Bkg dioxin 2010 san antonio c sandau
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Bkg dioxin 2010 san antonio c sandau Bkg dioxin 2010 san antonio c sandau Presentation Transcript

  • Case Study to Establish Background Soil Concentrations of PCDD/Fs Dioxin 2010 Conference in San Antonio, Texas – September 14, 2010 Presented By: Court D. Sandau, PhD, PChem
  • Introduction
    • Examine background dioxin levels in local area
      • No publications for Alberta levels
      • Some studies have been done for clients – data on background levels not publicly available
    • Hidden agenda:
      • Clients dealing with dioxin contaminated sites that need to know what background is
      • Examine background dioxin levels in local vicinity
  • What are PCDD/F?
    • Aromatic compounds with multiple chlorine groups (1 to 8)
    • 75 different congeners – “Dioxins”, PCDDs
    • 135 different congeners – “Furans”, PCDFs
    1 2 3 4 9 6 8 7 6 8 9 4 1 3 2 7
  • Sources of PCDD/Fs
    • Not produced intentionally and no known uses
    • Can be natural produced in forest fires ( abstract 1374 ) and volcanic activity
    • By-products of combustion when chlorine is present (e.g. medical or municipal waste incineration, barrel burning, diesel) ( abstract 1477 )
    • By-products during chemical manufacturing (e.g. PCP, 2,4,5-T, PCBs, etc.)
    • By-products of industrial process (e.g. steel mills, coal combustion, wood treatment, etc.)
    • Pulp and paper bleaching process – historically a major source
  • Ubiquitous
    • Found in measurable concentrations everywhere (in remote areas)
    • Local point sources contribute to concentrations
    • Redistribution and deposition via atmospheric transport
    • Concentrations vary dramatically in the environment
  • ToXICITY
    • Toxicity based on binding to Ah-receptor
    • Effects mediated by a receptor binding mechanism
    • Only 2,3,7,8 chlorine containing congeners bind with Ah-R
    • Therefore, 17 congeners measured routinely
    • 2,3,7,8-TCDD binds with highest affinity
  • teqS
    • Each of the 17 congeners bind with different affinity to the AhR
    • The binding affinity is represented by the toxic equivalency factor for that congener (TEF) relative to the 2,3,7,8-TCDD affinity (given a value of 1)
    • e.g. TEQ = sum of all ([congener] x TEF)
  • ND in TEQs?
    • What about NDs?
      • For risk assessment, ½ DL is standard procedure
      • If CDC, use DL / (2) 0.5
          • e.g. DL/2 x TEF for that congener
    • Artificially elevated concentrations (poster 266)
  • What’s the issue?
    • Canadian Council of Ministers of the Environment (CCME) reevaluating guidelines (as is EPA)
    • Current CCME guidelines are de minimus values based on “background” concentrations from studies in Canada (1990s)
    US EPA – Review of International Soil Levels for Dioxin, 2009 International Screening Levels and Action Levels
  • Summary of Detection limits in Study Establishing CCME Guidelines
    • Studies had high DLs
    • Artificially elevated total TEQs
  • What’s the issue?
    • Canada has a very low screening level
      • Likely due to large areas of uninhabited areas which makes it difficult to establish background level
      • Old methodologies with high DLs
    • Background concentrations vary for locations ( abstract 1162 – Huntley et al )
    • Therefore, what is background?
      • Where concentrations drops below 4 pg/g TEQ?
      • Certain distance away from local source?
      • No distinctive signature?
  • Additional issues
    • PCDD/F analysis is very expensive ($500-$1200)
    • Establishing background is expensive
      • What is considered background?
    • Non-detects cause overestimation of TEQ issues
    • Levels measured are very low
      • Scientific notation for ppt is 1x10 -12
      • For reference:
        • ppt is equal to pg/g (solids) and ng/L (solutions)
    • Watch for cross contamination (cow pies)
  • Goals of Study
    • Evaluate true background PCDD/F concentrations in Alberta
      • “ True ” background – away from roads, known sources, atmospheric collection areas (i.e. trees, buildings)
    • Examine patterns of PCDD/Fs in background samples
  • Methodology
    • Advantageous sampling
    • Cleaning sampling equipment
    • QA-QC samples
    • Temperature monitoring
    • Data review
    • Detection limit assessment
  • Study Summary
    • 36 samples from around southern Alberta
    • Locations were chosen based on:
      • advantageous sampling
      • land access public lands (or known land owners)
      • undisturbed
      • no known sources
      • away from major roads
  • Locations
    • Sundre
    • Cochrane
    • Airdrie
    • Strathmore
    • Okotoks
    • Brooks
    • Medicine Hat
  • Sampling Locations
  • Detection Limit Issues (10 vs 100 grams)
    • Standard EPA procedures call for 10 gram subsample
    • Increasing sample size lowered DLs
    • TEQs 33% lower for 100 gram samples (because of NDs)
    • TEQs for 100 gram samples more dependent on measured congeners
    0 0.1 0.2 0.3 0.4 2 3 5 29 30 35 Sample ID Conc. (pg/g) 10g 100g 42 23 92 71 72 56 Soil Total TEQ (pg/g) 99 95 100 100 54 13 % TEQ from ND congeners
  • Summary TEQ Results ND=0 ND=1/2DL Total TEQ (pg/g) Min 0.027 Max 0.61 Guideline – 4 pg/g TEQ 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 021 019 016 024 003 006 029 030 011 009 034 025 036 004 005 001 033 028 032 017 035 022 014 023 012 008 002 020 027 010 018 015 007 026 013 031
  • Results 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 Concentration (pg/g TEQ) 2 6 10 14 18 22 No. of obs. Max 0.61 Min 0.027 Mean 0.13 n=36 Guideline – 4 pg/g TEQ
  • Log Normalized 0.025 0.04 0.06 0.10 0.16 0.25 0.40 0.63 0 2 4 6 8 10 12 14 No. of obs. Concentration (pg/g TEQ) Guideline – 4 pg/g TEQ Max 0.61 Min 0.027 Mean 0.13 n=36 Geomean 0.090 95% UCL 0.17
    • Log normalized data
    • Better shows distribution data
  • Conclusions
    • True ‘background’ dioxin concentrations much lower than CCME guidelines
    • Now what?
    • How do dioxin patterns predict background?
  • Case Study for Patterns
    • Conducting remediation at site near former wood treatment facility
      • Near several of the background samples
    • Remediate to de minimus CCME value or demonstrate background near urban area
    • Many ways to conducted pattern assessment
      • 2378 summed congeners
      • Relative homologue
      • Relative TEQ
      • Total homologues
      • Unstandardized
  • Different Looks Total homologues Unstandardized Relative to 2378 Sum Total TEQ 700 pg/g Relative to total homologue Relative to total TEQ
  • Normalized to 2378 Sum Congeners
    • Each congener divided by summed total of 2378 congeners
    • Log scale to see low level congeners
    0 1 10 100 2,3,7,8-TCDD 1,2,3,7,8-PeCDD 1,2,3,4,7,8-HxCDD 1,2,3,6,7,8-HxCDD 1,2,3,7,8,9-HxCDD 1,2,3,4,6,7,8-HpCDD OCDD 2,3,7,8-TCDF 1,2,3,7,8-PeCDF 2,3,4,7,8-PeCDF 1,2,3,4,7,8-HxCDF 1,2,3,6,7,8-HxCDF 1,2,3,7,8,9-HxCDF 2,3,4,6,7,8-HxCDF 1,2,3,4,6,7,8-HpCDF 1,2,3,4,7,8,9-HpCDF OCDF
  • Conserved Dioxin Patterns
    • Dioxin patterns can be preserved even at low concentrations
    • Former wood treatment site showing patterns at different orders of magnitude concentrations
    • What is background? < 2 pg/g
    Concentration TEQ – 350 pg/g TEQ – 30 pg/g TEQ – 2 pg/g OCDD HpCDD OCDF HpCDF HpCDF Guideline – 4 pg/g TEQ
  • Dioxin Patterns PCP/Creosote Urban Dust Burn Barrel Diesel Exhaust Crematorium Alberta Background Concentration Concentration TEQ 0.61
  • Summary
    • DLs can play major role in data interpretation – watch % contribution
    • Background (true background) concentrations of PCDD/Fs in southern AB are well below 4 pptr TEQ (95% UCL 0.17 pg/g TEQ).
    • Forensics can be used to determine if signature has dissipated
    • Waiting for a CCME health based guideline to use for site assessment
  • Q u e s t i o n s ?