Bioaccumulation Criteria Jon Arnot Frank Gobas Barry Kelly
Bioaccumulation Criteria Jon Arnot Frank Gobas Barry Kelly James Armitage
Overview • Why, What, Where, When and How of bioaccumulation (‘B’) regulatory criteria • Current criteria concerns for assessments – Bioaccumulation workgroup – Bioconcentration Factor (BCF) – Air breathing organisms • Future considerations • Comments
Why do ‘B’ criteria exist? • Bioaccumulation is the net result of competing processes of chemical uptake and elimination in an organism • “Dose” (Paracelsus) • Identify chemicals that are bioaccumulative hazards for risk assessment – (e. g. , CEPA 1999)
What ‘B’ measurements are included in regulations? Where is this applied?
What ‘B’ measurements are included in regulations? • BAF • CB / CW (all routes) Where is this applied? Canada
What ‘B’ measurements are included in regulations? • BAF • BCF • CB / CW (water only) Where is this applied? Canada United States European Union
What ‘B’ measurements are included in regulations? • BAF • BCF • KOW • CO / C W Where is this applied? Canada United States European Union
What ‘B’ measurements are included in regulations? • • BAF BCF KOW BMF • CPredator / CPrey Where is this applied? Canada United States European Union Currently not used
When and How have ‘B’ assessments evolved? 1960 – 1970 s – today
n ~2, 400 (390 chemicals) ~3% DSL
n ~1, 300 (340 chemicals)
–Bioavailability (Ctotal vs Cfd) –Analytical –Metabolic transformation –Kinetics –Growth
~0. 3% DSL
= 5000 Organism-water partitioning Dietary uptake
What are ‘B’ criteria trying to identify? • Chemicals with biomagnification potential Beyond the scope of BCF data • By design they don’t include dietary exposure • Technical difficulties for high KOW chemicals • water concentrations low and variable • bioavailable fraction, exposure duration • Very $$ • BCFs are no substitute for BAFs
Aquatic Lipid-water exchange Terrestrial Lipid-air exchange
Observations of low KOW chemicals that biomagnify in terrestrial and marine mammalian food webs but not in aquatic food webs Chemical log KOW log KOA BMF (lipid/lipid) Species ß-HCH 3. 81 8. 17 28 -37 HCH 3. 81 8. 17 ~8 Ringed seals HCH 3. 81 8. 17 ~2 Beluga whale -endosulphan 3. 83 7. 6 ~10 Ringed seals Tetrachlorobenzene 4. 7 5. 84 ~7 Arctic wolves Pentachlorobenzene 5. 0 6. 5 3 -6 Arctic wolves PFOS ~3 12 >> 1 Various wolves
Chemicals with Biomagnification Potential Water ‘breathers’: log KOW > 5 and log KOW < 9 and TM, 1/2 > ~10 d Air ‘breathers’: log KOA > 5 and log KOW > 2 and TM, 1/2 > ~7 d In: QSAR Comb. Sci. 22: 337 -345 & 346 -351.
Canada’s Domestic Substance List 12, 000 Organic Chemicals ~40% 17. 8% In: QSAR Comb. Sci. 22: 346 -351.
Future considerations • BCF measurements alone are insufficient for assessing bioaccumulation / biomagnification potential • Don’t include dietary uptake • Restricted to aquatic species • ~3% of chemicals have empirical BCF data • For log KOW > 4 -5 ~0. 3% of empirical data • Since we have to use models lets use those that have the potential to identify bioaccumulative hazards
Future considerations • Key partitioning processes for air breathing organisms are important (i. e. , KOA) and are not explicitly included in regulatory criteria • Numerous incentives ($$) to establish consistent criteria in various jurisdictions
Future considerations • Criteria need to effectively identify potential hazards for chemical risk assessment • A single, universal BMF criterion (e. g. , 1) can be broadly applied to all species and identify those chemicals with biomagnification potential • Based on this strategy chemicals could be more effectively prioritized for assessment (e. g. , BMF of 0. 001 vs. 10 vs. 80) • Other criteria could also be developed • FWMF, k. M, ?
Thank you Comments?
- Slides: 25