Diphosphoric acid, copper salt

Bioaccumulation: aquatic / sediment

Link to relevant study record(s)

Reference

Endpoint:

bioaccumulation in aquatic species, other

Remarks:

and in sediment species

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

weight of evidence

Justification for type of information:

REPORTING FORMAT FOR THE ANALOGUE APPROACH
For further information please refer to read across justification in IUCLID section 13.

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Remarks on result:

other: By using a weight of evidence approach it is demonstrated that copper is well regulated in all living organisms and that BCF and BAF values have no meaning for a hazard assessment.

Key result

Remarks on result:

other: By using a weight of evidence approach it is demonstrated that copper is well regulated in all living organisms and that BCF and BAF values have no meaning for a hazard assessment.

Key result

Remarks on result:

other: By using a weight of evidence approach it is demonstrated that copper is well regulated in all living organisms and that BCF and BAF values have no meaning for a hazard assessment.

Key result

Remarks on result:

other: By using a weight of evidence approach it is demonstrated that copper is well regulated in all living organisms and that BCF and BAF values have no meaning for a hazard assessment.

Validity criteria fulfilled:

not applicable

Conclusions:

By using a weight of evidence approach it is demonstrated that copper is well regulated in all living organisms and that BCF and BAF values have no meaning for a hazard assessment.

Executive summary:

By using a weight of evidence approach it is demonstrated that copper is well regulated in all living organisms and that BCF and BAF values have no meaning for a hazard assessment.

Description of key information

For the purposes of assessing the bioaccumulation hazard of copper (II) pyrophosphate, the phosphate moiety is not considered to be bioaccumulated and therefore the chemical species of interest is copper. There is a considerable amount of copper accumulation data available. The data have been reviewed by two authors in view of assessing the relationship between the Cu BCF/BAF values and the copper concentrations in the water and sediment. Additionally some researchers have assessed the influence of water chemistry (dissolved organic matter), and the physiology of the organisms (species, age, seasons...) on the observed BCF/BAF values. The information demonstrates that copper is well regulated in all living organisms and that BCF and BAF values have no meaning for a hazard assessment. The data also demonstrate that waterborne exposure is most the critical exposure route and that copper is not biomagnified in aquatic ecosystems.

Additional information

A review of the bioaccumulation of copper assessed the literature related to bioconcentration, bioaccumulation and biomagnification of copper.

The section further includes critical data related to (1) the accumulation of copper on critical target tissues (eg gills in aquatic organisms); (2) the influence of environmental parameters (eg Organic Carbon, pH, Cationic Exchange Capacity) as well as food intake on the accumulation of copper. This information is relevant to the understanding of the accumulation as well as the mechanism of actions, described in the section "ecotoxicological information"

Information relevant to assessing copper toxicity from dietary exposure; of relevance to a secondary poisoning assessment is included in the section "ecotoxicological information".

Bioconcentration factors (BCF) and bioaccumulation factors (BAF)

There is a considerable amount of copper accumulation data available that could potentially be used to calculate bioconcentration factors (BCF) and bioaccumulation factors (BAF) in order to assess the corresponding potential risks in aquatic food chains. However, due to the homeostatic regulation of copper (and other metals), the BCF/BAF are not independent of exposure concentration (Review papers of Adams et al., 2003; Mc Geer et al., 2003; supported by many papers from many authors (see IUCLID supporting data). Increases or decreases in copper intake or elimination, leads to BCFs, BAFs that are inversely related to exposure concentration (i.e. decreasing BCF/BAFs with increasing exposure concentration (water and diet)). Particular to copper, this inverse relationship was clearly demonstrated for BCFs, BAFs and biota-sediment accumulation factors (BSAFs). The observed inverse relationship has been explained by homeostatic regulation of internal tissue concentrations: at low metal concentrations organisms are actively accumulating metals in order to meet their metabolic requirements while at high ambient metal concentration, organisms are able to excrete excess metals or limit uptake.

A more mechanistic understanding of the regulation of copper accumulation as well as internal copper binding mechanisms and sequestrations are provided by Borgmann (1993) and Rainbow (1980, 1985, 1989).

Additionally, different BCFs for different species, life stages and seasons have been observed, depending on the organism’s metabolic need (e.g. Cu-enzymes). As a result different copper levels are found in tissues from different strains, species and life stages of various organisms. Moreover, aquatic invertebrates such as gastropods, crustacea and bivalves, relying on phaetocyanin as respiratory pigment, typically have higher copper levels (and thus higher BCFs) than invertebrates relying on haemoglobin as respiratory pigment (eg Timmermans, 1989; Amiard et al., 1985).

Field data further show that copper concentrations in tissues of marine mammals and coastal seabirds, regardless of species, except brain, tend to decrease with increasing age (Eisler 1984, Lock et al., 1992). Neonatal marine mammals have higher copper levels compared to the mothers (Law et al., 1992).

As a result, use of a simple ratio Cbiota/Cwater or Cbiota/Csediments as an overall approach for estimating copper bioconcentration factors or copper body burdens is not appropriate. It is worth noting that the non-applicability of BCFs for metal and especially for essential metals was already recognised in the regulatory framework of aquatic hazard classification (OECD, 2001).

The ecotoxicology section further includes critical data relating to the accumulation of copper in the critical target tissue for copper (e.g. gills in aquatic organisms) and on the influence of dissolved organic matter, calcium and sodium on the accumulation of copper:

- Benoit (1975) Perez (1991) and Kaland (1993) described the importance of copper target accumulation to the gills.

- Playle (1993a) demonstrated that copper concentrations in the target organ (gills) correlates to the free copper concentration, not to the total copper concentration in the test water. The study provides a mechanistic understanding of the biotic ligand model by determining the Metal-Gill stability constant and thereby predicting metal accumulation on gills and therefore toxicity to fish.

- McGeer et al (2002) demonstrated that the addition of dissolved organic matter (administered as humic acids) decreased Cu accumulation in gills and liver.

- Playle (2003b) provides a mechanistic understanding of the protective effect of dissolved organic matter for copper toxicity to fish because: copper levels in gills decreased with increasing DOC. Lake of origin or molecular size fraction of DOC did not influence Cu binding to gills, while DO concentration did.

Also included are some critical data of relevance to secondary poisoning:

- Kamunde et al (2005) demonstrated interaction between Cu uptake from water and diet: from detailed copper uptake experiments, they demonstrated that elevated dietary NaCl modulates Na⁺and Cl^–homeostasis and reduces accumulation and toxicity of waterborne Cu.

-Taylor (2000) provided evidence on the interaction between water and food for the homeostasis of copper: The data suggest that the availability of food prevents growth inhibition and initial ion (Na) losses that usually result from waterborne Cu exposure. The data further demonstrate copper acclimation: a 2 fold increase in LC50 after pre-exposure of the fish to copper. 

- Kamunde (2001) observed that dietary copper pre-exposure decreased the uptake of Cu across the gills providing further evidence of homeostatic interaction between the two routes of uptake. Rainbow trout regulated dietary Cu at the level of the gut by increasing clearance to other tissues, at the liver by increasing biliary Cu excretion, and at the gill by reducing waterborne Cu uptake in response to dietary exposure. The modest morphological changes in the intestinal tract suggested high cell and organelle turnover and local regulation of Cu. In spite of possible increased energy demand for regulation and tissue repair, there was no significant growth inhibitory effect following dietary exposure.

- Hansen et al (2004) performed a metal exposure study on growth performance in rainbow trout fed a live diet pre-exposed to metal contaminated sediments. The study indicates the absence of copper toxicity at high dietary copper levels. 

- Allinson (2002) investigated the bioaccumulation of copper through a simple food chain (Lemna minor – C. destructor) and observed regulation of copper by the crayfish (C. destructor) with the gills being the main site for absorption and depuration of copper to and from the water column.C. destructordoes not appear to be sensitive to dietary copper.

- Nott (1994) showed that copper, detoxified by snails is unavailable to crabs and was shown to pass straight through the gut and appear in the faecal pellets.

Additional information of relevance to the absence of secondary poisoning is available from a well-designed study from De Schamphelaere et al (2004). This study clearly relates copper toxicity to waterborne and not dietary exposure route (see the section “ecotoxicological information”).

Importantly, the copper mesocosm study from Roussel (2007) reported in the section"additional ecotoxicological information"demonstrated a low sensitivity of the predating fish and did not show a concern from secondary poisoning. Also the freshwater pond mesocosm (Schaefers et al, 2002) and the marine pond mesocosm (Foekema et al, 2010), both reported in the section"additional ecotoxicological information", did not show a concern of secondary poisoning.    

Finally, secondary poisoning of birds and mammals via fish or mussels was investigated for metals, including copper, by RIVM (Smit et al, 2000) (also in the section“additional ecotoxicological information”) who concluded that for copper it was not necessary to integrate secondary poisoning aspects into the copper aquatic quality criteria.

Biomagnification factors (BMF)

The absence of copper biomagnification, with consistent BMFs <1, was shown from several papers:

- Barwick and Maher (2003), compared trace metal levels in a contaminated seagrass ecosystem in Lake Macquire, the largest estuary in New South Wales (Australia). The structure of the estuarine food web was studied in detail and all organisms were categorised as autotrophs, herbivores, planktivores, detrivores, omnivores and carnivores. The results of the analysis showed the absence of copper biomagnification in this estuarine system. Copper concentrations ranged between 0.27 µg Cu/g dry weight (Omnovore:Monacanthus)and 88 µg Cu/g dw (Herbivore:Bembicum auratum- gastropod with haemocyanin). The higher levels (eg.inB. auratum) were associated with species with active accumulation of copper into the respiratory pigment haemocyanin.

- Farag et al (1998) studied copper concentration in benthic invertebrates that represent various functional groups and sizes from de Coeur d’Alene river, Idaho. The river is known to be influenced by mining activities. The copper concentrations noted across the trophic chain demonstrated the absence of biomagnification from the sediment to herbivores, omnivores, detrivores and carnivores.

- Weis & Weis (1999) demonstrated the absence of trophic transfer of metals in consumers associated with chromated copper arsenate treated wood panels.

- Wang (2002) noted the biodiminution of metals in the classical marine planktonic food chain (phytoplankton to copepods to fish) and explained the phenomenon as the result of the effective efflux of metals by copepods and the low assimilation of metals by marine fish.

- Quinn et al (2003) evaluated trophic chain transfer of metals in insects (35 species) from a stream food web influenced by acid main drainage with copper levels up to 100 µg Cu/L. They demonstrated that metal concentrations were higher in water and insects closer to the mining sites and taxa richness increased with distance away from the site. The relationship between the trophic position, determined from¹⁵N radio isotopes, indicated that trophic chain had no effect on copper levels in the insects.