LINEAR ALKYLBENZENE SULFONATE (LAS) - UNEP Chemicals

OECD SIDS LINEAR ALKYLBENZENE SULFONATE (LAS)
Reference: Belanger, S.E., Bowling, J.W., Lee, D.M., LeBlanc, E.M., Kerr, K.M.,
McAvoy, D.C., Christman, S.C., and Davidson, D.H. 2002. Integration of
aquatic fate and ecological responses to linear alkyl benzene sulfonate (LAS)
in model stream ecosystems. Ecotoxicology and Environmental Safety.
52:150-171.
Reliability: 1 Valid without restriction
(b)
Results: Time averaged mean measured concentrations over the 28 day exposure
period were 0.03, 0.06, 0.12, 0.32, 0.52, 1.0 and 3.0 mg/L in the artificial
streams and 0.24, 0.81, and 2.0 mg/L in the downstream pools.
Problems were experienced with dosing LAS into the streams after day 45
due to extreme weather conditions causing freezing of stock solutions of LAS
in the delivery tubes. Results should therefore be treated with caution as
exposure data is extrapolated from 45 to 56 days. Time averaged mean
measured concentrations over the first 45 days of the 56 day study period
were 0.03, 0.06, 0.12, 0.32, 0.52, 1.0 and 3.0 mg/L in the artificial streams
and 0.22, 0.69, and 1.6 mg/L in the downstream pools.
A total of 65 taxa were identified in the artificial streams and downstream
pools. Effects data were generated for 24 endpoints, which included ten
invertebrate taxa, two fish species and algae. The inclusion of downstream
pool sections increased the range of taxa investigated. The downstream pool
community appeared generally less sensitive to the LAS than the stream
channel community. Individual taxa were found to differ in susceptibility to
LAS depending on their location in the stream channels. The same taxa were
generally more susceptible when in the riffle section than in the pool sections.
This may have been the result of differences in exposure or physiological
state of the organism.
Results from the first 28 days of the study concluded that there were no
NOECs below 0.12 mg/L. Extending the study to 56 days resulted in no
change in NOECs for the majority of endpoints. NOECs determined in the
artificial streams were in the range of 0.03 to >3.0 mg/L although the most
reliable NOECs were in the range 0.12 to 3.0 mg/L. In the downstream pools
the NOECs ranged from 0.69 to >1.6 mg/L. Only two NOECs were below
0.12 mg/L; the population density of Gammarus pulex in the riffle and
population density of Baetis sp. Some uncertainty is associated with the
extended 56 day study due to three main factors. First, lack of exposure data
between days 45 and 56. Further uncertainty is associated with the low
NOECs for some end points, particularly for G. pulex in the riffle section of
the artificial streams. Second, the uncertainty in the lower NOEC is due to
the times dependent effects (increased susceptibility at 56 compared to 28
days) only being observed for individuals of G. pulex in the riffle but not the
pool section of the artificial streams. Reduction in NOEC from 28 to 56 days
for G. pulex in the riffle was not evident in the pool section of the artificial
streams where the 28 and 56 day NOEC was 0.52 mg/L. The exact cause of
the difference between riffle and pool is unknown. Third, uncertainty was
due to variability of the G. pulex data and sensitivity to statistical
transformation.
Conclusion: The lowest NOEC value observed in this artificial stream study was 0.12
mg/L. However, the river water was seeded from field collections and a
hydrocyclone used to prevent colonization of biota throughout the study.
Drift therefore comprised only emigration and not immigration. This is an
ecologically restrictive study design that ignores the importance of recovery
vectors present in natural systems.
UNEP PUBLICATIONS 237