Benzenesulfonic acid, C10-13-alkyl derivs., sodium salts

Ecotoxicological Summary

Hazard for aquatic organisms

Freshwater

Hazard assessment conclusion:

PNEC aqua (freshwater)

PNEC value:

0.268 mg/L

Assessment factor:

1

Extrapolation method:

assessment factor

PNEC freshwater (intermittent releases):

0.017 mg/L

Marine water

Hazard assessment conclusion:

PNEC aqua (marine water)

PNEC value:

0.027 mg/L

Assessment factor:

10

Extrapolation method:

assessment factor

STP

Hazard assessment conclusion:

PNEC STP

PNEC value:

3.43 mg/L

Assessment factor:

10

Extrapolation method:

assessment factor

Sediment (freshwater)

Hazard assessment conclusion:

PNEC sediment (freshwater)

PNEC value:

8.1 mg/kg sediment dw

Assessment factor:

10

Extrapolation method:

assessment factor

Sediment (marine water)

Hazard assessment conclusion:

PNEC sediment (marine water)

PNEC value:

6.8 mg/kg sediment dw

Assessment factor:

10

Extrapolation method:

assessment factor

Hazard for air

Air

Hazard assessment conclusion:

no hazard identified

Hazard for terrestrial organisms

Soil

Hazard assessment conclusion:

PNEC soil

PNEC value:

35 mg/kg soil dw

Extrapolation method:

sensitivity distribution

Hazard for predators

Secondary poisoning

Hazard assessment conclusion:

no potential for bioaccumulation

Additional information

The PNEC for water is generally derived from the no observable effect concentrations (NOEC) for the most sensitive aquatic species, to which are applied the appropriate assessment factors. In the case of LAS there are a large number of chronic single species toxicity studies that have been conducted on a variety of aquatic species over the years. These data were used to develop a logical progression to evaluation of LAS in a highest tier model ecosystem study (Belanger et al. 2002). Prior to conducting the model ecosystem study, assessments of LAS toxicity using deterministic and probabilistic approaches were performed (van de Plaasche et al. 1999). Subsequently, most focus has been on probabilistic (statistical) assessments as warranted by the size of the data base, including summaries presented in OECD and USEPA HPV (High Production Volume) assessments).

An SSD assessment was performed using chronic aquatic toxicity values available from tests with various LAS homolog mixtures. The dataset of 19 chronic ecotoxicity studies included 4 species of algae, 2 aquatic macrophytes, 8 invertebrates and 5 fish. Development and analysis of the SSD followed ECHA procedures described in the REACH Technical Guidance Document R.10.3.1.3 (Calculation of PNEC for freshwater using statistical extrapolation techniques) supplemented with additional statistical evidence reflecting the state of the science.

The available chronic toxicity data on LAS spans a variety of mixtures which vary in their composition of alkyl chains. As has been previously well described in the peer reviewed literature and in OECD and USEPA HPV (High Production Volume) assessments 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 IUCLID 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 (see ECETOC 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_aquatic 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.