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Inhibition of oxygen utilization by substances in combination
Abstract:
Measurement of concentrations at which substances in combination become toxic is complex, especially if quantitative definition of additive, antagonistic or synergistic toxicity is desired. Using inhibition of oxygen utilized by aerobic micro-organisms in their metabolism of a standard substrate, seven chemicals were tested singly and in eight combinations for their graded toxic effects. In two of the experimental investigations the combined effects of three chemicals were determined. By comparing summations of the measured effects of the chemicals tested singly with similar results from testing the toxicity of actual combinations of the chemicals in solution it was found that the actual inhibitions of the oxygen utilization were essentially the same as predicted inhibitions over a range of aqueous concentrations. Statistical analysis of all combinations tested indicated the effects to be additive. Neither synergism nor antagonism was shown. The pure compounds tested were: mercuric chloride, potassium cyanide, nickel chloride, potassium chromate, copper sulfate, phenol and nitrobenzene. Although the toxicity of each chemical has been quite extensively studied, results regarding combined effects are relatively few. The methods presented here are applicable to many compounds in combination.
Insights
This study investigated the combined toxicity of seven chemicals using microbial oxygen utilization. Results showed that the chemicals exhibited additive toxic effects, with no evidence of synergism or antagonism.
Area of Science:
- Environmental Toxicology
- Microbiology
- Chemical Analysis
Background:
- Assessing combined chemical toxicity is challenging, particularly for defining additive, antagonistic, or synergistic effects.
- Limited data exists on the combined toxicological effects of common industrial chemicals.
Purpose of the Study:
- To quantitatively evaluate the combined toxic effects of seven chemicals.
- To determine if chemical combinations exhibit additive, synergistic, or antagonistic toxicity.
- To establish a methodology for assessing mixture toxicity.
Main Methods:
- Utilized the inhibition of oxygen consumption by aerobic microorganisms as a toxicity indicator.
- Tested seven pure compounds (mercuric chloride, potassium cyanide, nickel chloride, potassium chromate, copper sulfate, phenol, nitrobenzene) individually and in combinations.
- Compared predicted additive effects with observed effects in chemical mixtures.
Main Results:
- The measured toxic effects of chemical combinations were consistent with predicted additive effects.
- Statistical analysis confirmed that the combined toxicity of the tested chemicals was additive.
- No synergistic or antagonistic interactions were observed among the chemical mixtures.
Conclusions:
- The microbial oxygen utilization assay effectively predicts the additive toxicity of chemical mixtures.
- The tested chemicals, including heavy metals and organic compounds, act additively in their toxicity.
- The presented methodology is applicable for evaluating the combined toxicity of various chemical substances.