Environmental fate and effects of water-soluble synthetic organic polymers used in cosmetic products

Abstract

Because of their usually high molecular weight, polymers are generally considered as being of low environmental concern and are, therefore, exempted from registration and evaluation within REACH. This exemption is currently being reviewed by the European Commission. Against this background, data on the environmental fate and effects of selected water-soluble synthetic organic polymers used in cosmetic products were evaluated. The considered polymers include non-ionic polyethylene glycols (PEGs), anionic homo- and copolymers of acrylic acid (AA-P&CoPs), and cationic polyquaterniums (PQs). The PEGs are more amenable to biodegradation than the AA-P&CoPs and the PQs, which biodegrade slowly. In wastewater treatment plants, sorption and precipitation are expected to lead to an effective removal of the considered polymers from the wastewater. Uptake and bioaccumulation in aquatic organisms are limited by the large molecular size and, for AA-P&CoPs and PQs, the ionic charge of the polymers. In aquatic ecotoxicity tests, the PEGs and the AA-P&CoPs showed generally no to low toxicity. Effects of AA-P&CoPs on algae and crustaceans are attributed to the chelation of cationic nutrients in soft water, with toxicity being mitigated at higher water hardness. Toxicity of the cationic PQs to aquatic organisms ranged from absent to high, depending on the polymer structure, charge density and molecular weight, as well as on the test organism and test conditions. The observed effects most likely result from interactions with the organisms’ surfaces. Aquatic toxicity of the PQs is reduced by dissolved organic carbon, suspended solids, sediments minerals, and at higher water hardness, representative of natural conditions. Results from toxicity tests with sediment and soil organisms were only identified for homopolymers of acrylic acid, showing no toxicity. The evaluation of the available ecotoxicity data suggests that test methods may need to be adapted to the respective polymer type, and further standardised to improve reproducibility. Based on the identified data, the considered polymers are likely to be of low environmental concern. However, this conclusion must be seen as preliminary, since environmental concentrations could not be estimated, and further ecotoxicity data are required, e.g., for sediment and soil organisms.