Esterquats are a widely used class of cationic surfactants. They were introduced in the early 1980s when concerns were raised about the environmental profile of DHTDMAC (Di-Hardened Tallow Di-Methyl Ammonium Chloride) a fabric conditioner. Esterquats are similar to DHTDMAC except that ester links were introduced into the head-group of the molecules, making them more subject to degradation by hydrolysis and greatly facilitating biodegradation. Most, if not all, fabric conditioners marketed in Europe are now comprised of the three Esterquat groups, TEAQ (triethanol amine quat), DEEDMAC (diethyloxyester dimethylammonium chloride), and HEQ ((Z)-2-hydroxy-3-[(1-oxo-9-octadecenyl)oxy]propyltrimethylammonium chloride). They combine a good environmental profile, especially in terms of ready and ultimate biodegradability (OECD criteria), with the structural features required for an effective fabric conditioner.
The total volume of Esterquat surfactants used in Europe is estimated to be 130,000 tonnes/year on an active matter basis [HERA, 2004].
A large environmental data set is available for esterquats. The ester quats under consideration are assessed according to a group approach, which is scientifically justified by close similarities with regard to physico-chemical properties, structural aspects, and a homogeneous ecotoxicity profile of relevant endpoints. On the environmental fate side this is based on standard biodegradation studies, advanced simulation studies of removal in treatment systems, and effluent monitoring data. On the environmental effects side acute as well as chronic single-species data are available tested with laboratory test water as well as natural river water.
To assess the Predicted Environmental Concentration (PEC), chemical removal in waste water treatment plants was determined from advanced simulation test data. Monitoring studies on sewage treatment plant effluents indicated that the exposure estimates in this assessment are in good agreement with each other.
The Predicted No-effect Concentration (PNEC) was based on chronic ecotoxicity.
Based on this higher tiers exposure and effects data, it could be shown that the use of esterquats in HERA applications (household detergents and cleaning products) results in risk characterization ratios less than one for the micro-organisms in a sewage treatment plant as well as aquatic,sediment and terrestrial organisms indicating no concern for any of these environmental compartments.