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EC number: 213-234-5
CAS number: 931-36-2
In one skin irritation study moderate to severe erythema and moderate edema after an exposure of 20 hours to 2-ethyl-4-methylimidazole was observed. No signs of erythema nor edema were observed after an exposure of 1, 5 or 15 minutes. In another study, after 1 and 4 hours exposure, well defined to severe erythema and very slight to moderate edema was observed. Furthermore, necrosis and parchment-like skin developed which remained throughout the 8-day observation period. In a third study, no erythema or edema was observed.Application of the test substance to the eyes led to a conjunctivea score of 2, a cornea score of 3 and a chemosis score of 3. These effects were not reversible within 8 days. In another eye irritation study, exposure to the substance led to a cornea score of 1, an iris score of 1, a conjunctivea score of 3 and a chemosis score of 3.3.
In a skin irritation test similar to OECD guideline 404, the test
substance was applied in 80% aqueous solution to the skin of Vienna
White Rabbits (1977). Animals were treated for 1, 5, 15 min and 20 hours
using occlusive conditions. Observation took place for 8 days and skin
changes were recorded daily. Moderate to severe erythema and moderate
edema was observed after an exposure of 20 hours on the first day after
exposure. At day 8 symptoms had dissapeared. No signs of erythema nor
edema were observed after an exposure of 1, 5 or 15 minutes.
In another study performed similarly to OECD guideline 404, animals were exposed
to an 80% aqueous solution of 2-ethyl-4-methylimidazole for 1 and
4 hours using occlusive conditions followed by an eight day observation
period (1979). Animals exposed for one hour showed no signs of erythema
or edema. Animals exposed for 4 hours showed well defined to severe
erythema as well as edema ranging from very slight to moderate. Signs of
necrosis were also observed.
In a third skin irritation test performed in accordance to OECD
guideline 404, the test substance, in liquid form (normal melting point
between 36-42°C but lower this time due to impurities) was applied
semi-occlusive to the skin of Vienna White Rabbits using a 2.5 cm x 2.5
cm test patch absorbed with ca 0.5 ml test liquid (1985). After 4 hour
exposure a 72 hours observation period followed. No erythema or edema
was observed during the 72 hr after exposure.
A weight of evidence approach was applied to classify the test
substance. All studies were performed similar to OECD guideline 404,
however only one study (1985) applied the test substance semi-occlusive
as stated by the OECD guideline. No corrosive effects were observed in
that study. The observed necrosis in the other two studies could be a
result of the occlusive application. Furthermore, only the study of 1985
indicated that the test substance was not irritating to the skin while
the other two studies showed severe irritation as a result of the
application of the test substance. There is the possibility that the
aqueous solution of the test substance increases the irritating
potential of the test substance in comparison with the liquid form of
the test substance and therefore the test substance is considered to be
irritating to the skin instead of being corrosive.
In an eye irritation test comparable to OECD guideline 405, 50 µL
of the test substance was applied to the conjunctival sac of the eyes of
2 rabbits (1977). The animals were observed for eight days after
exposure and findings recorded at 1h, 24h and 8 days. Application
of the test substance led (on day 8) to a chemosis score of 3, a
conjuctivea score of 2 and a cornea score of 3. In addition during the
observation period bloody secretion, iritis, suppuration, and hairloss
In another study performed in accordance to OECD guideline 405,
0.1 mL of the test substance was applied to the conjunctival sac of the
eyes of 3 rabbits (1985). The animals were observed for 72 hours and
findings recorded at 1 hr, 24 hr, 48 hr, 72 hr after application. After
72 hours a cornea score of 1, an iris score of 1, a conjunctivea score
of 3 and a chemosis score of 3.3 was observed. Due to the severe effects
the study was terminated after 72 hours.
Based on the available studies, 2-ethyl-4-methylimidazole has to
be classified for skin irritation and eye damage. According to the EU
Classification, Labelling and Packaging of Substances and Mixtures (CLP)
Regulation (EC) No. 1272/2008, the classification is Skin Irrit. 2, H315
and Eye Damage 1, H318.
2-ethyl-4-methylimidazole crude contains 4 -methylimidazole (CAS
822 -36 -6), which is classified as H314, Skin category 1B according to
Regulation EC1272/2008. Hence, 2-ethyl-4-methylimidazole crude also has
to be classified as H314, Skin category 1B according to Regulation
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