LINEAR ALKYLBENZENE SULFONATE (LAS) - UNEP Chemicals

OECD SIDS LINEAR ALKYLBENZENE SULFONATE (LAS)
most sensitive endpoint and resulted in NOEC value of 100 mg/kg dw for all three species. The
EC50 values were 167, 289 and 316 mg/kg dw for the sorghum, sunflower and mung bean,
respectively. Figge and Schoberl (1989) tested the effects of a defined mixture of LAS
(composition not reported) to several crop species. Studies were conducted in a “plant metabolism
box” consisting of natural soil cores taken from two different ecosystems. Radiolabeled LAS
absorbed to digested sludge was incorporated into the soils, which were then planted with either
grass, bush beans, radishes, or potatoes and maintained for either 76 or 106 days. The resulting
NOEC values were 27.2 mg/kg dw for grass, beans and radishes, and 16.2 mg/kg dw for potatoes.
Table 17. Results of LAS Exposure on Terrestrial Plants (in mg/kg dry weight) 1
Species Endpoint EC10 EC50 NOEC Reference
Grass, Beans, Radishes Biomass 27.2*
Potatoes Biomass 16.2*
Sorghum bicolour (crop
sorghum)
Helianthus annuus
(sunflower)
Phaseolus aureus (mung
bean)
1 Reliability of Studies = (2)
* Highest concentration tested.
Figge and Schoberl 1989,
dossier 4.6.2b
Figge and Schoberl 1989,
dossier 4.6.2b
Growth 167 100 Windeat 1987
Growth 289 100 Windeat 1987
Growth 316 100 Windeat 1987
Additional terrestrial plant studies are included in the LAS dossier. The reliability of the NOEC
and EC10 values for these additional studies could not be adequately assessed because the original
studies were not available for review. Therefore, they are not included in Table 17.
The potential for LAS and other surfactants to influence defoliation in coastal trees was reviewed in a
literature review (Hamwijk 2002). In laboratory studies in which young trees are exposed to artificial
sea spray, it has been demonstrated that the presence of surfactants at a concentration that causes a
dynamic surface tension < 30 mN/m lead to an increased foliar penetration of NaCl via the stomata.
For example, Grieve and Pitman (1978) examined the influence of surfactants on foliar NaCl uptake
in Norfolk Island Pines (Araucaria heterophylla). Plants were exposed to seawater with different
concentrations of LAS. At 10 mg/L of LAS, which corresponds with a reduced surface tension of 32
mN/m, the Na + content in the foliage increased almost tenfold to a level of approximately 500 µmol/g
dw and damage symptoms were recorded. It was found that a low surface tension increases the
contact angle with the leave and makes it possible for an aqueous solution to enter the stomata.
Richard et al. (1996) reported the results of a 2-minute exposure of pine trees (Pinus halepensis) to
14 C-LAS (58 mg/L). LAS was primarily absorbed in the epicuticular waxes of the pine needles with
very little in other plant material. The amount of absorption, and changes in wax fine structure
(SEM), was much greater for LAS in seawater (where surface tension = 29 mN/m) than in distilled
water (surface tension = 45 mN/m). However, the concentrations of LAS in seawater (section 2.2.8)
are much lower than those required to increase foliar penetration in these studies, suggesting that this
mechanism may not be relevant to coastal tree defoliation.
UNEP PUBLICATIONS 47