Developing Standards for Environmental Toxicants: The Need to Consider Abiotic Environmental Factors and Microbe-Mediated Ecologic Processes

Abstract

This article suggests and discusses two novel aspects for the formulation of standards for environmental toxicants. First, uniform national standards for each pollutant will be underprotective for some ecosystems and overprotective for others, inasmuch as the toxicity of a pollutant to the indigenous biota is dependent on the physicochemical properties of the recipient environment. As the number of chemicals that need regulation is immense and as microbes appear to respond similarly to pollutant-abiotic factor interactions as do plants and animals, it is suggested that microbial assays be used initially to identify those abiotic factors that most influence the toxicity of specific pollutants. Thereafter, additional studies using plants and animals can focus on these pollutant-abiotic factor interactions, and more meaningful standards can then be formulated more rapidly and inexpensively. Second, it is suggested that the response to pollutants of microbe-mediated ecologic processes be used to quantitate the sensitivity of different ecosystems to various toxicants. Such a quantification, expressed in terms of an "ecological dose 50%" (EcD50), could be easily incorporated into the methodologies currently used to set water quality criteria and would also be applicable to setting criteria for terrestrial ecosystems.

Cadmium biosorption and toxicity to laboratory ‐ grown bacteria

“…In spite of recommendations to limit metal concentrations in the atmosphere, food and drinking water, the control of cadmium concentration in various compartments of the biosphere itself, does not provide information about the environmental effects of the metal. Particularly, toxicity depends•on the biological target and cadmium biovailability, which is controlled by temperature, pH, Eh, salinity, hardness, inorganic cations or chelatants (6). All these factors are not well understood and investigations using biological organisms are always needed to improve the knowledge of cadmium toxicity mechanisms.…”

Heavy metals alter the electrokinetic properties of bacteria, yeasts, and clay minerals

“…The biochemical and physiological mechanisms whereby metals exert their effects on microorganisms have been reviewed (2,5,7,15,18,27,45). The toxicity of heavy metal pollutants to microbes is affected by biotic and abiotic environmental factors (8,9,14,43,44), as are their mutagenicity and clastogenicity (3). Microbes can also be used to assay the toxicity and mutagenicity of heavy metals (10).…”

Review and evaluation of the effects of xenobiotic chemicals on microorganisms in soil. [139 references]

“…Time is a factor often overlooked. The effect of most xenobiotic compounds on soil microbial processes, such as respiration, is time dependent (Babich et a!. 1983).…”

“…xenobiotics on microbe-mediated processes. This method has been used successfully to quantify the effects of some heavy metals on selected microbe-mediated processes (e.g., glucose mineralization, respiration, nitrification) (Babich et al 1983), and it appears reasonable that the concept could be modified to quantify the results of toxicity tests that measure the effects of other xenobiotics on microbe-mediated processes. In assessing the effects of xenobiotic compounds on soil microorganisms, it is necessary to decide which microbial processes or properties should be evaluated.…”