LINEAR ALKYLBENZENE SULFONATE (LAS) - UNEP Chemicals

OECD SIDS LINEAR ALKYLBENZENE SULFONATE (LAS)
Methods: The effect of LAS on the structure and function of microbial communities
was studied in a flow-through model ecosystem containing several trophic
levels. The LAS was applied to 19-L glass aquaria in either well water
(Phase I) or sewage effluent (Phase II). In Phase I, duplicate chambers
contained water and 2.5 cm lake sediment (Winton Lake, Cincinnati, OH)
and several trophic levels (bacteria, algae, macrophytes [Elodea
canadensis,Lemna minor], macroinvertebrates [Daphnia magna,
Paratanytarsus parthenogenica], and fish [Lepomis macrochirus]).
Chambers were allowed to equilibrate for about four weeks and then were
exposed to 0.5 and 5.0 mg/L LAS. Flow rate in the proportional diluter
delivered 6 to 10 replacement volumes per day. In Phase II, the aquaria were
supplied with LAS in sewage effluent to simulate more closely the situation
in an actual receiving stream. Sewage effluent was generated in a
continuous activated sludge (CAS) unit and was adjusted to maintain 50
percent LAS degradation. Effluent from the CAS unit was then supplied to
the test chambers at sewage dilutions of 3 and 30 percent to achieve nominal
undegraded LAS concentrations of 0.5 and 5.0 mg/L, respectively. Test
duration was 28 days. Microbial structure was estimated by measurements
of total viable bacterial biomass as CFU/mL. Microbial function was
estimated in Phase I by measuring the rates of oxygen consumption during
the degradation of glucose and LAS. In Phase II, microbial function was
assayed by radiochemical methods.
Results: In Phase I, the structure of microbial communities was not affected, and no
significant differences were reported in mean biomass or number of colonyforming
units between the microorganisms exposed at the two levels. The
mean total biomass calculated for all tanks and across all sampling points was
about 3 x 10 5 CFU/mL. The function of the microbial communities was
reduced only at 5.0 mg/L. In Phase II, no effect was seen on the structure of
the microbial community, with mean CFU/mL in the low and high dose
aquaria (0.9 x 10 5 and 1.4 x 10 5 , respectively) similar to the control aquaria
(1.4 x 10 5 ). Also, no effects were observed microbial function in Phase II,
which was measured only as the degradation of LAS. Therefore, the NOEC
based on the most sensitive endpoint (microbial community function) is 0.5
mg/L.
Substance: LAS; radiolabeled C 14 -LAS with chain length C12 (91% purity) plus
unlabeled LAS with average chain length C11.6 (C10 9.7%, C11 27.9%, C12
54.4%, C13 8.0%; 95% purity)
Remarks: Function assays in Phase II were based on LAS degradation only, since the
Phase I results indicated that LAS degradation was the most sensitive
indicator of toxic effect levels.
Reference: Larson, R.J. and Maki, A.W. 1982. Effect of linear alkylbenzene sulfonate
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.
Reliability: 2 Valid with restrictions
(i)
Type: Laboratory aquaria
Methods: Two exposures were conducted. Phase I was designed to develop basic
toxicological information. Phase II introduced partially degraded LAS
contained within the effluent of a continuous activated sludge unit and was
designed to to simulate real-world fate and effects for LAS. In Phase I,
duplicate 19-L glass aquaria containing model ecosystems at four nominal
concentrations (0.5, 1.0, 2.0, 4.0 mg/L) contained water and 2.5 cm lake
sediment (Winton Lake, Cincinnati, OH) and several trophic levels (bacteria,
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