Benzenesulfonic acid, 4-(branched alkyl derivs.) and benzenesulfonic acid, 4-(linear alkyl dervis.), calcium salts

Bioaccumulation: aquatic / sediment

Description of key information

Calculation with BCFBAF v3.01 (EPIWIN software by US-EPA): 70.8 L/kg wet-wt, strong bioaccumulation is not expected.
Assessment of Calcium Sulfonates: no bioaccumulative substances 

Key value for chemical safety assessment

BCF (aquatic species):

70.8 L/kg ww

Additional information

The calcium sulfonate target substance (C15 -C36) has a predicted Bioconcentration Factor (BCF) of 70.8 L/kg (Chemservice S.A., 2013d) and partition coefficient (logPow) of > 6.65 at 20 °C (Fox and White, 2011) strong bioaccumulation in aquatic biota is not expected. Only limited bioaccumulation is assumed for compounds with a logPow < 4.5 or > 6 (based on ECHA REACH Guidance R.11 PBT Assessment). Concerning logPow exceeding 6, a gradual decrease of the Bioconcentration Factor (BCF) is observed practically. Examples are discussed in a literature study of the German Federal Environment Agency (Umweltbundesamt (Ed.): Comparative analysis of estimated and measured BCF data (OECD 305). Report No. (UBA-FB) 001435/E, ISSN: 1862-404, Dessau, March 2011).

For large lipophilic molecules (as the target UVCB substance), the molecular weight can be potential candidate for use as cut-off trigger for B/vB compounds, since substances with a molecular weight >600 revealed decrease in BCF values (BCF < 1000, hence below the REACH trigger values for B/vB). For details, refer to p. 31 of Fraunhofer Report FKZ36001043 (Literature study: Effects of molecular size and lipid solubility on bioaccumulation potential; Fraunhofer Institut Molekularbiologie und Angewandte Oekologie, Schmallenberg, Germany, February 2007).

Furthermore, it has been hypothesized by different authors in publications that a high logPow is more an effect of solubility than lipophilicity of the substance. In conclusion, according to REACH, Annex IX, Section 9.3.2 (column 2), this endpoint can be waived.

The prediction of the BCF was performed with the computer program BCFBAF v3.01 (EPIWIN software) by US-EPA (Chemservice S.A., 2013d). Also the whole body primary biotransformation rate estimation for fish was calculated with a normalized bio half-life of 10 g fish at 15 °C. With this result it is possible to predict the apparent metabolism half-life in fish for three different trophic levels (lower, mid and upper).In general, the bioconcentration factor of a substance describes the accumulation potential of a substance dissolved in water by an aquatic organism. BCFBAF v3.01 calculates also the BAF (Bioaccumulation factor) of the chemical, which is defined as the steady-state (equilibrium) ratio of the substance concentration in an organism to the concentration in the surrounding medium. However, this value is not taken into account for the risk assessment and is not relevant for a registration under REACH Regulation (EC) 1907/2006. Using the regression-based estimate (traditional method) of the computer program BCFBAF from US-EPA a Bioconcentration Factor (BCF) of 70.8 L/kg wet-wt was calculated for the test substance. Using the Arnot-Gobas method, which is based on mechanistic first principles, an aquatic BCF of 0.893 L/kg wet-wt is the result.

The whole body primary biotransformation rate estimate for fish results in a half-life of 5.274E+5 days, whereby the bio half-life is normalized to 10 g fish at 15 °C. The rate constant (kM) for 10 g fish is 1.314E-6/day. This is taken into account to predict the apparent metabolism half-life in fish. With the Arnot-Gobas method it is possible to differentiate between three trophic levels. For the lower trophic level the BCF results in 0.94 L/kg wet-wt, for a mid trophic level the result is 0.93 L/kg wet-wt and for the higher trophic level 0.90 L/kg wet-wt. As conclusion it can be stated, that a strong bioaccumulation in aquatic organisms is unlikely.

Calcium Sulfonates: Assessment of Bioaccumulation Potential

The weight of evidence presented below on calcium sulfonates demonstrates that CLP/GHS classification as hazardous to the aquatic environment is Not justifiable and that the hazard profile does Not meet the B or vB criteria. This assessment should apply to all calcium sulfonates whether natural or synthetic, whether high or low TBN and may also apply to other sulfonates (e.g., Mg, Na) based on further evaluation.

Basis for Not Bioaccumulative:

Substance	Data	Result
Calcium sulfonate (high TBN, Natural)	logPow  (OECD 107/117; Harlan 2012a)	> 6.65^a
Sodium sulfonate (high TBN, synthetic)	logKow (OECD 117; Environment & Resource Technology 2000)	10.88
Calcium sulfonate  EC# 274-263-7 CAS# 70024-96-0 (synthetic, high TBN)	logKow (QSAR; Safepharm 2004)	17.9
Calcium sulfonates (various)	logKow (HPV)	> 6.7
Calcium sulfonate	logKow (CSR for EC274-263-7;QSAR)	QSAR Weight of Evidence: 25.44 14.66 24.06 18.05 10.68 31.87 16.09 16.61
Various sulfonates e.g. EC#274-263-7	Classification and Labelling	Manufacturer MSDS sheets (e.g. Chemtura) and data presented on the ECHA websites (e.g. CAS 61789-86-4) shows Not classified as R53
Calcium sulfonate	BCF prediction	BCF in fish of 11 L/kg predicted by the CAESAR model BCF in fish less than 100 L/kg ww as predicted by EPISUITE 4.1 and Arnot-Gobas Method
Calcium sulfonate	Read Across to similar structures with experimental BCF	Japan CHRIP database presents 3 similar substances (CAS#81-11-8; 88-44-8; 121-03-9) with experimental BCF values in carp of <5 CAESAR model found two similar structures (ID 113 and 302) with experimental BCF values in fish which were less than 20 L/kg
Various sulfonates	Molecular weight	Molecular weight of surfactant portions is often > 1,000 which results in low potential for bioavailability and bioaccumulation
Various sulfonates	Water solubility	Water solubility is very low, measured values typically less than 0.1 ppm, thereby limiting potential for exposure and accumulation and making it technically not feasible to even run an experimental BCF study even if warranted.
Various sulfonates	Ecotoxicity	Low potential for acute and chronic ecotoxicity, suggesting limited potential for protein absorption, bioavailability, and bioconcentration
Various sulfonates	Molecular diameter	High diameter limits potential for bioaccumulation
Various sulfonates	Component analysis	Sulfonates are often produced and supplied in the presence of significant amounts of mineral oil (e.g. > 40 %) which is of low bioaccumulation potential and thereby limits the B potential of the overall substance

^aExperimental testing for water solubility and octanol-water partition coefficient for the calcium sulfonates is considered extremely challenging following OECD Guidelines because the sulfonate components can dissociate from the calcium atom an form a suspension with surfactant properties, which is why greater than values were used for logKow. The language in the Harlan report states that because the water solubility was so low, resulting in less than values for water solubility, it resulted in a partition coefficient estimate with a greater than value, and that the actual logKow would be greater than that value of >6.65 presented.

References:

1) SafePharm 2004. Calcium Sulfonate Determination of General Physico-Chemical Properties.SPL project 525/522.

2) Howes, D. (1975) The percutaneous absorption of some anionic surfactants.J Soc Cosmet Chem, 26: 47-63. 

3) Environment & Resource Technology 2000. Study 330-19. Determination of the partition coefficient of sodium sulfonate.

4) Harlan 2012a. Calcium sulfonate determination of water solubility and partition coefficient.Project 41100981.

5) Harlan 2012b. Calcium sulfonate determination of water solubility and partition coefficient.Project 41100982.

6) Harlan 2012c. Calcium sulfonate determination of water solubility and partition coefficient.Project 41100980.

7) U.S. Environmental Protection Agency High Production Volume Challenge Program (HPV) Test Plan for Petroleum Additive Alkaryl Sulfonate Category, Prepared by The American Chemistry Council,Petroleum Additives Panel, Health, Environmental, and Regulatory Task Group, October 2001 (http://www.epa.gov/hpv/pubs/summaries/alklsulf/c13206rt.pdf).