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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?
• 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 / CW
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
What ‘B’ measurements are included in regulations?
When and How have ‘B’ assessments evolved?
1960 – 1970s 1970s – today
0
2
4
6
8
0 2 4 6 8 10 12
log KOW
log
BC
F o
r lo
g B
AF
Empirical BCF
n ~2,400 (390 chemicals)
~3% DSL
0
2
4
6
8
0 2 4 6 8 10 12
log KOW
log
BC
F o
r lo
g B
AF
Empirical BCF
n ~1,300 (340 chemicals)
0
2
4
6
8
0 2 4 6 8 10 12
log KOW
log
BC
F o
r lo
g B
AF
Empirical BCF
Veith/Kosian 1979
Mackay 1982
–Bioavailability (Ctotal vs Cfd)
–Analytical
–Metabolic transformation
–Kinetics
–Growth
0
2
4
6
8
0 2 4 6 8 10 12
log KOW
log
BC
F o
r lo
g B
AF
Empirical BCF
Veith/Kosian 1979
Mackay 1982
Meylan 1999
0
2
4
6
8
0 2 4 6 8 10 12
log KOW
log
BC
F o
r lo
g B
AF
Empirical BAFEmpirical BCFVeith/Kosian 1979Mackay 1982Meylan 1999 ~0.3% DSL
0
2
4
6
8
0 2 4 6 8 10 12
log KOW
log
BC
F o
r lo
g B
AF
Empirical BAF
Empirical BCF
Veith/Kosian 1979
Mackay 1982
Meylan 1999
Arnot/Gobas 2003
0
2
4
6
8
0 2 4 6 8 10 12
log KOW
log
BC
F o
r lo
g B
AF
Veith/Kosian 1979
Mackay 1982
Meylan 1999
Arnot/Gobas 2003
EC criteria
Dietary uptakeOrganism-water partitioning
= 5000
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 $$
• BCFs are no substitute for BAFs
Aquatic
Lipid-water exchange Lipid-air exchange
Terrestrial
0.01
0.1
1
10
2 3 4 5 6 7 8 9 10
Log KOW
BM
F
1
10
100
4 5 6 7 8 9 10 11 12
log Koa
BM
F
Chemical log KOW log KOA BMF (lipid/lipid)
Species
ß-HCH 3.81 8.17 28-37 wolves
HCH 3.81 8.17 ~8 Ringed seals
HCH 3.81 8.17 ~2 Beluga whale
-endosulphan 3.83 7.6 ~10 Ringed seals
Tetrachlorobenzene 4.7 5.84 ~7 Arctic wolves
Pentachlorobenzene 5.0 6.5 3-6 Arctic wolves
PFOS ~ 3 12 >> 1 Various
Observations of low KOW chemicals that biomagnify in terrestrial and marine mammalian
food webs but not in aquatic food webs
Water ‘breathers’:
log KOW > 5 and log KOW < 9and TM,1/2 > ~10 d
Air ‘breathers’:
log KOA > 5 and log KOW > 2 and TM,1/2 > ~7 d
Chemicals with Biomagnification Potential
In: QSAR Comb. Sci. 22: 337-345 & 346-351.
-10
10
30
50
-10 -5 0 5 10 15 20
log KOW
log
KO
A
36%
5.6%
17.8%
Canada’s Domestic Substance List
12,000 Organic Chemicals
~40%
In: QSAR Comb. Sci. 22: 346-351.
Future considerations
• BCF measurements alone are insufficient for assessing bioaccumulation / biomagnification potential
• Don’t include dietary uptake
• Restricted to aquatic species
• ~3% of chemicals have empirical BCF data
• For log KOW > 4-5 ~0.3% of empirical data
• Since we have to use models lets use those that have the potential to identify bioaccumulative hazards
Future considerations
• Key partitioning processes for air breathing organisms are important (i.e., KOA) and are not explicitly included in regulatory criteria
• Numerous incentives ($$) 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, kM, ?
Thank you
Comments?
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