamoeba, aldrin, dieldrin, hexachlorobutadiene, manganese, metribuzin, naphthalene, sodium, and sulfate. Therefore, no new regulators maximum contaminant levels will be set during the first five-year cycle of the Unregulated Contaminant Monitoring Rule. Among the contaminants being reviewed for possible future regulators action are radon, methyl tert-butyl ether (MTBE) and perchlorate.

USEPA Guidelines for the Health Risk Assessment of Chemical Mixtures To address concerns over health risks from multichemical exposures, the USEPA published the Guidelines for the Health Risk Assessment of Chemical Mixtures in 1986 (8), available at

http://cfpub.epa.gov/ncea/raf/recordisplay.cfm?deid=20533.
(Click on the above link to go to that document)
The Guidelines describe broad concepts related to mixture exposure and toxicity and includes few specific procedures. In 1989 USEPA published guidance for the Superfund program on hazardous waste that gave practical steps for conducting a mixtures risk assessment. Also in 1989, USEPA published the revised document on the use of Toxicity Equivalence Factors for characterizing health risks of the class of chemicals including the dibenzo-dioxins and dibenzofurans. In 1990, USEPA published a Technical Support Document to provide more detailed information on toxicity of whole mixtures and on toxicological interactions (e.g., synergism) between chemicals in a binary (two-chemical) mixture. The concept of toxicological similarity was also discussed. The Environmental Criteria and Assessment Office (now the National Center for Environmental Assessment) followed this with the development of a Technical Support Document on Health Risk Assessment of Chemical Mixtures. When the 1986 Guidelines were published, the Agency recognized that they would need to be updated as the science of chemical mixture assessment evolved. After an overview of the background and scope, the Supplementary Guidance for Conducting Health Risk Assessment of Chemical Mixtures (9), available at:

http://www.epa.gov/ord/archives/2001/august/htm/art_science_policy.htm
(Click on the above link to go to that document)
was released. This document puts forth the actual risk assessment paradigm for mixtures. This paradigm begins with problem formulation, then briefly discusses hazard identification, dose-response assessment, exposure, and risk characterization. The document is organized according to the type of data available to the risk assessor, ranging from data-rich to data-poor situations. Procedures are described for assessment using data on the mixture of concern, data on a toxicologically similar mixture, and data on the mixture component chemicals. The state of the science varies dramatically for these three approaches. The whole-mixture procedures are most advanced for assessing potential carcinogenic risk, mainly because of the long use of in vitro mutagenicity tests to indicate possible carcinogenicity. In vitro test procedures for noncancer endpoints are still in the pioneering stage. In contrast, the component-based procedures, particularly those that incorporate information on toxicological interactions, are most advanced for noncarcinogenic toxicity. No single approach is recommended in this supplementary guidance. Instead, guidance is given for the use of several approaches depending on the nature and quality of the data. An evaluation of the data may lead the user to decide that only a qualitative analysis should be performed. This generally occurs in cases where data quality is poor, inadequate quantitative data are available, data on a similar mixture cannot be classified as "sufficiently similar" to the mixture of concern, exposures cannot be characterized with confidence, or method-specific assumptions about the toxicological action of the mixture or of its components cannot be met. When this occurs, the risk assessor can still perform a qualitative assessment that characterizes the potential human health impacts from exposure to that mixture. Such a risk characterization should discuss each element of the risk assessment paradigm, including available information on the mixture itself, on its component, and on potential interactions among the components. Any information on fate and transport of the mixture that would affect its final composition at the time of exposure should be noted. The assessment of chemical mixtures is an area of active scientific investigation. As new information relevant to health risk from exposure to chemical mixtures becomes available, additional guidance documents will be published.

Persistent Bioaccumulative and Toxic (PBT) Chemical Strategy The goal of this agency-wide, multimedia strategy, released in November 1998, is to identify and reduce risks to human health and the environment from current and future exposure to persistent, bioaccumulative pollutants. Persistent, bioaccumulative and toxic pollutants are chemicals that are toxic, persist in the environment, and bioaccumulate in food chains and, thus, pose risks to human health and ecosystems. The approach outlined in this strategy builds upon work initiated under the Great Lakes Binational Toxics Strategy and uses regulatory action where voluntary efforts are insufficient. The action plans will consider enforcement and compliance, international coordination, place-based remediation of existing persistent, bioaccumulative and toxic pollutant contamination, research, technology development and monitoring, community and sector-based projects, the use of outreach and public advisories, and opportunities to integrate efforts across chemicals.

Toxics Release Inventory Program The Toxic Release Inventory is a right to-know-program dealing with toxic chemical emissions and waste from manufacturing and other facilities. It is a publicly available USEPA database that contains information on toxic chemical releases and other waste management activities reported annually by certain covered industry groups as well as federal facilities. This inventory was established under the Emergency Planning and Community Right-to-Know Act of 1986 and expanded by the Pollution Prevention Act of 1990. The program has provided a strong incentive for chemical users to reduce chemical waste, emissions, and use.

High Production Volume Chemical Testing Production The USEPA, the Environmental Defense Fund (an environmental advocacy organization) and the American Chemistry Council entered into a voluntary agreement in 1999 to produce screening level data on 2,800 high production volume chemicals. Companies enter into consortia to provide this data. The program has generated a set of screening level data for most of the high production volume chemicals used in the US, and the USEPA has made this data available on their website.

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