Relative toxicological importance of aqueous and dietary metal exposure to a freshwater crustacean: implications for risk assessment.
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.
Wilding
Joanna
J
Department of Animal and Plant Sciences, The University of Sheffield, Western Bank, Sheffield S10 2TN, United Kingdom.
Maltby
Lorraine
L
D000818:Animals; D003445:Crustacea / Q000187:drug effects*; D004032:Diet / Q000662:veterinary*; D005618:Fresh Water; D018570:Risk Assessment; D015032:Zinc / Q000008:administration & dosage* / Q000633:toxicity*
D015032:Zinc