Bioaccumulation Of Metal Substances by

Aquatic Organisms Part 1

Bill Adams

OECD Meeting, Paris

September 7-8, 2011

Bioaccumulation – A Fish Story

Presentation Overview

• Bioaccumulation in aquatic organisms

• Inverse relationship between accumulation

factors (e.g., BCF/BAF/TTF) and exposure

concentration for metals

• Limitation on the use of BCFs and BAFs

• BCF and BAF comparisons

• Biomagnification summary for metals

• Trophic transfer factors (TTF)

• Proposed approach to assessing metal

bioaccumulation

Bioaccumulation Factors

Definition

Tissue Concentration

BCF/BAF = -----------------------------

Water Concentration

BCFs are based on water only exposures (lab data)

BAFs are derived from water and dietary exposure (field data)

Bioaccumulation Factors

• BCFs, BAFs, TTFs are inversely related to

exposure concentrations – they are not an intrinsic

property for metals

This identifies a problem for metal hazard assessment

• Big BCF/BAFs do not indicate hazard !!

• Larger values indicate low exposure and low

potential for chronic effects or secondary poisoning

• There is no one value above which hazard can be

ascribed

Bioaccumulation Factors

• BCF / BAF >1000 has been used to signify hazard

in many national regulatory schemes

• Such values have their origin with non-polar

organic compounds

• BCF / BAF >1000 for these substances denotes:

- significant and slow accumulation

- potential for chronic effects

- potential for food chain accumulation

• This is not the case for metal substances – why?

Bioaccumulation Factors

This is not the case for metal substances – why?

1.Nearly all metals (including iron) have BCF /BAFs

>1000 in natural ecosystems that are deemed to be

healthy and with aqueous concentrations at

background.

2.Extremely clean systems have even larger

BCF/BAFs

3.Metals accumulate different than organics

4.Metal regulation systems operate in most organisms

5.More………

Theoretical Basis - Metals

• Metals frequently occur as charged ions in

aqueous solutions and require active

transport to facilitate uptake for both

essential & non-essential elements

• Active transport mechanisms exhibit

saturable kinetics (i.e., rate limited & uptake

rates decline as exposure increases)

• Neutral lipophilic organics

– Uptake via passive diffusion across lipid bilayer

Pharmaco-Kinetic Model of Cu

Bioconcentration in Hyalella azteca Adapted from Borgmann et al. (1995)

1

10

100

1000

10000

100000

1000000

1 10 100 1000 10000 100000

Water Copper, µg/L

Tis

su

e C

op

per, µ

g/k

g

1

10

100

1000

10000

100000

1000000

BC

F

Tissue Burden

BCF

Bioconcentration Factor Concept – Non

Polar Organic Substances

Water Concentration

Tis

sue

Conce

ntr

atio

n

BCF

low high

BCF can be estimated

from Kow

Concentration (ug/L)

Tis

sue

con

c. (

ug/g

)

Homeostasis

1 10 100

Metal Regulation

0.01 0.1

Tissue Metal Concentration

Bioconcentration Factors (BCFs)

Supporting Data

Inverse relationship between tissue concentration

and exposure level for several metals

Bioconcentration Factors (BCFs)

Starting Point

- Fish metal BCFs often < 1000 in lab experiments

- Invertebrate BCF values are somewhat

larger than fish

- BCFs are derived in the laboratory via water

only exposures

- Lab tests that include diet show larger whole body

concentrations than water only exposures, i.e.,

BAFs > BCFs

Cadmium BCFs - Invertebrates

4.5

4.0

3.5

3.0

2.5

2.0

1.5

1.0

0.5

0.0

-0.5

-1.0 -3.0 -2.0 -1.0 0.0 1.0 2.0 3.0 4.0 5.0 6.0

Amphipod (Hyalella azteca) Caddisfly (Hydropsyche betteni) Cladoceran (Daphnia magna) Crayfish (Orconectes propinquus) Grass shrimp (Palaemonetes pugio) Midge (Chironomus riparius) Grass shrimp (Palaemonetes vulgaris)

Lo

g B

CF

Log Cadmium, µg/L

Lead BCFs for Fish and

Invertebrates 4.5

4.0

3.5

3.0

2.5

2.0

1.5

1.0

0.5

0.0

-0.5

-1.0

Lo

g B

CF

-3.0 -2.0 -1.0 0.0 1.0 2.0 3.0 4.0 5.0 6.0

Log Lead, µg/L

Amphipod (Hyalella azteca)

Caddisfly (Brachycentrus sp.)

Snail (Physa integra)

Stonefly (Pteronarcys dorsata)

Brook trout (Salvelinus fontinalis)

Copper BCFs - Invertebrates

4.5

4.0

3.5

3.0

2.5

2.0

1.5

1.0

0.5

0.0

-0.5

-1.0

Lo

g B

CF

-3.0 -2.0 -1.0 0.0 1.0 2.0 3.0 4.0 5.0 6.0

Log Copper, µg/L

Amphipod (Hyalella azteca)

Polychaete (Phyllodoce maculata)

Polychaete (Eudistylia vancouveri)

10000

1000

Nickel BCFs for Fish and

Invertebrates

4.5

4.0

3.5

3.0

2.5

2.0

1.5

1.0

0.5

0.0

-0.5

-1.0

Lo

g B

CF

-3.0 -2.0 -1.0 0.0 1.0 2.0 3.0 4.0 5.0 6.0

Log Nickel, µg/L

Cockle (Cerastoderma edule)

Blue mussel (Mytilus edulis)

Eastern oyster (Crassostrea virginica)

Fathead minnow (Pimephales promelas)

Zinc BCFs for Fish

4.5

4.0

3.5

3.0

2.5

2.0

1.5

1.0

0.5

0.0

-0.5

-1.0

Lo

g B

CF

-3.0 -2.0 -1.0 0.0 1.0 2.0 3.0 4.0 5.0 6.0

Log Zinc, µg/L

Atlantic salmon (Salmo salar)

Flagfish (Jordanella floridae)

Guppy (Poecilia reticulata)

Zinc BCFs - Invertebrates

4.5

4.0

3.5

3.0

2.5

2.0

1.5

1.0

0.5

0.0

-0.5

-1.0

Lo

g B

CF

-3.0 -2.0 -1.0 0.0 1.0 2.0 3.0 4.0 5.0 6.0

Log Zinc, µg/L

Amphipod (Allorchestes compressa)

Amphipod (Hyalella azteca)

Molybdenum BAFs

Literature data: indicate a decrease of the BAF with increasing Mo-levels in the environment: regulation/homeostasis (Van Tilborg, 2009)

The BCF at 12.7 mg/L (PNEC) has not been measured. Extrapolation of the BCF line results in a value of about 0.05. Measured value at 12.7 mg/L = 0.02-0.06 -BCFs in figure range from 90-0.02 -Mo is highly regulated

Bioaccumulation data

- OECD 305: FT fish test - Mo-levels in filets (muscle) and whole body were determined

• 60d uptake (Test concentrations: 0 – 1.0 – 12.7 mg Mo/L) • steady state reached at day 21

0

0.1

0.2

0.3

0.4

0.5

0.6

day 0 day 7 day 14 day 21 day 28 day 45 day 60 depuration

Mea

sure

d c

on

cen

trat

ion

(m

g M

o/L

)

Uptake phase

control filet

control whole body

1.0 mg/L filet

1.0 mg/L whole body

12.7 mg/L filet

12.7 mg/L whole body

Detection limit

Linear (Detection limit)

BCFs Cobalt: Note the phylogenetic differences

Species Phylogenetic Location BCF

Rhynchostegium riparioides FW Plant/moss 11005

Scapania undulata FW Bryophyte 8731

Fontinalis antipyretica FW Plant 7872

Cinclidotus aquaticus FW Plant 5000

Fissidens polyphyllus FW Plant 4800

Brachythecium rivulare FW Plant 4034

Lemna minor FW Plant 3935

Hyridella depressa Mollusk 1080

Velesunio ambiguus Mollusk 870

Mytilus galloprovincialis Mollusk 156

Mercenaria mercenaria Mollusk 3.5-73

Daphnia magna Zooplankton 265

Mixed zooplankton Zooplankton 3.9

Oncorhynchus mykiss FW Trout 4.6-11

Erynnis japonica Marine red sea bream 4.8

BAFs versus BCFs

- Field collected organisms

(dietary exposure)

- Species differences

- In depth look at bivalves

Zinc BAFs

10

100

1000

10000

100000

1000000

10000000

0.01 0.1 1 10 100 1000

Water, µg/L

BA

F

Mussels, calms, oysters

Amphipod (Allorchestes compressa)

Amphipod (Hyalella azteca)

Copper BAFs Vs BCFs

1

10

100

1000

10000

100000

1000000

0.01 0.1 1 10 100 1000 10000

Water, µg/L

BA

F

Mussels, clams, oysters

Amphipod (Hyalella azteca)

Polychaete (Phyllodoce maculata)

Polychaete (Eudistylia vancouveri)

Lead BAFs

1

10

100

1000

10000

100000

1000000

10000000

0.001 0.01 0.1 1 10 100 1000 10000

Water, µg/L

BA

F

5000

500

Mussels, calms, oysters

Snails

Stoneflies

50000

Iron BAFs

1

10

100

1000

10000

100000

1000000

0.1 1 10 100 1000 10000 100000

Water, µg/L

BA

F

Mussels, clams, oysters

Amphipod (Hyalella azteca)

Polychaete (Phyllodoce maculata)

Polychaete (Eudistylia vancouveri)

Conclusions

• Bioaccumulation factors (BCFs, BAFs, TTFs) are not an intrinsic property for metals

• BCFs and other Accumulation Factors for metals are clearly inversely related to water (& sediment concentrations)

• Hazard and potential for chronic effects cannot be evaluated by magnitude of BCFs or BAFS

Born to fish – forced to work