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--> Appendix D California Environmental Protection Agency Department of Toxic Substances Control (DTSC) Letter of Introduction, Overview, Concept Paper, and Appendices 1–4 from DTSC Report
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--> Risk-Based Criteria for Non-RCRA Hazardous Waste Volume 1 of 2 A Report to the National Research Council Introducing Proposed Changes to the Definition of Hazardous Waste in the California Code of Regulations Prepared by Human and Ecological Risk Division and Hazardous Materials Laboratory of the Science, Pollution Prevention, and Technology Program Department of Toxic Substances Control Environmental Protection Agency State of California February 27, 1998
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--> Risk-Based Criteria for Non-RCRA Hazardous Waste Table of Contents (revised, August 26, 1998) Tab*Title Page Volume 1 1 Overview and Letter of Introduction 1 2 Issues 10 3 Concept Paper. California's Non-RCRA Waste Classification System: Analysis and Proposed Revisions (with 4 Appendices) 13 4 TTLC Risk Assessment Models 75 4a Documents Describing Results and Input Values 76 4a1 CalTOX Adaptations for Derivation of Exit and Upper TTLC Criteria 78 4a2 CalTOX Version 2.3: Description of Modifications and Revisions 105 4a3 CalTOX: A Multimedia Total Exposure Model for Hazardous-Waste Sites 181 4a4 Analysis of Results and input Values of the Upper and Lower TTLCs Computed Using the CalTOX Model 520 4a5 The Distribution of California Landscape Variables for CalTOX 555 4a6 Parameter Values and Ranges for CalTOX 591 4a7 Draft Final Report: Intermedia Transfer Factors for Contaminants Found at Hazardous Waste Sites 647 I. Vinyl chloride 647 II. 2,3,7,8-Tetrachlorodibenzo-p-dioxin 687 III. Trichloroethylene 730 Volume 2 4b The DTSC Lead Risk Assessment Spreadsheet 775 4c The Preliminary Endangerment Assessment Model 784 4d De Novo Ecological Risk Assessments 844 5 Detection Limits and Background Level 858 5a Ambient and Background Concentrations 859 5b Analytical Issues 864 6 Concept Paper. Evaluation of the Suitability of the Federal Toxicity Characteristic Leaching Procedure (TCLP) in Lieu of California's Waste Extraction Test (WET) 869 (7) Comparison of California's Waste Extraction Test (WET) and the U.S. EPA's Toxicity Characteristic Leaching Procedure (TCLP) 880 (8) Leaching Potential of Persistent and Bioaccumulative Toxic Substances in Municipal Solid Waste Landfills 964 (9) Comparison of Short-term Extraction Tests with Extraction Using Municipal Solid Waste Leachates 1046 (10) Supplement to the RSU Extraction Test Project Summary Report: Phase 1 1078 (11) Supplement to the RSU Extraction Test Project Summary Report: Phase 2 1255 (11a) Tables for RSU Phase 2 1285 (11b) Figures for RSU Phase 2 1331 (11c) Appendices: Commercial Uses of Elements 1397 7 (12) Subtitle D Landfill Composite Liner Protection Factor 1485 * numbers in () correspond to Cal/EPA's original numbering system and may be referred to elsewhere in the document
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--> 1. Overview California's system for classifying wastes consists of two principal elements. One element is the federal system created under the authority of the Resource Conservation and Recovery Act (RCRA). As an authorized state, California has promulgated regulations mirroring those developed by the U.S. EPA under RCRA. These regulations are not part of this review. The second element is the non-RCRA system, which goes beyond and complements the RCRA system. The Department of Toxic Substances Control (Department) has undertaken an update of its entire non-RCRA waste scheme. The purpose of this update is to re-assess the need for the non-RCRA system, to update the scientific underpinnings of the system as needed, and to simplify the system where possible by eliminating redundancy and overlap, rewording confusing sections of regulation, and eliminating elements that have outlived their usefulness. It is the scientific basis for the proposed revised waste classification system that we are asking you to review. California's waste classification differs from the federal system in several ways: California has a list of approximately 800 chemicals which, when present in a waste, make it presumptively hazardous. However, a generator can use testing or knowledge to show that a waste containing one or more of the chemicals on the presumptive list does not exhibit a hazardous characteristic. Thus, California's non-RCRA system does not have ''listed'' hazardous wastes in the same way that the RCRA system does. California's non-RCRA system, like the RCRA system, includes the four hazardous characteristics of reactivity, ignitability, corrosivity, and toxicity. The first two are identical in the RCRA and non-RCRA systems. California's corresivity characteristic is slightly broader in that it includes corrosive solids. However, the characteristic that is most different between the two systems, and the one that is the subject of this review, is the toxicity characteristic. California's existing classification system comprises eight criteria for the toxicity characteristic (see table below). The Department proposes to retain all eight of the criteria, but to revise five of them. At present a single tier of thresholds creates a single tier of regulated waste: hazardous waste. A key aspect of the proposed changes is to add a second tier of regulatory thresholds for each of the first five criteria. This would create two tiers of regulated waste. The upper tier, to be called hazardous waste, would include the most toxic wastes (along with corrosive, ignitable, and reactive wastes). The lower tier would include wastes that are moderately toxic. The principal concern for these wastes is that they not be disposed of indiscriminately. The following table summarizes regulation number, description of the subject matter, decision and location of basis for the decision. The footnotes are numbered from those subsections undergoing the least revision to those undergoing the greatest revision.
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--> CCR* subsection Subsection description Decision Decision basis 66261.24(a)(1) Federal Definition of Hazardous Waste1 retain See below 66261.24(a)(2) Total Threshold Limit Concentration (TTLC)8 revise Tab 3: page 7 66261.24(a)(2) Soluble Threshold Limit Concentration (STLC)9 revise Tab 3: page 9 66261.24(a)(3) Acute Toxicity-Oral5 revise Tab 3: page 10 66261.24(a)(4) Acute Toxicity-Oral6 revise Tab 3: page 11 66261.24(a)(5) Acute Toxicity-Oral7 revise Tab 3: page 12 66261.24(a)(6) Fish Bioassay4 revise Tab 3: page 13 66261.24(a)(7) Carcinogens3 retain Tab 3: page 14 66261.24(a)(8) Experience or Testing ("New Threats")2 retain Tab 3: page 16 * Citation in Title 22 of the California Code of Regulation (CCR) 1. State RCRA programs must conform to federal law. 2. The Experience or Testing (new threats) subsection of the regulation will be retained as is. 3. Because of its economic importance, TTLCs and SERTs were derived for vinyl chloride. Therefore, vinyl chloride will be removed from the carcinogen list and added to the other two lists. The balance of the listed carcinogens will be retained, and if a waste contains any of these 15 chemicals at concentrations exceeding 10 ppm, they will be classified as hazardous. 4. Fish bioassay will be retained, but the single LC50 threshold for defining hazardous waste will be replaced with an upper and an exit LC50. The basis of this selection is in Appendix 4 of Tab 3. 5. The single oral LD50 value used to determine hazardous from non-hazardous waste will be replaced with an upper and exit LD50. The basis of this selection is described in Appendix 4 of Tab 3. 6. The single dermal LD50 value used to determine hazardous from non-hazardous waste will be replaced with an upper and exit LD50. The basis of this selection is described in Appendix 4 of Tab 3. 7. The algorithm used to determine hazardous from non-hazardous waste based on inhalation toxicity will replaced with two new algorithms. The basis of these algorithms is described in Appendix 4 of Tab 3. 8. See below for a discussion of TTLCs 9. See below for a discussion of SERTs (formerly STLCs) The changes described in footnotes 1–7 are relatively simple requiring short explanations. The bulk of documentation (Tabs 3–7) pertain to the new approaches proposed for replacing the values for each TTLC and SERT. Each of these criteria will be described in more detail under separate headings. Total Threshold Limit Concentrations (TTLCs) Thirty-eight chemicals (or groups of chemicals) each have a numerical TTLC. If the concentration in the waste exceeds the TTLC for any of the 38 chemicals, the waste is categorized as hazardous, otherwise it is unregulated by DTSC. The existing TTLCs were designed to protect human health and the environment from adverse effects resulting from all exposure pathways other than exposure via ground water. The TTLC for each chemical
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--> was computed by multiplying the current STLC value by 100 or 10. TTLCs have no counterpart in federal regulation and are deemed important to retain. However, some serious problems exist with the current TTLC values: Current TTLCs, being simply multiples of the STLCs are not necessarily relevant to non-ground water exposures. They are inflexible, in that they: Require all wastes be either rigidly regulated or completely unregulated by DTSC Cannot incorporate advances in technical information Provide no guidance for decisions on specific waste streams (variances or reclassifications) Do not provide a defined mechanism for regulating additional chemicals. Proposed TTLCs were developed using a multi-step, risk-based approach: Define potentially exposed humans for two waste management situations: 1) wastes managed as special wastes and disposed of in a landfill and 2) wastes unregulated by DTSC. Identify pathways by which chemical in waste could reach humans for each scenario. Develop a mathematical model to relate waste concentration to human health risk for each scenario. Implement these models as spreadsheets to make computation easy and transparent Using the spreadsheets, compute a human-health-based TTLC for each scenario for each chemical. For each chemical, determine if human health-based TTLCs protect other species. If not, compute a TTLC based on protection of non-human resources. Evaluate risk-based TTLCs for science policy considerations. The risk-based approach to deriving TTLCs addresses the four problems with the current TTLCs. The reader is encouraged to read Appendix 3 of Tab 3 for a general description of the derivation of TTLCs. This section is intended to be a "road map" directing the reader to the spreadsheet descriptions and showing where each fits into the overall process. Human Health Risk Assessment Scenarios and Models In order to develop a regulatory threshold, the fate and potential exposure scenarios and pathways for wastes that do not exceed the proposed threshold are evaluated. Thus, the scenarios for the upper TTLCs are associated with managed disposal in a municipal solid waste landfill meeting the specifications in RCRA subtitle D. Similarly, the scenarios for the exit-level TTLCs are associated with use of the waste as a soil amendment. There are many possible exposure scenarios, but DTSC has not identified any plausible scenarios in which exposures to toxic constituents in wastes is likely to exceed the exposures modeled using these scenarios. The scenarios and the models used to evaluate them are described below and summarized in a table following the description.
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--> The second screen involved a consideration of the soluble or extractable fraction of the ten waste constituents. The limiting ecological endpoint for nickel and copper was toxicity to aquatic plants (1). Since the proposed SERTs for these metals are based on Ambient Water Quality Criteria for the protection of aquatic life, the SERTs should protect aquatic plants. Therefore no changes are proposed in the human-health-based exit-level TTLCs for these elements. Vanadium The limiting ecological endpoint in the HWIR analysis for vanadium was phytotoxicity. Estimated no-effect concentrations range from 2 to 20 mg/kg (1,3). However, these values are below even minimum ambient levels in California and thus cannot be used as the basis for regulatory standards. The STLC is the basis of the the proposed TTLC for vanadium (see page 37). Cadmium The draft HWIR ecological exit concentration for cadmium, based on toxicity to soil fauna, is 5 mg/kg (1). The lowest Oak Ridge National Laboratory screening concentration of cadmium, based on phytotoxicity, is 3 mg/kg (3). Assuming that the waste is applied to the land at the rate of 7000 kg/ha/year for 20 years as described previously, the maximum cadmium concentration in the waste that would not result in a final soil concentration exceeding the 3 mg/kg screening level for phytotoxicity is 60 mg/kg. Lead The draft HWIR ecological exit concentration for lead is 1 mg/kg, based on toxicity to soil fauna (1). This value cannot be used as a basis for defining hazardous waste in California, where background soils contain a minimum of 14 times that amount of lead. The ORNL screening concentrations based on phytotoxicity and soil fauna toxicity are 50 and 500 mg/kg, respectively (2,3). Assuming that the waste is applied to the land at the rate of 7000 kg/ha/year for 20 years as described previously, the maximum concentration of lead in the waste that would not result in a final soil concentration exceeding the 50 ppm screening level for phytotoxicity is 990 ppm. Rounded to one significant figure, this results in a suggested exit-level TTLC of 1000 mg/kg. Zinc The draft HWIR ecological exit concentrations for zinc is 0.4 mg/kg, based on toxicity to soil fauna (1). The ORNL screening levels for zinc are 50 and 100 mg/kg, based on phytotoxicity and soil microorganisms, respectively. These concentrations are well below 90 th percentile background concentrations in the California soils (tab 9), and thus cannot be used as a basis for defining hazardous waste in California. Since no satisfactory criterion is available for total zinc, DTSC proposes to regulate zinc in solid waste only by its soluble or extractable concentration. Selenium The limiting toxicological endpoint for selenium is reproductive toxicity in waterfowl. The threshold for this endpoint can be estimated in a variety of ways (see Tab 8). The California EPA Office of Environmental Health Hazard Assessment (OEHHA) recommends calculating the endpoint using a benchmark dose and a sediment-fish transfer factor (ranging from 3.9 to 15.6), and assuming 100% foraging on a contaminated site as well as conditions favoring selenium uptake into dietary items of aquatic birds. However, in order to be consistent with the approach used throughout this proposed revision of the waste classification system, the approach of Van Derveer and Canton (Tab 8) was selected as the basis for the proposed lower TTLC for selenium. Those authors determined EC10 values (10th percentile estimates of the threshold for selenium toxicity in sediment) of 2.5 and 4.0 mg/kg, dry weight, associated with predicted and observed effects, respectively, in wild fish and birds. Assuming that the waste is applied to the land at the rate of 7000 kg/ha/year for 20 years as described previously, the maximum selenium concentration in the waste that would not result in a final soil concentration exceeding the 2.5 mg/kg EC10 based on predicted effects for waterfowl toxicity is 50 mg/kg. The proposed ecosystem-based, exit-level TTLC for selenium is therefore 50 mg/kg, dry weight (however, see page 37). Mercury According to the OEHHA analysis, the limiting pathway for mercury is biomethylation, uptake by benthic organisms, and food web transfer of the organomercury to fish and ultimately to predator fish, mammals, and birds (Tab 8). The belted kingfisher was chosen as the species of
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--> concern because it is a sensitive fish-consuming bird, and birds appear to be at least as sensitive to methymercury as fish or mammals. Using the mallard dietary reproductive no-adverse-effect concentration (NOAEL) for rnethylmercury of 0.05 mg/kg diet, with an interspedas conversion factor of 3.2 (reflecting a daily food consumption rate of 15.6% body weight for the mallard versus 50% body weight for the kingfisher), and a conservative assumption of 100% foraging on contaminated fish, a dietary NOAEL for the kingfisher would be 0.05/3.2 = 0.016 mg/kg diet. In order to relate the mercury concentration in the kingfisher's diet to a concentration in sediment, a sediment-to-fish transfer factor is needed. A range of sediment-to-fish transfer factors identified from the literature for California (0.013–20; Table 1, Tab 4d). Combining these transfer factors with the estimated dietary NOAEL for the kingfisher, an estimated range of maximum "safe" sediment concentrations for the kingfisher would be 0.0008 to 1.2 mg/kg sediment, dry weight. Assuming that the concentration in the sediment is the same as the concentration in the soil (for example, fields to which the waste has been applied may be flooded to form wetlands) and that the waste is applied to the land at the rate of 7000 kg/ha/year for 20 years as described previously, the maximum mercury concentration in the waste that would not result in a final sediment concentration exceeding the 0.0008 to 1.2 mg/kg sediment, dry weight 0.016 mg/kg screening sediment concentration for food-web toxicity is (0.0008 to 1.2) × 19.8 = 0.011 to 17 mg/kg sediment (geometric mean 0.19). Endrin The HWIR exit concentration for endrin is 0.1, based on toxicity to the great blue heron via the aquatic food web. This concentration was accepted as the eco-based TTLC for endrin because it was verified using the environmental transport modeling of endrin from waste to fish in CalTOX Land Conversion. Methoxychlor The HWIR exit concentration for methoxychlor is 3, based on toxicity to sediment-dwelling organisms. The HWIR benchmark dose for sediment-dwelling organisms is converted from the ambient water quality criterion for the protection of aquatic life (AWQC) of 0.00003 mg/l, using equilibrium partitioning. This conversion involves the implied assumption that toxicity to benthic organisms can be predicted by pore water concentration in sediment and that these organisms will be protected if pore water concentration does not exceed the AWQC. The same thing is accomplished by limiting the soluble or extractable concentration of endrin in the waste to 100 times the AWQC. The latter is DTSC's proposed approach. Thus, no change is proposed in the human-health-based TTLC of 100. References 1. U.S. Environmental Protection Agency, 1995, Technical Support Document for the Hazardous Waste Identification Rule: Risk Assessment for Human and Ecological Receptors, Office of Solid Waste Contract # 68-D2-0065, 68-W3-0028. 2. Oak Ridge National Laboratory, undated, Toxicological Benchmarks for Potential Contaminants of Concern for Effects on Soil and Litter Invertebrates and Heterotrophic Process, ES/ER/TM-126/R1. 3. Oak Ridge National Laboratory, 1995, Toxicological Benchmarks for Screening Potential Contaminants of Concern for Effects on Terrestrial Plants: 1995 Revision, ES/ER/TM-85/R2. 4. Wildlife Exposure Factors Handbook. US EPA 1993, EPA/600/R-93/187a Office of Research and Development
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--> Table 3: Risk-based Candidate TTLCs Upper TTLC (mg/kg) Lower TTLC(mg/kg) Chemical Nearby Residents Waste workers LCS Residents Ecological concerns Aldrin 0.006 3 0.0009 protectede Chlordane 1 30 0.06 protectede DDD 20 200 0.3 protectede DDE 1 150 0.3 protectede DDT 4 100 0.7 protectede 2,4-Dichlorophenoxyacetic acidi 3,000 1500 50,000d protectedf Dieldrin 0.2 3 0.004 protectede Endrin 70 150 0.8 0.1 Heptachlor 0.7 6 2d protectede Kepone 0.2 3 0.02 protectede Tetraethyl Lead 8 × 10-6 0.0003 0.0007d protectedf Lindane 60 30 5 protectede Methoxychlor 7,000 2,000 100 6,400 Mirex 0.9 2 0.04 protectedf Pentachlorophenoli 500 500 400 protectede Polychlorinated biphenyls (PCBs)a nd nd nd nd Tricholoethylene (TCE) 20 70 2,000d protectede Toxaphene 0.04 30 6d protectede 2,4,5-Trichlorophenoxyproprionic acidi 2,000 1000 40,000d protectede Vinyl chloride 0.2 0.7 50d protectedf 2,3,7,8-Tetrachlorodibenzodioxin 7 × 70-7 5 × 10-4 1 × 10-7 protectede Inorganic lead 20,000 6,000 5,000 1000 Antimony 15,000 700 4,000d protectede Arsenic 200 40 400d protectede Asbestosb nd nd nd nd Barium (excluding barite) >1,000,000 100,000 700,000d protectede Beryllium 300 20 200d protectede Cadmium 150 500 3,000 60 Trivalent Chromiumc >1,000,000 >1,000,000 >1,000,000 protectede Hexavalent Chromium 5 15 80d protectedf Cobalt 15,000 20,000 200,000d protectede Copper >1,000,000 70,000 400,000d protectedg Fluoride >1,000,000 100,000 600,000d protectede Ionic Mercury 10,000 500 3,000 0.2 Molybdenum 200,000 9,000 50,000d protectede Nickel 3,000 7,000 50,000d protectedg Selenium 200,000 9,000 50,000 40 Thallium 3,000 150 800d protectede Vanadium 300,000 10,000 70,000 2–20 Zinc >1,000,000 500,000 >1,000,000d protectedh
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--> a New TTLCs for PCBs have not been determined. b New TTLCs for asbestos have not been computed. c For these scenarios, Crill does not pose a health threat. d The lower TTLC values were greater than the upper TTLC. e Using the HWIR ratio, the residential TTLC protects ecosystems. f Chemical not considered by EPA to be a priority for eco-assessment. g The SERTs protect against toxicity to aquatic plants. h No acceptable eco-based concentration available. Zinc in waste will be limited by their soluble or extractable fraction only. i Chemical parameters for the unionized moiety were used. j Mercury range 0.011–17 with geometric mean of 0.19 mg/kg.(see text) The spreadsheets named in Table 1 and described in the sections above were used to compute risk-based concentrations for the four scenarios. The results of these computations are presented in the four columns of Table 3. The rows of Table 3 are divided with the organic chemicals (CalTOX) shown in the top half, inorganic lead (Lead spreadsheet) shown as a single line in the center, and other inorganic chemicals (PEA) shown in the bottom half. The list of chemicals for which TTLCs were computed is based on the list of chemicals for which TTLCs currently exist in regulation. The chemical names in Table 3 differ than those currently appearing in regulation for several chemicals. First, DDE DDT and DDD all appear separately in a box in the table. DDT can be converted into DDE or DDD. Therefore, risk-based TTLC values were computed for all three chemicals. The lowest of the six upper values (DDE-nearby resident) was selected as the risk-based upper-level TTLC. The lowest of the three land conversion residents (DDE) was selected as the lower risk-based TTLC. Second, risk-based computations require that a single chemical with specific chemical and toxicological properties be identified to compute TTLC. This can lead to identifying a single chemical as a surrogate for other similar chemicals. Tetraethyl lead is used as a surrogate for all organic lead. Third, vinyl chloride has been moved from to the list of carcinogens in section 66261.24 of the current regulation to this list because of the importance of this chemical. Fourth, total chromium has been replaced by trivalent chromium. All chromium is either considered trivalent or hexavalent because of the large differences in the toxicity of two valances. Fifth, mercury has been restricted to ionic mercury excluding organic mercury and elemental mercury. Sixth, silver has been eliminated from the list because the form found in the environment is known not to be bioavailable. There are also several explanations required of values in the Table 3. First, no new TTLCs are being proposed for PCBs or asbestos. Both the analytical methods and toxicity criteria for PCBs are in a state of change currently. Efforts are under way to create a toxicity equivalency factor approach for PCBs similar to dioxin. Therefore the department is waiting for the outcome of these efforts before proposing a new TTLC. Asbestos risks are based on fiber counts. This information has not changed greatly, so an update was deemed unnecessary. Second, the organic acids pentachlorophenol, 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4,5-trichlorophenoxyproprionic acid (2,4,5-T) exist in an unionized form at lower pHs. This form is more volatile and less water soluble than the ionized form. Since the objective of the TTLCs is to model the exposure pathways other than those involving ground water, the chemical characteristics of the unionized form were used to predict the fate of these chemicals in the environment. At pH values between 5 and 9, the environmental fate of pentachlorophenol will be well represented by the CalTOX equations; prediction errors are larger for 2,4-D and 2,4,5-T.
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--> Second Stage: Detection Limits and Ambient Concentrations Following the calculation of risk-based candidate TTLCs, these values are evaluated to determine whether they can be practically implemented as regulatory limits. First, a policy decision was made not to set any TTLC lower than could be measured, since a toxicity threshold is not a useful criterion if it is so low that it cannot be measured. Second, a policy decision was made not to set any TTLC lower than concentrations which are naturally present in California soils or widely distributed in the environment. Estimated Quantification Limits Estimated quantitation limits (EQLs) are defined as the lowest concentration that can be reliably achieved within specified limits of precision and accuracy during routine laboratory operating conditions (Tab 5a). The EQL considers the limitations of the analytical method and the effects of processing the sample matrix. The EQL for substances in complex matrices, such as oily sludges, can be quite high. An EQL is calculated for each chemical for each regulatory limit class (upper TTLC, lower TTLC). Each EQL is then multiplied by two because in order to statistically evaluate compliance with a standard, one must be able to measure concentrations above and below the standard. Risk-based candidate TTLC which were less than twice the EQL were changed to twice the EQL. The proposed upper TTLC for toxaphene and proposed lower TTLCs for chlordane, heptachlor, methoxychlor, toxaphene, Silvex, and vinyl chloride are based on EQLs. Comparison with Background Concentrations Inorganics: A two-step process was used to implement the policy decision to consider background concentrations in setting TTLCs for inorganic chemicals: (1) All calculated health-based levels for inorganic chemicals regulated by DTSC (except fluoride and hexavalent chromium), were compared with maximum background levels found in native California soils, as reported in the University of California, Riverside study. The risk-based concentrations for mercury and vanadium were less than their maximum background concentrations. (2) Determine the concentrations of vanadium and mercury in waste that would not cause a significant increase in background concentrations of these substances, when the wastes were mixed with soil as postulated in the land conversion scenario, discussed earlier. The following table shows the calculation steps for vanadium and mercury. UCR soils data USGS soils data average waste mean 90% difference mean 90% difference difference concentration mercury 0.26 0.612 0.352 0.154 0.47 0.316 0.3342 6.62 vanadium 24.3 185.2 161 124.8 200 75.2 118 2337 A ''significant increase'' was defined as the difference (columns 4 & 7) between the means (columns 2 & 5) and the ninetieth percentiles (columns 3 & 6). This calculation was done for the UCR data (1) and the USGS data (2), and the the results averaged (column 8). Since the land conversion scenario results in a 19.8-fold dilution of the waste as it is mixed with soil, the equivalent waste concentration is 19.8 times this average difference (column 9). This means
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--> that if waste containing mercury or vanadium at the concentration in column 9 is mixed with soil that contains average background concentrations of these metals, the resulting mix will contain no more mercury or vanadium than the 90th percentile of background. Organics: Dioxins and dibenzofurans are generally formed as a result of human activities. As sources of these compounds are brought under control, the levels in the environment are dropping and will probably continue to do so. Published data on the distribution of dioxins in the environment in the U.S. and the U.K. were used to estimate ambient concentrations in soils, which appear to have a mean and standard deviation of approximately 0.000008 mg/kg (TEQ). Second, the concentration of dioxin TEF in waste that would not cause a significant increase in background concentrations of these substances was determined. A 'significant increase' in this case, was defined as an increase of 1.28 standard devations, or 0.00001 mg/kg (TEQ). The concentration in waste that would produce such change in soil, estimated using the land conversion scenario, was 0.0002 mg/kg (0.00001 × 19.8). For each chemical, the value that is the basis for the TTLC is shown in bold in Table 4:
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--> Table 4: Comparison of Risk-based Levels with Quantitation Limits and Ambient Levels Upper TTLC (mg/kg) Lower TTLC(mg/kg) Chemical Risk-based Level Estimated Quantitation Limit Ambient Level Risk-based Level Estimated Quantitation Limit Ambient Level Aldrin 0.006 0.68 na 0.0009 0.046 na Chlordane 1 0.74 na 0.06 0.05 na DDT & congeners 1 0.5 na 0.3 0.034 na 2.4 D 3000 4 na noned Dieldrin 0.2 0.88 na 0.004 0.059 na Endrin 70 0.78 na 0.1 0.052 na Heptachlor 0.7 0.8 na noned Kepone 0.2 40 na 0.02 2.7 na Organic Lead 8 × 10-6 100 na 8 × 10-6f 10 Lindane 30 0.5 na 5 0.034 na Methoxychlor 2000 1.7 na 100 0.12 na Mirex 0.9 0.3 na 0.04 0.02 na Pentachlorophenol 500 1.5 na 400 0.1 na Polychlorinated biphenylsa nd nd nd nd nd nd Tricholoethylene (TCE) 20 1.2 na noned Toxaphene 0.04 1.7 na 0.04f 0.1 2.4.5-T 2000 1.5 na noned Vinyl chloride 0.2 1.2 na 0.2f 0.01 PCDD/PCDF (TEQs)b 7 × 10-7 See commentb 2 × 10-4 1 × 10-7 See commentb 2 × 10-4 Inorganic lead 6000 6 97.1 700 0.6 97.1 Antimony 700 120 1.95 noned Arsenic 50 20 11 noned Asbestosc nd nd nd nd nd nd Barium (excluding barite) 100,000 400 1400 noned Beryllium 30 10 2.7 noned Cadmium 200 10 1.7 40 1 1.7 Hexavalent Chromium 5 2 na noned Cobalt 10,000 100 46.9 noned Copper 60,000 50 96.4 noned Fluoride 100,000 100 na noned Ionic Mercury 500 0.4 0.54 0.2 0.04 7e Molybdenum 9,000 100 9.6 noned Nickel 3,000 80 509 noned Selenium 9,000 10 0.43 40 1 3.3e Thallium 100 20 36.2 noned Vanadium 10,000 100 190 20 10 2000e Zinc 500,000 40 236 noned
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--> a New TTLCs for PCBs were not determined. See text. b This is to be applied to dioxin TEQs not a single congener c New TTLCs for asbestos have not been computed and the existing TTLCs will be used. d The lower TTLC values were greater than the upper TTLC, therefore, no lower TTLC is proposed for these chemicals. e The maximum waste concentration based on background considerations. f These are the upper TTLC values. Four significant differences can be seen in the chemical names listed in Table 4 as compared with Table 3. (1) The three chemicals DDT, DDE and DDD have been reduced to a single line called DDT and congeners. The lowest risk-based concentration of the three congeners has been selected because DDT can be transformed into DDE or DDD. (2) The criterion for dioxins applies to 11 dioxin congeners, not just to 2,3,7,8 tetrachlorodibenzodioxin. This is based on the toxicity equivalence factors (TEFs) used by US EPA. Therefore, waste being classified according to their content of dioxins will need to be analyzed for these 11 congeners. The 11 TEFs will be used to compute an equivalent concentration of TCDD. (3) tetraethyl lead has been replaced with organic lead because tetraethyl lead was a surrogate for organic lead. (4) Since non-extractable chromium III and zinc were found to pose no significant effect on human health and the environment, the department proposes to regulate those chemicals only by their SERTs. References 1. Kearney Foundation of Soil Science, Division of Agriculture and Natural Resources, University of California, Riverside, 1996, Background Concentrations of Trace and Major Elements in California Soils. 2. Boerngen, J.G. and H.T. Shacklette (1981) Chemical analysis of soils and other surficial materials of the coterminous United States. Open-file Report 81-197, U.S. Department of Interior, Geological Survey.
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--> Appendix 4. Acute Toxicity Thresholds Oral LD50 DTSC has developed recommended acute oral toxicity thresholds for hazardous wastes and special wastes. Hazardous wastes would include wastes with an oral LD50 less than 30 mg/kg. Non-hazardous wastes would include those with an oral LD50 exceeding 500 mg/kg. Special wastes would include wastes with oral LD50s between 30 and 500 mg/kg. These thresholds are calculated as follows: The Hazardous waste threshold is based on an adult exposure scenario because Special Wastes would be accessible to adults but not ordinarily be accessible to children. Adults are assumed to ingest 0.31 mg of waste per kg body weight., The Special waste threshold is based on a child exposure scenario because in order to be unregulated by the Department, wastes should not be an acute toxicity threat to children. Children are assumed to ingest 5 mg of waste per kg body weight.. The waste ingestion rates for adults and children are 90th percentile estimates of inadvertent soil ingestion derived from the CalTOX model. The means (and coefficients of variation) of those distributions are 1.4e-7 (2) and 2.2e-6 (3), respectively. Uncertainty factors of ten to account for the use of laboratory animal toxicity data to predict human toxicity and ten to extrapolate from a lethal concentration to a minimal-effect concentration were multiplied by the waste ingestion rates to arrive at the acute oral toxicity thresholds. Dermal LD50 DTSC has developed recommended acute dermal toxicity thresholds for hazardous wastes and special wastes. Hazardous wastes would include wastes with a dermal LD50 less than 5500 mg/kg. Non-hazardous wastes would include those with an oral LD50 exceeding 7400 mg/kg. Special wastes would include wastes with oral LD50s between 5500 and 7400 mg/kg. These thresholds are calculated as follows: The hazardous waste threshold is based on a dermal contact rate of 55 mg of waste per kg body weight per day by an adult, with an uncertainty factor of 100. The special waste threshold is based on a dermal contact rate of 74 mg of waste per kg body weight per day by a child, with an uncertainty factor of 100. The dermal contact rates for adults and children are 90th percentile estimates of inadvertent contamination of skin by waste using exposure parameters from the CalTOX model. The parameters include fraction of skin surface exposed (mean 30%, SD 1%), soil adhesion (mean 0.5 mg/cm2,SD 0.2), and skin surface area (adult mean 0.024 m2/kg, SD 0.001, child mean 0.032 m2/kg, SD 0.003). Uncertainty factors of ten to account for the use of laboratory animal toxicity data to predict human toxicity and ten to extrapolate from a lethal concentration to a minimal-effect concentration were multiplied by the dermal contact rates to arrive at the acute dermal toxicity thresholds.
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--> Inhalation LC50 The purpose of the proposed revisions in the acute inhalation toxicity threshold is to take into account potential exposure as well as toxicity. The proposal would subdivide the regulated wastes into two categories based on the severity of the threat in order to avoid over-regulating wastes which have low exposure potential (low volatility and limited respirability). The waste being classified would not need to be tested if standard reference values are are available for its toxic constituents. Volatiles: In order to account for both a chemical's acute inhalation toxicity and its tendency to vaporize, classification of a waste containing volatile constituents would be based on the ratio of each constituent chemical's vapor pressure (in ppm @ 250 C) to its inhalation LC50 (in ppm). If this ratio exceeds 0.1, the waste containing the chemical would be a special waste. If this ratio exceeds 1, the waste containing the chemical would be a hazardous waste. These ratios must be summed for wastes with multiple volatile chemicals, i.e. σ(VP/LC50) > 0.1 yields a special waste classification and σ(VP/LC50) > 1 yields a hazardous classification. Vapor pressure in mm Hg is converted to vapor pressure in atmospheres by dividing by 760. This, in turn is converted to ppm by multiplying by 1 million. The rationale for the proposed thresholds is as follows: A chemical's vapor pressure in atmospheres multiplied by 1 million gives its theoretical maximum concentration in a closed space in ppm, i.e. concentration = 106 * Vp (in mm Hg) / 760, which can be simplified to VP / 0.00076. If this concentration exceeds the LC50 for a volatile chemical, then the chemical could form a lethal atmosphere, and is therefore considered a hazardous waste. Similarly, if a chemical's theoretical maximum concentration is one-tenth times its LC50, then it could form an atmosphere one-tenth of its lethal atmosphere even with and would be considered a special under this classification proposal. The table below is used to classify the waste: Particulates: Classification of a waste based on its particulate constituents would be based on the respirable fraction of the waste (PM10 the fraction with a particle size less than 10 microns) times the sum of the ratios of each chemical's concentration (in mg/kg) in the respirable fraction divided by its inhalation LC50 (in mg/m3). This ratio accounts for the tendency of the chemical to be suspended in the air and for its acute toxicity by inhalation. DTSC proposes to classify a waste as hazardous if the sum of the concentrations of individual chemicals in the respirable fraction of the waste (in mg/kg) divided by their inhalation LC50s (in mg/m3) times the respirable fraction of the waste exceeds 2×106, and to classify a waste as non-hazardous if the concentration of a chemical in the respirable fraction of the waste (in mg/kg) divided by its inhalation LC50 (in mg/m3) is less than 105. The rationale for these thresholds is as follows: The concentration of a chemical in the waste multiplied by the particulate concentration in the air yields the airborne concentration of the chemical, assuming that the dust is suspended waste. Simplistically, if this airborne concentration exceeds the LC50 of the chemical, then the resulting concentration will be lethal. However not all airborne particles are respirable. If only a fraction of the waste is respirable, the expression must be corrected to account for the fraction of the waste that is respirable (F), and the concentration of the chemical (C) in the respirable fraction (PM10) of the waste must be used in place of the concentration in the waste as a whole. Thus, the expression for the lethal concentration becomes (F * C * PM10 / LC50 > 1). Because the endpoint is 50% lethality, a safety factor of ten is incorporated, making the expression F * C ×
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--> PM10 / LC50 > 0.1. Finally, concentrations of the various toxic constituents in the waste must be added to determine the total toxic effect of the waste, i.e. F * σ(C × PM10 / LC50 > 0.1). The two assumed airborne dust concentrations are based on the OSHA standard for respirable suspended particulates in the workplace (10-6 kg/m3) and the federal ambient air quality standard for PM10 (5 × 10-8 kg/m3). Thus, the exit threshold becomes F * σ(C × 5 × 10-8 / LC50 > 0.1), and the hazardous threshold becomes F * σ(C × 10-6 / LC50 > 0.1). These expressions can be rearranged to give F * σ(C / LC50 > 2 × 106), and F * σ(C × / LC50 > 105), respectively The following table is used to classify the waste: Vapor Pressure/LC50 ratio sum Classification Concentration/LC50 sum VP/LC < 0.1 Non-hazardous waste C/LC50 < 105 0.1 < VP/LC < 1 Special Waste na VP/LC > 1 Hazardous Waste C/LC50 > 105 Aquatic Toxicity The current system classifies a waste as hazardous if its aquatic LC50 is less than 500 mg/l. DTSC proposes to classify a waste with an LC50 <500 mg/l as a special waste. A concentration of 500 mg/l would be equivalent to 7 tons in a two-acre lake five feet deep with complete mixing, which DTSC considers to be a reasonable worst-case release. As discussed in appendix 2, above, a composite liner meeting RCRA Subtitle D specifications is assumed to reduce leakage from a landfill by 18-fold (tenth percentile estimate). Therefore, the waste could be 18 times as toxic (assuming that fish exposure is directly proportional to flow rate) without causing toxic effects on fish if it is placed in a subtitle D landfill. Therefore the proposed threshold for the fully hazardous tier is 500/18 = 30, i.e. a waste with an LC50 <30 mg/l would be classified as a hazardous waste
Representative terms from entire chapter: