Comments of. Jeffery A. Foran, Ph.D. EHSI, LLC Whitefish Bay, WI. Draft U.S. EPA Human and Ecological Risk Assessment of Coal Combustion Wastes

Transcription

1 Comments of Jeffery A. Foran, Ph.D. EHSI, LLC Whitefish Bay, WI On the Draft U.S. EPA Human and Ecological Risk Assessment of Coal Combustion Wastes (6 August 2007) Prepared for Earthjustice th St., 6 th Floor Oakland, CA February 2008

2 Table of Contents Introduction 1 Human Health Risk Assessment 3 Inclusion All Exposure Pathways 4 Concurrent Exposure via Multiple Pathways 6 Concurrent Exposure to Multiple Contaminants 7 Inclusion of Exceptional Exposure Patterns 9 Ecological Risk Assessment 10 Inclusion of all Exposure Pathways 10 Ecological Criteria 11 Failure to Protect Threatened and Endangered Species 13 Concurrent Exposure to Multiple Contaminants and other Stressors 15 Inclusion of all CCW Constituents in the ERA 16 Other Issues 17 Choice of Percentiles and Risk Levels 17 Risk Attenuation Factors 18 Inclusion of all CCW Constituents in the Risk Assessment 20 Direct Releases to Surface and Groundwater 21 Community Participation in the Risk Assessment 22 Recommendations 24 Table 1 29

3 Introduction The U.S. EPA assessed the human and ecological risks of coal combustion waste (CCW) deposited in landfills and surface impoundments to determine whether CCW disposal practices pose unacceptable risks to human health and the environment. The risk assessment was designed to develop national human and ecological risk estimates associated with CCW management settings and practices in the U.S. These comments address the draft Human and Ecological Risk Assessment for Coal Combustion Wastes prepared for the U.S. EPA by RTI, Int., Research Triangle Park, NC. Human health (HHRA) and ecological risk assessments (ERA) were built upon probabilistic estimates of the release, transport, and fate of CCW constituents from landfills and surface impoundments. Probabilistic estimates of CCW concentrations in environmental media surrounding coal-fired utility power plants were developed and compared with concentrations that pose elevated or unacceptable risks to human and ecological receptors. 1

4 The analysis was intended to characterize waste management scenarios based on two management options (disposal of CCW onsite in landfills and in surface impoundments) and three waste types (conventional coal combustion waste CCW; co-disposed CCW and coal refuse, and fluidized-bed combustion wastes FBC). CCW transport and fate estimates were associated with leaching to groundwater and overland transport to surface waters. The draft report (RTI 2007) identified highly elevated and unacceptable risks to humans, non-human organisms, and ecological systems from the disposal of CCW in landfills and surface impoundments. For example, cancer risks associated with exposure to CCW constituents are as high as the risks of: Smoking a pack of cigarettes per day Breathing air with a radon concentration 20 times the safe level Consuming water contaminated with vinyl chloride at 20 times the acceptable risk level and 10 times the EPA maximum contaminant level - MCL (the EPA MCL- Goal for vinyl chloride is 0). The ecological risks of constituents in CCW are also extremely high. For example, Concentrations of arsenic and selenium are 10 times higher, concentrations of lead are 20 times higher, and concentrations of boron are 2000 times higher than levels that are safe for non-human organisms and ecosystems. 2

5 However, these human and ecological risk levels underestimate actual risks associated with disposal of CCW as a result of several significant errors and omissions in the risk assessment. Errors and omissions include failure to: Address all exposure pathways in human and ecological risk assessments Consider and address concurrent exposure to CCW constituents via multiple pathways (routes) Consider and address concurrent exposure to multiple contaminants Consider and include exceptional exposure scenarios in the HHRA Rely upon fully protective ecological criteria Address and protect threatened and endangered species Address and incorporate consideration of multiple stressors in ERA EPA also: Chose percentiles and risk levels that are not fully protective of public health Relied inappropriately on attenuation factors to assess (and dismiss) risk of some CCW constituents Failed to include all appropriate CCW constituents in the full-scale risk assessment Failed to include direct releases to ground- and surface water in the risk assessment Failed to include input and participation of affected stakeholders in the development of the risk assessment. 3

6 As a result of these failures and omissions, the report underestimates human and ecological risks associated with exposure to CCW constituents. Additional information about each of these issues is provided below. Human Health Risk Assessment EPA conducted cancer and non-cancer risk assessments of CCWs using a standard, multi-step approach for two exposure pathways groundwater to drinking water, and groundwater to surface water (consumption of contaminated fish). For humans exposed to CCW constituents via the groundwater-to-drinking-water pathway, arsenic in landfills poses a 90th percentile cancer risk of 5x10-4 for unlined units and 2x10-4 for clay-lined units. The 50th percentile risks are 1x10-5 (unlined units) and 3x10-6 (clay-lined units). Cancer risks are considerably higher for arsenic in surface impoundments, with 90 th percentile risks as high as 9x10-3 for unlined units and 3x10-3 for clay-lined units. At the 50th percentile, arsenic cancer risks for unlined surface impoundments are 3x10-4, and 9x10-5 for clay-lined units. Boron, cadmium, molybdenum and other CCW constituents have 90th percentile noncancer risks above an HQ of 1 (considered safe or acceptable) for unlined surface impoundments. For humans exposed via the groundwater-to-surfacewater (fish consumption) pathway, selenium (non-cancer) and arsenic (cancer) pose unacceptable 90 th percentile health risks. 4

7 These projections, while in some cases extremely elevated, underestimate human health risks associated with exposure to CCWs as a result of several significant errors and omissions in the human health risk assessment. Inclusion of all Exposure Pathways The full-scale human health risk assessment for CCWs was developed for two exposure pathways consumption of contaminated drinking water and consumption of contaminated fish from surface water. While EPA indicated that above ground pathways were considered (soil ingestion, inhalation, and consumption of produce, beef, and milk), these exposure routes were examined via a screening analysis 1 and, as a result, excluded from the full-scale risk assessment. EPA suggests in the screening analysis (Figure 1-1 and elsewhere) that inhalation exposure from above-ground pathways was considered for risk assessment purposes, although risks for this pathway did not reach unacceptable levels; therefore, the aboveground pathway was not included in the full scale HH risk assessment. This may be a significant error as EPA apparently used oral ingestion rather than inhalation as the route for above ground exposure to CCW constituents (EPA, personal communication, indicated that it did not have access to data on air concentrations of CCW constituents near waste management units - WMUs). While details of risk estimate derivation in the screening analysis are not available (EPA, personal communication, did not complete 1 RTI. Constituent Screening for Coal Combustion Waste. Prepared for the Office of Solid Waste, U.S. EPA, Research Triangle Park, NC. October Contract #68-W

8 Appendix I in the screening analysis, which was to provide such detail), it appears that use of oral ingestion for compounds such as chromium VI (a known human carcinogen by the inhalation route) may have resulted in an under-estimate of cancer risk from this constituent and inappropriate elimination of it from the full scale HH risk assessment. Rather, chromium VI was evaluated as a non-carcinogen (Table 3-1 in the screening analysis and Table 2-3 in the draft risk assessment) and EPA concluded that it did not pose an unacceptable human health risk. Similarly, it appears that EPA did not consider inhalational exposures for barium, beryllium, boron, and manganese, even though RfC s (reference concentrations for inhalational exposures) have been published for each of these substances, nor was inhalation considered for other toxicants including lead, cadmium, and zinc, among others, which likely occur in dust and other erosion sources from WMUs. Finally, EPA did not consider the input of CCW constituents from air to surface water systems with accumulation of constituents in water and aquatic biota, posing a threat to human health as well as ecological systems. Recommendation 1: The full-scale risk assessment should be conducted by assessing exposure via all pathways concurrently, including the above-ground pathway. In particular, evaluation of chromium VI as a human carcinogen via inhalation, as well as all non-carcinogens where inhalation exposure may occur (above ground pathway) must be conducted as part of the full-scale risk assessment to fully quantify the cancer and noncancer risks to individuals who inhale dust from nearby WMUs. EPA should also include the above-ground pathway as an input source to surface water systems, with consideration for accumulation of CCW constituents in water and in aquatic biota, and human exposure as a result of direct contact and consumption of aquatic biota. 6

9 Concurrent Exposure via Multiple Pathways EPA chose to separate assessments of risk associated with exposure to CCWs from consumption of contaminated drinking water and consumption of contaminated fish. This separation is inappropriate, as individuals living near WMUs and who harvest and consume fish will also consume drinking water derived from groundwater. EPA addresses this issue by suggesting that concurrent exposure to CCW constituents should be considered as an uncertainty in the analysis. While it is feasible that some anglers may consume CCW-contaminated fish and not consume CCW-contaminated drinking water (e.g., those that fish within but live outside the watershed in which the WMU is located), there is no rationale for the elimination of the potential for concurrent exposure from drinking water and fish consumption in a probabilistic exposure or risk analysis, which is designed to incorporate such considerations not as uncertainties but as components of an exposure distribution. Failure to consider concurrent exposure via consumption of drinking water and fish results in a considerable underestimation of human health risk. EPA also does not consider exposure through contact with contaminated surface water systems, nor does the draft report incorporate consideration of human harvest and consumption of aquatic plants such as wild rice. Exposure via these routes and sources may be particularly important among some indigenous peoples; thus, risk is underestimated as a result of failure to include these exposure routes. 7

10 Recommendation 2: EPA should conduct the full-scale human health risk assessment by including consideration of concurrent exposure to CCW constituents via consumption of groundwater and fish. EPA should also include consideration of concurrent exposure to CCW constituents via surface water contact and consumption of aquatic biota (e.g., aquatic plants) in combination with consumption of fish and drinking water. Concurrent Exposure to Multiple Contaminants EPA fails to consider the health risks of concurrent exposure to multiple contaminants, whether from single or multiple sources, although the agency acknowledges this issue in the section on uncertainty by stating that: the waste concentration data on CCWs (as well as recent field studies) suggest that exposure to multiple constituents is highly likely. The synergism or antagonism between different constituent combinations may elicit unexpected adverse impacts to humans and ecosystems. Hence, a single-constituent analysis may underestimate risks associated with multiple chemical stressors. Indeed, incorporation of risks of concurrent, multiple contaminant exposure will have significant implications not only for the full-scale risk assessment but also for decisions (inclusion and exclusion of contaminants) based on the results of the screening analysis. Assessment of health risks associated with concurrent exposure to multiple contaminants, and assumption that their effects/risks are additive requires that contaminants in the mixture share a common mechanism of toxicity by eliciting the same critical effect, the 8

11 same biochemical action, or the same target tissue of an affected organism. EPA did not evaluate the toxicity of CCW constituents to determine whether some or all cause similar adverse effects via one or more of these criteria. For example, EPA failed to acknowledge that chronic (independent) exposure to thallium, selenium, and molybdenum each cause alopecia in rodents (the same critical effect). Similarly, exposure (independently) to aluminum, manganese, and lead cause adverse effects on the central nervous system (potentially by the same biochemical mechanism), and exposure to aluminum and barium cause nephrotoxicity (same target tissue). EPA has not addressed this issue in any comprehensive fashion nor included assessment of joint toxicity in the risk assessment or the screening analysis. The likely result of this omission is that some CCW constituents excluded from the full scale risk assessment should be included, and health risks included in the current draft document are underestimates of risk to humans exposed to more than one CCW constituent. Recommendation 3: EPA must conduct the full-scale HH risk assessment for all CCW constituents for which adequate toxicity benchmarks exist and incorporate additivity as the default assumption to calculate risk estimates for concurrent exposure to CCW constituents. Inclusion of Exceptional Exposure Patterns EPA conducted the risk assessment for the fish consumption pathway based on consumption patterns of recreational anglers, assuming that these individuals represent the most highly exposed fish consumers. EPA states that only recreational anglers were 9

12 considered because they represent the reasonable maximum exposed individuals and because the streams, lakes, or rivers that are near CCW plants are not likely to be used by commercial fishing operations. However, subsistence fish consumers (e.g., Native harvesters) have significantly higher fish consumption rates than recreational anglers; thus, exclusion of consumption rates that reflect subsistence consumption patterns will result in an underestimate of consumption and of exposure to contaminants in fish. Recommendation 4: EPA must conduct the full-scale human health risk assessment by incorporating fish consumption rates that are representative of subsistence fish consumers such as Native American populations that harvest and consume fish as part of their native traditions and culture. Ecological Risk Assessment Ninetieth percentile risks associated with exposure to CCWs in landfills are elevated for boron (HQ = 200) and lead (HQ = 4) for ecological receptors exposed to CCW constituents via surface water (groundwater to surface water pathway). For surface impoundments, 90 th percentile risks for boron are extremely elevated (HQ = 2,000), while risks for lead, arsenic, cobalt, selenium, and barium are above acceptable levels (HQ > 1). While projections of ecological risk for several CCW constituents are elevated to unacceptable levels, these projections underestimate true ecological risks as a result of several significant errors and omissions in the ecological risk assessment. 10

13 Inclusion of all Exposure Pathways Above-ground pathway analysis was not conducted for any ecological receptor, even though boron and selenium pose above-ground risks to ecological systems including surface water systems. EPA states that, because the risks posed by these constituents to ecological communities via above-ground pathways are well documented in damage cases and field studies, we did not believe that a full-scale above-ground pathway analysis was necessary to confirm this conclusion for two constituents. Recommendation 5: While a decision not to reproduce existing ecological risk assessments for boron and selenium is understandable, the risks themselves must be reported fully in the document to ensure that the ecological risks from all CCW constituents is properly characterized and conveyed. Further, above-ground pathways should be assessed to determine the risk to ecological systems, including surface water systems, posed by CCW constituents via this pathway. Ecological Criteria EPA states in the draft risk assessment document that: Because CSCLs (chemical stressor concentration limits) were based on de minimis ecological effects, it is generally presumed that an HQ at or below 1 indicates a low potential for adverse ecological effects for those receptors included in the analysis for which data are available. However, it is important to 11

14 recognize that although this method provides important insight into the potential for adverse ecological effects, the results are relevant only to those receptors that were included in the assessment and for which data were available. The results have limited utility in interpreting the ecological significance of predicted effects, and caution should be exercised in extrapolating to ecosystems (e.g., wetlands) and receptors (e.g., threatened and endangered species) not explicitly modeled. EPA is correct in urging caution regarding the use of CSCLs and their limited utility in interpreting the ecological significance of predicted effects and their ability to predict effects on ecosystems. Ecological risk values used in the CCW assessment are based on the theory that protection of 95 percent of the species in the community will provide a sufficient level of protection for the community. EPA also assumes that: ecological criteria tend to be fairly conservative because the overall approach is based on no- effects or lowest-effects study data. In site-specific assessments, a de minimis effects approach is often replaced with an effects level similar to natural population variability (e.g., sometimes as high as a 20 percent effects level). As a result, the CSCLs used in this analysis are likely to overestimate risks for representative species and communities assumed to live in surface waters impacted by CCW WMUs. Because the difference between a lowest observed adverse effect level (LOAEL) and a NOAEL is often about a factor of 10, an HQ exceedance of roughly 10 may not be ecologically significant. In contrast, CSCLs 12

15 based on no effects data that are developed for the protection of threatened and endangered species are presumed to be protective. Here, EPA is grossly incorrect. Reliance upon ecological criteria that are assumed to be protective of 95% of the organisms in the toxicity database will result in contaminant concentrations that impose significant toxicity to aquatic and terrestrial organisms. Ecological criteria are calculated by taking the geometric mean of laboratory-derived NOAELs and LOAELs (to derive a maximum acceptable toxicant concentration - MATC); thus, some toxicity is expected since a criterion based on the MATC will be above the no-adverse-effect-level for a contaminant. This conclusion was confirmed by Suter s examination of the relationship between the MATC and effect levels for over 90 chemicals in 18 freshwater fish species. The MATC for these chemicals was associated with significant reductions in both parental survival and fecundity. Smaller but important reductions were also observed in larval survival, weight, and hatching success. A comparison of the MATC with the EC25 (effective concentration at which 25% of test organisms exhibited an adverse response) showed that the average MATC/EC25 ratio was greater than 2.0; thus, the ecological criteria (and CSCLs) are not, in fact, protective of fish populations. While a similar analysis has not been conducted for invertebrate biota, it is likely that criteria would be similarly under-protective. Further, sole reliance on laboratory-derived toxicity data fails to incorporate vast amounts of information from field studies of the ecological effects of compounds such as selenium. In many cases, field studies document adverse effects of a single contaminant at levels below laboratory- 13

16 derived toxicity data, likely as a result of concurrent exposure to other contaminants and other stressors (discussed below) in ecological systems. Recommendation 6: Until an approach to calculate ecological criteria is developed that is fully protective of communities and ecosystems, EPA should invoke a more conservative approach to assessing ecological risks associated with CCW constituents. Such an approach should include consideration of risk at the 95 th or 99 th percentile levels, as well as assessment of concurrent exposure to multiple contaminants and noncontaminant stressors. It should also incorporate information and data derived from field studies of individual and groups of contaminants and give this information primacy over laboratory-derived data where they demonstrate adverse effects at lower levels. Failure to Protect Threatened and Endangered Species Reliance upon ecological criteria is limited by the exclusion of toxicity data that address and are protective of threatened and endangered species. EPA acknowledges that the assessment of threatened and endangered species requires a site-based approach in which locations, habitats, and species of concern are identified and characterized with respect to the spatial scale of constituent releases. Such an analysis was not conducted for the CCW ecological risk assessment. Indeed, the report states that data limitations and other information suggest the possibility that threatened and endangered species or critical habitats may be at risk from CCW constituents. 14

17 In particular, data were not available to derive chronic effect CSCLs for amphibians. EPA suggests in the draft report that risk results can only be interpreted within the context of available data; thus, the absence of data does not necessarily indicate that adverse effects (on amphibian populations) will occur. It is remarkable, however, that EPA reverses itself (appropriately) later in the document by stating that: Recent studies have confirmed that amphibians are among the most sensitive taxa to metals found in CCW, and selenium appears to be a significant stressor in CCW disposal scenarios. The endpoints considered in these studies were related to population sustainability and, consequently, are highly relevant to ecological risk assessment. Recommendation 7: EPA must assess ecological risk by incorporating consideration of threatened and endangered species and by including field and other information on amphibians and other biota for which traditional ecological risk criteria are not available. Concurrent Exposure to Multiple Contaminants and other Stressors Ecological criteria address toxicity posed only by single chemical contaminants and are derived from laboratory toxicity data (NOAELs and LOAELs) gathered under ideal conditions. Criteria do not account for toxicity that may occur as a result of exposure to more than one contaminant concurrently, or to contaminants in combination with other stressors (e.g., habitat alteration, disease state, food limitation, elevated or lowered temperatures). There is abundant evidence that multiple (chemical and non-chemical) 15

18 stressors act to influence the structure and function of aquatic ecosystems. For example, the diversity and abundance of aquatic species in Newark Bay Estuary have been reduced by multiple chemical, biological, and physical impacts associated with industrialization and urbanization. Similarly, numerous biological, physical, and chemical factors (nutrient loading, contamination by heavy metals and persistent organic contaminants, solids loadings, and invasion of exotic species) are responsible for the deterioration of Green Bay, Lake Michigan. An organism s sensitivity to a toxicant may be increased where other stressors are acting concurrently with toxicity associated with chemical exposure; thus, the true criterion (protective in combination with other stressors) may be significantly lower than a single chemical criterion (CSLC) derived under ideal conditions. The U.S. EPA Ecological Risk Assessment Guidelines cite the importance of identifying and evaluating the adverse effects of biological, physical, and chemical stressors in ecosystems and on their components, and guidance has been provided for the assessment of multiple stressors in ecosystems. However, no such approach was used in the draft ecological risk assessment for CCW constituents. Recommendation 8: The ecological risk assessment must be conducted by incorporating risks of concurrent exposure to multiple contaminants and concurrent effects of multiple stressors that commonly occur in natural ecosystems. Inclusion of all CCW Constituents in the Ecological Risk Assessment 16

19 EPA indicates that resources did not allow full-scale ecological risk modeling of 6 constituents - chromium, vanadium, beryllium, copper, silver, and zinc. These constituents had surface water pathway HQs in the screening analysis ranging from 16 to 110 for landfills, and four (chromium, vanadium, copper, and silver) had screening HQs ranging from 14 to 33 for surface impoundments. It is remarkable, and unwarranted, that the CCW constituents with hazard quotients 10 to 100 times acceptable (safe) levels are not considered adequately hazardous to warrant a full scale risk assessment of their effects on ecological systems. Recommendation 9: The full-scale ERA must include all CCW constituents, regardless of HQs established in a screening analysis, but particularly where constituent HQs are above acceptable levels (HQ > 1). Other Issues Choice of Percentiles and Risk Levels EPA has not taken a conservative or protective approach in its choice of risk levels and exposure/risk percentiles for the human and ecological risk assessments. EPA chose a cancer risk level of as a benchmark to define acceptable risk. However, a more stringent cancer risk level of is appropriate and has been used in many cases. In light of the significant deficiencies in the risk assessment (as described throughout this document), and in light of the significant national implications for health risks of 17

20 exposure to CCW constituents, EPA should choose a more conservative cancer risk level of for decisions regarding inclusion or exclusion of CCW constituents in the risk assessment as well as other decisions that are based on a cancer risk levels. Similarly, EPA has presented 90 th percentile exposure and risk estimates for humans and ecological receptors. It is more appropriate to present risks at the 95 th percentile, particularly where a public health approach to assessment and decision-making is used and where median (50 th percentile) risk levels are also presented. In fact, EPA has established a precedent through its use of 95 th percentile risk estimates in variety of risk assessments following the U.S. EPA Administrator s 2 recommendation that the agency present information on the ranges of exposures and the use of multiple risk descriptors including the high end of individual risk, the central tendency, and risks for important subgroups. The high end of the risk distribution is, conceptually, above the 90 th percentile of the (exposure or risk) distribution (emphasis added). Recommendation 10: In light of the significant deficiencies in the human and ecological risk assessments and in light of the national implications for risk-based decisions regarding the management of CCW constituents, EPA should base all decisions regarding cancer on a risk level of Further, in recognition of the public health significance of risks associated with CCW constituents and following established EPA policy (as well 2 Guidance on Risk Characterization for Risk Managers and Risk Assessors - F. Henry Habicht, Deputy Administrator, U.S. EPA. 26 February

21 as recommendations of the National Academy of Sciences 3 ), the agency should report non-cancer risks as follows: Worst Case Assume maximum exposure scenarios including exposure 24 hours/day, 365 days/year for 70 years; High End 95 th percentile based on national human activity pattern distributions; Central Tendency 50 th percentile (or median) risk based on national human activity pattern distributions. Risk Attenuation Factors Five CCW constituents (chromium, fluoride, manganese, vanadium, and nickel) had adequate human health data, and six constituents (chromium, vanadium, beryllium, copper, silver, and zinc) had ecological risk data available to conduct a full-scale risk assessment but were excluded from the assessment via the screening risk assessment (Table 1). EPA attempted to address these constituents with surrogate risk attenuation factors, which were developed by dividing screening risk results for constituents modeled in the full-scale risk assessment by risks for those same constituents developed from fullscale assessment. Screening level risks for the excluded constituents were then divided by 10 th percentile or 50 th percentile attenuation factors to determine whether results would exceed risk criteria (HQ > 1). EPA suggests that differences in attenuation among the modeled constituents reflect differences in contaminant sorption and mobility (e.g., the 10th percentile attenuation factor was selected as a conservative value representing the more mobile constituents such as arsenic, selenium, and molybdenum; the 50th percentile attenuation factor represents a central tendency value). Use of a 10th percentile risk attenuation factor reduced (EPA terminology) human health risk 3 Committee on Risk Assessment of Hazardous Air Pollutants, Board on Environmental Studies and Toxicology, Commission on Life Sciences, National Research Council. Science and Judgment in Risk Assessment, National Academy Press, Washington, D.C

22 estimates to acceptable levels (HQ < 1) for only one (nickel) of the five constituents. Tenth percentile attenuation factors reduced ecological risk estimates to acceptable levels (HQ < 1) for only two (beryllium and zinc) of six excluded constituents. The rationale for use of attenuation factors to compare risks between screening and fullscale assessments is not provided in the report, there is no background support for the approach, nor is there an intuitive basis for such a comparison. The approach does not account for the cumulative risk of concurrent exposure to excluded constituents from multiple pathways (drinking water and fish consumption). Each screening risk estimate is also limited by the same problems associated with risk estimates generated from the full-scale analysis, as they were generated using the same methodology. As such, they likely underestimate true risk and, therefore, reduction of the estimates via attenuation factors is inappropriate. Recommendation 11: All CCW constituents should be assessed via the full-scale analysis, and reliance on attenuation factors to estimate risk should be eliminated from the analysis. Inclusion of all CCW Constituents in the Risk Assessment Thirty-six CCW constituents were identified and of those, EPA determined that human health or ecological benchmarks were either inadequate or unavailable for 14, which were not addressed in the risk analysis (Table 1, this report). Of the remaining 22 constituents with adequate health or ecological benchmarks, 9 were excluded from the risk assessment based on the screening analysis and 12 were included in the full-scale 20

23 probabilistic risk assessment (Table 1). Mercury was excluded from the screening and full-scale analyses because of the high number of non-detects in the CCW database. Notable among the constituents excluded from the risk assessment based on inadequate benchmarks are sulfate, phosphate, and chloride, which pose significant ecological hazards. Also notable among constituents excluded as a result of the screening analysis were seven with ecological HQs one to two orders of magnitude greater than acceptable levels (HQ = 1) including chromium, vanadium, beryllium, copper, nickel, and zinc. Silver, with an HQ one hundred times greater than an acceptable level was also excluded from the full-scale analysis. The only rationale that EPA provides for excluding these compounds is that resources did not allow full-scale modeling to be conducted for all 21 constituents that had 90th percentile risks above the screening criteria. The draft report indicates that aluminum was included in the full-scale human health risk assessment for CCW wastes. However, results of the HH risk assessment for aluminum are not reported in tables or figures in the draft report, and EPA reports in the screening analysis that the human health HQ for aluminum is less than one; thus, it appears that EPA did not include aluminum in the full-scale human health risk assessment (although it was included in the ecological risk assessment). The screening risk assessment document and the draft full-scale risk assessment indicate that the reference dose used in the analysis for aluminum was 2.0 mg/kg/day, based on a 2002 ATSDR intermediate risk value. However, the 2007 ATSDR intermediate and chronic duration risk values for aluminum are 1.0 mg/kg/day. Had EPA used 1.0 mg/kg/day in the screening analysis, it 21

24 is likely that an HQ for aluminum would have been greater than 1 and evaluation via the full-scale human health risk assessment would be warranted. Recommendation 12: As result of these deficiencies, human and ecological risks are likely underestimated in the draft HHRA and ERA. Therefore, EPA should conduct the full-scale risk assessment for all CCW constituents for which there are adequate human or ecological benchmarks. Further, EPA should conduct a thorough review of the literature to ensure that it is using the most recent benchmarks for each contaminant, including aluminum. Direct Releases to Surface and Groundwater CCW releases, and hence media concentrations and risk estimates, are based on leaching to groundwater and, for surface water systems, infiltration of contaminated groundwater to surface water systems. The analysis does not incorporate inputs from direct discharges to groundwater (e.g., injection), to surface waters from surface impoundments (e.g., point source discharges and flooding), or from point and nonpoint sources not directly related to WMUs. These discharges can be a significant source of CCW contaminants to surface water, as evidenced by numerous NPDES permits issued to CCW surface impoundments and the documented discharge of elevated levels of contaminants, such as arsenic and selenium, to surface waters from CCW surface impoundments. As a result, estimated media concentrations and risks do not account for contributions from permitted releases or discharges that result from storm water runoff and flooding. Concentrations of CCW constituents will be underestimated in ground- and surface water systems where those 22

25 systems also receive point and non-point source discharges of constituents from sources other than groundwater infiltration. Risk estimates will, therefore, also be underestimated. Recommendation 13: Direct discharges to ground- and surface water systems from all sources (e.g., direct injection to groundwater, point and nonpoint discharges to surface water systems) should be considered sources of CCW constituents to groundwater and surface systems. Inputs from these sources should be combined with CCW inputs from leaching to groundwater to calculate the full load of CCW constituents to groundwater and surface water systems. Community Participation in the Risk Assessment There is no indication in the draft risk assessment that community members participated in any meaningful way in its development. Yet, it is these individuals who will ultimately be affected by CCW risks and decisions that address amelioration of risks. Community participation is becoming a standard component in the development of human health and ecological risk assessments, and such participation is both warranted and necessary as EPA pursues development of risk assessments for CCW wastes. Recommendation 14: As EPA continues development and revision of the CCW constituent risk assessment, the agency should create an advisory committee composed of affected individuals and other stakeholders associated with the management of CCW. The Committee should be an active participant in every aspect of the risk assessment, 23

26 development of decisions based on the risk assessment, and implementation of those decisions. 24

27 Recommendations Recommendation 1: The full-scale risk assessment should be conducted by assessing exposure via all pathways concurrently, including the above ground pathway. In particular, evaluation of chromium VI as a human carcinogen via inhalation, as well as all non-carcinogens where inhalation exposure may occur (above ground pathway) must be conducted as part of the full-scale risk assessment to fully quantify the cancer and noncancer risks to individuals who inhale dust from nearby WMUs. EPA should also include the above ground pathway as an input source to surface water systems, with consideration for accumulation of CCW constituents in water and in aquatic biota, and human exposure as a result of direct contact and consumption of aquatic biota. Recommendation 2: EPA should conduct the full-scale HH risk assessment by including consideration of concurrent exposure to CCW constituents via consumption of groundwater and fish. EPA should also include consideration of concurrent exposure to CCW constituents via surface water contact and consumption of aquatic biota (e.g., aquatic plants) in combination with consumption of fish and drinking water. Recommendation 3: EPA must conduct the full-scale HH risk assessment for all CCW constituents for which adequate toxicity benchmarks exist and incorporate additivity as the default assumption to calculate risk estimates for concurrent exposure to CCW constituents. 25

28 Recommendation 4: EPA must conduct the full-scale HH risk assessment by incorporating fish consumption rates that are representative of subsistence fish consumers such as Native American populations that harvest and consume fish as part of their native traditions and culture. Recommendation 5: While a decision not to reproduce existing ecological risk assessments for boron and selenium is understandable, the risks themselves must be reported fully in the document to ensure that the ecological risks from all CCW constituents is properly characterized and conveyed. Further, above-ground pathways should be assessed to determine the risk to ecological systems, including surface water systems, posed by CCW constituents via this pathway. Recommendation 6: Until an approach to calculate ecological criteria is developed that is fully protective of communities and ecosystems, EPA should invoke a more conservative approach to assessing ecological risks associated with CCW constituents. Such an approach should include consideration of risk at the 95 th or 99 th percentile levels as well as assessment of concurrent exposure to multiple contaminants and noncontaminant stressors. It should also incorporate information and data derived from field studies of individual and groups of contaminants and give this information primacy over laboratory-derived data where they demonstrate adverse effects at lower levels. 26

29 Recommendation 7: EPA must assess ecological risk by incorporating consideration of threatened and endangered species and by including information on amphibians and other biota for which traditional ecological risk criteria are not available. Recommendation 8: The ecological risk assessment must be conducted by incorporating risks of concurrent exposure to multiple contaminants and concurrent effects of multiple stressors that occur in natural ecosystems. Recommendation 9: The full-scale ERA must include all CCW constituents regardless of HQs established in a screening analysis, but particularly where constituent HQs are above acceptable levels (HQ > 1). Recommendation 10: In light of the significant deficiencies in the human and ecological risk assessments and in light of the national implications for risk-based decisions regarding the management of CCW constituents, EPA should base all decisions regarding cancer on a risk level of Further, in recognition of the public health significance of risks associated with CCW constituents and following established EPA policy (as well as recommendations of the National Academy of Sciences), the agency should report non-cancer risks as follows: Worst Case Assume maximum exposure scenarios including exposure 24 hours/day, 365 days/year for 70 years; High End 95 th percentile based on national human activity pattern distributions; Central Tendency 50 th percentile (or median) risk based on national human activity pattern distributions. 27

30 Recommendation 11: All CCW constituents should be assessed via the full-scale analysis, and reliance on attenuation factors to estimate risk should be eliminated from the analysis. Recommendation 12: As result of deficiencies presented in this report, human and ecological risks are likely underestimated in the draft HHRA and ERA. Therefore, EPA should conduct the full-scale risk assessment for all CCW constituents for which there are adequate human or ecological benchmarks. Further, EPA should conduct a thorough review of the literature to ensure that it is using the most recent benchmarks for each contaminant, including aluminum. Recommendation 13: Direct discharges to ground- and surface water systems from all sources other than groundwater infiltration (e.g., direct injection to groundwater, point and nonpoint discharges to surface water systems, etc.) should be considered sources of CCW constituents to groundwater and surface systems. Inputs from these sources should be combined with CCW inputs from leaching to groundwater to calculate the full load of CCW constituents to groundwater and surface water systems. Recommendation 14: As EPA continues development and revision of the CCW constituent risk assessment, the agency should create an advisory committee composed of affected individuals and other stakeholders associated with the management of CCW. The Committee should be an active participant in every aspect of the risk assessment, 28

31 development of decisions based on the risk assessment, and implementation of those decisions. 29

32 Table 1. Constituents identified in CCW and considered for risk assessment. Benchmark Screening Constituents Aluminum Excluded 1 Excluded 2 Included 3 * Ammonia Antimony Arsenic Barium Beryllium Boron Cadmium Calcium Carbon Chloride Chromium Cobalt Copper Cyanide Fluoride Iron Lead Magnesium Manganese Mercury** Molybdenum Nickel Nitrate/Nitrite Phosphate Potassium Selenium Silicon Silver Sodium Strontium Sulfate Sulfide Sulfur Thallium Vanadium Zinc Other constituents: ph, total dissolved solids, total organic carbon, dissolved organic carbon 1. Constituents without adequate or appropriate health or ecological benchmarks 2. Constituents eliminated from the full-scale assessment as a result of screening. 3. Constituents included in the full-scale risk assessment. * Assessed via ecological risk assessment only (not assessed for human health risks) ** Mercury not addressed because of high proportion of non-detects in CCW database. 30

33 GEO-HYDRO, INC Consulting in Geology and Hydrogeology 1928 E. 14 th Avenue Denver, Colorado (303) February 11, 2008 Notice of Data Availability on the Disposal of Coal Combustion Waste in Landfills and Surface Impoundments Environmental Protection Agency Mailcode: 5305T 1200 Pennsylvania Ave., NW Washington, DC Re: Docket ID No. EPA-HQ-RCRA Dear Administrator Johnson: These comments are intended to supplement the comments of Jeffrey A. Foran regarding the Draft USEPA Human and Ecological Risk Assessment of Coal Combustion Wastes submitted to you on February 11, In the course of preparing his comments, Dr. Foran expressed concerns regarding the fate and transport assumptions and modeling upon which the risk assessment relies and suggested that Sections 3.2 through 3.5 be reviewed by people with an appropriate modeling experience to provide comment. Dr. Foran s concerns were called to our attention. Geo-Hydro, Inc., (GHI) has reviewed Sections 3.2 through 3.5 and offers the following comments: Use of EPACMTP as Groundwater Model The authors of the risk assessment devote the introductory comments of Section 3.2 as a defense of EPACMTP in an attempt to create the impression that EPACMTP (full-scale or lite version) is capable of generating results upon which a meaningful risk assessment can be founded. The preponderance of that defense is that it is a program that has historically been used for such purpose and that the program has been coded properly to reflect its underlying assumptions. The problems with EPACMTP, of course, are well known and are not with the program coding, but with the assumptions that are coded into the program. In recent years, the shortcomings of EPACMTP are increasingly recognized. GHI participated in 1999 in a major review of EPACMTP (Norris and Hubbard, 1999). The results of that review were provided to USEPA as part of the public comment for the 2000 Regulatory Determination for CCWs, and it should not be necessary to belabor those findings. That report is incorporated by reference. The authors of this draft risk assessment cite two documents published subsequent to the Norris and Hubbard review, implying that the cited documents further establish the efficacy of

34 GEO-HYDRO, INC EPACMTP. In fact, if one critically reads either of the cited documents, USEPA, 1999, or SAB, 2004, it is clear they are anything but ringing endorsements of EPACMTP. The USEPA, 1999, document, among other shortcomings of EPACMTP points out that results of the program have been tested against only 4 sites in the entire history of reliance upon the program. The SAB, 2004, establishes that few among the board members rank EPACMTP as either best available technology for groundwater modeling or even the appropriate technology for regulatory purposes. Particularly problematic with using EPACMTP as a foundation for this risk assessment is that where EPACMTP fails, the failure will almost invariably result in underestimating risk, not overestimating risk. Beyond the problems identified by Norris and Hubbard, critical failings of EPACMTP with respect to modeling impacts to groundwater include the following: EPACMTP cannot simulate a scenario where the leachate from disposal setting changes the basic chemistry of the aquifer receiving the leachate. CCW can be highly alkaline and create ph plumes downgradient of the disposal settings. It is well established that ph has a major impact on the mobility of many CCW-associated contaminants, particularly oxyanions. EPACMTP cannot simulate variable Eh conditions in either leachate or leachateimpacted aquifer water. Like ph, Eh has is a major control on contaminant mobility, and Eh also has a major control on changing the toxicity of elements such as arsenic and chromium, which depends upon valent speciation. EPACMTP cannot evaluate the effect of contaminant-plume mobilization of non-waste related metals from the aquifer itself due to altered aquifer water quality. For example, simply increasing aquifer ph can mobilize oxyanions of arsenic or selenium in the aquifer completely independently of the presence or concentration of those contaminants in the leachate. EPACMTP cannot consider either pre-existing occupation of adsorption sites in the aquifer by naturally occurring metals or competition for remaining sites by multiple contaminants from the waste disposal area. EPACMTP is programmed to assume that every potential adsorption site is fully available initially and is invariably available for each leachate contaminant, without regard to competition from other contaminants. EPACMTP cannot simulate scenarios where the waste is disposed within the underlying aquifer, a disposal scenario that is definitely not unusual in the case of CCW disposal. EPACMTP allows high infiltration rates to produce mounding in the underlying aquifer. However, any such mounding does not correspondingly reduce the thickness of the unsaturated zone; the unsaturated zone and its attendant attenuation remain constant. The only effect of mounding in EPACMTP is to increase the flow gradient, and hence rate, in the aquifer. As a result, mounding beneath a waste disposal unit due to a strong recharge through the waste unit has the curious effect in EPACMTP calculations of reducing 2

35 GEO-HYDRO, INC plume concentrations over the non-mounding scenario due to higher dilution produced by the gradient increase in the aquifer. EPACMTP cannot simulate anything but the simplest of geologic and hydrogeologic conditions. For example, the only system that can be defined is one with no changes in geologic or hydrogeologic properties no matter how far from the disposal site. Another example is that EPACMTP cannot simulate groundwater flow in fractured rock. EPACMTP can accept only a single leachate composition. CCW mineralogy and leachate chemistry are known to evolve with time as the waste strives to reach equilibrium with the disposal environment. These are processes that cannot be simulated with this program. This is not a total list of the failings of EPACMTP. However, in each of these examples, the effect of the failure is that EPACMTP will compute a lower concentration in the plume at any given point in space and time than would a realistic model. By relying on EPACMTP, a risk assessor evaluates a scenario with an inappropriately low assessment of risk. The results of this draft human and ecological risk assessment must be filtered with the understanding that the realworld risks are greater than reported because the assessments relied upon the computations of EPACMTP. Source Term Model The use of EPACMTP requires the deterministic assignment of concentrations in the waste unit for leachate that is discharging to the groundwater environment. As noted in the discussions of the modeling, One of the most sensitive parameters in the risk assessment is infiltration rate. (Pg 4-39) In EPACMTP program logic, this is numerically equivalent to saying that source-term concentration is one of the most sensitive parameters in the risk assessment. The determination or estimation of the contaminant concentrations in the leachate for each, or any, waste disposal unit is a non-trivial problem, but absolutely fundamental to the results. The method by which the source-term concentration was determined for input into EPACMTP is ambiguous as described in the draft risk assessment. Appendix A discusses the development of the source-term concentrations. Particularly important are the limited discussions in Section A.2.3 and the information in Table A-4. Table A-4 (pg. A-5) appropriately recognizes that not all leachate composition determinations are equal. In particular, it is recognized that of the available methods, the standard laboratory index tests such as TCLP and SPLP are the least representative of leachate that will form from a given CCW, even though these tests produce the majority of the available data. Having acknowledged that the most abundant data are the least reliable, however, it appears from the cursory discussion in A.2.3 that the data acknowledged as least reliable will control the 3