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EC number: 287-476-5
CAS number: 85535-84-8
Mean treatment absorbances and growth rates
as a percentage of the corresponding solvent control
Nominal concentration (ug/l)
Measured concentration (ug/l). Day 0.
% Solvent control
* p = 0.01
In a well reported study, the toxicity of
Chlorowax 500C (a C10 -12 chlorinated paraffin; 58% chlorination) to the
marine alga, Skeletonema costatum was investigated. Triplicate samples
of the 5-day old culture were exposed to nominal concentrations of 0,
5.6, 10, 18, 32, 56 or 100 ug/L (mean measured concentrations of 0, 4.5,
6.7, 12.1, 19.6, 43.1 or 69.8 ug/L) for up to 10 days. Six replicate
control and three replicate solvent control cultures were also used. The
effects on cell density were assessed by measuring the absorbance and
particle count, and the effects on growth rate were also examined.
The test substance affected growth during
the early stages of the test but the affected cultures ultimately
attained cell densities similar to the controls. After 4 days, cell
density, as estimated by absorbance, was significantly lower (p=0.01)
than in the solvent control at nominal concentrations of 56 ug/L and 100
ug/L (the highest tested concentration), at which the reductions
compared with the solvent control were 18 and 74%, respectively. After
10 days, there were no significant differences between the test
substance treatments and the solvent control. Growth rates during the
first 2 days were significantly lower (p=0.01) than in the solvent
control at nominal concentrations of 32 ug/l and above, but remained
lower only for the 100 ug/l treatment during the day 2-3 interval.
Growth rates after day 3 were at least as great as in the solvent
control for all treatments. The 96h EC50s for cell density, based on
measured concentrations, were 0.056 and 0.043 mg/L when measured by
absorbance and particle count, respectively. The 48 h EC50 for growth
rate was 0.032 mg/L and a 96 h NOEC of 0.012 mg/L was obtained.
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