LINEAR ALKYLBENZENE SULFONATE (LAS) - UNEP Chemicals

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OECD SIDS LINEAR ALKYLBENZENE SULFONATE (LAS) and coworkers (Freeberg et al. 1986, Cormier et al. 1995). These studies investigated exposure of manufacturing employees and consumers to laundry, household and personal cleaning products containing LAS and other chemicals. While concentrations were not reported in the Freeberg et al. publications, the coalition survey indicates that LAS concentrations in US consumer products range from 0.1-25% and in commercial products from 1-30%, with the exception of one reported product at 45% in concentrated form that is mechanically dispensed into dilution for dishwashing. The results of the Freeberg et al. studies indicate that in accidental exposure situations, the effects were moderate, transient and reversible. In the Freeberg et al. (1984) study (n=514), 88.1% of the eyes cleared in 4 days or less with no reported permanent eye damage. All eyes cleared in 28 days. Labeling of consumer products containing LAS and other surfactants include warnings of the potential for eye irritation and with first aid instruction to rinse with water. Conclusion (Skin and Eye Irritation) LAS was found to be not irritating to skin at concentrations of 1% and 2.5%, moderately irritating at 5%, and more severely irritating at higher concentrations of about 47-50%. LAS is generally not irritating to the eyes of rabbits at concentrations up to about 1% (some congestion does occur at 0.05-0.5%), moderately irritating at 5%, and more severely irritating at 47-50%. At these higher concentrations the irritation may be present for up to 14 days. In studies that included rinsing, irritation effects diminished with rinsing after 30 seconds of exposure and were slight with rinsing after 4 seconds of exposure. Human experience has established that irritation effects of consumer products containing LAS and other surfactants are moderate, transient and reversible. 3.1.4 Sensitization Studies in Animals Three studies are reported in which skin sensitization in guinea pigs was examined (RBM 1985 [dossier section 5.3c]; Murmann 1988 [dossier section 5.3b]; European Commission 2000 [dossier section 5.3a]). Studies were conducted according to OECD Guidelines and used induction concentrations of 1, 3 or 25% LAS. No sensitization was observed. A.D. Little (1991) reported that LAS may be a weak sensitizer in guinea pigs under exaggerated exposure conditions (e.g., injection induction), but that clear no-effect levels were well below anticipated exposure levels. Studies in Humans Human exposure studies, with volunteers who provided informed consent, are also available for LAS. In a repeat insult patch test, LAS was applied at 0.10% to the upper arms of 95 volunteers (Procter & Gamble, unpublished data). The 24 hour exposure was repeated 3 times a week for 3 weeks during the induction period. After a 14-17 day rest, a 24-hour challenge patch was applied. No evidence of skin sensitization occurred in any of the 95 volunteers. Nusair et al. (1988) conducted extensive patch tests in which 2,294 volunteers were exposed to LAS as a raw material and 17,887 were exposed to LAS in formulations. Again, no evidence of sensitization was observed. In a study reported in the IUCLID Data Set, LAS was found to be sufficiently compatible with the skin after it was applied as a 1% solution to the skin of middle Europeans (Matthies 1989). Conclusions Skin sensitization studies with guinea pigs showed no sensitization at either lower (6.7%) or higher (50%) concentrations. Results of animal studies, human exposure studies and actual use support the conclusion that LAS does not have significant skin sensitization properties. UNEP PUBLICATIONS 26
OECD SIDS LINEAR ALKYLBENZENE SULFONATE (LAS) 3.1.5 Repeated Dose Toxicity Numerous repeated dose toxicity studies are available, and include studies on rats, mice, and rhesus monkeys and oral, dermal, and drinking water exposures. The results are summarized in Table 6. Studies in Animals Oral Many studies have investigated the effects of repeated doses of LAS via the oral exposure route, mainly in the feed but also by gavage and through the drinking water. In a key study, groups of 8 or 9 rats of each sex were given LAS in drinking water at equivalent doses of 85, 145, and 430 mg/kg bw/day for 9 months (Yoneyama et al. 1976). Body weight gain was suppressed in the male 430 mg/kg bw/day group. Hematological examination revealed no significant change in any of the experimental groups, but a dose-related decrease in cholesterol level was seen in males. Significant decreases in the activities of glutamate-oxalate transaminase and lactate dehydrogenase were seen in males at the middle dose and a dose-related increase in the activity of glutamate-oxalate transaminase in females. A significant decrease in renal Na,K-ATPase was seen in the middle-dose group. No organ weight changes were observed. The NOAEL is 85 mg/kg bw/day. Other studies show similar responses, with commonly reported effects at higher doses including diarrhea, suppression of body weight gain, increases in relative weight of the liver, changes in other organ weights, differences in enzymatic and serum-biochemical parameters (e.g., ATPase, LDH, G6Pase), and mild degeneration and desquamation of the tubular epithelium in the kidneys. Occasionally, other effects have been observed, including marked degeneration of renal tubes, proteinaceous degeneration in the liver, and effects on subcellular components (Yoneyama et al. 1972; Gupta et al. 1986; Mathur et al. 1986; Watari et al., 1977). Dermal LAS was applied for 15 days to the backs of male Wistar rats at daily doses of 0.5 g of solutions at 20 and 30% (about 286 and 427 mg/kg bw/day) (Sadai and Mizuno 1972). Body weight gain was suppressed in the 20% group and the body weight was decreased in the 30% group. An infiltrating, yellowish-reddish brown crust was observed 2-3 days in the 20% group, and at 1-2 days in the 30% group. At 4-6 days the crust was abraded and erosion occurred at the abraded site. Histological examinations of the application site revealed severe necrosis of the region from the epidermis cuticle to the upper layer of the dermis, severe infiltration of leukocytes in the necrotic site, diffuse inflammatory cell infiltration of all layers of the corium. No changes were observed in the tongue, but the oral mucosa revealed atrophy and slight degeneration of the epithelium. No systemic effects were observed. The effects on body weight are considered to be related to LAS irritation. Therefore, the local LOAEL for dermal exposure from this study in rats is 286 mg/kg bw/day. Inhalation No long term studies on LAS inhalation are available. Based on its irritant nature, it is expected that repeat inhalation of LAS might be irritating to the respiratory tract. Conclusion LAS has been tested for toxicity resulting from repeated exposures via the oral and dermal routes in rodents (rats and mice) and non-rodents (monkeys). Test durations ranged from 15 days up to 9 months and exposure doses ranged from 8.8 up to 1,030 mg/kg bw/day. LOAELs ranged from 115 to 750 mg/kg bw/day and the highest NOAEL (below the lowest LOAEL) is 85 mg/kg bw/day. This overall NOAEL was selected as the most appropriate value based on the study duration (9 months) and the data from all the studies. UNEP PUBLICATIONS 27
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