Sodium N-chlorobenzenesulphonamide

Ecotoxicological Summary

Hazard for aquatic organisms

Freshwater

Hazard assessment conclusion:

PNEC aqua (freshwater)

PNEC value:

0.005 mg/L

Assessment factor:

10

Extrapolation method:

assessment factor

Marine water

Hazard assessment conclusion:

PNEC aqua (marine water)

PNEC value:

0.001 mg/L

Assessment factor:

100

Extrapolation method:

assessment factor

STP

Hazard assessment conclusion:

PNEC STP

PNEC value:

1 mg/L

Assessment factor:

10

Extrapolation method:

assessment factor

Additional information

The acute toxicity to fish is characterized by the 96 hour LC₅₀value which is 17.6 mg/L (95% C.L: 12.2 – 23.0 mg/L). The corresponding 96 hour NOEC for lethal effects is 13.3 mg/L. The 96-hour LC₁₀₀value is 32 mg/L. Long term exposure to early life stages for 30 days revealed that the most sensitive endpoint was the fish body weight. The corresponding 30 day EC₁₀is 0.19 mg/L (C.I. not determined). The 30 day NOEC for fry mortality is 0.25 mg/L. The 30 day EC₁₀for the endpoint hatchability is 1.93 mg/L (95% C.I.: 1.14 to 2.70).

 

The acute toxicity to aquatic invertebrates is characterized by the following values for the endpoint immobilization: 48 hour NOEC: 3.6 mg/L, 48-hour EC₅₀: 4.77 mg/L (95% C.L: 2.59 – 6.94 mg/L). The corresponding 48-hour EC₁₀₀value is 5.2 mg/L. Long term exposure to aquatic invertebrates revealed that the 21 day EC₁₀for the endpoint reproduction is 0.26 mg/L. The 21 day EC₁₀ is 0.3 mg/L for the endpoint immobilization of parent daphnids.

 

The substance inhibits the biomass production of freshwater algae at a 72-hour EC₅₀ of 0.029 mg/L. The corresponding 72-hour NOEC is < 0.017 mg/L. Algae growth rates are affected at the 72-hour EC₅₀ of 0.141 mg/L, with an 72-hour NOEC of 0.053 mg/L.

The substance inhibits STP microorganisms at 3-hr EC₅₀ of 165 mg/L (95% confidence interval: 98.9 – 313 mg/L). The corresponding 3-hr EC₂₀ was calculated as 45.3mg/L (95% confidence interval: 12.9– 78.8 mg/L). The 3-hr EC₈₀ was at 598 mg/L (95% confidence interval: 314 – 3010 mg/L). At a concentration of 10 mg/L, the test substance causes 1% inhibition, whereas 96.2% inhibition was caused at a concentration of 1000 mg/L.

In conclusion, the most sensitive acute toxicological values are the 72-hour NOEC and EC50 value for the algae biomass production: < 0.017 mg/L and 0.029 mg/L. The most sensitive chronic toxicity endpoint is the 30 day EC10 for juvenile fish body weight: 0.19 mg/L (C.I. not determined)

Decomposition of the test substance during testing.

During all ecotoxicological tests, the test substance disappeared with time. Example analytical experiments showed that disappearance was due to dechlorination of the substance under test conditions, since its metabolite Benzenesulphonamide (BSA) was formed. The results indicate that the degree of disappearance is influenced by at least the following factors: test substance concentration and the following exposure conditions: temperature, light intensity, movement of the test solution. The experiments furthermore showed that disappearance from deionised water was comparable with the disappearance from algae medium without algae and from algae medium with algae. The findings lead to the conclusion that the observed disappearance is a function of the test design and hence needs to be considered as an artefact. Based on the results of a valid hydrolysis study, the substance is stable at pH 7 and 9 in deionised water, i.e., no dechlorination takes place. Abiotic degradation is analyzed in closed vessels in the dark, without agitation and air exchange. Since however the experimental conditions of ecotoxicological studies of the aquatic environment may reflect real life exposure conditions, decomposition with time can be anticipated, leading to the formation of the dechlorinated metabolites Benzenesulphonamide (BSA).

Supporting studies with Benzenesulphonamide, the dechlorinated form of the substance, indicate that this metabolite is far less toxic that the submission substance. The EC (b and r)-50 (72 hrs) of BSA for algae was > 150 mg/L. The EC-50 (48) hours on daphnids was > 150 mg/L. Hence and in conclusion, should CAS 127 -52 -6 "trihydrate” be dechlorinated during use and/or water discharge to STPs and/or dechlorination measures during STP clearance and/or natural exposure conditions, the substance is not considered toxic for the environment. A 90% dechlorination under realistic application conditions was verified in 0.01 and 0.1 g/L aqueous solutions within 0.5 and 14 hours, and after application of 50 g/L onto surfaces for disinfection purpose (residual chlorine up to 50 cm above ground: < 0.025 ppm).

Conclusion on classification

Classification is based on the toxicity of algae, EC-50 0.029 mg/L (< 1 mg/L).