The chemical forms of inorganic components in water are widely varied and range from simple aquo complexes in solution to complicated silicate minerals in suspension. A variety of techniques are used to determine the total quantities of components in a particular aqueous environment by summation of the individual chemical species present. The biological response of organisms is not in general related to the total concentration of the components present but only to some fraction of the total, i.e., those chemical forms which interact most strongly with the biota and are absorbed. Chemical equilibria calculations are used to provide an estimate of the distribution of metal and ligand species in Lake Superior water and may be used to define important parameters of the system for study and measurement. Comparisons of calculated chemical species distribution with the direct toxic response of aquatic organisms show that only a small fraction of total copper is toxic while much larger fractions of the total are toxic for cadmium and mercury. When metals are bound in silicate minerals they do not exhibit direct toxic effects of fish but their internal organs do show metal uptake. Some inorganic components of Lake Superior have been identified and show concentrations in drinking water for lead, 0.1-150 micrograms; s suspended solids, 0.5-39 mg/l; inorganic fibers, up to one billion cummingtonite-grunerite (amosite) and fiberglass, depending upon the time and place of sampling.