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Toxicity to microorganisms

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In a reliable (Klimisch 1, guideline- and GLP-compliant) study of the toxicity of terephthalic acid to aquatic microorganisms (Lebertz, 1991), the 3 -h EC50, based on inhibition of respiration of activated sludge, was 1392.8 mg/L. Inhibition, relative to the untreated control, was observed at concentrations >/= 1000 mg/L and the NOEC was 500 mg/L. All the nominal concentrations applied exceeded the water-solubility of the test substance (dosed as the free acid), although it is likely that some more highly soluble terephthalate salts were formed by interaction between the acid and the mineral constituents of the synthetic sewage present in the test system. No pH measurements were reported; consequently it is uncertain to what degree a lowering of pH may have caused or contributed to the observed effect.

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