Relative toxicological importance of aqueous and dietary metal exposure to a freshwater crustacean: Implications for risk assessment

Abstract

Aquatic organisms can take up toxicants from water (aqueous exposure) and from food (dietary exposure), yet current environmental regulations often fail to consider the toxic effects of dietary exposure. Such unrealistic exposure scenarios may lead to ineffective water-quality standards or discharge consents that fail to provide adequate protection of the receiving water. Both dietary and aqueous exposure routes contributed to the bioaccumulation of zinc by Gammarus pulex, and both influenced the lethal and sublethal effects of zinc exposure. However, little concordance was found between body burden and magnitude of effect on feeding rate, and the duration of the postexposure response differed between exposure routes. Feeding inhibition, resulting from water-only or simultaneous aqueous and dietary exposure, persisted after the contaminant was removed, but feeding inhibition resulting from dietary exposure alone did not. These results imply that whereas aqueous exposure resulted in either irreversible or slowly reversible physiological damage, feeding inhibition in response to dietary zinc exposure involved an avoidance response. Water-only exposure studies underestimated the effects of simultaneous exposure to contaminated food and contaminated water. Therefore, regarding compounds for which dietary exposure is important, regulatory toxicity tests should either incorporate dietary exposure routes or be subjected to an additional uncertainty factor.

Cadmium and Chromium Toxicity to Pseudokirchneriella subcapitata and Microcystis aeruginosa

“…The metal accumulated by the cell could be interpreted as the total particulate metal (metal species as quantified in this study). For example, the metal that is transported with the cell to other trophic levels, as demonstrated in literature (Fisher and Hook 2002;Wilding and Maltby 2006;Geffard et al 2008). In addition, M. aeruginosa showed higher sensibility to the metals in comparison to the green algae, showing that the cyanobacterium was more suitable for monitoring the contaminated aquatic bodies with Cd and Cr.…”

Effect of Food and Light on the Sensitivity of Copper and Zinc to Freshwater Benthic Ostracod Heterocypris incongruens

“…Zinc may be adsorbed on phytoplankton and onto the algal cell surface or adhesion to the exoskeleton of crustaceans may cause physical effect or dietary effect. In the study by Wilding and Maltby (2006), the effect on growth can be explained by an inhibition of feeding rate when the test organisms were both exposed to aqueous and dietary Zn exposure. Similar effect was observed by Nguyen et al (2012) wherein they observed avoidance reactions and selective feeding behavior of Hyalella azteca.…”

Improving the Value of Standard Toxicity Test Data in REACH

“…food, particles) may influence bioavailability and bioaccumulation of both metals and hydrophobic organic substances, either by reducing or increasing uptake (e.g. Fliedner 1997, McGeer et al 2002, De Schamphelaere et al 2004, Wilding and Maltby 2006, Thorsson et al 2008). Klüttgen and Ratte (1994) found that the development of juvenile D. magna was inhibited by cadmium at low food concentrations, while a body length reduction was clear at higher doses of food.…”