Conducting Ecological Risk Assessments of Inorganic Metals and Metalloids: Current Status

TLDR

Ecological risk assessment of inorganic metals and metalloids must be substance‑specific because most metals are naturally occurring, some are essential, and speciation and environmental and organismal factors determine bioavailability. The study seeks to define the key information needed for metal ERA, including emissions, pathways, internal dose relationships, and the incidence and severity of effects. The authors ground‑truth their approach in contaminated sites, delineate specific requirements for each ERA component and information category, and organize the assessment across three tiered levels: Problem Formulation, Screening Level ERA, and Detailed Level ERA. Despite remaining data gaps, recent progress over the past three years has substantially improved the foundation for metal ERA.

Abstract

Ecological risk assessment (ERA) of inorganic metals and metalloids (metals) must be specific to these substances and cannot be generic because most metals are naturally occurring, some are essential, speciation affects bioavailability, and bioavailability is determined by both external environmental conditions and organism physiological/biological characteristics. Key information required for ERA of metals includes: emissions, pathways, and movements in the environment (Do metals accumulate in biota above background concentrations? ); the relationship between internal dose and/or external concentration (Are these metals bioreactive? ); and the incidence and severity of any effects (Are bioreactive metals likely to result in adverse or, in the case of essential metals, beneficial effects?) — ground-truthed in contaminated areas by field observations. Specific requirements for metals ERA are delineated for each ERA component (Hazard Identification, Exposure Analysis, Effects Analysis, Risk Characterization), updating Chapman and Wang (2000). In addition, key specific information required for ERA is delineated by major information category (conceptual diagrams, bioavailability, predicted environmental concentration [PEC], predicted no effect concentration [PNEC], tolerance, application [uncertainty] factors, risk characterization) relative to three different tiered, iterative levels of ERA: Problem Formulation, Screening Level ERA (SLERA), and Detailed Level ERA (DLERA). Although data gaps remain, a great deal of progress has been made in the last three years, forming the basis for substantial improvements to ERA for metals.