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EC number: 270-115-0
CAS number: 68411-30-3
was also made to in situ studies conducted in which lake water
was bottled and suspended in Lake Acton (Ohio) for 3 hour periods. The
mean 3-h EC50(photosynthesis) for the in situ studies
was 3.4 mg/L (0.5-8.0 mg/L).Using
the acute to chronic ratio calculation (documented in Annex 3 of the LAS
SIAR), the EC50/3 for Microcystis is 0.3 mg/L.
NOEC normalized by van de Plassche et al. (1999) to C11.6LAS
was 0.35 mg/L.
In a 96 hour algae growth inhibition test, the green algae Microcystis
aeruginosa was exposed to Linear Alkylbenzene Sulfonate (C11.9 LAS)
in accordance with USEPA OPPTS 850.5400. The nominal test concentrations
were 0 (control), 0.01, 0.05, 0.1, 0.5, 1.0 and 1,000 mg a.i./L.
The 96 hour EC50, based on cell number, was 0.91 mg a.i./L (0.84 -10.0).
The NOEC is estimated to be 0.35 mg/L for C11.6 LAS (van de Plassche et
This algal growth inhibition test satisfies the guideline requirements
of the USEPA OPPTS 850.5400.
Four key studies are used to
characterize the toxicity of LAS to aquatic algae. In the first study
(Lewis 1986; Lewis and Hamm 1986; Larson and Schaeffer 1982; van de
Plassche et al 1999), the toxicity of the test substance to aquatic
algae was evaluated. Pseudokircheneriella subcaptitata, formerly Selenastrum
capricornutum,was exposed to the test substance for 96 hrs and the
cell density measured. The 96 hr NOEC was 0.5 mg/l, the LOEC was 1 mg/L,
and the EC50was 29.0 mg/L based on cell density. When
normalized to C11.6LAS, the NOEC value becomes 0.58 mg/L.
Similarly, in a second algae growth inhibition test (Ward 1982; van de
Plassche et al 1999), the green algae Microcystis aeruginosa was
exposed to C11.9LAS for 96 hours. Nominal test concentrations
were 0 (control), 0.01, 0.05, 0.1, 0.5, 1.0 and 1,000 mg a.i./L. The
resultant 96 hour EC50, based on cell number, was 0.91 mg
a.i./L. The NOEC normalized for C11.6LAS is estimated to be
In a third study (Scholz 1992), Scenedesmus
subspicatus was exposed to concentrations of 0, 0.6, 2.4, 10, 40, or
160 mg/L of C11.6LAS for 72 hours. The 72-hr NOEC was 2.4
mg/L, the EbC50was 47.3 mg/L, and the ErC50was
127.9 mg/L for algae. Normalization is not required since the compound
tested was already C11.6LAS. Similarly, in a fourth study
(Muehlberg 1984), the algae Chlorella kessleri was exposed to
concentrations of 0, 0.01, 0.03, 0.1, 0.3, 1, 3, 10, 30, 100, 300, and
1000 mg/L (nominal) of C11.6LAS for 15 days. The resultant
NOEC was 3.1 mg/L active ingredient, and the LOEC was 10 mg/L active
ingredient. Again, no normalization is required because the study was
conducted on C11.6LAS.
In general, algae were not affected by C12LAS or increased in density,
particularly blue-green algae, and autotrophic activity increased with
increasing C12 LAS. In contrast, some invertebrates declined in density
at concentrations >0.293 mg/L, as a result of increasing drift from the
shock of the initial dose or from long-term toxicity and habitat
changes. Microbes acclimated to mineralizing C12 LAS. Overall, the
heterotrophic periphyton community remained robust and did not change
their food (amino acid) uptake rate.
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