Risk Assessments-executive summary
Substance Group: Fatty Acid Salts

Fatty acid salts (soap)
are widely used in household cleaning products, cosmetics, lubricants (and other miscellaneous industrial applications) and coatings. Uses in household cleaning products, the scope of this HERA assessment, include fabric washing products, fabric conditioners, laundry additives, and surface and toilet cleaners. These uses cover chain lengths of C10-22 predominantly with counterions of sodium and potassium.

According to data received from a survey conducted among detergent formulator companies, an overall annual tonnage of 71306 tonnes of fatty acid salts for use in HERA applications was estimated. This was compiled using data from 4 out of the 6 main formulator companies. This value is estimated to cover greater than 80% of the tonnage used within the HERA use categories. Calculations of PEC in the risk assessment have been based on 71306 tonnes per annum. A scaling factor of 1/0.8 = 1.25 is used as a final calculation of risk characterisation ratios to convert these values into estimates for total use in HERA applications.

There are a number of acute data for fatty acids and fatty acid salts to aquatic organisms although there is a predominance of data for fatty acid. There are few toxicity values for terrestrial organisms. Data availability / quality covering all the taxonomic groups for specific fatty acid salt chain lengths is poor. The chronic data set is very limited.

For chain lengths >C12, solubility decreases to a degree where an adverse effect would not be expected in the environment due to reduced biovailability. Data for longer chain lengths have been generated using solvents which makes interpretation more difficult.

The data set for environmental fate includes standard biodegradation studies (looking at aerobic and anaerobic degradation), some degradation in surface water studies and field monitoring data.

Removal from wastewater was determined using measured monitoring data. The PNEC values for C10 and C12 were determined from measured toxicity data. For chain lengths >C12 all observed toxicity values were above the limit of solubility and were not used in PNEC derivation. In determining the PNECs for these chain lengths, assumptions were made based on the toxicity values for shorter more soluble chain lengths. The PNEC values for the longer chain lengths are likely to be conservative since the concentration of the soluble fraction will be lower than that at which toxicity would be observed. PNEC and PEC calculations are further complicated by the predominance of calcium and magnesium ions in waste water leading to rapid formation and predominance of relatively insoluble Ca and Mg salts that will not be bioavailable.

By means of higher tier exposure and effects data, it could be shown that the use of fatty acid salts in HERA applications (household detergents and cleaning products) poses no concern in any environmental compartment. The risk characterisation ratios are considered conservative. This is largely due to the conservative nature of the derived PNEC values for chain lengths >C12 as described above.