Secondary poisoning risk assessment of terrestrial birds and mammals exposed to Nickel

Abstract

The European Union's Existing Substances regulation (EEC 793/93) was developed to assess the ecological risks posed by chemical substances such as Ni and includes the assessment of secondary poisoning risks. The basic structure of this secondary poisoning risk assessment followed the Technical Guidance Document on Risk Assessment and thus included development of predicted exposure concentrations (PECs) and predicted no-effect concentrations (PNECs). A PEC to PNEC ratio greater than 1.0 is indicative of potential risk. The Technical Guidance Document on Risk Assessment provides a generic framework for assessing secondary poisoning risks and prescribes the following terrestrial food chain: soil → earthworm → worm-eating bird or mammal. This secondary poisoning evaluation was conducted at the regional level, and it was found that the generic approach resulted in widespread estimates of potential risk, even at ambient Ni soil concentrations. Accordingly, a tiered approach was used with increasing levels of refinement, including consideration of bioavailability, consideration of a variable diet, and development of dose-based PNEC values. Based on the refined approach, all PEC to PNEC ratios were less than 1.0, except for a ratio of 1.4 in a scenario focused on a regional clay soil, which was of natural origin. This regional-level secondary poisoning evaluation highlighted key risk assessment components that should be considered in future localized secondary poisoning assessments of Ni and other metals, including ingestion rate to body weight ratios for the test organisms used to derive PNECs versus the representative wildlife species evaluated, the appropriateness of high assessment factors for deriving PNECs for naturally occurring essential elements, representative dietary compositions, relative metal bioavailability between the dietary toxicity study and natural diets, and ground-truthing of the risk predictions versus background concentrations.

A microcosm study to support aquatic risk assessment of nickel: Community‐level effects and comparison with bioavailability‐normalized species sensitivity distributions

“…However, the Ni concentration in the snails was always below that in periphyton and macrophytes, the snail BAFs were lower than the periphyton and macrophyte BCF, and the snail biomagnification factor was always below 1, all of which indicates that biomagnification did not occur in this part of the food chain (periphyton to snails). This conclusion is consistent with an analysis of Ni biomagnification potential for terrestrial food webs . McGeer et al report in their meta‐analysis of metal bioconcentration data a trend of increased Ni body concentrations with increased exposure concentration for aquatic organisms.…”

Transfer of elements relevant to nuclear fuel cycle from soil to boreal plants and animals in experimental meso- and microcosms

“…Snails are also regarded as key components of terrestrial food webs, and they may contribute to the transfer of pollutants from soil and plants to top predators (de Vaufleury et al, 2006). Earthworms are commonly tested in bioaccumulation studies, because they have a high exposure potential to chemicals in soil, and are important part of diet to a variety of wildlife species (DeForest et al, 2011).…”

Recommendations to improve wildlife exposure estimation for development of soil screening and cleanup values

“…There is ample evidence that soil properties, other than metal concentrations, can influence trace metal accumulation in plants and animals. For example, DeForest et al () observed an inverse relationship between Ni BAFs for earthworms and soil Ni concentrations, as well as between BAFs and soil cation exchange capacity (CEC). Similarly, Pauget et al () found that inclusion of pH and CEC into regression models allowed a significantly better prediction of Cd and Pb concentrations in snail tissue than those derived using metal concentration alone.…”

“…The source of many of the limitations associated with applying the secondary poisoning assessment to metals is that the guidance was developed with organic contaminants in mind. Metal‐specific guidance has been developed (ECHA ), and this guidance recognizes many of the steps that DeForest et al () used in their refinement of the Ni secondary poisoning assessment.…”