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Toxicity to soil microorganisms

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Description of key information

The test item at the concentrations ranging from 125 to 2000 mg/kg dry weight of soil statistically significantly inhibited the process of nitrogen transformation to nitrate.
The concentration of the test item causing a 50% inhibition of nitrogen transformation to nitrate (EC50) is 553.9 mg/kg dry weight of soil.
The concentration of the test item causing a 25% inhibition of nitrogen transformation to nitrate (EC25) is 126.0 mg/kg dry weight of soil.
The concentration of the test item causing a 10% inhibition of nitrogen transformation to nitrate (EC10) is <125.0 mg/kg dry weight of soil.

Key value for chemical safety assessment

Long-term EC10 or NOEC for soil microorganisms:
125 mg/kg soil dw

Additional information

Antimicrobial activity of xanthates was evident from median inhibitory limit on amonia oxidation in Nitrosomonas of 12 ppm(Bremner J. M. and Yeomans J. C., 1986, Biol. Fertil. Soils 173-179)

Potassium ethyl xanthate(CAS# 140-89-6) is a nitrification microbial inhibitor and was observed to inhibit soil denitrification at concentration about 50 ppm (US EPA, Washington DC, Full Public Report, Sodium Ethyl Xanthate, Priority Existing Chemical No.5, Canberra, May 1995).

 

Sodium ethyl(CAS# 140-90-9):The test item at the concentrations ranging from 125 to 2000 mg/kg dry weight of soil statistically significantly inhibited the process of nitrogen transformation to nitrate.

The concentration of the test item causing a 50% inhibition of nitrogen transformation to nitrate (EC50) is 553.9 mg/kg dry weight of soil.

The concentration of the test item causing a 25%inhibition of nitrogen transformation to nitrate(EC25) is 126.0 mg/kg dry weight of soil.

The concentration of the test item causing a 10%inhibition of nitrogen transformation to nitrate(EC10) is <125.0 mg/kg dry weight of soil.(Anna Arendarczyk, Institute of Industrial Organic Chemistry Branch Pszczyna, Department of Ecotoxicology,43-200 Pszczyna Poland)

Sodium ethyl(CAS# 140-90-9) or sodium isopropyl xanthates(CAS# 140-93-2) depending on concentration inhibit or activate mushroom tyrosinase (enzyme). The thiol compounds can act as inhibitors of tyrosinase due to their ability to chelate Cu+2. Tyrosinase also known as polyphenol oxidase, is a copper containing mixed - function oxidase widly distributed in microorganisms, animals and plants. The investigated xanthates act as activators at concentration about 11.5µM but as inhibitors at 20 - 50 µM(Saboury A. A., et all, J. Chinese Chem. Soc. 2008,55,937-942)

The inhibitory effect of n-alkyl xanthates on mushroom tyrosinase depend on alkyl chain length. Shorter alkyl radical gives a more potent inhibitor(Saboury A. A., et all, 2007, Acta Biochimica Polonica 54, 183-192)

Toxicity of Carbon disulfide(CAS# 75-15-0) to soil dwelling microorganisms:

Test conditions: natural soil, 

Endpoint: inhibition

Result: NOEC: 15 kg of CS2per 100 m2.

(UCLID Dataset, Carbon disulfide, 2000 European Chemicals Bureau)

Carbon disulfide (CAS# 75-15-0) is a soil disinfectant and toxic to bacteria(EPA, 1986, Health and environmental effects profile for carbon disulfide, EPA/600/X-86/155,129).