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EC number: 204-847-9
CAS number: 127-52-6
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
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).
Classification is based on the toxicity of algae, EC-50 0.029 mg/L (< 1
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