Bioaccumulation Of Metal Substances by Aquatic Organisms Part 1

Transcription

1 Bioaccumulation Of Metal Substances by Aquatic Organisms Part 1 Bill Adams OECD Meeting, Paris September 7-8, 2011

2 Bioaccumulation A Fish Story

3 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

4 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)

5 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

6 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?

7 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

8 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

9 Tissue Copper, µg/kg BCF Pharmaco-Kinetic Model of Cu Bioconcentration in Hyalella azteca Adapted from Borgmann et al. (1995) Tissue Burden BCF Water Copper, µg/l 1

10 Tissue Concentration Bioconcentration Factor Concept Non Polar Organic Substances BCF can be estimated from Kow BCF low Water Concentration high

11 Tissue conc. (ug/g) Metal Regulation Tissue Metal Concentration Homeostasis Concentration (ug/l)

12 Bioconcentration Factors (BCFs) Supporting Data Inverse relationship between tissue concentration and exposure level for several metals

13 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

14 Log BCF Cadmium BCFs - Invertebrates Amphipod (Hyalella azteca) Caddisfly (Hydropsyche betteni) Cladoceran (Daphnia magna) Crayfish (Orconectes propinquus) Grass shrimp (Palaemonetes pugio) Midge (Chironomus riparius) Grass shrimp (Palaemonetes vulgaris) Log Cadmium, µg/l

15 Log BCF Lead BCFs for Fish and Invertebrates Amphipod (Hyalella azteca) Caddisfly (Brachycentrus sp.) Snail (Physa integra) Stonefly (Pteronarcys dorsata) Brook trout (Salvelinus fontinalis) Log Lead, µg/l

16 Log BCF Copper BCFs - Invertebrates Amphipod (Hyalella azteca) Polychaete (Phyllodoce maculata) Polychaete (Eudistylia vancouveri) Log Copper, µg/l

17 Log BCF Nickel BCFs for Fish and Invertebrates Cockle (Cerastoderma edule) Blue mussel (Mytilus edulis) Eastern oyster (Crassostrea virginica) Fathead minnow (Pimephales promelas) Log Nickel, µg/l

18 Log BCF Zinc BCFs for Fish Atlantic salmon (Salmo salar) Flagfish (Jordanella floridae) Guppy (Poecilia reticulata) Log Zinc, µg/l

19 Log BCF Zinc BCFs - Invertebrates Amphipod (Allorchestes compressa) Amphipod (Hyalella azteca) Log Zinc, µg/l

20 Molybdenum BAFs Literature data: indicate a decrease of the BAF with increasing Molevels 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 Measured value at 12.7 mg/l = BCFs in figure range from Mo is highly regulated

21 Measured concentration (mg Mo/L) Bioaccumulation data - OECD 305: FT fish test - Mo-levels in filets (muscle) and whole body were determined 60d uptake (Test concentrations: mg Mo/L) steady state reached at day control filet 0.5 control whole body mg/l filet 1.0 mg/l whole body 12.7 mg/l filet 12.7 mg/l whole body Detection limit 0 day 0 day 7 day 14 day 21 day 28 day 45 day 60 depuration Linear (Detection limit) Uptake phase

22 BCFs Cobalt: Note the phylogenetic differences Species Phylogenetic Location BCF Rhynchostegium riparioides FW Plant/moss 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 Daphnia magna Zooplankton 265 Mixed zooplankton Zooplankton 3.9 Oncorhynchus mykiss FW Trout Erynnis japonica Marine red sea bream 4.8

23 BAFs versus BCFs - Field collected organisms (dietary exposure) - Species differences - In depth look at bivalves

24 BAF Zinc BAFs Mussels, calms, oysters Amphipod (Allorchestes compressa) Amphipod (Hyalella azteca) Water, µg/l

25 BAF Copper BAFs Vs BCFs Water, µg/l Mussels, clams, oysters Amphipod (Hyalella azteca) Polychaete (Phyllodoce maculata) Polychaete (Eudistylia vancouveri)

26 BAF Lead BAFs Mussels, calms, oysters Snails Stoneflies Water, µg/l

27 BAF Iron BAFs Mussels, clams, oysters Amphipod (Hyalella azteca) Polychaete (Phyllodoce maculata) Polychaete (Eudistylia vancouveri) Water, µg/l

28 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

29 Born to fish forced to work