Secondary Alkane Sulfonate (SAS) is an anionic surfactant, also called paraffine sulfonate. It was synthesized for the first time in 1940 and has been used as surfactant since the 1960ies. SAS is one of the major anionic surfactants used in the market of dishwashing, laundry and cleaning products.
The European consumption of SAS in detergent application covered by HERA was about 66.000 tons/year in 2001.
This Environmental Risk Assessment of SAS is based on the methodology of the EU Technical Guidance Document for Risk Assessment of Chemicals (TGD Exposure Scenario) and the HERA Exposure Scenario.
SAS is removed readily in sewage treatment plants (STP) mostly by biodegradation (ca. 83%) and by sorption to sewage sludge (ca. 16%). Only around 1% of the mass load from sewage is discharged into surface water and readily biodegraded in river as well.
The Predicted Environmental Concentrations (PECs) for STP, water, sediment and soil were estimated for both scenarios (HERA and TGD). Due to the low volatility of SAS air concentrations are very low and are therefore not considered in this assessment.
For the aquatic compartment acute and chronic data for all three trophic levels are available and the PNECaquatic was calculated from the NOECreproduction based on a 21d Daphnia study. As no sediment and terrestrial ecotoxicity data are available the equilibrium partitioning method was used to derive a PNECsediment and PNECsoil. The PNECSTP was derived from a chronic study on bacterial cell growth.
The Environmental Risk Characterisation for all compartments (STP, water, sediment and soil) and both scenarios (HERA and TGD) gave PEC/PNEC quotients below 1. From the comparison of the Predicted Environmental Concentrations with measured data it is obvious that the HERA Scenario is more realistic than the TGD Scenario.
Indirect exposure of humans via the environment was also taken into account. Based on the calculated local and regional doses in drinking water and food indirect exposure for humans can be neglected.
The presence of SAS in many commonly used household detergents gives rise to a variety of possible consumer contact scenarios including direct and indirect skin contact, inhalation, and oral ingestion derived either from residues deposited on dishes, from accidental product ingestion, or indirectly from drinking water.
The consumer aggregate exposure from direct and indirect skin contact as well as from inhalation and from oral route in drinking water and dishware results in an estimated total body burden of 3.87 µg/kg bw/day.
The toxicological data show that SAS was not genotoxic in vitro or in vivo, did not induce tumors in rodents after two years daily dosing using both, the oral and dermal route of exposure, and failed to induce either reproductive toxicity or developmental or teratogenic effects. The critical adverse effects identified are of local nature mainly due to the irritating properties of high concentrated SAS.
Comparison of the aggregate consumer exposure to SAS with a systemic NOEL of 180 mg/kg body weigh per day (assuming 90% absorption; adapted from Michael, 1968) which is based on a chronic feeding study, results in an estimated Margin of Exposure (MOE) of 46500. This is a very large Margin of Exposure, large enough to account for the inherent uncertainty and variability of the hazard database and inter species and intra species extrapolations (which are usually conventionally estimated at a factor of 100).
Neat SAS is an irritant to skin and eyes in rabbits. The irritation potential of aqueous solutions of SAS depends on concentration. However, well documented human volunteer studies indicate that SAS up to concentrations of 60% active matter is not a significant skin irritant in humans. Local effects of hand wash solutions containing SAS do not cause concern given that SAS is not a contact sensitizer and that the concentrations of SAS in such solutions are well below 1% and therefore not expected to be irritating to eye or skin. Laundry pre-treatment tasks, which may translate into brief hand skin contact with higher concentrations of SAS, may occasionally result in mild irritation easily neutralized by prompt rinsing of the hands in water. Potential irritation of the respiratory tract is not a concern given the very low levels of airborne SAS generated as a consequence of cleaning spray aerosols or laundry powder detergent dust.
In view of the extensive database on toxic effects, the low exposure values calculated and the resulting large Margin of Exposure described above, it can be concluded that use of SAS in household laundry and cleaning products raises no safety concerns for the consumers.