LINEAR ALKYLBENZENE SULFONATE (LAS) - UNEP Chemicals

OECD SIDS LINEAR ALKYLBENZENE SULFONATE (LAS)
Test Substance: C10-14 LAS, activity 66.62%; average alkyl chain length = C11.7
Remarks: In most cases, sea water samples showed a similar evolution of
bacterioplankton over time, characterized by three phases: (a) a progressive
increase in bacterial density; (b) a later decrease; and (c) a fluctuating
stationary phase. Bacterioplankton degraded the LAS by growing to
populations with a high percentage of viable bacteria. The bacteria were
readily grazed by protozoa, preventing anomalous high bacterial growth and
ensuring the later channeling of LAS carbon to upper trophic levels.
Reference: Vives-Rego, J., Lopez-Amoros, R., Guindulain, T., Garcia, M.T., Comas, J.,
and Sanchez-Leal, J. 2000. Microbial aspects of linear alkylbenzene
sulfonate degradation in coastal water. Journal of Surfactants and
Detergents. 3:303-308.
Reliability: 2 Valid with restrictions
(v)
Type: Respirometer
Method: Degradation of LAS in Ohio River water collected below the discharge of a
municipal wastewater treatment plant (Muddy Creek, OH) was measured in
an electrolytic respirometer. Background LAS concentrations were less than
0.5 mg/L. Oxygen consumption over time was determined at five LAS
concentrations (5, 10, 20, 40, and 80 mg/L) plus a control until plateau values
were reached. The maximum initial rates of oxygen uptake were calculated
based on methods described in Larson and Perry (1981).
Results: LAS degradation was not affected in river water until the LAS concentration
exceeded 10 mg/L. The degradation was partially affected at 20 mg/L but
was not completely inhibited until 40 mg/L.
Substance: LAS; average chain length C11.6.
Remarks: The level at which inhibition of degradation was complete (40 mg/L) is
significantly higher than the levels observed in model ecosystem studies
conducted by these researchers [see 4.7 (h) and (i)].
Reference: 1) Larson, R.J. and Maki, A.W. 1982. Effect of LAS on the structure and
function of microbial communities in model ecosystems. Aquatic
Toxicology and Hazard Assessment: Fifth Conference, ASTM STP 766,
Pearson, J.G., Foster, R.B., and Bishop, W.E., Eds., American Society for
Testing and Materials, pp. 120-136.
2) Maki, A.W. 1981. A laboratory model ecosystem approach to
environmental fate and effects studies. Unpublished Internal Report,
Environmental Safety Department Procter & Gamble Company, Cincinnati,
Ohio.
3) Larson, R.J. and Perry, R.L. 1981. Water Research 15:697-702.
Reliability: 2 Valid with restrictions
(w)
Type: aerobic [X]; anaerobic [ ]
Substance: LAS
Remarks: The biodegradation of LAS has been thoroughly studied for its primary and
total degradation and catabolism. It is mineralized biologically to form
carbon dioxide, water and sulphate. Using UV spectroscopic analysis,
Swisher (1987) and others showed the aromatic ring to be degradable up to
80%. Using the more reliable tracer technique with 14 C-ring labelled LAS, it
was determined that degradation of the ring is predominantly between 50 and
80%. Further studies have shown that LAS degradation proceeds through
oxidative conversion of the methyl groups of the alkyl chain into a carboxyl
group (ω-oxidation), oxidative shortening of the alkyl chain by 2-carbon
units (β-oxidation), oxidative ring splitting, then cleavage of the carbonsulfur
bond. This process forms sulfophenyl carboxylates (SPCs) as
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