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Impending IRIS Updates - Potential Impacts on Site Cleanup


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Impending IRIS Updates - Potential Impacts on Site Cleanup

  1. 1. Impending IRIS Updates Potential Impacts on Site Cleanup <br />Florida Chamber<br />Environmental Permitting Summer School <br />July 22, 2010<br />Chris Saranko, PhD, DABT<br />Environmental Planning Specialists <br /><br />
  2. 2. Overview<br />The toxicological properties of several of the most widespread and problematic chemicals dealt with at waste cleanup sites in Florida are under consideration by the EPA’s IRIS program – potentially resulting in more stringent cleanup requirements<br />Regulation of carcinogens – the crux of the problem<br />Linear vs. non-linear modes of action<br />Florida’s statutory target risk limits<br />Chemicals affected<br />Inorganic Arsenic<br />Hexavalent Chromium<br />Polycyclic Aromatic Hydrocarbons (PAHs)<br />2,3,7,8-TCDD (Dioxin)<br />
  3. 3. EPA’s IRIS Program<br />IRIS – Integrated Risk Information System<br />Widely used resource for information on the effects of chemicals on human health<br />Database for EPA “toxicity factors” used by EPA and state environmental agencies (including FDEP) in human health risk assessments and risk-based screening levels<br />High profile re-assessments have historically moved at a snail’s pace<br />The current administration has made a commitment to expedite this process<br />
  4. 4. New IRIS Process – 5/09<br />Total: 23 Months<br />
  5. 5. Cancer - Linear or Non-Linear?<br />EPA Guidelines for Carcinogen Risk Assessment (updated 2005)<br />Long-awaited changes recognizing that all chemical carcinogens are not created equal<br />Provided guidance for the agency to consider a chemicals “mode of action” (MOA) in determining:<br />Whether or not that MOA is relevant to humans; and<br />If relevant, which dose-response models are most appropriate to characterize potential cancer risks to humans (the linear vs. non-linear argument)<br />EPA has been reluctant to meaningfully implement these guidelines<br />
  6. 6. Florida’s Statutory Requirements<br />F.S. §§ 376.30701, 376.81<br />In establishing soil cleanup target levels for human exposure to each contaminant found in soils from the land surface to 2 feet below land surface, the department shall apply the following, as appropriate: calculations using a lifetime cancer risk level of 1.0E-6; a hazard index of 1 or less; and the best achievable detection limit. However, the department shall not require site rehabilitation to achieve a cleanup target level for an individual contaminant that is more stringent than the site-specific, naturally occurring background concentration for that contaminant. <br />
  7. 7. Arsenic<br />Naturally occurring and widely dispersed - 20th most abundant element<br />Found in fossil fuels at low levels – concentrated in combustion wastes (e.g. coal ash)<br />Historically used in agriculture<br />Common chemical of concern for site assessment and remediation<br />
  8. 8. Health Basis for Arsenic Regulation<br />Arsenic regulated by EPA as a carcinogen<br />EPA toxicity values based on human exposure to arsenic in drinking water<br />In the later half of the 20th century, aid organizations worked to bring clean drinking water to people in rural south and east Asia<br />Many residents of this region previously drank from surface water sources with high bacterial loads<br />This region has high levels of natural arsenic (50 – 3,000 ppb)<br />Chronic health effects took years to appear <br />Extent of problem only recently became clear (~60 million people affected)<br />Long-term (chronic) health effects<br />Skin lesions, Blackfoot disease<br />Cancer (skin, liver, lung)<br />
  9. 9. Chronic Arcinosis<br />
  10. 10. EPA Arsenic Regulatory Activities<br />Ext. Draft IRIS <br />Oral CSF<br />(Lung / Bladder)<br />Standard<br />50 ppb<br />MCL <br />50 ppb<br />MCL <br />10 ppb<br />Final IRIS<br />Value<br />IRIS Oral CSF<br />(Skin Cancer)<br />Draft IRIS <br />Tox. Review <br />June<br />2010<br />Feb <br />2010<br />April<br />2010<br />2001<br />1999<br />201?<br />1998<br />1976<br />1942<br />2007<br />2005<br />SAB As<br />Workgroup<br />SAB<br />Review<br />NAS Report<br />(50 not health protective)<br />Full SAB Meeting<br />
  11. 11. Draft EPA Cancer Slope Factor <br />EPA Office of Water is lead agency<br />Oral CSF<br />Current value = 1.5 per mg/kg-day<br />Proposed value = 27.5 per mg/kg-day <br />“Theoretical” Drinking Water Risks<br />Current 1×10-4 cancer risk - 2 ppb<br />Proposed 1×10-4 cancer risk - 0.1 ppb<br />Theoretical risk from Arsenic at 10 ppb MCL = 1.1 ×10-3 <br />Proposed changes to CSF not likely to have an imminent effect on MCL<br />~18-Fold Higher!<br />
  12. 12. Impacts to Soil Screening Levels <br />Revised Soil Screening Levels <br />FDEP (1E-06 target risk, using bioavailability)<br /><ul><li>Residential SCTLs = 0.1 mg/kg (currently 2.1)
  13. 13. Industrial SCTLs = 0.7 mg/kg (currently 12) </li></ul>EPA (1E-06 target risk, no bioavailability)<br /><ul><li>Residential RSL = 0.02 mg/kg (currently 0.4)
  14. 14. Industrial RSL = 0.09 mg/kg (currently 1.6)</li></ul>Both residential and industrial values are below natural background levels across Florida<br />Potentially below detection limits<br />
  15. 15. Natural Background As Levels in FL Soils<br />Ma et al., 1997<br />
  16. 16. Arsenic Bioavailability<br />University of Florida “monkey study”<br />FDEP adopted a 33% bioavailability factor<br />Site-specific studies can be placed at UF (~$50k)<br />Bioavailability can’t counter 18X toxicity change<br />
  17. 17. Flaws in IRIS Tox Review<br /><ul><li>Fails to appropriately consider mode of action data
  18. 18. Does not consider negative cancer data in animals and weak or negative epidemiological studies
  19. 19. Low-dose Danish cohort (Bastrup et al. 2008)
  20. 20. No association between arsenic and lung, bladder, kidney, liver, prostate, or colorectum cancer.
  21. 21. Potential exposure misclassification in the epi data used to generate the cancer slope factor
  22. 22. Epi studies relied upon do not adequately control for smoking</li></li></ul><li>Harsh Critiques<br />Sam Cohen, MD, PhD (University of Nebraska)<br />“Based on the 2005 cancer guidelines as well as the evolving mode of action/human relevance framework, at the very least the EPA should be evaluating the dose response relationship based on a non-linear, threshold approach, not resorting to a default of linear, non-threshold. Such a default assumption for arsenic-induced cancer is no longer scientifically tenable.” <br />Susan Griffin, PhD (EPA Region 8 toxicologist)<br />“I regret to inform you that we can not concur with the final arsenic file…”<br />“Not only was the 20-fold increase in the oral slope factor unexpected and bewildering, it didn’t make any sense from an actual exposure perspective (e.g., dietary intake of arsenic now represents a 10-3 cancer risk)”. <br />
  23. 23. Time Frame<br />At June meeting, full SAB referred the review back to the SAB As Workgroup for additional consideration of issues raised in public comments<br />Unclear how much longer SAB review could take<br />Changes would be immediate for soil cleanup at EPA lead sites <br />FDEP changes would require Chapter 62-777, F.A.C. revision<br />MCL changes (if any) years away<br />
  24. 24. Chromium<br />Naturally occurring - 21th most abundant element<br />Average concentration in earth’s crust 100 ppm (lower in FL)<br />Oxidation (valence) state is critical !!<br />Chromium III <br />Most abundant and stable in environment<br />Almost non-toxic (industrial soil SCTL 1,000,000 ppm)<br />Chromium VI<br />Almost all chromium ore is processed to Chromium VI compounds<br />Carcinogen (industrial soil SCTL 470 ppm – based on inhalation)<br />
  25. 25. Chromium (VI) as a Carcinogen<br /><ul><li>CrVI Known human carcinogen by inhalation route
  26. 26. New animal studies from NTP indicate it can induce cancers following oral administration
  27. 27. NJ and CA have developed oral cancer slope factors for CrVI
  28. 28. NJ cancer slope factor applied in EPA RSL table (starting 12/09)
  29. 29. Re-evaluation of epidemiological data by Cal-EPA suggests carcinogen by oral route
  30. 30. EPA IRIS reassessment is underway
  31. 31. Current IRIS Track schedule indicates final assessment in Q4 2010 – Not Possible</li></li></ul><li>Impacts to Soil Screening Levels <br />Revised Soil Screening Levels – CrVI<br />EPA (1E-06 target risk, based on NJ CSF, includes mutagenic adjustment factor)<br /><ul><li>Residential RSL = 0.29 mg/kg
  32. 32. Industrial RSL = 5.6 mg/kg</li></ul>FDEP (1E-06 target risk, assuming NJ CSF)<br /><ul><li>Residential SCTLs = 2.1 mg/kg (currently 210)
  33. 33. Industrial SCTLs = 12 mg/kg (currently 470) </li></ul>Comparisons with Background<br />Residential values are below natural background levels across Florida<br />Industrial values higher or lower than background depending on area<br />
  34. 34. Natural Background Cr Levels in FL Soils<br />Chen et al. 1999<br />
  35. 35. Issues for Site Investigation<br /><ul><li>Comment from Georgia EPD regulator:</li></ul>“note that the screening levels for chromium have been revised in the most recent update to the Regional Screening Levels (RSLs) (EPA 2010). The revised screening levels for hexavalent chromium are based on an oral carcinogenic slope factor from the state of New Jersey. EPA is in the process of updating our IRIS toxicity assessment for hexavalent chromium (due by September 2010), and in the interim, the RSL table is recommending the New Jersey value as a Tier 3 value for screening purposes. If the sample data exceed the RSL based on analysis of total chromium, reanalysis of soil samples for hexavalent chromium should be done in order to fairly estimate the health risks. “<br /><ul><li>Problem is…. all Cr is above residential RSL
  36. 36. Speciation in every sample can significantly raise investigation costs </li></li></ul><li>Polycyclic Aromatic Hydrocarbons (PAHs)<br />
  37. 37. Benzo(a)pyrene – The Sentinel PAH<br />Binds to DNA - Mutagenic<br /><ul><li>Six other Carcinogenic PAH
  38. 38. All have same mechanism of action
  39. 39. Each has a cancer potency factor “relative” to B(a)P
  40. 40. RPF = Relative Potency Factor
  41. 41. RPF of 0.1 = 10x less potent than B(a)P</li></ul>Metabolic activation<br />
  42. 42. Draft EPA Guidance for RPFs <br /><ul><li>External draft guidance issued February 2010
  43. 43. Benzo(a)pyrene still reference compound
  44. 44. All of the existing RPFs changed – all but one went up
  45. 45. EPA added 18 new compounds to the list of “carcinogenic” PAHs
  46. 46. Several with very large RPFs (up to 60)
  47. 47. Public listening session held April 2010
  48. 48. Numerous negative comments
  49. 49. This guidance has a lower threshold for approval (no IRIS changes involved)
  50. 50. Final guidance pending – exact date and modifications (if any) uncertain</li></li></ul><li>Proposed Relative Potency Factors <br />Effect will be to increase the equivalent concentration of B(a)P in environmental samples<br />EPA Guidance Addresses Additional PAHs<br />Many have no established analytical methods<br />
  51. 51. Dioxins / Furans<br />Viktor Yushchenko President of Ukraine <br />Before and after dioxin poisoning<br />
  52. 52. Dioxins / Furans - Background <br /><ul><li>Dioxins = polychlorinated dibenzo-p-dioxins or PCDDs.
  53. 53. 75 structurally-related chemicals, or congeners
  54. 54. Furans = polychlorinated dibenzo-p-furans or PCDFs.
  55. 55. 134 structurally-related PCDF congeners
  56. 56. As with PAHs, risk currently assessed through RPF approach with 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD).</li></li></ul><li>Updated Dioxin Assessment (5/10) <br /><ul><li>Dioxin is the poster child for long-running EPA assessments
  57. 57. EPA Issued the initial Draft Dioxin Reassessment in 2000
  58. 58. In various stages of review by the National Academies of Science (NAS) and revision by the EPA since then
  59. 59. Most recently… EPA issued “Reanalysis of Key Issues Related to Dioxin toxicity and Response to NAS Comments” (May 2010)
  60. 60. 690 pages without appendices
  61. 61. In this document EPA has once again defaulted to a linear, no-threshold approach to set a cancer slope factor
  62. 62. Controversial because of dioxin’s well characterized mode of action</li></li></ul><li>Implications of Proposed Dioxin CSF <br /><ul><li>No current IRIS value – FDEP uses value from the discontinued Health Effects Assessment Summary Tables (HEAST) from the late 1990s
  63. 63. HEAST value = 1.5E+5 per mg/kg-day
  64. 64. Proposed CSF = 1E+6 per mg/kg-day (slightly more conservative)
  65. 65. Revised FDEP SCTLs?
  66. 66. Residential = 1 ng/kg (ppt) (currently 7 ppt)
  67. 67. Industrial = 5 ng/kg (currently 30 ppt)
  68. 68. Both are at or below anthropogenic background levels in most areas</li></li></ul><li>EPA Guidance for Mutagens<br />Supplemental Guidance for Assessing Susceptibility from Early Life Stage Exposure to Carcinogens (EPA 2005)<br />Age-Dependent Adjustment Factors (ADAFs)<br />New Safety Factor for carcinogens that act through a mutagenic mode of action<br />Only applicable for exposures involving children<br />EPA lists 12 mutagenic compounds where this factor should be applied (PAHs and Cr VI included)<br />Impact will be to reduce cleanup targets for mutagens by approximately 3-fold for residential values<br />
  69. 69. Implications for Florida Sites<br />Exact timeframe for these changes at federal level is currently uncertain<br />Some more imminent than others<br />Arsenic / PAHs > Chromium VI > Dioxin<br />Even less certainty with FDEP<br />62-777 will be re-opened eventually, but when?<br />Dealing with these uncertainties at new sites with one or more of these chemicals will be a challenge<br />
  70. 70. Questions??<br />