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Ecotoxicological information

Toxicity to microorganisms

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Description of key information

The value of 634.4 mg (SO3)2-/L (ECT, 2010) is put forward for the environmental assessment of sulfite/disulfite compounds to micro-organisms.	

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:
634.4 mg/L

Additional information

Five different studies reported on the effect on sufites/disulfites on microbial activity in the aquatic environment.

Growth inhibition tests with the bacteria Pseudomonas putida were conducted with three different sulfite compounds: potassium sulfite (K2SO3), sodium metabiosulfite (Na2S2O5) and potassium metabisulfite (K2S2O5). Table below gives an overview of the different effect levels that were determined in this study.

 

Compound

MM

%S

17h-EC50

(mg test item/L)

17h-EC50

(mg S/L)

17h-EC50

(mg SO32-/L)

K2SO3

158.26

20.3

410

83.1

207.2

K2S2O5

222.32

28.8

65

18.8

46.8

Na2S2O5

190.1

33.7

56.1

18.9

47.2

 

 

 

 

 

 

Compound

MM

%S

17h-EC10

(mg test item/L)

17h-LC10

(mg S/L)

17h-EC10

(mg SO32-/L)

K2SO3

158.26

20.3

153

31

77.3

K2S2O5

222.32

28.8

32

9.2

23.0

Na2S2O5

190.1

33.7

30.8

10.4

25.9

 

 

Expressed as SO32-, similar 17h-EC50,10 values were obtained for sodium and potassium metabisulfite. Somewhat lower toxicity was noted when potiassium sulfite was used as test substance.

An OECD No. 209 respiration inhibition test (under GLP) was conducted witt sodium sulfite (Na2SO3) as test substance. The activated sludge originated from the sewage treatment works in Frankfurt/Main Niederrad treating predominantly domestic sewage. No effects on respiration were noted at 1000 mg test substance/L. Therefore the 3h-EC50 and 3h-NOEC – expressed as SO32-, were equal to (or higher than) 634.4 mg/L (or 254.4 mg S/L). The absence of any effect at these levels is confirmed by Alsop et al (1980) who conducted a growth inhibition test on a mixed culture of bacteria, and who reported a 16h-EC50o f 2000 mg NaSO3/L (i.e., 1268 mg SO32-).

 

As respiration tests with activated sludge is a more relevant test design for evaluating effects of a substance on micro-organisms, and taking into account that the ECT (2010) study was an OECD Guideline GLP-study, the data reported by ECT (2010) are put forward for the effects assessment of sulfites/disulfites for micro-organisms.

 

The value of 634.4 mg SO32-/L is put forward for the environmental assessment of sulfite/disulfite compounds to micro-organisms.