Selenium sublethal

Lemly, A.D. 1982a. Response of juvenile centrarchids to sublethal concentrations of waterborne selenium. I. 

Selenium, in the form of selenate or selenite, is toxic to D. desulfuricans (Tomei et al. 1995) and Wolinella succinogenes (Tomei et al. 1992) at elevated levels. At sublethal levels of 0.1-1. OmM selenite or 10 mM selenate, minimal levels of growth is observed with both D. desulfuricans and Wolinella succinogenes. With both selenate and selenite, colloidal elemental selenium (Se°) is produced inside the cell and released into the culture fluid after cell death. This reduction of Se(VI) and Se(IV) by these anaerobes is not coupled to growth and proceeds by mechanisms that have not yet been identified. Selenite and selenate reduction with formation of elemental selenium by these nonrespiratory processes serve to detoxify the environment for future bacteria and may be important for the geochemical cycle of selenium. 

No intermediate inhalation studies were located in animals. Intermediate-duration inhalation studies, in which selenium is administered as selenium dioxide, hydrogen selenide, or selenium dust, might help to identify air concentrations of these substances that produce sublethal effects not only on the respiratory system, but also on the hepatic, renal, hematological, and cardiovascular systems. As exposure to the selenoamino acids is via ingestion, inhalation studies of these compounds would not be necessary. 

Styblo M, Kalouskova J, Klas J. 1991. Comparison of the kinetics of a trace and a sublethal dose of selenite in rats, with particular attention being given to blood selenium distribution. J Trace Elem Electrolytes Health Dis 5(3) 155-164. 

The protective effect of selenium against cadmium is also evident in lower forms of animals. In the presence of sublethal amounts of selenium, the sensitivity of a freshwater mollusc to cadmium was reduced by nearly 50% (Van Puymbroeck et aL, 1982). A reverse interaction is also demonstrable, since sublethal amounts of cadmium give protection against the toxic effects of selenium. This level of cadmium completely prevented mortality due to high doses of selenite (3 mg/liter) and selenate (15 mg/ liter), concentrations which are highly toxic in the absence of cadmium. 

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