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4
Past and Future Strategies for Sorting and Ranking Chemicals: Applications to the 1998 Drinking Water Contaminant Candidate List Chemicals
John D. Walker, D. Anthony Gray, and Michelle K. Pepling
The 1998 Drinking Water Contaminant Candidate List (CCL) includes chemicals, chemical classes, and microorganisms. This paper discusses only chemicals and chemical classes. However, the strategies for sorting and ranking drinking water contaminant chemicals and chemical classes discussed here are probably applicable to and should be considered for sorting and ranking other types of chemicals as well as drinking water contaminant microorganisms.
EPA'S Responsibilities
Under the August 1996 Amendments to the Safe Drinking Water Act (SDWA), the U.S. Environmental Protection Agency (EPA) must publish the CCL in February 1998 and every five years thereafter, develop the National Drinking Water Contaminant Occurrence Database (NCOD) in August 1999, publish the Unregulated Contaminant Monitoring Regulation List (UCMR) in August 1999 and every five years thereafter, and identify five drinking water contaminants for potential regulation by August 2001 and every five years thereafter.
The EPA published the Draft CCL on October 6, 1997 (EPA, 1997a). After soliciting public comment on the proposed list as mandated under Section 1412(b)(1) of the SDWA, the EPA published the 1998 CCL on March 2, 1998
Under the 1996 Amendments to the SDWA, the EPA must also consider whether drinking water contaminant chemicals should be screened for endocrine disruption potential. As a result, the 206 chemicals with Chemical Abstract Service (CAS) Registry numbers that were on the Draft CCL were included in the Endocrine Disruptor Priority Setting Database (Walker et al., 1999). During development of the Endocrine Disruptor Priority Setting Database, the strengths and weaknesses of the Draft CCL were proposed strength—prepared by screening many sources of chemicals that were likely to contaminate public drinking water systems; weaknesses-concentrations, frequencies of occurrence, and locations of contaminants were not provided, and there were uncertainties concerning the probabilities that proposed contaminants could persist in drinking water. These weaknesses are likely to be addressed as EPA develops the NCOD in August 1999 and publishes the UCMR in August 1999 and every five years
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thereafter. In the interim the EPA asked the National Research Council to establish a Committee on Drinking Water Contaminants.
Committee on Drinking Water Contaminants
The Committee on Drinking Water Contaminants was asked to assist the EPA with three tasks: (1) developing a scientifically sound approach for deciding whether or not to regulate contaminants on the current and future CCL(s), (2) convening a workshop that will focus on emerging drinking water contaminants and the database that should be created to support future decision making on such contaminants, and (3) creating a scientifically sound approach for developing future CCLs.
As part of its effort to assist the EPA with these tasks, the Committee on Drinking Water Contaminants issued a report entitled, Setting Priorities for Drinking Water Contaminants (NRC, 1999). That report described the committee's review of 10 existing prioritization schemes, review of methods for assessing microbial pathogens, approaches used to develop the 1998 CCL, and suggestions for selecting candidates on the CCL for future action. The committee concluded that processes that rank contaminants are not appropriate for selecting regulatory candidates, contaminants occurring at frequencies and concentrations that cause health effects should be regulated, and processes that rank contaminants may be useful to sort and select future contaminants.
In their discussion of processes for ranking contaminants, the committee recommended that professional judgments be used to select regulatory candidates. In addition, the Committee on Drinking Water Contaminants suggested that drinking water contaminants could be organized into four categories: Category 1, Ready for Rule-Making; Category 2, Ready for Guidance Development (e.g., health advisories); Category 3, Needing Additional Occurrence Data; and Category 4, Needing Additional Research (e.g., health effects).
The committee recognized that, as expected, the quantity and quality of information would be different for each drinking water contaminant and based its categorization criteria on that premise. The committee also recommended a staged process for assessing drinking water contaminants: Stage 1, review existing data (health effects, exposure, treatment, analytical methods); Stage 2, conduct preliminary risk assessment; Stage 3, prepare decision document (regulation, drop, additional research); and Stage 4, prepare data development plan to meet five-year SDWA Requirements.
Stages 1 through 3 of the committee's process for assessing drinking water contaminants could be used to assign contaminants to one of the four categories listed above. The review of existing data is more extensive than ordinarily required to categorize chemicals because options for treatment must be considered as well as analytical methods for measuring contaminants in drinking water. The preliminary risk assessment recommended by the committee is analogous to that conducted by the EPA for the premanufacture of new chemicals under the Toxic Substances Control Act (i.e., a 90-day process that uses models to estimate exposure potential and structure activity relationships (SARs) and quantitative structure activity relationships (QSARs) to predict toxicity). The
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decision document is necessary to assure a consistent decision-making process. The need to prepare a data development plan is critical to publishing the CCL, publishing the UCMR List, and identifying five drinking water contaminants for potential regulation every five years to meet the statutory deadlines of the 1996 amendments to the SDWA.
Past Techniques for Prioritizing Chemicals
With very few exceptions, there are two major differences between past techniques for prioritizing chemicals and those currently being developed for future use: (1) past techniques did not have distinct sorting and ranking phases and (2) past techniques were not peer-reviewed or published in peer reviewed journals or books. The exception to those that did not have distinct sorting and ranking phases and have not been published in peer reviewed journals or books were those developed by and for the Toxic Substances Control Act (TSCA) Interagency Testing Committee (ITC) (Welsh and Ross, 1982; Walker, 1993a). The exception to those that have not been peer-reviewed are those that have been proposed for public comment (e.g., those developed for the ITC, the Agency for Toxic Substances and Disease Registry, the EPA's Office of Solid Waste, and California's Office of Environmental Health Hazard Assessment). The techniques developed by and for the ITC were the first techniques used by the U.S. government to sort and rank chemicals (Davis et al., 1997). Sequential sorting and ranking are critical because they promote simultaneous allocation of resources to highest-ranking chemicals within classes that have been sorted based on chemical structure or categories that have been sorted based on uses, human exposures, environmental releases, environmental fate parameters, health or ecological effects, and so forth. Peer review is significant because it provides credibility to the chemical sorting and ranking process.
Techniques Reviewed by the Committee on Drinking Water Contaminants
The Committee on Drinking Water Contaminants reviewed 10 existing chemical prioritization schemes and considered their relevance for developing a prioritization scheme for drinking water contaminants (NRC, 1999). Three prioritization schemes were developed by private organizations for drinking water contaminants. Three schemes were developed by federal and state organizations to prioritize all contaminants. Four schemes were developed by federal organizations to prioritize contaminants for specific media.
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Schemes to Prioritize Drinking Water Contaminants
The first prioritization scheme for drinking water contaminants was initiated by compiling a list of chemicals from a few of the sources proposed by the EPA (1997a). This scheme provided a risk index score based on four weighted criteria: production quantity, exposure quantity, occurrence in water, and human health effects. If one criterion was missing, the chemical was not scored. The second scheme provided a sequential prioritization process for health effects, exposure potential, controlling release and treatment technology. No chemicals were evaluated using this scheme, which apparently does not exclude a chemical if all data were not available. The third scheme for drinking water contaminants was not used to evaluate any chemicals but would exclude a chemical if all data were not available (NRC, 1999).
Schemes to Prioritize All Contaminants
The first prioritization scheme for all contaminants was used to screen a number of chemicals and provided a chemical score based on toxicity (human health or ecological effects), persistence, bioaccumulation, and mass of the contaminant in waste streams. The second prioritization scheme was used to sort chemicals by chemical substructure and associated health or ecological effects as provided by expert opinions; exposure and toxicity could be scored by using empirical data or predictions, including SARs or QSARs, and a need for data by a U.S. government organization(s) could be factored into the weighting criteria. The third scheme uses toxicity information and expert opinion to assign priorities and exposure information to determine the order in which priority toxic chemicals are assessed (NRC, 1999).
Schemes to Prioritize Contaminants for Specific Media
The first scheme to prioritize contaminants for specific media ranks hazardous waste sites and is relevant to setting priorities for drinking water contaminants, because the contaminants at the hazardous waste sites determine the potential to cause adverse effects to human health or the environment. The second scheme ranks hazardous waste sites and the contaminants at hazardous waste sites for potential to cause adverse human health effects. The third scheme to prioritize contaminants for specific media is used to indicate sediment contamination potential. The fourth scheme is used to estimate the potential for pesticides applied to apples and potatoes to contaminate groundwater (NRC, 1999).
Other Techniques
There are two other techniques for ranking chemicals that may be relevant to developing a prioritization scheme for drinking water contaminants. The Michigan Critical Materials Register ranks chemicals that may threaten water quality in
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Michigan. The Ontario Ministry of the Environment Scoring System ranks chemicals that may threaten surface water quality in Ontario. Both of these techniques have been described by Davis et al. (1997).
Future Procedures for Sorting and Ranking Chemicals
Future procedures for sorting and ranking chemicals must consider the continued resource and testing facility limitations for assessing the risks of chemicals, promoting pollution prevention and so forth. Strategic planning will be required to assure that these resources are effectively allocated. Formulation of strategic plan should involve development of a scheme that considers vital information and facilitates sorting and ranking of chemicals into phased programs that can be accomplished with the given resources. A scheme that considers vital information and facilitates sorting and ranking of chemicals into phased data collection and testing programs is illustrated in Figure 4-1. This scheme to sort and rank structural classes of chemicals for data collection, testing, and risk assessment includes:
a process to organize chemicals into structural classes;
a review of existing data and predictions for structural classes of chemicals;
consideration of legal (e.g., statutory-mandated) requirements;
development of a relational database, consisting of exposure, effects, fate and other compartments, chemicals sorted into categories within each compartment (e.g., within the effects compartment, there may be chemicals sorted into carcinogenicity, acute toxicity, aquatic toxicity categories, etc.), and chemicals ranked (when possible) within each category (e.g., within the aquatic toxicity category, chemicals could be ranked on fish LC50 values, aquatic invertebrate EC50 values, etc.);
use of the relational database to produce output scenarios (e.g., chemicals with annual production volumes exceeding a certain threshold that have been measured in surface waters (the concentration of which is given) and that are toxic to fish (the LC50 values are given) that can be used with professional judgments to sort chemicals into groups for which (1) no additional data are needed at that time (defer), (2) more data need to be obtained, (3) testing (including screening tests) should be conducted or, (4) risk should be assessed);
a phased short- and long-term program to which highest-ranking chemicals (from database categories of ranked chemicals and professional judgments) within groups needing data or testing are assigned to the first phases of data collection or testing;
processes that assure that results from phased data collections and testing are reviewed and decisions to defer, test, or assess risk are made; and
feedback loops that provide pathways for phased testing data to be (a) used for development and validation of SAPs and QSARs, (b) incorporated into risk assessments and (c) included in future data assessments of structurally related chemicals.
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1998 Drinking Water Contaminant Candidate List
The 1998 Drinking Water Contaminant Candidate List consists of 48 chemicals with unique Chemical Abstract Service Registry numbers and chemical structures (See Table 4-1). There are 20 industrial organic chemicals, 22 pesticides, and six inorganic chemicals on the list.
TSCA Interagency Testing Committee (ITC)
The ITC is an independent advisory committee to the EPA administrator that was created in 1976 under Section 4(e) of the TSCA. Sixteen U.S. government organizations are ITC members: the Agency for Toxic Substances and Disease Registry (ATSDR), the Council on Environmental Quality (CEQ), the Consumer Product Safety Commission (CPSC), the U.S. Department of Agriculture (USDA), the U.S. Department of Commerce (DOC), the U.S. Department of Defense (DOD), Food and Drug Administration (FDA), the U.S. Department of the Interior (DOI), the U.S. Environmental Protection Agency (EPA), the National Cancer Institute (NCI), the National Institute of Environmental Health Sciences (NIEHS), the National Institute for Occupational Safety and Health (NIOSH), the National Library of Medicine (NLM), the National Science Foundation (NSF), the National Toxicology Program (NTP) and the Occupational Safety and Health Administration (OSHA). Members from these U.S. government organizations nominate industrial chemicals to the ITC when their organizations need data that can be obtained through the ITC. These data include unpublished production volume, use, exposure, monitoring, environmental fate, ecological effects, and health effects data. The ITC coordinates data needs for the nominated chemicals with those of other member organizations and determines if these chemicals should be (1) added to the Priority Testing List and recommended or designated for testing, (2) deferred for testing and not added to the list or (3) removed from the list. The ITC meets monthly to identify and coordinate federal data needs for industrial chemicals, recommends these chemicals in Federal Register Reports to the administrator every May and November, and establishes partnerships with manufacturers, importers, processors, and users of recommended chemicals to discuss data needed. By coordinating federal data needs and establishing partnerships, the ITC provides an infrastructure to obtain information on industrial chemicals (http://www.epa.gov/opptintr/itc/).
ITC Decisions for the 1998 CCL Chemicals
The ITC has made testing decisions on about 40,000 chemicals (Walker, 1993a). The ITC has deferred testing on 1998 CCL chemicals that are only used as pesticides because chemicals that are registered active pesticide ingredients are regulated under the Federal Insecticide Fungicide Rodenticide Act, not TSCA (See Table 4-2). However, the ITC does review data on pesticides to facilitate
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toxicity and persistence predictions for structurally related industrial chemicals and to develop SARs and QSARs. Eleven of the 1998 CCL chemicals were recommended for testing by the ITC in Federal Register reports to the EPA administrator (Table 4-2). Eight of the recommended 1998 CCL chemicals have been removed from the Priority Testing List because the EPA implemented the ITC's testing recommendations (Table 4-2).
As result of the ITC's recommendations and EPA's implementation of the ITC's testing recommendations, many of the 1998 CCL chemicals recommended for testing by the ITC are well-characterized industrial chemicals. The most well-known 1998 CCL chemical recommended by the ITC is probably methyl-tert butyl ether (MTBE), because it was recommended by the ITC before it was commercially significant and at a time in the commercial life cycle of the chemical when it was easiest to request voluntary development of test data (Walker, 1993b).
TSCA Section 4 and 8(d) Studies Indexed in the TSCA Test Submissions (TSCATS) Database
As a result of ITC recommendations and related EPA actions, over 1,300 unpublished studies have been submitted to the EPA for the 1998 CCL chemicals (See Table 4-3). These studies are indexed in the TSCATS database. For each study there is a reference in TSCATS, and the reference may be a document that contains more than one study, explaining why the number of studies in Table 4-3 is equal to or greater than the number of references. Procedures for retrieving studies indexed in TSCATS were recently published (Walker and Smock, 1995). TSCATS is a pointer system—that is, it is a database that points to unpublished studies that have been submitted to EPA under TSCA. It can be accessed through the World Wide Web from the following universal resource locators: (url) http://www.rtk.net or http://igm.nlm.nih.gov/. From the Right-To-Know (RTK) page the user must search on databases. From the NLM page the user must select TOXLINE and then, under the "Apply Limits" section, choose "Toxic Substances Control Act Test Submissions."
When the EPA publishes a Federal Register notice under TSCA Section 4(a), manufacturers and processors of chemicals mentioned in that notice can provide TSCA Section 4(a) studies to reduce the possibility of having to conduct tests under a TSCA Section 4(a) rule or they can provide TSCA Section 4(d) studies that were conducted as a result of testing to meet the requirements of a TSCA Section 4(a) notice. The total number of TSCA Section 4 studies listed in Table 4-3 includes both TSCA Section 4(a) and 4(d) studies.
When the ITC adds a chemical to the Priority Testing List, the EPA automatically promulgates a TSCA Section 8(d) Health and Safety Data Rule. This rule requires manufacturers and processors of chemicals recommended by the ITC to submit unpublished health and safety studies (health effects, environmental fate, ecological effects, environmental and occupational monitoring, industrial hygiene, etc.) to the EPA. By comparing the chemicals recommended or designated by the ITC (Table 4-2) with the number of TSCA
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Section 8(d) studies for 1998 CCL chemicals (Table 4-3), it is obvious that there are some chemicals that were deferred by the ITC for which a number of TSCA Section 8(d) studies have been submitted to the EPA. There are two explanations for this: (1) EPA published a TSCA Section 8(d) rule for chemicals other than those recommended by the ITC or (2) when manufacturers and processors submitted documents (references) in response to a TSCA Section 8(d) rule, the documents contained studies on other chemicals that were not subject to the rule. The ITC encourages manufacturers and processors of ITC-recommended chemicals to submit these and other studies electronically through the Voluntary Information Submission Innovative Online Network (VISION; http://www.epa.gov/opptintr/itc/vision/).
Uses and Substructure-Based Computerized Chemical Selection Expert System (SuCCSES) Chemical Classes for the 1998 CCL Chemicals
Uses were identified for the 1998 CCL chemicals; most are used as herbicides or insecticides (See Table 4-4). Identifying uses is important because it promotes pollution prevention through the recognition that less toxic and less persistent chemicals can be substituted for more toxic and more persistent chemicals with similar uses.
SuCCSES is the first computerized system that uses expert opinions to predict potential environmental-human health interactions of individual chemicals and chemical classes that share common substructures (Walker, 1995a; Walker and Gray, 1999). For chemical categories in SuCCSES, expert opinions were offered on the potential of chemicals containing specific substructures to cause adverse human health effects or to cause effects on the environment by adversely affecting ecologically diverse classes of organisms. SuCCSES contains over 100 chemical substructures associated with about 10,000 chemicals. Effects on human health indicated potential for chemicals containing one or more of these substructures to cause acute, chronic, mutagenic, oncogenic, developmental, reproductive, or neurotoxic effects or membrane irritation (Walker, 1991, 1995a). Effects on the environment included predictions on chemicals containing one or more of these substructures to potentially cause adverse effects to algae, aquatic invertebrates, birds, fish, mammals, microorganisms, plants, or terrestrial invertebrates (Walker and Bink, 1989; Walker, 1991).
Using SuCCSES it was possible to assign the 1998 CCL chemicals to one of 17 SuCCSES classes (Table 4-4). Organizing chemicals into SuCCSES classes is critical for estimating potential health or ecological effects of structurally related chemicals and developing or validating SARs and QSARs.
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Log Octanol Water Partition Coefficient (log Kow) Values, Soil or Sediment Sorption Coefficient (Koc) Values, and Henry's Law Constant for 1998 CCL Chemicals
The log Kow values, Koc values and Henry's Law constants for the 1998 CCL chemicals (arranged by SuCCSES class) are listed in Table 4-5. These three environmental fate parameters were selected to estimate the potential of chemicals to remain in drinking water. These parameters can be used when reservoirs (containing aquatic species that can bioconcentrate chemicals and sediment to which chemicals can sorb) are the source of drinking water. For other drinking water sources, different parameters may have to be used. Using previously described criteria for log Kow values, Koc values, and Henry's Law constants it was possible to estimate the potential of chemicals to bioconcentrate, sorb to sediment or soil, and evaporate from water, respectively (Walker, 1995b). These criteria are listed below:
log Kow
Bioconcentration Potential
Koc
Sorption Potential
Henry's Law Constant (atm m3/mole)
Evaporation Potential
<3
Low
<2,700
Low
>10-2
High
3-8
Moderate to High
>2,700
High
10-2- 10-7
Moderate
>8
Low
<10-7
Low
By organizing the 1998 CCL chemicals into SuCCSES classes (number of chemicals in each class in parentheses), it was possible to estimate the potential of chemicals within these classes to remain in reservoirs of drinking water:
High potential to remain in reservoir water (low bioconcentration, sorption, and evaporation potential): acetanilides (2), phenols (2), triazines (7), and ureas (2).
Moderate potential to remain in reservoir water (moderate bioconcentration, sorption, or evaporation potential): aliphatic halides (8) (aldrin, dieldrin, and hexachlorobutadiene may bioconcentrate or sorb to soil or sediment); aromatic halides (4) (DDE may bioconcentrate or sorb to soil or sediment); aromatic hydrocarbons (2); carbamic acid esters (1); ethers (1); halophenols (2); hydrazines (1); nitroaromatics (3); phosphonothioates (1); phosphorodithioates (2); and phosphorothioates (1).
Low potential to remain in reservoir water (low bioconcentration and sorption potential but high evaporation potential): aliphatic halides (2) (1,1-dichloropropene and 2,2-dichloropropane); aromatic hydrocarbons (1) (p-isopropyltoluene).
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Log Kow, Koc, and Henry's Law constants may be used to estimate the potential of chemicals and chemical classes to remain in drinking water. However, some professional judgment should be used before these chemicals or chemical classes are sorted or ranked (Figure 4-1). Professional judgment would consider other environmental fate parameters that could affect the ability of some chemicals or chemical classes to remain in drinking water (e.g., hydrolysis of carbamic acid esters, hydrazines).
Application Of Past Chemical Sorting Techniques To The 1998 Ccl Chemicals
As noted earlier, almost all past techniques did not have distinct sorting and ranking phases. However, a few techniques developed in the recent past do promote sorting (e.g., the Use Cluster Scoring System, SuCCSES, and the Endocrine Disruption Priority Setting Database (EDPSD).
The Use Cluster Scoring System can be used to sort chemicals into use categories (Davis et al., 1997). SuCCSES was described earlier. The EDPSD can be used to sort chemicals into structural classes and categories based on uses, production volumes, environmental fate parameters, occurrences in fish and wildlife tissues, reproductive effects, estrogen receptor binding affinity potentials, and so on (Walker et al., 1999). Past sorting techniques (uses and environmental fate parameters) were applied to the 1998 CCL chemicals; the results are summarized in Table 4-5 and discussed earlier.
Application Of Past Chemical Ranking Techniques To The 1998 Ccl Chemicals
To illustrate the application of past ranking techniques, the aliphatic halides from Table 4-5 were ranked based on exposure and effects scores developed by and for the ITC (Walker, 1993b, 1995a).
Exposure Scores
Exposure scores and criteria for assigning scores to exposure factors that were relevant to ranking aliphatic halides are production volume, environmental persistence, and bioaccnmulation potential (See Table 4-6). These scores and criteria were applied to the aliphatic halides from the 1998 CCL (See Table 4-7). Ranking on production volume indicated that there were three groups of aliphatic halides: those with annual production volumes greater than 10 million pounds, greater than 1 million pounds, or less than 1 million pounds (Table 4-7). Ranking on environmental persistence indicated that there were two groups of aliphatic halides: those that could persist for years and those that could persist for months (Table 4-7). Ranking on bioaccumulation potential indicated that there were three groups of aliphatic halides based on based on log Kow (Table 4-7). The three aliphatic halides that could persist for years (aldrin, dieldrin, and
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hexachlorobutadiene) were the same three that could bioconcentrate or sorb to soil or sediment (Table 4-5).
Effects Scores
Four biological effects that were relevant to ranking the 1998 CCL chemicals were acute toxicity, mutagenicity, carcinogenicity, and ecotoxicity (See Table 4-8). The scores and criteria for these biological effects were applied to the aliphatic halides from the 1998 CCL (See Table 4-9). Positive scores (based on empirical data) and negative scores (based on predictions) for biological effects were evaluated separately. Based on acute toxicity and ecotoxicity scores, aldrin and dieldrin would rank the highest and 1,1-dichloropropene and 2,2-dichloropropane the lowest. Based on mutagenicity and carcinogenicity scores, 1,3-dichloropropane would rank the highest and 2,2-dichloropropane the lowest.
Application Of Future Chemical Sorting Procedures To The 1998 CCL Chemicals
Procedures related to chemical properties, waste management, and resource productivity have been suggested for scoring and ranking chemicals in the future (Jensen et al., 1997). While only the procedures related to chemical properties were described in sufficient detail to warrant immediate consideration, there are merits to waste management and resource productivity approaches as evidenced by EPA's development of the Waste Minimization Prioritization Tool, which was proposed for public comment on June 23, 1997 (EPA, 1997b), substantially revised in response to public comments, and published with the Draft Resource Conservation Recovery Act Persistent Bioaccumulator Toxics list on November 9, 1998 (EPA, 1998b). Procedures related to chemical properties that might be considered in the future include flammability, ignitability, explosivity, oxidizability, reactivity, corrosivity, chemical-environmental interactions, global warming potential, ozone depletion potential, photochemical oxidant creation potential, odor threshold values, eutrophication potential, and acidification potential (Jensen et al., 1997). While criteria have been proposed to score all these chemical properties, it was not possible to use them to sort the 1998 CCL chemicals. However, two new procedures not considered by Jensen et al. (1997) could be used to sort the 1998 CCL chemicals.
The first procedure, based on a chemical's mode of toxic action, was used in conjunction with SuCCSES classes to sort the 1998 CCL chemicals (See Table 4-10). Results from testing the acute toxicity of about 600 chemicals to fathead minnows were used to develop a computer-based expert system that predicts mode of toxic action based on chemical structure (Russom et al., 1997). The models and substructure search methods were designed for the ASsessment Tools for the Evaluation of Risk (ASTER) expert system and database. ASTER is an integration of the AQUatic toxicity Information REtrieval (AQUIRE)
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TABLE 4-9
Biological Effects Scores for Aliphatic Halides from the 1998 CCL Chemicals
CAS No.
Chemical Name
Acute Toxicity
Mutagenicity
Carcinogenicity
Ecotoxicity
000060-57-1
Dieldrin
+3
+2
0
+3
000074-83-9
Methyl bromide
+2
+2
0
+2
000075-34.3
1,1-Dichloroethane
+1
+1
+1
+2
000079-34-5
1,1,2,2-Tetrachloroethane
+2
+2
+2
+2
000087-68-3
Hexachlorobutadiene
+2
+2
+1
+3
000142-28-9
1,3-Dichloropropane
+1
+3
-2
+2
000309-00-2
Aldrin
+3
+2
+2
+3
000542-75-6
1,3-Dichloropropene
+2
+2
+3
+2
000563-58-6
1,1-Dichloropropene
-1
+1
-1
-2
000594-20-7
2,2-Dichloropropane
-1
-1
-1
-2
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TABLE 4-10
Modes of Toxic Action for the 1998 CCL Chemicals Arranged by SuCCSES Classes
CAS No.
Chemical Name
Mode of Action
Acetanilides
034256-82-1
Acetochlor
Nonpolar narcosis
051218-45-2
Metolachlor
Nonpolar narcosis
Aliphatic halides
000060-57-1
Dieldrin
Neurotoxicant: Cyclodiene-type
000074-83-9
Methyl bromide
Nonpolar narcosis
000075-34-3
1,1-Dichloroethane
Nonpolar narcosis
000079-34-5
1,1,2,2-Tetrachloroethane
Nonpolar narcosis
000087-68-3
Hexachlorobutadiene
Reactivity: Alkylation or arylation reaction
000142-28-9
1,3-Dichloropropane
Nonpolar narcosis
000309-00-2
Aldrin
Neurotoxicant: Cyclodiene-type
000542-75-6
1,3-Dichloropropene
Reactivity: Alkylation or arylation reaction
000563-58-6
1,1-Dichloropropene
Nonpolar narcosis
000594-20-7
2,2-Dichloropropane
Nonpolar narcosis
Aromatic halides
000072-55-9
DDE
Nonpolar narcosis
000108-86-1
Bromobenzene
Nonpolar narcosis
000887-54-7
DCPA mono-acid degradate
Nonpolar narcosis
002136-79-0
DCPA di-acid degradate
Nonpolar narcosis
Aromatic hydrocarbons
000091-20-3
Naphthalene
Nonpolar narcosis
000095-63-6
1,2,4-Trimethylbenzene
Nonpolar narcosis
000099-87-6
p-Isopropyltoluene
Nonpolar narcosis
(p-cymene)
Carbamic acid esters
000759-94-4
EPTC (s-ethyl-dipropylthio-carbamate)
Nonpolar narcosis
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CAS No.
Chemical Name
Mode of Action
Elements
007429-90-5
Aluminum
N.A.*
007439-96-5
Manganese
N.A.
007440-23-5
Sodium
N.A.
007440-42-8
Boron
N.A.
007440-62-2
Vanadium
N.A.
Ethers
001634-04-4
Methyl-t-butyl ether (MTBE)
Nonpolar narcosis
Halophenols
000088-06-2
2,4,6-Trichlorophenol
Polar narcosis
000120-83-2
2,4-Dichlorophenol
Polar narcosis
Hydrazines
000122-66-7
1,2-Diphenylhydrazine
Reactivity: hydrazines
Inorganics
014808-79-8
Sulfate
N.A.
Nitroaromaties
000098-95-3
Nitrobenzene
Nonpolar narcosis
000121-14-2
2,4-Dinitrotoluene
Reactivity: dinitroaromatic group
000606-20-2
2,6-Dinitrotoluene
Reactivity: dinitroaromatic group
Phenols
000051-28-5
2,4-Dinitrophenol
Uncoupler of oxidative phosphorylation
000095-48-7
2-Methylphenol (o-cresol)
Polar narcosis
Phosphonothioates
000944-22-9
Fonofos
Organophosphate mediated acetylcholinesterase inhibition
Phosphorodithioates
000298-04-4
Disulfoton
Organophosphate mediated acetylcholinesterase inhibition
013071-79-9
Terbufos
Organophosphate mediated acetylcholinesterase inhibition
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CAS No.
Chemical Name
Mode of Action
Phosphorothioates
000333-41-5
Diazinon
Organophosphate mediated acetylcholinesterase inhibition
Triazines
000121-82-4
RDX
Nonpolar narcosis
001610-18-0
Prometon
Nonpolar narcosis
002212-67-1
Molinate
Nonpolar narcosis
005902-51-2
Terbacil
Nonpolar narcosis
006190-65-4
Triazines (atrazine-desethyl)
Nonpolar narcosis
021087-64-9
Metribuzin
Nonpolar narcosis
021725-46-2
Triazines (cyanazine)
Nonpolar narcosis
Ureas
000330-54-1
Diuron
Nonpolar narcosis
000330-55-2
Linuron
Nonpolar narcosis
* N.A. = not available.
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TABLE 4-11
Carcinogenicity Concern Levels for the 1998 CCL Chemicals Arranged by SuCCSES Classes
CAS No.
Chemical Name
Carcinogenicity Concern Levels
Comments
Acetanilides
034256-82-1
Acetochlor
Moderate
+Data
05121845-2
Metolachlor
Moderate
Aliphatic halides
000060-57-1
Dieldrin
Moderate
+Data
000074-83-9
Methyl bromide
Moderate
000075-34-3
1,1-Dichloroethane
Low
- Data
000079-34-5
1,1,2,2-Tetrachloroethane
Moderate
+ Data
000087-68-3
Hexachlorobutadiene
Moderate
+ Data
000142-28-9
1,3-Dichloropropane
Moderate
000309-002
Aldrin
Moderate
+ Data
000542-75-6
1,3-Dichloropropene
High
+ Data
000563-58-6
1,1-Dichloropropene
Moderate
000594-20-7
2,2-Dichloropropane
Low
Aromatic halides
000072-55-9
DDE
Moderate
+ Data
000108-86-1
Bromobenzene
Moderate
000887-54-7
DCPA mono-acid degradate
Low
002136-79-0
DCPA di-acid degradate
Low
Aromatic hydrocarbons
000091-20-3
Naphthalene
Moderate
+ Data
000095-63-6
1,2,4-Trimethylbenzene
Low
000099-87-6
p-Isopropyltoluene (p-cymene)
Low
Carbamic acid esters
000759-94-4
EPTC (s-ethyl-dipropylthiocarbamate)
Moderate
Elements
007429-90-5
Aluminum
Low
007439-96-5
Manganese
Low
007440-23-5
Sodium
Low
007440-42-8
Boron
Low
007440-62-2
Vanadium
Low to moderate
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CAS No.
Chemical Name
Carcinogenicity Concern Levels
Comments
Ethers
001634-04-4
Methyl-t-butyl ether
Moderate
+ Data
Halophenols
000088-06-2
2,4,6-Trichlorophenol
Moderate
+ Data
000120-83-2
2,4-Dichlorophenol
Low
- Data
Hydrazines
000122-66-7
1,2-Diphenylhydrazine
Moderate
Inorganics
014808-79-8
Sulfate
Low
Nitroaromatics
000098-95-3
Nitrobenzene
Moderate
000121-14-2
2,4-Dinitrotoluene
High
+ Data
000606-20-2
2,6-Dinitrotoluene
Moderate
+ Data
Phenols
000051-28-5
2,4-Dinitrophenol
Moderate
000095-48-7
2-Methylphenol (o-cresol)
Low
Phosphonothioates
000944-22-9
Fonofos
Low
Phosphorodithioates
000298-04-4
Disulfoton
Low
- Data
013071-79-9
Terbufos
Low
- Data
Phosphorothioates
000333-41-5
Diazinon
Low
Triazines
000121-82-4
RDX
Moderate
001610-18-0
Prometon
Low
Equivocal data
002212-67-1
Molinate
Moderate
+ Data
005902-51-2
Terbacil
Low
- Data
006190-65-4
Triazines (atrazine-desethyl)
Moderate
+ Data for parent compound
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CAS No.
Chemical Name
Carcinogenicity
Concern Levels
Comments
021087-64-9
Metribuzin
Low
Equivocal data
02172546-2
Triazines (cyanazine)
Moderate
+ Data for parent
Ureas
000330-54-1
Diuron
Low
- Data
000330-55-2
Linuron
Moderate
+ Data
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TABLE 4-12
Wildlife Species Contaminated with the 1998 CCL Chemicals
Chemical
Species
Records
Individuals
Matrix
Range (µg/g)
Aldrin
Blue jay
1
1
Brain
0.04
Fulvous whistling duck
2
30
Liver
0.0021, 0.0094
Sharp-shinned hawk
1
1
Brain
0.04
Aluminum
American alligator
3
13
Egg
1.3-2.0
American
2
12
Eggshell
52.36
crocodile
Egg
10.86
Black-crowned night-heron
1
7
Egg
9.55
Muskrat
3
76
Kidney
3.45-13.19
Peregrine falcon
10
10
Egg
6.74-17.4
Short-tailed shrew
5
5
Carcass
130.0-561.0
Snapping turtle
2
19
Liver
15.97, 78.83
White-footed mouse
4
4
Carcass
45.0-180.0
Boron
Common tern
10
10
Egg
22.4-36.8
Peregrine falcon
3
3
Egg
0.75-1.29
Snapping turtle
1
12
Liver
3
Tree swallow
3
9
Egg
1.52-3.55
Diazinon
American brant
2
21
Liver
0.003
Small intestine
0.002-3.2
Gizzard
0.12-0.77
American robin
2
3
Gizzard
1.5
Blackbird
1
60
blot given
Blue jay
2
3
Alimentary canal
0.09-3.48
Boat-tailed grackle
1
3
Gizzard
12
Bobwhite quail
1
160
Wing
2.93
Canada goose
12
112
Gizzard
0.34-9.13
Liver
0.014-0.05
Common grackle
4
72
Gizzard
16
Mallard
9
74
Brain
161
Gizzard
0.32-3000
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Chemical
Species
Records
Individuals
Matrix
Range (µg/g)
Disulfoton
American robin
1
9
Not given; birds poisoned
Naphthalene
Common tern
6
6
Egg
0.01 for all
Vanadium
Common tern
7
7
Egg
0.005-0.007
Muskrat
3
76
Kidney
0.045-1.10
Short-tailed shrew
3
3
Carcass
0.5-0.7
Snapping turtle
1
12
Liver
0.85
White-footed mouse
1
1
Carcass
0.3
Manganese
Birds: 20 species
94
1,006
Nine
0.005-20.2
Muskrat
3
76
Kidney
5.23-6.60
White-footed mouse
4
4
Carcass
8.6-16.00
American alligator
3
16
Egg
0.14-0.15
Pine snake
8
248
Carcass
11.72-16.27
Skin
1.35-7.26
DDE
102 bird species; 8 mammal species; 6 reptile species; 1 amphibian species
1,608
21,585
0.002-228.00
Dieldrin
77 bird species; 9 mammal species; I reptile species; I amphibian species
1,067
14,889
0.0007-21.60
NOTE: These data were extracted from the Contaminant Exposure and Effects—Terrestrial Vertebrates database (Rattner et al., 1999). The column labeled "records" refers to the number of records in the database for each species that contain the given contaminant. (A record can represent one or many individuals and usually gives a mean concentration of the chemical.) "Individuals" represents the total number of individuals for all records. "Matrix" is where the chemical concentration was measured, and "range" is the concentration range in the given matrix for each species (generally dry weight for metals and wet weight for organics).
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TABLE 4-13
Aliphatic Halides (not on the 1998 CCL) with Uses Similar to Those of 1,1,2,2-Tetrachloroethane (on the 1998 CCL)
Uses
CAS No.
Chemical
Machinery
Polystyrene
SBR Rubber
Rubber
Varnish
Total Uses
79-34-5
1,1,2,2- Tetrachloroethane
X
X
X
X
X
5
71-55-6
1,1,1- Trichloroethane
X
X
X
X
X
15
56-23-5
Carbon tetrachloride
X
X
X
9
79-00-5
1,1,2-Trichloroethane
X
X
X
3
TABLE 4-14
Production, Use, and Environmental Release Volumes for Aliphatic Halides (not on the 1998 CCL) that Have Similar Uses to 1,1,2,2-Tetrachloroethane (on the 1998 CCL)
Chemical Name
Production Volume
Use Volume
Toxics Release Inventory Volume (lbs.)
1,1,2,2-Tetrachloroethane
High
Low
16,000
1,1,1-Trichloroethane
Extremely high
Medium to high
8,800,000
Carbon tetrachloride
Extremely high
Low to medium
400,000
1,1,2-Trichloroethane
Very high
Low
340,000
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TABLE 4-15
Log Octanol-Water Partition Coefficient (log Kow) Values, Soil, or Sediment Sorption Coefficient (Koc) Values, and Henry's Law Constants for Aliphatic Halides (not on the 1998 CCL) that Have Similar Uses to 1,1,2,2-Tetrachloroethane (on the 1998 CCL)
Chemical Name
Log Kow
Koc
Henry's Law Constant (atm m3/mol)
1,1,2,2-Tetrachloroethane
2.39
107
3.67E-04
1,1,1-Trichloroethane
2.49
85
1.72E-02
Carbon tetrachloride
2.83
71
2.76E-02
1,1,2-Trichloroethane
1.89
97
8.24E-04
Representative terms from entire chapter:
drinking water