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EC number: 217-568-2
CAS number: 1889-67-4
The mean DPM per animal (two lymph nodes)
was determined by dividing the sum of the measured values from lymph
nodes of all animals within a group by the number of animals in that
group (5 animals). The following mean DPM values were determined:
Vehicle Control: 429.1
5 % test item: 1718.3
10 % test item: 2158.1
20 % test item: 3210.7
The following SI values were determined:
Vehicle control: 1.00
5 % test item: 4.00
10 % test item: 5.03
20 % test item: 7.48
Since all SI values are above the threshold
of 3, the EC3 value could not be calculated. Instead it was extrapolated
using the higher SI and the lower SI from the dose response plot (refer
to table 1).
Table 1 Extrapolated EC3 = Estimated
concentration for a S.I. of 3.
Test item concentration %
Test group 4
Test group 3
Extrapolated EC3 = 2(log2 (c) + (3-d)/(b-d) *(log2 (a)- log2 (c))) = 2.7 % (w/v)
In the study the test item
1,1'-(1,1,2,2-tetramethylethylene)dibenzene dissolved in methyl ethyl
ketone was assessed for its possible skin sensitising potential
according to OECD guideline 429 and EU method B.42.
For this purpose a local lymph node assay
was performed using test item concentrations of 5, 10, and 20 %. The
highest concentration tested was the highest concentration that could be
achieved whilst avoiding systemic toxicity and excessive local skin
irritation as confirmed by a pre-experiment.
The animals did not show any signs of
systemic toxicity during the course of the study and no cases of
mortality were observed. From day 2 to 6, the animals treated with a
test item concentration of 20 % showed an erythema of the ear skin
(Score 1). Animals treated with the vehicle alone or 5 and 10 % test
item concentration did not show any signs of local skin irritation. A
statistically significant relevant increase in ear weights and ear
thickness was not observed in any treated group in comparison to the
vehicle control group.
In this study Stimulation Indices (SI) of
4.00, 5.03, and 7.48 were determined with the test item at
concentrations of 5, 10, and 20 % in methyl ethyl ketone, respectively,
all exceeding the trigger value of 3 for a biologically relevant S.I.
increase. An outlier was identified in the low dose group (DPM value
determined for animal number 6). However, as exclusion of the outlier
did not change the overall test result, the value in question was not
excluded from the calculation. A statistically significant increase in
DPM value was observed in all dose groups in comparison to the vehicle
control group. A statistically significant and biologically relevant
increase in lymph node weight was observed in the mid and high dose
groups in comparison to the vehicle control group. The EC3 value could
not be calculated, since all obtained SI's were above the threshold
value of 3. However, due to the clear dose response, an extrapolated EC3
of 2.7 % could be calculated.
The test item
1,1'-(1,1,2,2-tetramethylethylene)dibenzene was found to be a skin
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