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EC number: 287-476-5
CAS number: 85535-84-8
Table 1: no. of offspring produced/female
Nominal concentration (ug/L)
Mean total no of offspring/parent
% dead offspring
Table 2: Lengths of surviving parent
Daphnia after 21 days
Nominal concentration (ug/l)
Means (micrometer eyepiece scale divisions)*
Mean lengths (mm)*
*Calibration of scale: Divisions x 0.625 = mm
In a well conducted GLP study, the 21-day
toxicity of Chlorowax 500C (a C10-12 chlorinated paraffin; 58%
chlorination) to the freshwater crustracean, Daphnia magna, was
investigated using a continuous flow procedure (in brackish water).
Replicate samples of 10 Daphnia/group, aged <24 h, were exposed to
nominal concentrations of 3.2, 5.6, 10, 18, 32 and 56 ug/L (mean
measured concentrations of 2.7, 5.0, 8.9, 16.3, 25.5 and 38.7 ug/L) for
21 days. The animals were fed throughout exposure and the effects on
survival, reproduction and growth were assessed.
All parent Daphnia exposed to measured
concentrations of 16.3 ug/L and above died within 6 days. Only one
animal was recorded as immobilised in addition to the mortalities and
therefore immobilisation effects were not analysed separately. In the
surviving groups, there was no significant effects on parental length or
on total young production. Offspring were produced in all vessels by day
8, with a significantly greater number of those produced at a measured
concentration of 8.9 ug/L being found dead when compared with the
solvent controls. There were no significant effects on survival,
reproduction and growth (length after 21 days) for Daphnia exposed to a
measured concentration of up to 5 ug/L. Therefore, the NOEC for
Chlorowax 500C under these conditions was 5 ug/L and the LOEC was 8.9
ug/L. The "maximum acceptable toxicant concentration" (MATC) was,
therefore, between 5.0 and 8.9 ug/L, the geometric mean being 6.7 ug/L.
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