LINEAR ALKYLBENZENE SULFONATE (LAS) - UNEP Chemicals

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OECD SIDS LINEAR ALKYLBENZENE SULFONATE (LAS) eliminated via the urine, with sulfophenyl butanoic and sulfophenyl pentatonic acid as metabolites. Approximately 35% of the absorbed dose was excreted in the bile. Although the metabolites in the bile were not identified, it was shown that no unchanged LAS was eliminated via this pathway. In oral studies with pigs, Havermann and Menke (1959) found that at 200 hours after oral administration, the radiolabeled LAS was relatively high in bristles and bones, while low in liver, kidney and spleen. After 10 weeks only traces of radioactivity were still in the body. At 40 hours after administration, 40% of the dose was excreted into the urine and 60% of the dose via the feces. In another study (Sunakawa et al. 1979), rats were dosed orally with 14C-LAS and radioactivity was detected 0.25 hours after administraton, reaching a maximum at 2 hours. The biological halflife was calculated to be 10.9 hours. The distribution was high in the digestive tract and in the bladder at 4 hours after administration, with high concentrations also found in the liver, kidney, testis, spleen and lung. At 168 hours after administration, the rates of excreted radioactivity were 47% in the urine and 50% in the feces. Toxicokinetics has also been studied in adult rhesus monkeys (Cresswell et al. 1978). Two male and two female monkeys were given single or repeated oral (30, 150 or 300 mg/kg) or subcutaneous (0.1, 0.5 or 1 mg/kg) doses of 14C-LAS. For example, after single 30 mg/kg oral doses, the radioactivity was rapidly excreted, mostly during the first 24 hours. Means of 71.2% and 23.1% of the dose were excreted in the urine and feces, respectively, during 5 days. During seven consecutive daily (30 mg/kg/day) or subcutaneous (1 mg/kg/day) doses, there was no accumulation of radioactivity in plasma. Mean peak concentrations and biological half-lives were similar after the first and seventh doses. No unchanged LAS was detected in the urine after oral or subcutaneous doses. Five metabolites were excreted but they were not identified. Studies in Humans Studies were conducted with isolated human skin preparations using two solutions of C12 LAS (Howes 1975). The results demonstrated that penetration through the skin and subsequent absorption does not occur to any significant extent (less than 1%) at 24 to 48 hours. 3.1.2 Acute Toxicity Acute mammalian toxicity data are available for all three potential routes of exposure (inhalation, dermal, oral), as summarized below and in Table 5. Studies in Animals Oral Eight acute oral toxicity studies are available for LAS using rats, and one acute oral study is available using mice (Murmann 1984a,b,c; Ito et al. 1978; Kynoch 1986a; Monsanto 1971, 1972a,b). All of the studies were conducted on the low average chain length LAS (C11.2-C11.7). The resultant LD50 values ranged from 1,080 up to 1,980 mg/kg bw for rats and greater than 2000 mg/kg bw for mice, with no significant difference between sexes. Mortality and symptoms of toxicity occurred at the high doses tested in each study, and usually within the first few hours or days, after which surviving animals generally recovered. Symptoms noted in most of the studies included piloerection, hunched posture, abnormal gait (waddling), lethargy, reduced appetite, decreased respiratory rate, ptosis, pallor of the extremities, and diarrhea. All oral studies are reliability 1 or 2, except for those by Ito et al. (1978), which were rated unassignable (4) since the original reports were not available for review. However, these studies were considered reliable because they have been reviewed by the International Program on Chemical Safety. UNEP PUBLICATIONS 22
OECD SIDS LINEAR ALKYLBENZENE SULFONATE (LAS) Dermal The acute dermal toxicity of LAS was studied in rats under OECD Guideline 402 and GLP conditions (Kynoch 1986b). The LAS used in this study was C11.2 LAS, which has an average alkyl chain length slightly shorter than the range of chain lengths currently used in the United States (C11.2-C12.6). There were no deaths or systemic reaction to five male and five female rats following a single dermal application of 2000 mg/kg bw of LAS at 47% active matter. Well defined or slight erythema and slight edema were observed at all test sites after removal of the occlusive dressing on Day 2. All test sites were entirely covered by scab formation from Day 7. Sloughing from the scabbed skin began at various times between Day 7 and Day 12 and was completed before termination. Low bodyweight gains or loss of body weight were recorded for one male and three females in Day 8. Two of the same females and a third female also showed low bodyweight gain between Days 8 and 15. Terminal necropsy findings were normal. Additional dermal toxicity studies (Monsanto 1971, 1972a, b) are included in Table 5 but the reliability was rated unassignable (4) due to deficiencies in the number of animals per dose. Inhalation Acute inhalation data are available for LAS (CAS #25155-30-0; Kinney 1985). In this reliability 2 study, groups of six 8-week old rats underwent nose-only exposures to aerosol atmospheres containing 65, 120, 260 or 310 mg/m 3 respirable-sized particulate LAS (MMAD = 2.5 microns) for 4 hours, followed by 14 days of observations for clinical signs. No mortality occurred at concentrations up to 260 mg/m 3 . At 310 mg/m 3 , one rat died during the exposure and two rats died one day post exposure. Given these results C12-LAS is considered moderately toxic by inhalation (see SIAR section 2.3.2 for discussion of inhalation exposure). Conclusion The available acute toxicity data by the oral route of exposure indicate that LAS exhibits slight acute oral toxicity, with symptoms of toxicity and mortality at high doses but not at lower doses. LD50 values for rats and mice range from 1,080 to 1,980 mg/kg bw. No effects were observed in dermal exposure studies with rats at 2,000 mg/kg bw, indicating low dermal hazard potential. Inhalation toxicity data indicate that LAS is moderately toxic, with mortality occurring at respirable particle concentrations of 310 mg/m 3 (MMAD = 2.5 microns). However, less than 0.1% of the total volume sprayed from consumer product spray nozzles consists of respirable particles. Estimates of exposures from consumer spray products indicate that inhalation is not a route of concern. UNEP PUBLICATIONS 23
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LINEAR ALKYLBENZENE SULFONATE (LAS) - UNEP Chemicals

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