4
Approach Used to Develop the 1998 CCL

Among other changes, the Safe Drinking Water Act (SDWA) Amendments of 1996 significantly restructured the development process for drinking water standards that was established under the 1986 SDWA amendments. Prior to enactment of the 1996 amendments, every three years EPA was required to publish a drinking water priority list (DWPL) of contaminants that served as candidates for future regulation. EPA was also required to develop standards for 25 new DWPL contaminants every three years. Now, instead of publishing a DWPL and then regulating 25 new contaminants every three years, the 1996 amendments require EPA to ''publish a list of contaminants, which, at the time of publication, are not subject to any proposed or promulgated national primary drinking water regulation, which are known or anticipated to occur in public water systems, and which may require regulation under this title." As discussed in Chapter 1, this new list, the Drinking Water Contaminant Candidate List (CCL), will provide the basis for deciding whether to regulate at least five new contaminants every five years. EPA published a draft of the first CCL on October 6, 1997, following a two-month public comment period, and published the final CCL on March 2, 1998 (EPA, 1998a). This chapter briefly summarizes the background and development processes for the draft and final versions of the current CCL.

EPA's Contaminant Identification Method

As discussed in Chapter 1, shortly after passage of the SDWA Amendments of 1996 EPA began work on a conceptual, risk-based approach, the Contaminant



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--> 4 Approach Used to Develop the 1998 CCL Among other changes, the Safe Drinking Water Act (SDWA) Amendments of 1996 significantly restructured the development process for drinking water standards that was established under the 1986 SDWA amendments. Prior to enactment of the 1996 amendments, every three years EPA was required to publish a drinking water priority list (DWPL) of contaminants that served as candidates for future regulation. EPA was also required to develop standards for 25 new DWPL contaminants every three years. Now, instead of publishing a DWPL and then regulating 25 new contaminants every three years, the 1996 amendments require EPA to ''publish a list of contaminants, which, at the time of publication, are not subject to any proposed or promulgated national primary drinking water regulation, which are known or anticipated to occur in public water systems, and which may require regulation under this title." As discussed in Chapter 1, this new list, the Drinking Water Contaminant Candidate List (CCL), will provide the basis for deciding whether to regulate at least five new contaminants every five years. EPA published a draft of the first CCL on October 6, 1997, following a two-month public comment period, and published the final CCL on March 2, 1998 (EPA, 1998a). This chapter briefly summarizes the background and development processes for the draft and final versions of the current CCL. EPA's Contaminant Identification Method As discussed in Chapter 1, shortly after passage of the SDWA Amendments of 1996 EPA began work on a conceptual, risk-based approach, the Contaminant

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--> Identification Method (CIM), to identify unregulated chemical and microbiological drinking water contaminants as priorities for its drinking water program (EPA, 1996). EPA originally developed completely separate risk-based approaches for prioritizing unregulated chemical and microbiological contaminants under the CIM. In brief, the approach for chemical contaminants consisted of four hierarchical stages: (1) initial identification, (2) preliminary screening, (3) ranking and risk assessment, and (4) program decisions. Ultimately, EPA used only concepts from the first two stages of the chemical CIM approach to identify and select contaminants for inclusion on the CCL. No attempt was made to rank and prioritize contaminants quantitatively for future regulatory action. As noted in Chapter 1, this was largely because of time constraints associated with meeting the legislatively mandated publication deadline of February 6, 1998 (see Figure 1-1). At the time of the CIM working draft report, EPA was uncertain whether a feasible and objective approach could be developed for microbiological contaminants using the same or similar criteria as that used for chemical contaminants. EPA considered two basic approaches for identifying and prioritizing pathogens: (1) preparation of an initial list of known and potential pathogens that would be peer reviewed and expanded by an expert panel of microbiologists and public health specialists and (2) development of a conceptual risk-based approach utilizing weighted criteria. As will be discussed later in this chapter, EPA chose the first approach in its development of the first CCL. Draft Drinking Water Contaminant Candidate List When published on October 6, 1997, the draft CCL included 58 unregulated1 chemical contaminants and contaminant groups (further divided into data need categories) and 13 unregulated microbiological contaminants (EPA, 1997a). During development of the draft CCL, EPA consulted extensively with stakeholders (including water utilities, trade associations, and environmental groups), the Science Advisory Board, and the National Drinking Water Advisory Council's (NDWAC's) Working Group on Occurrence and Contaminant Selection. NDWAC played an integral part in the development of the draft CCL. Established in 1975 under the authority of the Federal Advisory Committee Act, NDWAC provides independent advice to EPA on SDWA policies. Following enactment of the SDWA Amendments of 1996, NDWAC formed several work- 1   Contaminants on the draft CCL were not subject to any proposed or promulgated national primary drinking water regulation, with the exception of nickel, aldicarb and its degradates, and sulfate, which were included because of pre-existing obligations to complete regulatory action for them (EPA, 1997a).

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--> ing groups, including the Working Group on Occurrence and Contaminant Selection, to assist EPA in the implementation of many of its new and revised statutory requirements. This group included engineers, microbiologists, toxicologists, and public health scientists selected from federal, state, and local regulatory agencies, public and private water systems, and other organizations concerned with safe drinking water. The working group developed recommendations concerning which chemical contaminants to be included for initial consideration and criteria for EPA to use in narrowing this initial list. The recommendations were later endorsed by the full NDWAC. Also, at the recommendation of the working group, EPA sought external expertise on microbiological contaminants and convened a workshop of microbiologists and public health specialists to develop an initial list of current and emerging pathogens for possible inclusion on the draft CCL. The findings and recommendations from the workshop were fully adopted by the working group. Identification and Selection of Microbiological Contaminants Participants in the workshop used to develop a list of pathogens for potential inclusion on the first draft CCL included experts from academia, EPA and other federal agencies, and the water industry (EPA, 1997b). At the outset, EPA prepared and distributed a list of microbiological contaminants and criteria for selecting and prioritizing microbiological contaminants for initial consideration by workshop members. The initial list included protozoa, viruses, bacteria, and algal toxins. Inclusion was based on disease outbreak data, published literature documenting the occurrence of known or suspected waterborne pathogens, and other related information (EPA, 1997a). Prior to reviewing EPA's proposed straw man criteria for evaluating microbiological contaminants, the participants established a set of baseline criteria related to an organism's (1) public health significance, (2) known waterborne transmission, (3) occurrence in source water, (4) effectiveness of current water treatment, and (5) adequacy of analytical methods (EPA, 1997b). All of the microorganisms included on EPA's initial list, as well as other potential microbiological contaminants that arose during deliberations, were individually evaluated against these criteria. This evaluation also assessed the basic research and data needs for each microorganism. When published, the draft CCL included every microbiological contaminant recommended by the workshop and subsequently adopted by NDWAC. Identification and Selection of Chemical Contaminants At the first meeting of the NDWAC working group, EPA proposed a total of 391 contaminants (including 25 microorganisms) from ten lists of potential drinking water contaminants as a reasonable starting point for developing the draft

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--> CCL (EPA, 1997a). Most of the lists originated from a variety of EPA programs, including some from the Office of Water for use in the development of future drinking water priority lists. As briefly summarized in Table 4-1, eight lists were ultimately retained and combined to provide the working group with an initial list of 262 chemical contaminants for consideration. EPA made it clear that the number of contaminants on the draft and final CCL would have to be reduced from 262. TABLE 4-1 Initial Chemical Lists Considered for Development of Draft CCL List Summary and Notes 1991 Drinking water priority list 56 total, not including disinfection byproducts for which regulations are being developed under the Disinfectants and Disinfection Byproducts Rule Health advisories (HAs) All contaminants with HAs or HAs under development in EPA's Health Advisory Program (108 total) Integrated Risk Information System (IRIS) 48 contaminants adopted from IRIS based on a risk-based screen developed by EPA in anticipation of the 1994 DWPL Contaminants identified by public water systems List of 22 non-target contaminants identified in public water systems in anticipation of the 1994 DWPL ATSDR list of contaminants found at Comprehensive Environmental Response, Compensation and Liability Act (CERCLA) sites Top 50 contaminants from a 1995 CERCLA list of 275 prioritized hazardous substances Stakeholder summary list 59 contaminants proposed as candidates by participants in a December 2-3, 1997 stakeholder meeting on EPA's CIM Toxic Release Inventory (TRI) list 51 chemicals that met criteria for assessing the potential of a contaminant to occur in public water; derived from an original 1994 TRI list of 343 chemicals Office of Pesticide Programs (OPP) ranking 65 pesticides and degradates taken from OPP ranking of pesticides from highest to lowest potential to leach to ground water   SOURCE: EPA, 1997a.

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--> TABLE 4-2 Contaminants Deferred by EPA Based Solely on Suspected Endocrine Disruption Amitrole Parathion Benomyl Permethrin Dicofol (Kelthane) Synthetic Pyrethroids Esfenvalerate Transnonachlor Ethylparathion Tributyltin oxide Fenvalerate Vinclozolin Kepone Zineb Mancozeb Ziram Metiram Octachlorostyrene Mirex Polybrominated biphenyls Nitrofen Penta-to nonyl-phenols Oxychlordane     SOURCE: EPA, 1997a. Deferred Groups of Potential Contaminants: Endocrine Disruptors In developing the draft CCL, EPA initially prepared a list of contaminants that were suspected of having adverse effects on endocrine (hormonal) functions of humans and wildlife (EPA, 1997a). This list resulted, in part, from an interim EPA report that assessed this concern pending an extensive review by the National Research Council's Board on Environmental Studies and Toxicology, to be published in the late fall of 1998. Under the SDWA, as amended, and the 1996 Food Quality Protection Act, EPA is required to establish a program to screen, assess, and test potential endocrine-disrupting contaminants (EPA, 1997a). In response, EPA established the Endocrine Disruptor Screening and Testing Advisory Council to advise EPA on implementing a testing and screening program. The advisory council completed its final report in August 1998 (EDSTAC, 1998). The report was reviewed jointly by EPA's Science Advisory Board and the Federal Insecticide, Fungicide, and Rodenticide Act Scientific Advisory Panel. Pending completion of these reviews, EPA withdrew 21 contaminants (see Table 4-2) from consideration for the draft CCL based solely on the possibility of endocrine disruption (i.e., each chemical did not appear on any of the other nine initial lists of potential contaminants). However, several contaminants (all pesticides) implicated as endocrine disruptors were considered and included on the draft CCL for other reasons (e.g., dieldrin and metribuzin). Deferred Groups of Potential Contaminants: Pesticides During the development of the draft CCL, EPA sought assistance from EPA's Office of Pesticide Programs (OPP) in determining which pesticides should be

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--> TABLE 4-3 Deferred Pesticides Asulam Halofenozide Prometryn Bensulfuron methyl Halosulfuron Propazine Bentazon Hexazinone Prosulfuron Bromacil Imazamethabenz Pyrithiobac-Na Cadre Imazapyr Rimsulfuron Chlorimuron ethyl Imazaquin Sulfentrazone Chlorsulfuron Imazethapyr Sulfometuron methyl Diazinon-oxypyrimidine MCPA (methoxone) Tebufenozide Dicamba Methsulfuron methyl Terbufos sulfone Ethylenethiourea Nicosulfuron Thiazopyr Fenamiphos Norflurazon Triasulfuron Fluometuron Primisulfuron methyl     SOURCE: EPA, 1997a. priorities for the drinking water program (EPA, 1997a). In response, OPP provided a list of pesticides for consideration based on physical-chemical properties, occurrence, and extent of use. The list was ranked using a ground water risk score, which is a calculated potential for the pesticide to leach into ground water. Pesticides with a risk score of 2.0 or greater were included for initial consideration by the NDWAC working group (see Table 4-1). During subsequent data evaluation and screening phases of the draft CCL, the working group decided to defer many pesticides from consideration when the risk score of 2.0 or greater was the only factor for inclusion on the CCL. In addition, several new pesticides for which no other data exist (besides a ground water risk score) were also deferred. In all, 35 pesticides were deferred pending further evaluation of their potential to occur at levels of health concern; these are listed in Table 4-3. Contaminant Screening and Evaluation Criteria As previously noted, the NDWAC working group developed criteria for screening and evaluating potential chemical contaminants for inclusion on the draft CCL. The working group members adopted two general premises: (1) they would consider only chemical contaminants included on EPA's initial list that did not have National Primary Drinking Water Regulations, and (2) they would consider occurrence, or anticipated occurrence, first, before any evaluation of health effects information. EPA used data from the Storage and Retrieval Database, the Hazardous Substances Database, IRIS, published literature, and other regulatory agency reports, where available, to screen and evaluate potential contaminants.

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--> Occurrence Criteria If a specific chemical contaminant or group of contaminants met any portion of either of the following two occurrence elements, it was to be moved to the health effects phase of the evaluation: Was the contaminant looked for and found in drinking water,2 or in a major drinking water source,3 or in ambient water at concentrations that would trigger concern about human health?4 If not looked for, was the contaminant likely to be found in water based on surrogates for occurrence, including known TRI releases5 or high production volumes,6 coupled with physical-chemical properties likely to result in occurrence in water supplies, or high OPP ground water risk scores.7 If both occurrence elements were negative, the contaminant was excluded from further evaluation and not included on the draft CCL (EPA, 1997a). Health Criteria Any contaminant that met the criteria for occurrence was subsequently evaluated using health effects criteria (EPA, 1997a). The major component of the health criteria evaluation was designed to determine whether there was any evidence, or suspicion, that a contaminant causes adverse human health effects. An affirmative response to any of the following criteria resulted in that contaminant's inclusion on the draft CCL: 2   "Looked for and found" was defined as meaning the contaminant was identified in a drinking water survey that included a population of 100,000 or more, two or more states, ten or more small public water systems, or a data set such as EPA's Unregulated Contaminant Monitoring Database (which predates the SDWA Amendments of 1996). 3   "Major drinking water source" was defined as a source of drinking water that served a population of 100,000 or more, or more than two states. 4   Concentrations of concern were defined as those in ambient water samples that are within an order of magnitude of the level that is likely to cause health effects (e.g., a health advisory, drinking water equivalent level, cancer risk of 106) or as 50 percent of these risk levels if at least half the samples contained the contaminant at these levels. 5   Using the Toxic Release Inventory, a release of 400,000 or more pounds of substance to surface water per year and physical-chemical properties indicated persistence and mobility. 6   Production volume in excess of 10 billion pounds per year and physical-chemical properties indicated persistence and mobility. 7   A high score was defined as 2.0 or greater; however, some pesticides were deferred because of lack of additional data (see Table 4-3).

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--> Is listed by California Proposition 65. This initiative is also known as the Safe Drinking Water and Toxic Enforcement Act of 1986. It requires the Governor of California to publish a list of chemicals that are known by the State of California to cause cancer, birth defects, or other reproductive harm (CAEPA, 1997). Has an EPA health advisory. A health advisory is a nonregulatory (i.e., nonenforceable) concentration of a drinking water contaminant at which no adverse health effects would be anticipated to occur over specific exposure durations, including a margin of safety (EPA, 1996). Is a known (based on human data) or likely (based on animal data) carcinogen according to EPA or the International Agency for Research on Cancer. Has been linked to adverse effects in more than one human epidemiological study indicating adverse effects. Has an oral value (reference dose) in EPA's Integrated Risk Information System. An oral reference dose (or RfD) is an estimate of the concentration of a substance that is unlikely to cause appreciable risk of adverse health effects over a lifetime of exposure, including in sensitive subgroups (Barnes and Dourson, 1988). Is regulated in drinking water by another industrial country. Is a member of a chemical class or family of known toxicity. Has a structure-activity relationship that indicates toxicity. A negative response to every question resulted in the contaminant's exclusion from the draft CCL. EPA noted that the most useful health criteria elements were those that provided a health concentration of concern that could be compared to reported levels in water (e.g., health advisories). Conversely, a listing in California Proposition 65 or being a member of a chemical family of known toxicity was considered by the working group to be of only limited use in selecting contaminants for inclusion on the draft CCL (EPA, 1997a). Final Drinking Water Contaminant Candidate List The purpose of publishing the draft CCL prior to the final CCL was to seek public comment on various aspects of its development. To this end, EPA formally requested public comments on both the approach used to develop the draft CCL and on specific contaminants on the list (EPA, 1997a). EPA also sought comments on the data and research need categories contained in the draft CCL. EPA received 71 comments on the draft CCL from many segments of the stakeholder community, including trade associations, environmental groups, industries, chemical manufacturers, state and local health and regulatory agencies, water utilities, and unaffiliated private citizens (EPA, 1998a). The majority of comments were generally supportive of the CCL development process, although

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--> many commenters advised that more robust criteria are needed for selecting contaminants for future CCLs (EPA, 1998b). In addition, many of the commenters provided suggestions, data, and information on specific contaminants they thought should be included or excluded from the final CCL. Approximately 60 issues, both contaminant-specific and related to the development of a process for preparing future CCLs, were raised by the commenters. A notebook containing all comments and EPA responses related to the draft CCL is available (EPA, 1998b). EPA considered all comments, data, and other information provided by the public in preparing the final CCL. In response to requirements mandated by the SDWA Amendments of 1996, the final CCL was published on March 2, 1998, in the Federal Register (EPA, 1998c). In all, it contains 50 chemical and 10 microbiological contaminants and contaminant groups (see Table 1-1 for a complete alphabetical listing). Four microbiological and eight chemicals and chemical group contaminants were removed from the draft CCL, and one chemical (perchlorate) was added based on public comments and the continued input of the working group. Modifications to the draft CCL were also reviewed by the full NDWAC. Expanding on EPA's original data and research needs categories for draft CCL chemical contaminants, the final CCL was divided into similar future action ("next step") categories, as listed in Table 4-4. The final CCL does not include the development of guidance as a separate future regulatory action category, as originally envisioned in the draft CCL and EPA's 1996 CIM. Rather, the development of guidance for specific contaminants has been integrated into the future action categories (e.g., sodium and acanthamoeba). As noted by EPA, sufficient data are necessary to conduct analyses on extent of exposure and risk to populations via drinking water in order to determine appropriate regulatory action (EPA, 1998c). If sufficient data are not available, additional data must be obtained before any meaningful assessment can be made for a specific contaminant. At the time of the final CCL's publication, the "regulatory determination priorities" category of the CCL included those contaminants for which EPA had sufficient data to conduct exposure and risk analyses. Therefore, the five or more contaminants considered for regulation by August 2001, as required by the SDWA amendments, would likely be selected from this category. However, EPA cautioned that the future regulatory action categories of the final CCL were based on current information, and some movement between categories could be expected as additional data are obtained and evaluated. The contaminants included in the research priorities category were those with significant data gaps in health, treatment, or analytical methods areas (EPA, 1998a). These represent EPA's priority contaminants for future data and research gathering. Similarly, the contaminants included in the occurrence priorities category have significant gaps in occurrence data. The newly revised Unregulated Contaminant Monitoring Regulation and the newly established National

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--> TABLE 4-4 CCL Future Action Categories   Research Priorities       Regulatory Determination Priorities Health Research Analytical Treatment Research Methods Research Occurrence Priorities Acanthamoeba (guidance) Aeromonas hydrophila Adenoviruses Adenoviruses Adenovirusesa 1,1,2,2-tetrachloroethane Cyanobacteria (blue-green algae), other freshwater algae, and their toxins Aeromonas hydrophila (blue-green algae), other freshwater algae, and their toxins Cyanobacteria Aeromonas hydrophila 1,1-dichloroethane Calciviruses Cyanobacteria (blue-green algae), other freshwater algae, and their toxins Calciviruses Cyanobacteria (blue-green algae), other freshwater algae, and their toxinsa 1,2,4-trimethylbenzene Helicobacter pylori Coxsackieviruses (Information Collection Rule [ICR] data) Helicobacter pylori Calcivirusesa 1,3-dichloropropene Microsporidia Calciviruses Microsporidia Coxsackieviruses (ICR data) 2,2-dichloropropane Mycobacterium avium intercellulare (MAC) Echo viruses (ICR data) 1,2-diphenylhydrazine Echo viruses (ICR data)

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-->   Research Priorities       Regulatory Determination Priorities Health Research Analytical Treatment Research Methods Research Occurrence Priorities Aldrin 1,1-dichloropropene Helicobacter pylori 2,4,6-trichlorophenol Helicobacter pyloria Boron 1,3-dichloropropane Microsporidia 2,4-dichlorophenol Microsporidiaa Bromobenzene Aluminum Mycobacterium avium intercellulare (MAC) 2,4-dinitrophenol 1,2-diphenylhydrazinea Dieldrin DCPA mono-acid and di-acid degradates Aluminum 2-methyl-phenol (o-cresol) 2,4,6-trichlorophenola Hexachprobutadiene Methyl bromide MTBE Acetochlor 2,4-dichlorophenola p-isopropyltoluene Methyl-t-butyl ether (MTBE) Perchlorate Alachlor ESA 2,4-dinitrophenola Manganese Perchlorate   Fonofos 2,4,-dinitrotoluene Metolachlor Sodium (guidance)   Perchlorate 2,6-dinitrotoluene Metribuzin     RDX 2-methyl-phenola Naphthalene       Acetochlora Organotins       Alachlor ESAa

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-->   Research Priorities       Regulatory Determination Priorities Health Research Analytical Treatment Research Methods Research Occurrence Priorities Triazines and degradation products (including, but not limited to, cyanazine and atrazinedesethyl)       DCPA mono-acid and di-acid degradates Sulfate       DDE Vanadium       Diazinone         Disulfoton         Diuron         s-ethyl-dipropylthiocarbamate (EPTC)         Fonofosa         Linuron         Molinate         MTBE         Nitrobenzene         Perchloratea         Prometon         RDXa         Terbacil         Terbufos a Suitable analytical methods must be developed prior to obtaining occurrence data. SOURCE: EPA, 1998a.

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--> Drinking Water Contaminant Occurrence Database, when operational, will be the primary sources for these data (see Chapter 1). In addition, as noted in Table 4-4, several contaminants included in the CCL occurrence priority category require the development of suitable analytical methods before occurrence data can be obtained. Summary The SDWA Amendments of 1996 significantly restructured the development process for drinking water regulations established under the 1986 SDWA amendments. Shortly after passage of the 1996 amendments, EPA began work on a conceptual, risk-based approach, the CIM, for identifying and selecting unregulated chemical and microbiological drinking water contaminants as priorities for its drinking water program. However, further development of the CIM was postponed because of the tight time constraints stipulated by the SDWA amendments. In its place, a simplified and rapid process for identification and evaluation of chemical and microbial contaminants for inclusion on the CCL was adopted. For chemicals, the lead was taken by a working group of the NDWAC, using existing occurrence data as an initial screen, followed by ad hoc consideration of health effects data. A total of 50 chemical contaminants and contaminant groups were included on the final CCL. For microbial contaminants, an expert workshop was convened by EPA, and the results of its deliberations were directly adopted by the agency to select the 10 microbial agents included on the final CCL. References Barnes, D. G., and M. Dourson. 1988. Reference dose (RfD): Description and use in health risk assessments. Regulatory Toxicology and Pharmacology 8:471-486. CAEPA (California Environmental Protection Agency). 1997. Proposition 65 in plain language! Proposition 65 Related Documents. Online. California Environmental Protection Agency, Office of Environmental Health Hazard Assessment. Available: http://www.calepa.cahwnet.gov/oehha/docs/p65plain.htm [27 October 1997]. EDSTAC (Endocrine Disruptor Screening and Testing Advisory Committee). Final Report: Volume I. August 1998. EPA (U.S. Environmental Protection Agency). 1996. The Conceptual Approach for Contaminant Identification (Working Draft). EPA/812/D/96/001. Washington, D.C.: EPA, Office of Ground Water and Drinking Water. EPA. 1997a. Announcement of the Draft Drinking Water Contaminant Candidate List; Notice. Federal Register 62(193):52194-52219. EPA. 1997b. EPA Drinking Water Microbiology and Public Health Workshop. Washington, D.C.: EPA, Office of Ground Water and Drinking Water, May 20-21, 1997. EPA. 1998a. Announcement of the Drinking Water Contaminant Candidate List; Notice. Federal Register 63(40):10274-10287. EPA. 1998b. U.S. EPA Response to Comment Document: Draft Drinking Water Contaminant Candidate List . Washington, D.C.: EPA, Office of Ground Water and Drinking Water. EPA. 1998c. Definition of a Public Water System in SDWA Section 1401(4) as Amended by the 1996 SDWA Amendments. Federal Register 63(150):41939-41946.