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EC number: 213-254-4
CAS number: 932-64-9
Since no concentration tested resulted in ≥ 50% immobilization, the
48-hour EC50 value was empirically estimated to be > 9.5 mg a.i./L, the
highest geometric mean measured concentration tested. The
No-Observed-Effect Concentration (NOEC) was determined to be 2.4 mg
Further testing to define an EC50 value was not performed since the
highest nominal concentration tested (i.e., 10 mg a.i./L) represents the
highest test concentration at which the pH of the exposure solutions was
appropriate for the survival of Daphnia magna.
During the test period no immobilisation in the tested concentrations
0.47, 1.4 and 2.4 mg a.i./L was observed. Observed effects occured in
the 4.9 mg/L concentration and in the 9.5 mg/L concentration. The latter
was determined to be the NOEC whereas the 9.5 mg/L concentration did not
reach a nkuber from what the EC50 value could be derived.
The study reveals a negligible toxicity of the parent compound, and a
far higher toxicity of photodegradation products. However, these have
not been chemically quantified sufficiently and consequently not been
According to the computer program EPISUITE, the test substance, NTO, was
predicted to have LC50 of 222.878 mg/L after 48 hours exposure.
As stated in the published data (Haley Mark V., Kuperman Roman G.,
Checkai Ronald T. ) the 48h LC50 to Ceriodaphnia dubia is 460 mg/L for
pH-adjusted media and 62 mg/L for non-pH-adjusted media.
Kennedy et al .reported for NTO a relatively low toxicity of around 800
mg/L and a so-called "NSDS" ( not significantly different from the
control) comparable to a NOEC of 366 mg/L. In contrast, a BAE study
revealed a far lower NOEC of 2.4 mg/L in a very sensible system, what
did not let conclude on a EC50 value, as the pH was shifiting towards
levels which limited the applicability of the test system for the
substance. Accordingly the Kennedy study was assessed as the more
relevant in this case.
The short term toxicity to aquatic invertebrates was determined using
the computer program EPISUITE, based onLog Kow and water solubility. The
test substance, NTO, was predicted to have LC50 of 222.878 mg/L after 48
Determination of short term toxicity to aquatic invertebrates,
Ceriodaphnia dubia, has been also described in published data (Haley
Mark V., Kuperman Roman G., Checkai Ronald T. ) describing the test
performed at RESEARCH AND TECHNOLOGY DIRECTORATE. The 48h LC50 to
Ceriodaphnia dubia is 460 mg/L for pH-adjusted media and 62 mg/L for
From a BAE system study no EC50 could be derived due to to test material
inherent pH changing properties.
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