Over- and under-regulating hazardous waste

ECONOMIC/MARKET REGULATORY REQUIREMENTS

OVER- AND UNDER-REGULATING HAZARDOUS WASTE Tom Loranger and Damon Delistraty Washington State Department of Ecology

Hazardous waste regulations in the United States tend to over-regulate certain wastes and under-regulate others. Over-regulation is related to the listing strategy, whereas under-regulation is primarily a result of failing to assess waste toxicity directly. Hazardous waste regulations in individual states are required to be at least as stringent as federal rules. As such, the state of Washington has added several waste criteria, including acute toxicity, persistence, and carcinogenicity. Recently, the acute toxicity threshold for the fish bioassay has been lowered and the carcinogenicity criterion has been deleted to avoid over-regulating waste. Approximately 36% of the total hazardous waste reported annually in Washington state is designated as state-only waste, with 93% of this stateonly fraction classified by acute toxicity. Thus, a significant portion of hazardous waste in Washington state is captured by state criteria. This waste is removed from the environment, enhancing protection of human and ecological receptors.  1999 Elsevier Science Inc.

Introduction Hazardous waste regulations in the United States (US) are codified in the federal Resource Conservation and Recovery Act (RCRA) (CFR 1997a). RCRA tends to over-regulate certain wastes while under-regulating others. Because state hazardous waste regulations must be at least as stringent as federal requirements, states effectively can alter only the under-regulation aspect. As such, hazardous waste regulations in the state of Washington

Address requests for reprints to: Damon Delistraty, Ph.D., Washington State Department of Ecology, N. 4601 Monroe, Suite 202, Spokane, WA 99205, USA. E-mail: [email protected] ENVIRON IMPACT ASSESS REV 1999;19:99–108  1999 Elsevier Science Inc. All rights reserved. 655 Avenue of the Americas, New York, NY 10010

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include several provisions unique to the state (WDOE 1998a), as well as the basic federal RCRA requirements. The state-only criteria capture substantially more waste than the RCRA program alone. The purpose of this article is to describe (1) how RCRA over- and under-regulates hazardous waste, (2) the approach adopted by Washington state to address this problem, and (3) the resulting benefits to human health and the environment. Federal Regulation The US Congress enacted RCRA in 1976 in order to specify requirements for properly managing solid and hazardous waste. The overall goals of RCRA were to protect human health and the environment, to conserve energy and natural resources, and to reduce the generation of hazardous waste (Wagner 1990). Consequently, the US Environmental Protection Agency (EPA) established a complex system for managing hazardous waste from its generation to disposal (i.e., “cradle to grave”). Central to this task was crafting a definition for hazardous waste. As such, the EPA developed a framework for this definition based on waste properties with a system of characteristics and lists (Table 1). Waste characteristics included ignitability, corrosivity, reactivity, and toxicity. Criteria for listing wastes included exhibiting any of these characteristics, eliciting human or surrogate mammalian toxicity, or containing toxic constituents catalogued in Appendix VIII of 40 CFR Part 261 (CFR 1997a). Within the federal system, a potential exists for both over- and under-regulation of hazardous wastes. Over-regulation of wastes can result from the listing strategy and various rules concerning waste mixtures. Listed wastes are defined as hazardous through a general evaluation to determine whether the waste or production process meets descriptions specified in 40 CFR Part 261 (CFR 1997a). These wastes remain hazardous until they are delisted through a separate administrative proceeding. A listed waste is hazardous regardless of the concentration of hazardous constituents, even if these constituents pose a negligible risk. This over-regulation can be compounded further by classifying waste as hazardous if it is a mixture of a listed waste and a solid waste (“mixtures rule”), it is a listed waste contained within another material (“contained-in rule”), or it is a solid waste generated from the treatment, storage, or disposal of a listed waste (“derived-from rule”) (Wagner 1990). Again, concentration of hazardous constituents may be so low as to pose negligible risk. On the other hand, under-regulation of wastes can result from failing to assess directly waste toxicity, the high cost of listing a waste, and specific federal exclusions. Although RCRA specifies acute toxicity as a basis for listed wastes, it does not directly evaluate acute toxicity when classifying a given waste. Subsequently, many wastes exhibiting acute toxicity may not be regulated as hazardous under the federal system. Note too that the

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TABLE 1. Federal and Washington State Hazardous Waste Categories Federal and State Listingsa

Federal and State Characteristicsb

State-Only Additionsc

Non-specific sources (F codes) Specific sources (K codes) Discarded commercial chemical products (P and U codes)

Ignitability

Acute toxicity

Corrosivity

Persistence

Reactivity

Solid corrosives

Toxicitye

Certain polychlorinated biphenyl (PCB) wastes

Federal-Only Exclusionsd Fossil fuel combustion wastes Oil and gas exploration wastes Mineral and ore processing wastes Cement kiln dust

Injected groundwater Certain used oil filters De minimis wastewaters Source, special nuclear, or byproduct material as defined by the Atomic Energy Act a Non-specific source wastes are generated by generic processes (e.g., solvent wastes), specific source wastes are generated from specific industrial processes, and discarded commercial chemical product wastes are in unused form (e.g., off-specification products). b Characteristic wastes are defined by quantitative or qualitative specifications and associated laboratory test protocols. c These waste categories are unique to Washington state. d These exclusions do not apply to Washington state (WDOE 1996b). e Designed to identify wastes that are likely to leach hazardous constituents into groundwater used as a drinking water source. Source: CFR (1997a) and WDOE (1998a).

toxicity characteristic in the federal hazardous waste regulations is based on chemical leachability, not on toxic effect per se. With regard to cost, Williams and Cannon (1991) have noted that the listing process averages over 1 million US dollars per waste stream. This high cost serves as a disincentive to list a waste. For example, the EPA has listed only approximately 400 wastes or waste constituents as hazardous of the 50,000 commercial products and uncounted number of waste streams that potentially could become hazardous wastes. Finally, several wastes have been exempted explicitly from RCRA regulations (Table 1), even though they may pose a potential risk. Washington State Provisions Similar to RCRA, the Washington state legislature passed a law pertaining to proper management of hazardous waste (WDOE 1976). In this regard, the legislature directed the Washington State Department of Ecology (WDOE) to regulate wastes that have an existing or potential hazard to

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TABLE 2. Acute Toxicity Endpoints Used by Washington State to Designate Hazardous Waste Toxic Category

Fish LC50 (mg/L)a

Rat Oral LD50 (mg/kg)b

Rat Inhalation LC50 (mg/L)c

Rabbit Dermal LD50 (mg/kg)d

X A B C D

,0.01 0.01–,0.1 0.1–,1 1–,10 10–100

,0.5 0.5–,5 5–,50 50–,500 500–5,000

,0.02 0.02–,0.2 0.2–,2 2–,20 20–200

,2 2–,20 20–,200 200–,2,000 2,000–20,000

a Fish median lethal concentration (LC50) should be based on salmonids, fathead minnows, or other fish species (in that order) with an aquatic exposure period $24 hours. b Rat oral median lethal dose (LD50) should be based on a single oral dose with a 14-day observation period. c Rat inhalation LC50 should be based on a #4-hour exposure to the respiratory tract with a 14-day observation period. d Rabbit dermal LD50 should be based on a single dermal dose applied for 24 hours with a 14-day observation period. Source: WDOE (1998a).

human health or the environment. As noted previously, state hazardous waste regulations must be at least as stringent as federal requirements. Thus, the WDOE attempted to offset the under-regulation pitfalls described in the federal rules by incorporating additional criteria (e.g., acute toxicity, persistence, carcinogenicity) and disallowing several federal exclusions (Table 1). The state-only criteria are detailed following, along with several amendments that later tempered these criteria so as not to over-regulate hazardous waste.

Acute Toxicity In a review of hazardous substance classification systems, the EPA (1975) reported that acute toxicity data were the primary criterion used for classification. Acute toxicity data are useful, because these data are more extensive and definitive than chronic toxicity data. The WDOE developed a toxicitybased classification matrix derived from EPA spill regulations (CFR 1997b) and the pesticide labeling system of the Federal Insecticide, Fungicide, and Rodenticide Act (CFR 1997c). The approach incorporated methods that were cost effective and adaptive to complex waste mixtures with multiple constituents, enabling hazardous waste generators to use existing toxicity data in the literature (book designation approach) or to perform laboratory testing (bioassay approach) to determine waste status. The book designation procedure utilizes concentration data for known waste constituents and four acute toxicity endpoints, including a fish median lethal concentration (LC50), rat oral median lethal dose (LD50), rat inhalation LC50, and a rabbit dermal LD50 (Table 2). These endpoints cover a variety of exposure pathways and incorporate surrogates for human and ecological receptors. Toxicity categories represent order of magnitude rankings for toxic endpoints. Acute toxicity data for known constituents in a

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waste, corresponding to the endpoints in Table 2, are compiled from the literature and the toxic category is determined for each known constituent. The “equivalent concentration” (EC), the sum of all known constituent concentrations normalized to the most toxic category (X), is then calculated as follows: EC (%) 5 (RX) 1 (RA/10) 1 (RB/100) 1 (RC/1,000) 1 (RD/10,000) where R(X,A,B,C,D) 5 sum of concentrations (%) of all known constituents in each toxic category. If EC $ 0.001% (10 ppm), the waste designates as hazardous waste. For example, if a waste has a single known constituent with a rat oral LD50 5 1 mg/kg, the constituent is Toxic Category A (Table 2), requiring a concentration of at least 0.01% (100 ppm) to designate the waste as hazardous (i.e., EC 5 0.01%/10 5 0.001%). It should be noted that certain wastes in RCRA were listed on the basis of toxicity with a rat oral LD50 , 50 mg/ kg, a rat inhalation LC50 , 2 mg/L, or a rabbit dermal LD50 , 200 mg/ kg (CFR 1997a). These correspond to toxic categories X, A, and B in the Washington state classification system (Table 2). Although most state toxic waste is book designated, a bioassay approach is adopted in certain cases. The laboratory test protocol specifies either a 14-day rat oral bioassay or a 96-hour salmonid fish bioassay with LD50 and LC50 endpoints, respectively (WDOE 1996a). The rat bioassay tests wastes at a concentration of 5,000 mg/kg, whereas the fish bioassay test wastes at 100 mg/L. These test concentrations correspond to the thresholds for book designation (Table 2). Actual tests are more meaningful than book designation for complex waste mixtures, because bioassays integrate chemical bioavailability and interactions among multiple constituents. The threshold for the fish LC50 endpoint for acute toxicity (Table 2) initially was established at 1,000 mg/L. By experience, it was found that the fish LC50 threshold (1,000 mg/L) was generally more stringent than the rat oral LD50 threshold (5,000 mg/kg). This observation was supported by our own analysis (Delistraty et al. 1998), which showed that the fish bioassay was approximately two orders of magnitude more sensitive than the rat oral bioassay for a selected group of chemicals (median rat oral LD50/median trout LC50 5 156, n 5 213). Interspecies variation in sensitivity to chemicals is related to taxonomic position (Hoekstra et al. 1994; Sloof et al. 1986; Suter et al. 1983) and associated toxicokinetic differences (Rozman and Klaassen 1996). Therefore, in order to more closely align these two test methods so as to encourage more fish bioassay testing of wastes, the fish LC50 threshold was decreased from 1,000 to 100 mg/L.

Persistence WDOE investigated other simple book designation and testing procedures to identify classes of compounds characterized by high environmental per-

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sistence. Regulatory limits were established for halogenated hydrocarbons and polycyclic aromatic hydrocarbons (PAHs) at 0.01% (100 ppm) and 1.0% (10,000 ppm), respectively. WDOE eventually incorporated standard EPA test methods (EPA 1986), as well as provided their own testing guidance for these compounds (WDOE 1998b).

Carcinogenicity WDOE adopted a list of carcinogens classified as known, probable, or possible carcinogens by the International Agency for Research on Cancer (IARC 1987) and the EPA (IRIS 1998). A regulatory threshold of 0.01% (100 ppm) was assigned to these compounds. Most wastes containing these carcinogenic compounds were evaluated with a book designation approach, rather than actual testing. It was later recognized that many of the carcinogenic compounds were regulated redundantly as hazardous waste by the state toxicity and persistence criteria, as well as by lists and characteristics in the federal RCRA program. Moreover, implementing the carcinogenicity criterion had proven difficult, because the carcinogen list was extensive, laboratory analyses were expensive, and test methods were unavailable or not standardized for many of these compounds. Therefore, WDOE deleted the carcinogen list from the state regulation. Regarding a potential relationship between carcinogenicity and acute toxicity, several studies have demonstrated strong correlations between cancer potency and acute toxicity in rodents (Parodi et al. 1982; Travis et al. 1990; Zeise et al. 1986). Our own analysis (Delistraty 1995) showed a significant correlation between rat oral LD50 and oral cancer slope factor (r 5 20.58, p , 0.0001, n 5 48). Although controversy relates as to whether these relationships are causal or spurious (Bernstein et al. 1985; Metzger et al. 1989; NRC 1993), these results supported a strategy to regulate carcinogens as hazardous waste based in part on acute rat oral toxicity. Benefits to Human Health and the Environment An analysis of hazardous waste data for the years 1989 to 1991 (WDOE 1994) confirmed that Washington state waste designation criteria captured a relatively large amount of waste not regulated by the RCRA (Table 3). Waste regulated solely by state criteria comprised approximately 36% of the total state plus federal hazardous waste reported. For the state waste fraction, toxicity was the dominant classification (93%), whereas persistence (4%) and carcinogenicity (1%) classifications were relatively minor. Cryolite waste, generated during aluminum production, comprised the major type of state-only hazardous waste in Washington, designated by the toxicity criterion. This wastestream approached approximately 50,000 tons annually (WDOE 1994). Other commonly designated wastes, captured

253 2,300 86,576 92,373 278,428

1989 104 1,818 51,313 55,109 127,500

1990 1,308 2,960 46,862 50,730 150,000

1991 555 2,359 61,584 66,071 185,309

Tons 0.8 3.6 93.2 100.0 NA

0.3 1.3 33.2 35.7 100.0

(% of Total State-Only Plus RCRA Waste)

Average for 1989 to 1991 (% of Total StateOnly Waste)

b

Recurrent refers to wastes from ongoing processes. Excluded are most wastewaters, wastes from clean-up projects, and radioactive mixed wastes. Data do not sum exactly due to double counting errors and state-only waste streams, which are not tabulated here (e.g., solid corrosives, polychlorinated biphenyls). NA 5 not applicable. Source: Adapted from WDOE (1992), WDOE (1994), and WDOE (1998c).

a

State-only carcinogenic State-only persistent State-only toxic Total state-onlyb Total state-only plus RCRA

Waste Type

Tons

TABLE 3. Recurrent Hazardous Waste Generation Reported in Washington State During 1989 to 1991a

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solely by the state’s toxicity criterion, included machine cooling fluid containing phenolic compounds, plating solutions containing nickel, sand blast grit containing copper, nickel, or benzene, hydraulic oil containing tributyl phosphate, waste water containing copper, nickel, or zinc, and oil and sludge containing metals and PAHs. The state persistence criterion captured additional hazardous waste, albeit markedly less than the toxicity criterion (Table 3). There were generally less than 2,000 tons of wastes reported annually in Washington that were designated as hazardous due solely to PAH content (WDOE 1994). Typical waste streams containing PAHs included coal tar pitch, creosote-treated wood, and tank pumpings. Similarly, there were less than 1,000 tons of waste reported annually in Washington that were designated as hazardous due solely to halogenated hydrocarbons (WDOE 1994). Typical wastestreams containing halogenated hydrocarbons included residuals from the manufacture of chlorine, wastewater sludge, and fiberglass, graphite, and kevlar wastes. These types of acutely toxic and persistent wastes can have adverse effects on human health and the environment. Many acutely toxic chemicals also exhibit chronic toxicity at lower concentrations (Eaton and Klaassen 1996; Kenaga 1982; Layton et al 1987), whereas persistent chemicals have long residence times and may bioaccumulate (Rozman and Klaassen 1996). It is therefore beneficial to manage waste streams with these properties as hazardous waste. This strategy reduces exposure of hazardous constituents to human and ecological receptors, thereby minimizing human health and ecological risk. We thank Curt Mehlhaff (University of Puget Sound) and Dennis Bowhay (WDOE) for preparing background documentation for this project, as well as for numerous insightful discussions. This work was supported by the Hazardous Waste and Toxics Reduction Program, Washington State Department of Ecology.

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