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.

Toward a Framework for Environmental Fate and Exposure Assessment of Polymers

“…Given that polymer molecules in solution can also exist in the nano-size range (Armstrong et al, 2004;Arp & Knutsen, 2020;Xiong, Miller, et al, 2018), it may also be relevant to test and verify the applicability domain of equilibrium-based parameters to such polymers. Furthermore, as has been discussed by Cumming (2008) and Duis et al (2021) in the context of the environmental fate of polyquaterniums, polyethylene glycols, and acrylic acid polymers, conformation of polymer chains is likely to play a role in sorption and desorption, which will affect partitioning to soils and sediment in the environment for dissolved polymers.…”

“…It is likely that for lower-tier, worst-case ERA scenarios, existing exposure-assessment methods will be generally sufficient for polymers, with only information on usage/production volumes and emissions estimates being necessary, although the availability of these data for many current-use polymers may limit characterization of exposure (Duis et al, 2021). However, for more complex, higher-tier environmental exposureassessment studies which incorporate data on fate behavior, additional considerations are likely to be necessary for polymers.…”

“…However, for more complex, higher-tier environmental exposureassessment studies which incorporate data on fate behavior, additional considerations are likely to be necessary for polymers. Only a limited number of environmental exposure and risk assessments have been performed for polymers to date, including for polyethoxylated surfactants, polycarboxylates, and polyquaterniums (see Cumming, 2008;DeLeo et al, 2020;HERA, 2004HERA, , 2009HERA, , 2014aHERA, , 2014b, with detailed information on polymer characteristics often being limited (Duis et al, 2021). For example, the assessment of polyquaterniums conducted by Cumming (2008) was limited by insufficient information to estimate the mixture of polyquaterniums present or their range of charge densities and MWs.…”

“…In particular, environmental exposure and risk assessments have been conducted for alcohol ethoxylates, alcohol ethoxysulfates, and polycarboxylate homo-and copolymers as part of the HERA project (HERA, 2004(HERA, , 2009(HERA, , 2014a(HERA, , 2014b, with degradation data for these classes of polymers being summarized as part of these risk assessments. In addition, Duis et al (2021) gathered available data for several polycarboxylate polymers, polyethylene glycols, and polyquaterniums.…”

“…While there are degradation data in a range of media available for many of these polymer groups (Table 2), it should be noted that these groups cover only a small fraction of the polymer types in current use, and degradation data for environmental matrices (surface waters, soils, and sediments) are limited. There are also few data available for polyquaterniums as a class (Duis et al, 2021), despite potential concerns relating to the environmental hazard of cationic polymers (see USEPA, 1997). In addition, a lack of information on experimental methods limits assessment of the quality of some results (Duis et al, 2021) as well as comparison and verification between studies, highlighting the need for transparency and standardization of methods for adequate risk assessment.…”