Handbook Of Pollution Control And Waste Minimization - Chapter 17 pptx

17 Risk-Based Pollution Control and Waste Minimization Concepts Gilbert J. Gonzales Los Alamos National Laboratory, Los Alamos, New Mexico and New Mexico State University, Las Cruces, New Mexico 1 INTRODUCTION Ecological risk assessment is defined as “the qualitative or quantitative appraisal of impact, potential or real, of one or more stressors (such as pollution) on flora, fauna, or the encompassing ecosystem.” The underlying principles behind risk reduction and integrated decision making that are detailed in U.S. Environmental Protection Agency (EPA) strategic initiatives and guiding principles include pollution prevention (1). Pollution control (PC) and waste minimization (WM) are probably the most effective means of reducing risk to humans and the environment from hazardous and radioactive waste. Pollution control can be defined as any activity that reduces the release to the environment of substances that can cause adverse effects to humans or other biological organisms. This includes pollution prevention and waste minimization. Waste minimization is defined as pollution prevention measures that reduce Resource Conservation and Recovery Act (RCRA) hazardous waste (2). Reduced risk is one benefit of these practices, and it results most directly from lower concentrations of contaminants entering the environment from both planned and accidental releases. Copyright 2002 by Marcel Dekker, Inc. All Rights Reserved. Although it is difficult to quantify the reductions in the release of contam- inants to the environment that have resulted from reductions in waste, the reductions have most assuredly reduced risk to humans and the environment posed by toxicants. Using examples from Los Alamos National Laboratory (LANL), we will discuss the interrelatedness of pollution prevention/waste min- imization with risk reduction and how risk assessment can be generally applied to the field of pollution prevention and waste minimization. While emphasis in this chapter is on “ecological risk assessment,” the concepts and principles can also be applied to human health risk assessment. For purposes of this chapter, distinction is not made between pollution prevention, waste minimization, re- cycling or other waste management techniques, and other related terms. Rather, emphasis is on source reduction, which includes any practice that reduces the amount of contaminant entering a waste stream or the environment. It is evident that the EPA’s hierarchy of general pollution prevention and waste minimization methods is implicitly related to risk reduction (2). The preferred method, source reduction, results in the greatest reduction in human and ecological risk from contaminants. Source reduction is followed in effectiveness by recycling, treatment, and disposal. While it is possible, depending on the technology used, that recycling and treatment may increase risk to worker health because of increases in contact handling of waste, the prioritized list (source reduction → recycling → treatment → disposal) generally results in a decrease in risk to the public and the environment as one progresses from the least preferred to the most preferred method. The reason for this is simple. The preferred method results in little, if any, release of contaminants into the environ- ment compared to the less preferred methods; with the less preferred methods, not only does the quantity of contaminants potentially released into the environ- ment increase, the potential to release them increases. With this premise, it is then important to realize the magnitude of risk reduction achieved by employing pollution prevention and waste minimization at facilities such as LANL. 2 SITE DESCRIPTION AND CHARACTERIZATION LANL is located in north-central New Mexico, approximately 60 miles northwest of Santa Fe (Figure 1). LANL is a U.S. Department of Energy-owned complex managed by the University of California that was founded in 1943 as part of the Manhattan Project to create the first nuclear weapon. Since then, LANL’s mission to design, develop, and test nuclear weapons has expanded to other areas of nuclear science and energy research. The Laboratory comprises dozens of individual technical areas located on 43 square miles of land area; about 1400 major buildings and other facilities are part of the Laboratory. The Laboratory is situated on the Pajarito Plateau, which consists of a series of fingerlike mesas separated by deep east-to-west–oriented Copyright 2002 by Marcel Dekker, Inc. All Rights Reserved. RIO ARRIBA COUNTY SANTA FE COUNTY 0 0.5 1 2 mi 0 0.5 1 2 km SANTA FE COUNTY SANDO- VAL CO. SANDOVAL COUNTY LOS ALAMOS COUNTY SANDOVAL COUNTY WHITE SANTA FE NATIONAL FOREST S A N T A F E N A T I O N A L F O R E S T BANDELIER NAT. MON. SAN ILDEFONSO PUEBLO LANDS Rio Grande ★ Taos Los Alamos Grants Albuquerque Socorro Las Cruces Santa Fe NEW MEXICO To Espanola To Santa Fe LOS ALAMOS COUNTY LOS ALAMOS COUNTY RIO ARRIBA COUNTY TAOS COUNTY SANDOVAL COUNTY SANTA FE COUNTY BERNALILLO COUNTY Tierra Amarilla Taos Los Alamos Santa Fe Bernalillo Albuquerque LOS ALAMOS COUNTY Pajarito R oad East Jemez Road Los Alamos National Laboratory Technical Area boundaries County boundaries Other political boundaries Major paved roads ROCK NM CO UT AZ TX OK cARTography by A. Kron 4/5/00 BANDELIER NATIONAL MONUMENT N 4 4 30 4 502 502 502 501 4 U. S. A. LOS ALAMOS FIGURE 1 Location of the Los Alamos National Laboratory. Copyright 2002 by Marcel Dekker, Inc. All Rights Reserved. canyons cut by intermittent streams (Figure 2). Mesa tops range in elevation from approximately 7800 ft on the flanks of the Jemez Mountains to about 6200 ft at their eastern termination above the Rio Grande. Researchers at Los Alamos work on initiatives related to the Laboratory’s central mission of enhancing global security as well as on basic research in a variety of disciplines related to advanced and nuclear materials research, devel- opment, and applications; experimental science and engineering; and theory, modeling, analysis, and computation. As a fully functional institution, LANL also engages in a number of related activities including waste management; infrastruc- ture and central services; facility maintenance and refurbishment; environmental, FIGURE 2 Overhead view of the topography in and around the Los Alamos National Laboratory. Copyright 2002 by Marcel Dekker, Inc. All Rights Reserved. ecological, cultural, and natural resource management; and environmental resto- ration, including decontamination and decommissioning. As result of the scien- tific and technical work conducted at Los Alamos, the Laboratory generates, treats, and stores hazardous, mixed, and radioactive wastes. About 2120 contaminant potential release sites (PRSs) have been identified at LANL. The LANL PRSs are diverse and include past material disposal areas (landfills), canyons, drain lines, firing sites, outfalls, and other random sites such as spill locations. Categorizing contaminants into three types—organics, metals, and radionuclides—Los Alamos has all three present. The contaminants include volatile and semivolatile organics, polychlorinated biphenyls (PCBs), asbestos, pesticides, herbicides, heavy metals, beryllium, radionuclides, petroleum prod- ucts, and high explosives (3). The primary mechanisms for potential contaminant release from the site is surface-water runoff carrying potentially contaminated sediments and soil erosion exposing buried contaminants. The main pathways by which released contaminants can reach off-site residents are through infiltration into alluvial aquifers, airborne dispersion of particulate matter, and sediment migration from surface-water runoff. Like many other sites, the predominant pathway by which contaminants enter terrestrial biological systems is the inges- tion of soil, intentional or not. Diverse topography, ecology, and other factors make the consideration of issues related to contamination in the LANL environment complex. “Since 1990, LANL’s environmental restoration project has conducted over 100 cleanups. The environmental restoration project has also decommissioned over 30 structures and conducted three RCRA closure actions during this period. Schedules have been published for the planned cleanup of approximately 700 to 750 additional sites. This schedule encompasses a period of about 10 years, beginning with fiscal year 1998. The number of cleanups per year varies from approximately 100 in fiscal year 2002 to 18 in fiscal year 2008. An important and integral part of this pollution prevention technology and of identifying interim protection measures is ecological risk assessment” (3). 3 POLLUTION PREVENTION AND WASTE MINIMIZATION AT LANL The pollution prevention program at the Laboratory has been successful in reducing overall LANL wastes requiring disposal by 30% over the last 5 years. The program is site wide but has facility-specific components, especially for the larger generators of radioactive and hazardous chemical wastes. Past reductions indicate that waste generation in the future should be less than that projected. The Site Pollution Prevention Plan for Los Alamos National Laboratory (4) describes the LANL Pollution Prevention and Waste Minimization Programs, including a general program description, recently implemented actions, specific volume Copyright 2002 by Marcel Dekker, Inc. All Rights Reserved. reductions resulting from recent actions, and current development/demonstration efforts that have not yet been implemented. More specifically, LANL has achieved reductions in the generation of hazardous waste, low-level radioactive waste (LLW), and mixed LLW. These and two other waste types are defined as follows: Hazardous waste—Any substance containing waste that is regulated by RCRA, the Toxic Substances Control Act, and New Mexico as a Special Waste. Low-level radioactive waste (LLW)—Radionuclide-containing substances with a radionuclide activity (sometimes referred to as concentration) of less than 100 nCi/g. Mixed LLW—Substances containing both RCRA constituents and LLW. Transuranic radioactive (TRU) waste—Radionuclide-containing substances with a radionuclide activity (concentration) equal to or greater than 100 nCi/g. Mixed TRU waste—Substances containing both RCRA and TRU waste. Estimated reduction rates of chronically generated waste, by waste type, over a 6-year period are (D. Wilburn, personal communication, 2000) Hazardous waste: 11%/yr (65% from 1993 to 1999) LLW: 11%/yr (67% from 1993 to 1999) Mixed LLW: 12%/yr (72% from 1993 to 1999) Production of TRU and mixed TRU waste combined has increased by an average of 38%/yr (228% from 1993 to 1999). The Laboratory has dozens of pollution prevention projects ongoing and planned. Some of the efforts are pollution prevention and waste minimization in the strictest sense and some (e.g., separation of waste types or satellite treatment followed by centralized treatment) are pollution control in the broadest sense, including efforts where cost savings is the primary goal and pollution control is a secondary benefit. Three examples of pollution control/waste minimization at LANL follow. Generator Set-Aside Fee-Funded (GSAF) Plutonium Ingot Storage Cubicle Project. “An aliquot casting and blending technique is under imple- mentation at LANLs Plutonium Facility. The aliquot process allows out-of-specification plutonium to be blended with other plutonium so that the final mixed batch meets specifications and is uniform. This avoids the cost and waste generation related to reprocessing out-of-specification plutonium ingots through the nitric acid line. In addition the more uniform product will reduce the reject rate and will avoid reprocessing and remanufacturing wastes. This project will fabricate a storage system Copyright 2002 by Marcel Dekker, Inc. All Rights Reserved. with 20 cubicles. It is expected that 12.5 m 3 of TRU waste can be avoided over the 25 year life of the cubicle system. This project has an estimated 100% return on investment when prior investments are included in the base project cost. This project is the final step necessary to achieve aliquot blending. The GSAF program is funding purchase of the storage cubicle and the operating group has programmatic support for installing and qualifying the cubicle.” GSAF Reduction of Acid Waste and Emissions. “The Laboratory’s Analyti- cal Chemistry Sciences Group’s performance of analytical services at one of the Laboratory’s technical areas requires the dissolution of up to 20,000 samples per year. The current process is hot plate digestion which requires large quantities of chemicals, mostly acids, and results in the volatilization and release to the atmosphere of 90% of those chemicals. The yearly consumption of HNO 3 , HCl, HF, HClO 4 and NH 4 OH is estimated to be 3395 kgs. About 3095 kgs of these chemicals are volatilized and become air emissions from the stacks; the balance is diluted and discharged to the Laboratory’s Radioactive Liquid Waste Treatment Facility via the LLW acid line. The stack emissions constitute about 30% of the Laboratory’s annual hazardous air pollutant discharges. By switching to a microwave and muffle furnace oven process, annual consumption of the chemicals listed above can be reduced to about 370 kgs, an 89% reduction. It is estimated that implementing the new process will reduce the Laboratory’s hazardous air pollution discharges by three tons. The estimated return on investment for this project is 82%.” Waste Minimization and Microconcentric Nebulization for Inductively Cou- pled Plasma-Atomic Emission Spectroscopy. “One of the most popular techniques for multi-element analysis is inductively coupled plasma atomic emission spectroscopy (ICP-AES). The most common method of introducing samples into the ICP torch is pneumatic nebulization. The standard nebulizers, in conjunction with typical spray chambers, exhibit very low transport efficiency. Because of this inefficiency the ICP-AES generates almost a liter per day of rinse water that consists primarily of dilute nitric acid mixed with other contaminants. The other contaminants can be TRU waste, LLW, mixed LLW or hazardous waste depending on the samples analyzed. Under this project an existing microconcentric nebulizer will be deployed with the ICP-AES and optimized for analysis of trace elements in a variety of plutonium-containing matrices. It is expected that using an optimized microconcentric nebulizer will reduce the daily rinse water from the spray chamber drain to about 50 ml. This represents a 95% or 200 l/yr reduction in the volume of waste requiring disposal. A 50 liter per year reduction in LLW plastic sample containers is expected. Reducing the volume of samples in the glovebox will Copyright 2002 by Marcel Dekker, Inc. All Rights Reserved. simplify the ICP-AES operation, reducing various risk parameters. The return on investment ranges from 10–50%.” 4 ECOLOGICAL RISK ASSESSMENT Ecological risk assessment is defined as “the qualitative or quantitative appraisal of impact, potential or real, of one or more stressors (such as pollution) on flora, fauna, or the encompassing ecosystem.” The Laboratory is employing the EPA’s iterative and tiered approach to ecological risk assessment whereby less complex assessments with greater conservatism and uncertainty are employed first, fol- lowed by the advancement of potential problem areas and contaminants to progressively more complex and realistic assessments with lower uncertainty. The purpose of this section is not to present ecological risk assessment methods, as there are many excellent sources on this subject (5–8). Rather, the purpose is to introduce concepts in ecological risk assessment that could be considered in designing pollution control and waste minimization programs. 4.1 History at the Los Alamos National Laboratory Ecological risk assessment (“ecorisk”) at the Laboratory is a work in progress. Methods for ecorisk screening and “tier 2” assessments have been in development and implementation since approximately 1993. Most screenings and assessments completed at the Laboratory thus far are based on the U.S. EPA hazard quotient method, whereby hazard quotient values are calculated for receptors for each contaminant by area and may be thought of as a ratio of a receptor’s exposure at the site to a safe limit or benchmark: HI i = ∑ j=1 n HQ ij (1) where HI i is the hazard index for receptor I to n contaminants of potential concern (COPCs), and HQ ij = exposure ij safe limit ij (2) where HQ ij is the hazard quotient for receptor I to COPC j exposure ij is the dose to receptor i for COPC j safe limit is an effects or no effects level, such as a chronic no-observed- adverse-effects level (NOAEL) Copyright 2002 by Marcel Dekker, Inc. All Rights Reserved. 4.1.1 Screening In 1995 a very conservative method for screening contaminants and contaminated areas was developed (9). The method involved the selection of ecological endpoints that focused on animal feeding guilds, a listing of candidate contami- nants, exposure/dose–response estimation, estimation of food and soil ingestion, and risk characterization. A comparison value or safe limit was based on foraging mode, behaviors, types of food consumed, the amount consumed, and NOAELs or radiation dose limits when available. The safe limits for radionuclides were largely laboratory-derived rat-based values used in human risk assessments. As such, this and the use of other conservative factors or assumptions resulted in a method that likely overestimated potential risk by orders of magnitude, espe- cially for radionuclides. At least one application of the method is known to have occurred (10). Currently at LANL, ecorisk screening encompasses qualitative “scoping evaluation” as the basis of problem formulation and “screening evaluation” to identify contaminants of potential concern (COPCs) by exposure media. The screening evaluation focuses on identifying sites that require further investigation and risk characterization (11). A key component to the screening evaluation, and one of interest to PC/WM, is the ecological screening level (ESL) concept. An ESL is basically a contaminant safe limit, or acceptable effects level, below which measurable effects are not expected. ESLs are most useful in units of contaminant amount per quantity of soil, so that measurements of contaminant levels in soil can be quickly and directly compared. The ESLs are developed for each ecolog- ical receptor of interest, each chemical, and are media specific. They are deter- mined so that if an area has levels of a chemical above the ESL in any medium, then the area is deemed to pose a potentially unacceptable risk to ecological receptors. Calculations of ESLs require toxicity information, including toxicity reference values (TRVs), preferably chronic NOAELs, and knowledge of transfer coefficients including bioconcentration and bioaccumulation factors. Details on this information and on the process for calculating and selecting ESLs are documented in a LANL report (11); however a summary is provided here. Nonradionuclides. “Although soil ESLs are based on exposure of terres- trial receptors—plants, invertebrates (earthworms), and wildlife—they are deter- mined differently for each receptor. The different approaches are required because of the different ways that toxicological experiments are performed for these organisms. For plants, earthworms and other soil-dwelling invertebrates, effects are based on the concentration of a COPC in soil. Therefore, ESL values are directly based on effects concentrations and modeling is not required. For plants and invertebrates the soil ESL was ‘back-calculated’ from No-Observed-Effect- Concentrations. Exposure to wildlife, however, is dependent on exposure of the organism to a chemical constituent from a given medium (such as soil or Copyright 2002 by Marcel Dekker, Inc. All Rights Reserved. foodstuff) through direct and indirect means (i.e., ingestion, inhalation, and dermal). Wildlife ESL values were based on the dietary regimen of the receptor, including consumption of plants, invertebrates, and vertebrate flesh, with some incidental soil ingestion (11).” The soil ESL was “back-calculated” as the soil concentration of a COPC resulting from exposure to the NOAEL. Starting with the EPA’s general terrestrial wildlife exposure model (12), inverting to convert soil concentration to dose, relating food intake to soil intake, and solving for COPC- and receptor-specific ESLs, models such as Eq. (3) for omnivores were used to compute ESLs for nonradionuclides: ESL ij = NOAEL ij I i ⋅(fs i + fp i ⋅ TF plant,j + fi i ⋅ TF invert,j (3) where ESL ij is the soil ESL for omnivore i and COPC j (mg/kg) NOAEL ij is the NOAEL for omnivore i and COPC j (mg/kg/day) fs i is the fraction of soil ingested by omnivore i, expressed as a fraction of the dietary intake I i is the normalized daily dietary ingestion rate for omnivore i (kg/kg/day) fp i is the fraction of plants in diet for omnivore i TF plant,j is a unitless transfer factor from soil to plants for COPC j fi i is the fraction of invertebrates in diet for omnivore i TF insect,j is a unitless transfer factor from soil to insects for COPC j For any given COPC, the soil ESL used for initial screening was often the lowest receptor-specific soil ESL value among plants, invertebrates, robin, kestrel, shrew, mouse, cottontail, and fox. Models were developed for sediment and water. More detail can be found in Ref. 11. Radionuclides. Radionuclide dose limits are the equivalent of the NOAELs used to develop nonradionuclide ESLs (11). For screening at LANL, radionuclide ESLs were based on the International Atomic Energy Agency (IAEA)-recommended dose limit of 0.1 rad per day (13). At LANL the radionu- clide dose to terrestrial biota was taken as the sum of the dose from internally deposited radionuclides and external dose from gamma emitting radionuclides in soil [Eq. (4)]. Total acceptable dose = 0.1 (rad/day) = internal dose + external dose (4) Detailed formulas can be found in Ref. 11. Conservative assumptions about the size of the organism, its diet, the geometry of the contaminated source, and the location of the receptor relative to the contaminated source are used by LANL for estimating internal and external doses for screening purposes. The internal dose Copyright 2002 by Marcel Dekker, Inc. All Rights Reserved. [...]... dinitrotoluene[2, 4-] Chlorophenol[ 2-] Benzo(a)pyrene 174 6-0 1-6 7 2-5 5-9 5 0-2 9-3 1267 2-2 9-6 7 2-2 0-8 2296 7-9 2-6 744 0-2 8-0 5 8-8 9-9 6 0-5 7-1 743 9-9 7-6 1109 6-8 2-5 1109 7-6 9-1 8 4-7 4-2 9 9-6 5-0 5346 9-2 1-9 14 3-5 0-0 7 6-4 4-8 744 0-2 2-4 9 1-2 0-3 11 7-8 1-7 744 0-6 2-2 11 8-9 6-7 8 7-8 6-5 1854 0-2 9-9 11 5-2 9-7 744 0-3 6-0 778 2-4 9-2 744 0-4 8-4 744 0-3 8-2 60 6-2 0-2 31 9-8 5-7 744 0-4 1-7 744 0-4 3-9 5 7-1 2-5 269 1-4 1-0 133 0-2 0-7 12 1-1 4-2 9 5-5 7-8 5 0-3 2-8 ... 8 3-3 2-9 744 0-4 7-3 1267 4-1 1-2 5 6-5 5-3 21 8-0 1-9 12 0-8 2-1 5 9-5 0-7 12 7-1 8-4 1940 6-5 1-0 742 9-9 0-5 743 9-9 6-5 744 0-6 1-1 8 8-7 2-2 12 1-8 2-4 744 0-4 2-8 9 1-5 7-6 3557 2-7 8-2 9 9-0 8-1 7 5-0 9-2 9 9-3 5-4 20 5-9 9-2 10 8-9 5-2 6 5-8 5-0 7 2-4 3-5 8 2-6 8-8 744 0-6 6-6 9 9-9 9-0 800 1-3 5-2 19 1-2 4-2 19 3-3 9-5 10 6-4 6-7 744 0-5 0-8 20 7-0 8-9 9 8-9 5-3 12 9-0 0-0 8695 4-3 6-1 1.80E+00 1.90E+00 2.10E+00 2.10E+00 2.20E+00 2.30E+00 2.50E+00 3.10E+00 3.20E+00... 1426 9-6 3-7 1396 8-5 5-3 1396 6-2 9-5 1511 7-9 6-1 1398 2-7 0-2 744 0-6 1-1 744 0-3 9-3 744 0-2 9-1 10 8-9 0-7 20 6-4 4-0 8 6-7 3-7 6 7-6 6-3 7 9-3 4-5 13 2-6 4-9 7 1-4 3-2 10 8-8 8-3 744 0-3 2-6 7 5-3 5-4 54 0-5 9-0 8 5-0 1-8 13 1-1 1-3 5 3-6 3-0 20 8-9 6-8 11 7-8 4-0 744 0-2 4-6 12 0-1 2-7 1009 8-9 7-2 8 5-6 8-7 1411 9-3 2-5 1019 8-4 0-0 1468 3-2 3-9 1396 7-7 0-9 1425 5-0 4-0 1.70E+01 1.70E+01 1.80E+01 1.90E+01 1.90E+01 2.00E+01 2.00E+01 2.00E+01 2.00E+01 2.00E+01... Di-n-octylphthalate Strontium Anthracene Strontium-90 + Yttrium-90 Butyl benzyl phthalate Plutonium-241 Cobalt-60 Europium-152 Cesium-134 Lead-210 Copyright 2002 by Marcel Dekker, Inc All Rights Reserved CAS no ESLb Rank 1398 1-1 6-3 1427 4-8 2-9 1511 7-4 8-3 1399 4-2 0-2 1559 4-5 4-4 1698 4-4 8-8 743 9-9 2-1 744 0-0 2-0 1398 2-6 3-3 1426 9-6 3-7 1396 8-5 5-3 1396 6-2 9-5 1511 7-9 6-1 1398 2-7 0-2 744 0-6 1-1 744 0-3 9-3 744 0-2 9-1 ... Methoxychlor[4,4 -] Pentachloronitrobenzene Zinc p-Nitrotoluene Toxaphene Benzo(g,h,i)perylene Indeno(1,2,3-cd)pyrene Dichlorobenzene[1, 4-] Copper Benzo(k)fluoranthene Nitrobenzene Pyrene Americium-241 Copyright 2002 by Marcel Dekker, Inc All Rights Reserved CAS no ESLb Rank 6 7-6 4-1 7 9-0 1-6 510 3-7 1-9 510 3-7 4-2 47 9-4 5-8 5 3-7 0-3 8 3-3 2-9 744 0-4 7-3 1267 4-1 1-2 5 6-5 5-3 21 8-0 1-9 12 0-8 2-1 5 9-5 0-7 12 7-1 8-4 1940 6-5 1-0 742 9-9 0-5 ... 5 0-3 2-8 1.80E-06 1.80E-03 2.80E-03 3.00E-03 3.40E-03 1.60E-02 3.30E-02 3.40E-02 4.10E-02 5.00E-02 5.00E-02 1.20E-01 1.30E-01 1.60E-01 1.60E-01 1.60E-01 1.80E-01 2.00E-01 2.00E-01 2.40E-01 2.50E-01 3.00E-01 3.20E-01 3.50E-01 3.50E-01 5.00E-01 5.00E-01 5.10E-01 5.70E-01 7.40E-01 9.70E-01 1.00E+00 1.00E+00 1.00E+00 1.00E+00 1.10E+00 1.20E+00 1.20E+00 1.80E+00 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19... Calcium Chloride Iron Lithium Magnesium Molybdenum Potassium Sodium Carbazole Dichloroethane[1, 2-] CAS no ESLb Rank 7 5-3 4-3 7 8-9 3-3 1396 6-3 2-0 7 1-5 5-6 7 8-1 1-5 1002 8-1 7-8 1526 2-2 0-1 744 0-7 0-2 1688 7-0 0-6 743 9-8 9-6 743 9-9 3-2 743 9-9 5-4 743 9-9 8-7 744 0-0 9-7 744 0-2 3-5 8 6-7 4-8 10 7-0 6-2 5.50E+02 7.30E+02 9.50E+02 1.00E+03 2.80E+03 1.40E+04 2.10E+04 3.50E+04 n/a n/a n/a n/a n/a n/a n/a n/a n/a n/a 124 125 126 127... rad rad rad rad Name Plutonium-238 Thorium-228 Plutonium-239/240 Neptunium-237 Thorium-229 Fluoride Lead Nickel Radium-226 Thorium-230 Uranium-233 Uranium-234 Uranium-235 Uranium-236 Uranium-238 Barium Thorium-232 Chlorobenzene Fluoranthene Fluorene Chloroform Tetrachloroethane[1,1,2, 2-] Dibenzofuran Benzene Toluene Titanium Dichloroethylene[1, 1-] Dichloroethylene[1, 2-] Phenanthrene Dimethylphthalate... Trichloroethene Chlordane[alpha-] Chlordane[gamma-] Tetryl Dibenz(a,h)anthracene Acenaphthene Chromium, total Aroclor-1016 Benzo(a)anthracene Chrysene Trichlorobenzene[1,2, 4-] Chloro-3-methylphenol[ 4-] Tetrachloroethene 4-amino-2,6-dinitrotoluene Aluminum Manganese Uranium o-Nitrotoluene RDX Boron Methylnaphthalene[ 2-] 2-amino-4,6-dinitrotoluene m-Nitrotoluene Methylene chloride sym-Trinitrobenzene Benzo(b)fluoranthene... Tetrachlorodibenzodioxin[2,3,7, 8-] DDE[4,4 -] DDT[4,4 -] Aroclor-1248 Endrin Mercury (methyl) Thallium BHC[gamma-] Dieldrin Mercury (inorganic) Aroclor-1260 Aroclor-1254 Di-n-butylphthalate m-Dinitrobenzene Aroclor-1242 Kepone Heptachlor Silver Naphthalene Bis(2-ethylhexyl)phthalate Vanadium Trinitrotoluene[2,4, 6-] Pentachlorophenol Chromium VI Endosulfan Antimony Selenium Cobalt Arsenic dinitrotoluene[2, 6-] BHC[beta-] Beryllium . Tetrachlorodibenzodioxin[2,3,7, 8-] 174 6-0 1-6 1.80E-06 1 pest DDE[4,4 -] 7 2-5 5-9 1.80E-03 2 pest DDT[4,4 -] 5 0-2 9-3 2.80E-03 3 pcbs Aroclor-1248 1267 2-2 9-6 3.00E-03 4 pest Endrin 7 2-2 0-8 3.40E-03 5 inorg Mercury. Aroclor-1260 1109 6-8 2-5 5.00E-02 11 pcbs Aroclor-1254 1109 7-6 9-1 1.20E-01 12 svocs Di-n-butylphthalate 8 4-7 4-2 1.30E-01 13 he m-Dinitrobenzene 9 9-6 5-0 1.60E-01 14 pcbs Aroclor-1242 5346 9-2 1-9 1.60E-01 15 pest. Kepone 14 3-5 0-0 1.60E-01 16 pest Heptachlor 7 6-4 4-8 1.80E-01 17 Inorg Silver 744 0-2 2-4 2.00E-01 18 pahs Naphthalene 9 1-2 0-3 2.00E-01 19 svocs Bis(2-ethylhexyl)phthalate 11 7-8 1-7 2.40E-01 20 inorg