LINEAR ALKYLBENZENE SULFONATE (LAS) - UNEP Chemicals

OECD SIDS LINEAR ALKYLBENZENE SULFONATE (LAS)
3.1.3 Irritation
Skin Irritation
Several skin irritation studies have been conducted on rabbits for LAS at a concentration of about
50% (Liggett and Parcell 1986a; Biolab 1989a; Kaestner 1997; Murmann 1983a). Findings in all
the studies were consistent and showed similar irritation effects, as would be expected with a
surface active agent.
In the most reliable study (Liggett and Parcell 1986a), conducted under OECD protocols and GLP
conditions, a 47% LAS concentration was applied to the clipped intact skin of three rabbits. Well
defined to moderate skin reactions were observed in all three animals, as was desquamation of the
stratum corneum. These reactions gradually ameliorated from days 5, 10, and 11, respectively, and
had resolved completely in one animal by day 12. Similar results were observed in studies of 50%
concentration LAS reported by Biolab (1989a), Kaestner (1997), and Murmann 1983a. Several
older studies conducted on a neat commercial LAS material (0.5 g moistened with water) resulted in
a classification as a severe skin irritant (Monsanto 1971, 1972a,b).
Additional skin irritation studies have been conducted with lower concentrations of LAS (Biolab
1989b,c,d). At 1% and 2.5% LAS, no skin irritation was observed in rabbits following exposure
under OECD Guidelines. At 5%, LAS was classified as a moderate skin irritant.
Eye Irritation
Several eye irritation studies on rabbits are available for LAS at a concentration of about 50%
(Liggett and Parcell 1986b; Biolab 1989d; Murmann 1983b; and Kaestner 1987). All studies had
consistent findings and showed significant irritation effects.
The most reliable study (Liggett and Parcell 1986b) was performed under OECD Guidelines and
GLP conditions in which each of three rabbits received LAS at 47% placed into the lower everted
lid of one eye. Significant conjunctivae chemosis was observed in all animals, with minor effects
on cornea opacity and conjunctivae redness in two animals. One animal showed significant ocular
reactions in all sites, which had not cleared at day 14. Concurrent with this study, the eyes of other
rabbits were rinsed following 4 or 30 second eye exposures. Irritation was still present but
diminished after the 30 second rinsing and only slight after the 4 second rinsing. Other studies of
50% LAS conducted on rabbits using OECD Guidelines also resulted in a classification of irritating
with effects noted in the iris and conjunctivae that were persistent at day 6 (Biolab 1989d; Murmann
1983b).
In two Japanese studies conducted on LAS tested at low concentrations (Oba et al. 1968; Iimori et
al. 1972), no abnormalities were seen at 0.01% but slight congestion was seen at 0.05% and
considerable congestion was seen at 0.1% that disappeared within 24 hours. Marked responses
were observed at 0.5% LAS and higher, including severe congestion and edema, increased
secretion, turbidity of the cornea, and disappearance of the corneal reflex. These effects
disappeared completely after 120 hours. The results of two additional rabbit studies conducted
under OECD Guidelines indicated no irritation at 1% LAS but marked reactions for conjunctival
redness and chemosis at 5% (Biolab 1984). Finally, three older non-standard studies are available
in which 100 mg of finely ground solid commercial LAS sample was placed in the eyes of rabbits
(Monsanto 1971, 1972a,b). The resultant scores ranged from 10 to 19 out of 110, which classifies
this as a mild irritant.
Comparisons between animal test results and human eye irritation experiences indicate that the
rabbit eye irritation test is not well correlated to human responses for 29 surfactant-based cleaning
products. Human experience with eye exposure to surfactants was reported by Freeberg et al (1984)
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