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EC number: 813-331-8
CAS number: 24948-66-1
In the preliminary screening test: no signs of
systemic toxicity, visual local skin irritation or irritation
indicated by an equal to or greater than 25% increase in mean ear
thickness were noted.
In the definitive test, there were no deaths or
signs of systemic toxicity. Body weights were comparable to that
observed in the corresponding control group over the same period.
The disintegrations per minute (DPM) and stimulation index (SI) are
given in the table for all test item concentrations. There were no
signs of local skin irritation (maximum erythema score = 0) at up to
Table 1.0 –
Individual Disintegrations per Minute and Stimulation Index during
Test item concentration
DPM values measured / individual
Mean DPM per individual
Group Mean S.I.
Vehicle: acetone/olive oil (4:1, v/v)
a = Total number of lymph nodes per individual is 2
b = Stimulation Index of 3.0 or greater indicates a
n/a = Not applicable
* = Significantly different from control group p
** = Significantly different from control group p
*** = Significantly different from control group p
The study was performed to OECD TG 429 under GLP to
assess the skin sensitisation potential of the test material in the
CBA/CaOlaHsd mouse following topical application to the dorsal surface
of the ear. In a preliminary screening test, single mice were treated by
daily application of 25 μl of the test item at specified concentrations
to the dorsal surface of each ear for three consecutive days (Days 1, 2,
3). The mouse was observed twice daily on Days 1, 2 and 3 and once daily
on Days 4, 5 and 6. Local skin irritation was scored daily. Any clinical
signs of toxicity, if present, were also recorded. The bodyweight was
recorded on Day 1 (prior to dosing) and on Day 6. No signs of systemic
toxicity, visual local skin irritation or irritation indicated by an
equal to or greater than 25% increase in mean ear thickness were noted.
The preliminary test was conducted: undiluted (100%v/v). No signs of
systemic toxicity, visual local skin irritation or irritation indicated
by an equal to or greater than 25% increase in mean ear thickness were
noted. Based on the preliminary test, concentrations of 100%v/v, 50%v/v
and 25%v/v in acetone/olive oil (4:1, v/v)
vehicle were selected for the main test. The mice were treated by
daily application of 25 µL of the appropriate concentration of the test
item to the dorsal surface of each ear for three consecutive days (Days
1, 2, 3). The test item formulation was administered and spread over the
dorsal surface of the ear. Any changes in the ear thickness were noted.
Mean ear thickness changes were calculated between Days 1 to 3 and Days
1 to 6. A mean ear thickness increase of equal to or greater than 25%
was considered to indicate excessive irritation and limited biological
relevance to the endpoint of sensitisation. All animals were observed
twice daily on Days 1, 2 and 3 and on a daily basis on Days 4, 5 and 6.
Any signs of toxicity or signs of ill health during the test were
recorded. The bodyweight of each mouse was recorded on Day 1 (prior to
dosing) and Day 6 (prior to termination). At test termination, five
hours after administration of 3HTdR, the test organisms were humanly
euthanized. For each individual animal of each group the draining
auricular lymph nodes were excised and processed. The proliferation
response of lymph node cells was expressed as the number of radioactive
disintegrations per minute per animal and as the ratio of 3HTdR
incorporation into lymph node cells of test nodes relative to that
recorded for the control nodes. The substance was regarded as
sensitising if at least one concentration of the substance resulted in a
3-fold or greater increase in 3HTdR incorporation compared to control
values. Any substance failing to produce a 3-fold or greater increase in
3HTdR incorporation was classified as non-sensitising.In the main test,
there were no deaths or signs of systemic toxicity, and body weights
were comparable to controls. A stimulation index (SI) of more than 3 was
noted at the 100%v/v (undiluted), 50%v/v and 25%v/v in acetone/olive
oil (4:1, v/v) test concentrations. The 100%v/v, 50%v/v and 25%v/v
groups generated a SI = 7.06, 4.74 and 3.53, respectively. The test item
EC3 value was calculated by log-linear extrapolation of the data. The
EC3 value was determined to be 18.45%. Accordingly, the test item was
considered to be sensitising under the conditions of the test. Applicant
assessment indicates that the log-linear extrapolation method for
determining EC3 values is indicated in reference: Ryan, C. et al.,
Extrapolating Local Lymph Node Assay EC3 Values to Estimate Relative
Sensitizing Potency. Cutaneous and Ocular Toxicology, 26: 135–145.
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