Benzenesulfonic acid, 4-C10-13-sec-alkyl derivs.

Endpoint summary

Description of key information

Short-term aquatic toxicity

Two studies are presented to characterize the potential short-term aquatic toxicity to fish of LAS (read across). In a 96-hour acute toxicity study (key study), bluegill sunfish (Lepomis macrochirus) were exposed to C11.8 LAS under static conditions. The measured concentrations were 79 % of nominal concentrations but were not reported. The 96-hour LC50 value, based on measured concentrations, was 1.67 mg a.i./L. In a second study, 48-hour acute toxicity tests with fathead minnows (Pimephales promelas) were conducted on high molecular weight LAS, individual pure homologues, non-linear LAS components (dialkyl tetralin or indane sulfonates, DTIS), and model biodegradation intermediates (sulfophenylundecane, SOU) in order to determine whether biodegradation decreases toxicity. All of the toxicity tests were conducted in 5 L of 100 mg/L hardness water using 5 fathead minnows per concentration. Results indicated that the length of the alkyl chain is the most important factor influencing acute toxicity, which increases as the alkyl chain increases. These longer alkyl chain homologues are the first constituents of the LAS mixture to degrade. The nonlinear components (DTIS) showed 1/2 to 1/10 the toxicity of LAS with the same carbon chain length. Therefore, toxicity of biodegradation intermediates is significantly less than the parent LAS.

Six studies characterize the potential for short-term toxicity to aquatic invertebrates using LAS (read across). In the key study (Hooftman and van Drongelen-Sevenhuijsen 1990), Daphnia magna were exposed for 48 hours to LAS at nominal concentrations of 0 (Control), 3.2, 5.6, 10, 18, 32, 56 and 100 mg/L under static conditions. The sample was 12.1% active ingredient, and results were adjusted to the active ingredient basis. The resultant 48-h EC₅₀ value based on mobility was 2.9 mg a.i./L. Four additional aquatic invertebrate studies are available, all with EC50 values greater than 2.9 mg/L. In the sixth study (Kimerle and Swisher 1977), the toxicity of high molecular weight LAS, individual LAS homologues, and nonlinear LAS components (DTIS) was measured in a series of aquatic toxicity tests with Daphnia magna. Results show that biodegradation of LAS influences the toxicity, with the remaining LAS becoming less toxic, confirming the results of the study (above) with fathead minnows.

Four studies characterize the potential for short-term toxicity to aquatic algae using LAS (read across). In the study with the lowest EC50 value (Brill 2011), the effect of LAS on Scenedesmus subspicatus was determined in a 72 hr algae growth inhibition test, following the OECD 201 guideline. The LAS was comprised of C10-C13 alkyl chain lengths, with an average chain length of C11.6. Measured concentrations were 99-109% of nominal (0, 1.25, 2.50, 5.0, 10.0 and 20.0 mg/L). The 72 h ErC50 was 7.39 mg/L. In a series of tests using the same algal species (Verge and Moreno 1996), 72 -hour aquatic toxicity values were determined on the C10 through C14 homologues of LAS. ErC50 values ranged from 18 mg/L for the C14 homologues to 270 mg/L for the C10 homologue. Two short-term studies are available on Selenastrum capricornutum. In the first study on this species (Hanstveit and Goossen 1990), two 72 hr algae growth inhibition tests were conducted on C11.8 LAS.  Taking the average of the results from the two tests, the ErC50 was 13.85 mg/L. In the second study on this species (Ward et al. 1982, Lewis and Hamm 1986), a 72 hour algal growth inhibition test was conducted on C11.9 LAS. The ErC50 value is 235 mg/L.  

Long-term aquatic toxicity

To characterize the long-term aquatic toxicity of LAB Sulfonic Acid, single species toxicity studies as well as a model ecosystem study have been conducted on LAS (read across). The single species studies consist of 19 species, included 5 fish, 8 aquatic invertebrates, 4 algae, and 2 aquatic macrophytes.

Fish

Five fish studies are presented. In the first study (Pickering and Thatcher 1970; van de Plassche et al 1999), fathead minnows were exposed to concentrations of 0.34, 0.63, 1.2 and 2.7 mg/L LAS in continuous flow systems for a total of 196 days. Each of the four test concentrations plus control received 12 randomly assigned fish obtained from ponds at the Newtown Fish Farm, Ohio Division of Wildlife. Pieces of half-tile were placed in each 10-gallon aquarium for spawning sites. After spawning had been completed, the cluster of eggs was removed and counted. Four replicates of 100 eggs from each concentration were reared for 14 days and mortality of eggs and fry recorded daily. Results indicate that lethality of LAS to newly hatched fry was the most critical factor found. The 196 day NOEC level was 0.63 mg/L. The LOEC was 1.2 mg/L.

In a second study (Chattopahyay and Konar 1985; van de Plassche et al 1999), the long-term toxicity of the test substance to fish was determined using Tilapia mossambica (tilapia). Groups of 15 fish were exposed to concentrations of 0.0, 0.25, 0.38, 0.51, and 1.10 mg/L for 90 days. Test solutions were renewed every 15 days. The feeding rates decreased significantly at 0.25, 0.38 and 1.10 mg/L. In addition, fish showed erratic behaviour, irregular opercular movement, and at higher concentrations, blood exuded from the base of the pectoral and pelvic fins and head. No apparent difference in condition factor (K) was observed at any concentration. The maturity index (MI) of both male and female fish appeared to decrease at all concentrations, but the biological significance of this is questionable. Fecundity decreased at 0.51 mg/L but not at 1.10 mg/L. The gastrosomatic index (GSI) was significantly different at 0.51 and 1.10 mg/L. Based on the most reliable endpoints (GSI and fecundity), the NOEC would be 0.38 mg/L and the LOEC would be 0.51 mg/L. However, in view of certain reporting limitations as described in the dossier, and the fact that previous evaluations of this study have reported a NOEC of 0.25 mg/L (van de Plassche et al., 1999), a conservative (protective) NOEC for this study is considered to be 0.25 mg/L and the LOEC considered to be 0.51 mg/L.

In the third long-term study (Canton and Slooff 1982; van de Plassche et al. 1999), groups of 50 guppies (Poecilia reticulata) were exposed to various concentrations of LAS for 28 days. Test solutions were renewed three times per week. The only effect (98% mortality at 10 mg/L) occurred within 2 days of study initiation.The 28-day NOEC normalized by van de Plassche et al. (1999) to C_11.6LAS was 3.2 mg/L.The 28-day LOEC was 10 mg/L.

In another study (Unilever 2010), fertilized eggs of rainbow trout (Oncorhynchus mykiss, formerly Salmo gairdneri) were exposed to mean measured concentrations of 0.03, 0.23, 0.35, 0.63, 0.95 and 1.9 mg/L, for 72 days. The responses recorded included the survival of eggs, time to eyed egg stage, time to hatch, survival and final weight of sac-fry (eleutheroembryos), and time and extent of swim-up (external feeding). The lowest NOEC value found was 0.23 mg/L based on survival of eggs exposed from eyed stage, survival of eggs exposed from fertilization, survival of sac fry, and overall survival from fertilization to swim-up. The data are for C_11.6LAS and no normalization is required.

Finally, a long term toxicity test to juvenile bluegills (Lepomis macrochirus) was conducted on C₁₂LAS (Maki 1981). Fish growth was determined after 28 days exposure in a flow-through model ecosystem to measured concentrations of 0, 0.5, 1.0, 2.0, and 4.0 mg/L. Results showed that the growth of juvenile bluegills was not affected at 0.5 and 1.0 mg LAS/L, but was reduced at 2.0 and 4.0 mg/L. At the end of the exposure period, fish at 1.0 mg/L LAS had a biomass of 44 gm/m² compared to 10.5 gm/m² for the 2.0 mg/L concentration. Based on these effects on growth rate, the NOEC was 1.0 mg/L.

Aquatic invertebrates

In the first study (Maki 1977; van de Plassche et al 1999), the toxicity of C_11.8LAS was evaluated in a 21-day survival and reproduction test with Daphnia magna. Four replicates per concentration, five organisms per replicate, were tested in a flow-through system. Mean measured concentrations were 0.32, 0.59, 1.18, 2.52, and 4.85 mg/L C_11.8LAS as active ingredient. Survival was monitored at 24-hr, 96-hr, 7 days and daily thereafter. Reproduction was monitored beginning with the production of the first brood on day 7 or 8, and daily thereafter. Results, based on the mean measured concentration of the active ingredient, indicate that the 21-day NOEC was 1.18 mg/L. The 21-day LC₅₀ was 1.67 mg/L, while the EC₅₀s, based on total young production, average brood size, and percent days reproduction occurred, were 1.50, 2.30, and 2.31 mg/L, respectively. These results were then normalized to a C_11.6LAS according to the methods of van de Plassche et al. (1999), and the final NOEC value is 1.41 mg/L.

In another study (Taylor 1984; van de Plassche et al 1999), a 7-day chronic toxicity test on C_11.8LAS was conducted with Ceriodaphnia sp. under semi-static conditions. Ceriodaphnia were fed either a yeast diet, or an algae/trout chow diet. The test medium was renewed three times in the seven days. Nominal test concentrations were 0, 0.5, 1, 2, 3.5, 5 and 7 mg/L of active ingredient. The resultant 7-day LC₅₀values were 5-7 mg/L for both diets. The no effect concentrations differed between diets. The 7-day NOEC for the yeast diet was 0.5 mg/L (based on reproduction) while the 7-day NOEC for the algae/trout chow diet was 5 mg/L (based on mortality and reproduction). When normalized to a C_11.6LAS, the lowest NOEC is 0.59 mg/L.

In the third study (Maki 1979, 1981; van de Plassche et al 1999), effects on the midge were examined. Groups of P. parthenogenica were exposed for 28 days to concentrations of 0.5, 1.0, 2.0, or 4.0 mg/L (nominal) of LAS. The LOEC was 4 mg/L based on survival and reproduction, and the NOEC was 2.0 mg/L. When normalized to C_11.6LAS, the NOEC value becomes 2.8 mg/L.

The chronic toxicity of C_12.3LAS was evaluated in a 2-day whole life cycle bioassay the rotifer, Brachionus calyciflorus (Procter & Gamble 1996; van de Plassche et al 1999). Six newly hatched rotifers (<3 hours old) were placed in each replicate beaker, and exposed to C_12.3LAS for 48 hours. Results were based on the total number of live, swimming organisms (both adults and offspring) and measured concentrations. The resultant EC₁₀ value was 1.18 mg a.i./L, the EC₂₀ was 1.4 mg a.i./L, and the EC₅₀ was 2.0 mg a.i./L. When normalized to a C_11.6LAS, the EC₁₀ value becomes 1.69 mg/L.

Finally, the chronic toxicity of C₁₂LAS was determined in a 32-day test (Versteeg 2001; Versteeg and Rawlins 2003; van de Plassche et al 1999) with three aquatic invertebrates (Corbicula, Elimia, Hyalella). The invertebrates were caged in the tail pools of an environmental stream mesocosm study of C₁₂LAS. Toxicity was based on water concentrations at which adverse effects were observed. Results were also calculated based on the tissue concentrations at which adverse effects were observed. All invertebrates were exposed to nominal concentrations of 0, 0.15, 0.30, 1.0, and 3.0 mg a.i./L. As mean measured concentrations were 84-99% of nominal, results are based on measured concentrations. On days 0, 8, 16, and 32, the invertebrates were examined for growth and survival. The results can be summarized as follows (all normalized to C11.6):  For Corbicula, the 32 day EC₂₀was 0.39 mg/L based on growth (length), for Elimina, the 32 day NOEC was 4.15 mg/L based on survival and for Hyalella the 24 day EC₂₀was 1.36 mg/L based on survival.

Algae

Seven studies characterize the toxicity of LAS (read across) to four species of aquatic algae. In the first algae growth inhibition test (Ward 1982; van de Plassche et al 1999), the green algae Microcystis aeruginosa was exposed to C_11.9LAS 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 C_11.6LAS is estimated to be 0.35 mg/L.

In a second study (Scholz 1992), Scenedesmus subspicatus was exposed to concentrations of 0, 0.6, 2.4, 10, 40, or 160 mg/L of C_11.6LAS for 72 hours. The 72-hr NOEC was 2.4 mg/L, the E_bC₅₀ was 47.3 mg/L, and the E_rC₅₀ was 127.9 mg/L for algae. Normalization is not required since the compound tested was already C_11.6 LAS. In a series of tests using the same algal species (Verge and Moreno 1996), 72 -hour aquatic toxicity values were determined on the C10 through C14 homologues of LAS. NOEC values based on growth ranged from 7 mg/L for the C14 homologue to 80 mg/L for the C10 homologue.

In a third 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 C_11.6LAS 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 C_11.6LAS.

Three studies were conducted on the fourth species of aquatic algae to be evaluated, Pseudokircheneriella subcaptitata, formerly Selenastrum capricornutum. In the first study on this species (Hanstveit and Goossen 1990), two 72 hr algae growth inhibition tests were conducted on C11.8 LAS at nominal concentrations of 0, 0.12, 0.372, 1.2, 3.84, 13.8, 21.6, 38.4, 67.2 mg a.i./L (test #1), and at nominal concentrations of 0, 0.12, 0.372, 1.26, 3.84, 11.88, 21.6, 38.4, 67.2 mg a.i./L (test #2) test in accordance with OECD Guideline 201. Taking the average of the results from the two tests, the ErC10 was 6.56 mg/L. In the second study on this species (Ward et al. 1982, Lewis and Hamm 1986), a 72 hour algal growth inhibition test was conducted on C11.9 LAS. The nominal test concentrations were control, 16, 32, 63, 125, 250, 500, and 1,000 mg a.i./L. The 72 hour ErC10 value is 13.1 mg/L. In the third study conducted on this species (Huges and Alexander 1991), a 96 h algae toxicity study was conducted on C12.3 LAS and cell density measured. Nominal test concentrations were 0, 0.25, 0.5, 1, 2, 4, 8, 16, 32, and 64 mg a.i./L. The 96 hr NOEC was 0.5 mg/L.

Aquatic macrophytes

Two aquatic plant (other than algae) studies were conducted using LAS (read across). In the first study (Maki 1981), the long term toxicity of C_11.6LAS to the aquatic plant (Elodea canadensis) was determined in a 28 day model ecosystem test. The nominal test concentrations were 0.5, 1.0, 2.0, and 4.0 mg/L, and were confirmed by analytical measurements. Growth inhibition was not observed even at the highest tested concentration (4 mg/L). Growth throughout the exposure period approximately doubled the initial biomass of the vegetative shoots used at the start of the exposure. Hence, the NOEC was found to be >4 mg/L. The data are for C11.6 LAS and no normalization is required.

In the second study (Bishop and Perry 1981; Bishop 1980; van de Plassche et al 1999), the duckweed, Lemna minor, was exposed to C_11.8LAS. Endpoints included frond count, dry weight, growth rate, and root length after a 7 day exposure period in a flow through study. The measured test concentrations were 0, 2.1, 3.8, 8, 17 and 34 mg/L. The resultant EC₁₀ value, based on frond number, was 0.21 mg/L. The EC₅₀ value, also based on frond number, was 2.30 mg/L C_11.8LAS. Normalizing the EC₁₀ of 0.21 mg/L to C_11.6LAS results in a final value of 0.30 mg/L.

Model ecosystem study

Belanger et al. 2002 determined the effect of C₁₂LAS on an ecosystem in an indoor flowing stream mesocosm (model ecosystem). The stream mesocosm drew water from a high-quality stream (a National Scenic River) in southwestern Ohio, USA. Stream channels were naturally colonized by algae and invertebrates for 56 days prior to dosing. Five stream channels were dosed with the test substance at measured concentrations of Control, 0.126, 0.293, 0.927, and 2.978 mg active ingredient/L (84, 98, 93, 99% of nominal, respectively) for an additional 56 days.

Invertebrate endpoints measured included densities of the invertebrate community, sensitive taxa (EPT), dominant taxa, selected ecologically important families (mayfly, caddisfly, true fly, midges, aquatic worms), emerging insects, and drifting invertebrates. Taxonomic richness, Shannon diversity, functional feeding group composition, and community-level multivariate response were derived. For algal populations and communities, algal cell and biovolume density for each dominant taxa and the algal community were determined. Taxonomic richness, Shannon diversity, and community-level multivariate response were assessed. Ecological functional endpoints included heterotrophic activity and acclimation (amino acid uptake and surfactant mineralization) and autotrophic activity (bicarbonate uptake). Sorption, microbial biomass, and microbial diversity shifts using phospholipid fatty acids (PLFA) were also evaluated. Assessments were conducted weekly to bi-weekly depending on the endpoint.

Collectively, results for all taxa and endpoints were considered in determining the 56-day NOEC for the model ecosystem exposed to C₁₂LAS. This NOEC was 0.293 mg/L total active ingredient (0.268 mg/L soluble active ingredient adjusted for bioavailability). In general, algae were not affected by C₁₂LAS or increased in density, particularly blue-green algae, and autotrophic activity increased with increasing C₁₂LAS. 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 C₁₂LAS. Overall, the heterotrophic periphyton community remained robust and did not change their food (amino acid) uptake rate.

Additional information

LAS provides suitable read across for LAB Sulfonic Acids as both form the identical chemical species in aqueous solutions at neutral (physiological) pH, namely, the LAS ion (C_10-13linear alkyl benzene-SO₃^-) and would be expected to have similar ecotoxicological properties.

 

Measurement of the LAB Sulfonic Acid octanol-water partition coefficient of single LAS carbon chain homologues demonstrates that log Pow increases with increasing alkyl chain lengths of single chain homologues (IUCLID section __4.7) of LAS (read across). Increased log Pow with increasing alkyl chain length would be expected to increase aquatic toxicity. The increase in LAS aquatic toxicity with increasing alkyl chain length has been observed in studies in fathead minnow and in aquatic algae, conducted with LAS homologues (C10-C14).

 

Based on QSAR studies on surfactants such as LAS, the most important factor influencing aquatic toxicity of mixtures is the average alkyl chain length (Roberts 1991). This has been demonstrated in fathead minnows by studies with two LAS mixtures (Pantera and Venoco) with closely matched alkyl chain lengths (C11.6-C11.8) which produced similar acute toxicity values (96 hour LC50 values of 2.88 mg/L and 2.22 mg/L, respectively) despite differences is alkyl chain composition (Pantera: C10-C13, Venoco: C10, C12 and C14).

 

Short-term aquatic toxicity of LAS has been evaluated in fish, five species of invertebrates and two species of algae as summarized in Table A below. Test materials are considered to represent the range of materials in the category. The average alkyl chain lengths of tested materials ranged from C11.1 to C12.3, compared to C11.6 for the LAB Sulfonic Acids/LAS typically used in European detergent formulations. The C14 homologue content of tested materials ranged from <1% to 19.6%, compared to <1% for LAB Sulfonic Acids/LAS used in European detergent formulations.  The lowest acute data point is a 96 hour LC50 of 1.67 mg/L for Bluegill Sunfish using C11.8 LAS, with a C14 content of 4.9%.

Based on studies conducted in fish and invertebrates, the toxicity of biodegradation intermediates is significantly less than the parent LAS. Sulphophenyl undecanoate (SɸU), the first biodegradation intermediate of C11 LAS, is 5 to 40 times less toxic than C11 LAS. Shorter chain biodegradation intermediates, such as sulphophenylvalerate and sulphophenylbutyrate, are 20 to 100 times less toxic than SɸU.

 

Alkyl Chain Lengths and C14 Content of LAS Used in Aquatic Toxicity Tests

Table A: Alkyl Chain Lengths and C14 Content of LAS Used in Short-Term Aquatic Toxicity Tests

Test	Average Alkyl Chain Length	C14 Homologue Content	Results
Fish
.018 (Bluegill Sunfish,Lepomis macrochirus)	C11.8	4.9%	96 hour LC50 = 1.67 mg/L
Invertebrates
.001 (Daphnia,D. magna)	C11.1	1.1%	48 hr EC50= 2.9 mg/L
Sediment tox.003 (midge,Chironomus riparius), acute test, water only	C11.8	8.7%	72 hr. LC50 >1.0 mg/L, <4.7 mg/L
Amphipod (Hyalella azteca)*	C12.3	19.6%	96 hour LC50 = 3.5 mg/L
Midge (Chironomus riparius)	C12.3	19.6%	96 hour LC50 = 6.5 mg/L
Oligocheate (Limnodrilus hoffmeister)	C12.3	19.6%	96 hour LC50 = 1.8 mg/L
Algae
.005 (Scenedesmus subspicatus)	C11.6	<1%	72 hr. ErC50 = 7.39
.010 (Scenedesmus subspicatus)	C10 homologue	<1%	72 hr. ErC50 = 270
.014 (Scenedesmus subspicatus)	C11 homologue	<1%	72 hr. ErC50 = 111
.012 (Scenedesmus subspicatus)	C12 homologue	<1%	72 hr. ErC50 = 48
.011 (Scenedesmus subspicatus)	C13 homologue	11%	72 hr. ErC50 = 30
.013 (Scenedesmus subspicatus)	C14 homologue	82%	72 hr. ErC50 = 18
.008 (Selenastrum capricornutum)	C11.8	<1%	72 hr. ErC50 = 13.85 mg/L
.009 (Selenastrum capricornutum	C11.9	8.7%	72 hr. ErC50 = 235 mg/L

To evaluate the chronic aquatic toxicity of LAB Sulfonic Acid, a large number of single species toxicity studies that have been conducted on LAS (read across). As summarized in Table B below, this data set consists of chronic ecotoxicity studies conducted on 19 species, included 5 fish, 8 invertebrates, 4 algae, and 2 aquatic macrophytes. Test materials are considered to represent the range of materials in the category. The average alkyl chain lengths of tested materials ranged from C11.04 to C12.35, compared to C11.6 for the LAB Sulfonic Acids/LAS typically used in European detergent formulations. The C14 homologue content of tested materials ranged from <1% to 19.6%, compared to <1% for LAB Sulfonic Acids/LAS used in European detergent formulations.  The lowest chronic data point is a 7 day EC10 of 0.21 mg/L for the macrophyteLemna minorusing C11.8 LAS, with a C14 content of 4.9%.

  Table B: Alkyl Chain Lengths and C14 Content of LAS Tested in Long-Term Aquatic Toxicity Tests

Test	Average Alkyl Chain Length	C14 Homologue Content	Used for Species Sensitivity Distribution  Calculation*	Results
Fish
.001 (Pimephales promelas)	C12	N/A	Yes	196 day NOEC = 0.63 mg/L
.002 (Tilapia mossambica)	C11.6	N/A	Yes	90 day NOEC = 0.25 mg/L
.003 (Poecilia reticulate)	C11.04	6.5%	Yes	28 day NOEC = 5.4 mg/L
.004 (Salmo gairdneri= Oncorhynchus mykiss)	C11.6	<1%	Yes	70 day NOEC = 0.23 mg/L
.005 (Lepomis macrochirus)	C11.6	<1%	Yes	28 day NOEC = 1.00 mg/L
Invertebrates
.001 (Daphnia magna)	C11.8	<1%	Yes	21 day NOEC = 0.23 mg/L
.002 (Ceriodaphnia dubia)	C11.8	<1%	Yes	7 day NOEC = 1.18 mg/L
.003 (P. parthenogenica)	C11.6	<1%	Yes	28 day NOEC = 2.00 mg/L
.004 (Brachionus calyciflorus)	C12.3	19.6%	Yes	2 day EC10 = 1.18 mg/L
.005 (Corbicula fluminea)	C12 (pure homologue)	<1%	Yes	32 day EC20  = 0.27 mg/L
.005 (Elimia)	C12 (pure homologue)	<1%	Yes	32 day EC20 = 2.9 mg/L
.005 (Hyallea aztecia)	C12 (pure homologue)	<1%	Yes	32 day EC20  = 0.95 mg/L
Sediment tox.003 (midge,Chironomus riparius), water phase	C11.8	8.7	Yes	24 day NOEC = 2.40 mg/L
Algae
.002 (Microcystis aeruginosa)	C11.9	8.7%	Yes	96 hr. NOEC = 0.35 mg/L
.010 (Scenedesmus subspicatus)	C10 homologue	<1%	No	72 hr. ErC10 = 80
.014 (Scenedesmus subspicatus)	C11 homologue	<1%	No	72 hr. ErC10 = 40
.012 (Scenedesmus subspicatus)	C12 homologue	<1%	No	72 hr. ErC10 = 18
.011 (Scenedesmus subspicatus)	C13 homologue	11%	No	72 hr. ErC10 = 12
.013 (Scenedesmus subspicatus)	C14 homologue	82%	No	72 hr. ErC10 = 7
.016 (Scenedesmus subspicatus = D. subspicatus)	C11.6	<1%	Yes	72 hr. NOEC = 2.4 mg/L
.017 (Chlorella kessleri)	C11.6	<1%	Yes	15 day NOEC = 3.5 mg/L
.008 (Selenastrum capricornutum = P. subcapitata)**	C11.8	<1%	Yes	72 hr. ErC10 = 6.56 mg/L
.009 (Selenastrum capricornutum)	C11.9	8.7%	No	72 hr. ErC10 = 13.1 mg/L
.015 (Selenastrum capricornutum)	C12.35	18.9%	No	96 hr. NOEC = 0.5 mg/L
Aquatic Plants (macrophytes)
.001 (Elodea canadensis)	C11.6	<1%	Yes	28 day NOEC = 4.00 mg/L
.002 (Lemna minor)	C11.8	4.9%	Yes	7 day EC10 = 0.21 mg/L

* Belanger et al. 2016.

Because the LAS chronic aquatic toxicity studies consists of data on nearly 20 species in four groups of aquatic organisms (fish, invertebrates, algae and mycrophytes), calculation of a species sensitive distribution (SSD) is appropriate (REACH Technical Guidance Document R.10.3.1.3,Calculation of PNEC for freshwater using statistical extrapolation techniques).As has been previously well described in the peer reviewed literature and in OECD and USEPA HPV (High Production Volume) assessments, LAS mixtures were first normalized to C_11.6LAS by use of conventional Quantitative Structure-Activity Relationships (see van de Plaasche et al. 1999; OECD 2005). Similar normalization processes for environmental risk assessment have also been performed for alcohol sulfates, alcohol ethoxysulfates, alcohol ethoxylates and long chain alcohols (van de Plaasche et al. 1999; HERA 2002; Belanger et al., 2006, 2009). The normalization procedures followed the process first described by van de Plaasche et al. (1999) and replicated for HPV (OECD 2005). Chronic aquatic toxicity data normalization outcomes are cited in the respective IUCLID5 entries in the Chemical Safety Report for the registered substance (LAS: CAS# 68411-30-3).

 

The C_11.6LAS-normalized chronic data were then fitted to a log-logistical function from which the HC₅ (the SSD_0.05) of 0.19 mg/L was calculated (95% Lower and Upper Confidence Limits of 0.06 to 0.36 mg/L), respectively). The HC₅ value was equal to or lower than any of the normalized chronic values contained in the dataset. The quality of the dataset and the sensitivity and stability of the SSD were validated using recommended criteria and conventional statistical procedures. These included “leave-one-out” and “add-one-in” statistical simulations using hypothetical data. These evaluations demonstrated that the chronic toxicity data were highly ordered, and strongly adhered to statistical assumptions. The SSD, and the resulting HC₅, were highly stable to either deletion or addition of new data.

A model ecosystem study of LAS concluded a NOEC of 0.268 mg/L and is used to derive the PNEC water for LAS. ECHA describes the interactive roles of statistical extrapolation techniques with the deterministic based PNECs for mesocosms in the REACH Technical Guidance Document Sections R.10.3.1.2 (Calculation of PNEC for freshwater using assessment factors) and R.10.3.1.3 (Calculation of PNEC for freshwater using statistical extrapolation techniques). Stream model ecosystems are considered the most appropriate for assessing this chemical (versus ponds) due to the wide dispersive use and route of discharge to receiving waters via wastewater treatment plants. In the case of the model ecosystem study summarized by Belanger et al. (2002), the following considerations support no additional application factor to be applied to the result when deriving the PNEC water (seeECETOC 1997, Giddings et al. 2002, OECD 2006). The most important factors are knowledge of the biological complexity, sensitivity, study duration, exposure determination, and relevance to natural systems for the specific system being assessed. For the model ecosystem study of LAS:

1)           The model ecosystem was biologically complex, containing a highly diverse community with 117 invertebrate genera assessed (including ~500 insect species). Approximately 150 algal species were studied, dominated by sensitive diatom flora. Protozoa which were not studied in this particular investigation historically accounted for an additional 300 species.

2)           The model ecosystem was sensitive. The system was optimized for statistical and biological sensitivity. Key endpoints evaluated possessed Minimum Detectable Differences using inferential statistics of 5-20% (change needed to be identified as statistically different from the control). Use of PRC, Principal Response Curve Analysis, corroborated use of repeated measure ANOVAs on single population endpoints and coincides with NOECs on the most sensitive taxa and taxonomic groups. The dominant invertebrate taxa were sensitive species of the EPT group (mayflies, stoneflies, and caddisflies; a total of 28 genera were represented). Dominant algae were diatoms, many known as sensitive species. Functional endpoints were also investigated including photosynthesis, organic matter processing, in situ biodegradation, organism drift, insect emergence.

3)           The model ecosystem study was longer than most chronic toxicity tests (approximately 4 months duration). Colonization of the streams, leading to stable, consistent and testable communities, was for 10 weeks with exposure of stream communities to LAS was for 8 weeks. Repeated sampling insured ecological and toxicological shifts were tracked.

4)           The exposure to LAS was verified weekly and found to be nearly 100% of nominal. For example the streams exposed to nominal concentrations of 0.300 and 3.000 mg/L were measured at 0.293 mg/L and 2.973 mg/L, respectively. A dynamic sorption model based on detailed weekly investigations of sorption, daily evaluations of suspended solids, and weekly assessments of DOC, TOC were used to express exposure based on the free fraction of dissolved LAS.

5)           The study is relevant to natural systems. Studies by the sponsor demonstrated the model ecosystem was nearly indistinguishable from the source system and representative streams that were relatively uninfluenced by man. Dyer and Belanger (1999) showed ESF stream communities were as or more sensitive than >80% of streams in Ohio surveyed at >1200 locations from the period of 1985-1995. The more sensitive systems were Appalachian mountain slope, first or second order systems that never have seen effect or been exposed to human influences to any degree. Peterson et al. (2001) and Morrall et al. (2006) demonstrated community function of the test system was similar to that of low order streams across the globe (including systems outside of the United States) and that predator-prey relationships in the ESF were equivalent to the source river used to deliver water to the streams.

In summary, the NOEC of LAS measured from the ESF model ecosystem study was equal to 293 µg LAS/L which corresponds to 268 µg LAS/L as free (dissolved and not associated with organic or particulate matter). Further, an Application Factor (AF) of 1 is justified, especially when viewed in concert with the chronic toxicity Single Species Sensitivity Distribution (SSD) of 0.19 mg/L). Based on this data, the PNEC_freshwater was calculated as the model ecosystem study NOEC/1 or 0.268 mg LAS/L.

To calculate the PNEC_marine the aquatic NOEC of 0.268 mg/L from the model ecosystem study was used as a starting point.The AF for the marine PNEC is generally 10 applied to the PNEC_freshwater resulting in a PNEC_marine of 0.0268 mg/L.This AF is considered appropriate given the detailed literature reviews regarding marine and freshwater organism sensitivity to LAS (Temara et al. 2001). Temara et al. (2001) provided conclusions that were similar to observations from van de Plaasche et al. (1999), but with additional data to derive a chronic marine SSD to compare with a chronic freshwater SSD. In these investigations, the sensitivity of marine taxa versus freshwater is typically 10-fold, consistent with the AF consistent with principals described in the   REACH Technical Guidance Document Sections R.10.3.2.3 (Calculation of PNEC for marine water).

Finally, the PNEC_{intermittentreleases} was calculated as normal by using the lowest acute LC50 value and applying an AF of 100 to get a final PNEC_{intermittentreleases} value of 0.0167 mg/L.

 

Toxicity to Microorganisms

 

LAS (read across) produced no toxicity to microorganisms when tested at 35.3 mg/L in a Ready Biodegradability study (OECD 301B Modified Sturm Test). This value was used to derive the PNECstp following the guidance of Section R.10.4.2 of Guidance 10, which states that the PNECstp can be derived from the available ready or inherent biodegradation tests using as assessment factor of 10.