Synopsis of Discussion Session on the Bioavailability of
William H. Benson (Chair), James J. Alberts, Herbert E. Allen, Carlton D. Hunt, and Michael
Bioavailability is a widely accepted concept based on the implicit knowledge that
before an organism may accumulate or show a biological response to a
chemical, that element or compound must be available to the organism. While
the concept of bioavailability is widely accepted, the processes that control it are
poorly understood. This latter situation results from an incomplete understanding
of basic processes in aquatic systems, which is further exacerbated by the
numerous and sometimes conflicting qualitative definitions of bioavailability used
by investigators from different scientific disciplines.
Bioavailability is defined here as the degree to which a chemical is able to move
into or onto an organism. This definition is given here only to provide a
framework in which to discuss limitations in the understanding of bioavailability
as it pertains to inorganic species in aquatic systems-not because we feel that this
should be the only definition. We focus on the bulk chemistry of the aquatic
phase as it affects speciation and, presumably, availability of inorganic
contaminants. It is assumed that transfer mechanisms operate within the diffusion
layer existing between the bulk phase and membrane(s) to move the chemical
into the organism. We further assume that transfer must occur within the solution
phase regardless of the membrane type or location within the organism (e.g., gill,
gut, or dermis). Thus, inorganic species in phases that are not dissolved within
the bulk solution must involve dissolution for the chemical to become
SREL Reprint #1862
Benson, W.H., J.J. Alberts, H.E. Allen, C.D. Hunt, and M.C. Newman. 1994.
Synopsis of discussion session on the bioavailability of inorganic contaminants. p.
63-71. In Bioavailability: Physical, Chemical and Biological Interactions, edited
by J.L. Hamelink, P.F. Landrum, H.L. Bergman, and W.H. Benson. Lewis
Publishers. Proceedings of the Thirteenth Pellston Workshop, Pellston, MI.
To request a reprint