Natural but threatening? (I) A systematic aquatic ecotoxicity evaluation of biopolymers and modified natural polymers

Synthetic polymers and modified natural polymers are subject to EC 2023/2055, whereas biopolymers can be considered as important unregulated substituents. However, as regulatory requirements for biopolymers and a regulatory accepted hazard evaluation concept for polymers in general is missing, potential ecotoxicological effects are unknown. Biopolymers are often categorized as environmentally uncritical due to their origin, even though supporting data are missing. To assess potential environmental effects, we considered six biopolymers and modified natural polymers in a systematic ecotoxicity screening with aquatic organisms, hypothesising that the selected polymers are not ecotoxic. We tested alginate, chitosan, cellulose fibres Jelucel® HM 200, xanthan, carboxymethyl cellulose and modified starch Emwaxy® Jel 100 in OECD TG 201 (standard), 202 (miniaturised) and 236 (adapted to include OMICs) with algae, daphnids and zebrafish embryos, respectively. A screening of transcriptomic changes in zebrafish embryos was used to identify potential toxic modes-of-action of the polymers in fish. The polymers were applied in a concentration range of 1-100 mg/L as filtrates to consider potential intrinsic effects. Additionally, the impact of particulate polymers was evaluated by exposing algae and daphnids to polymer suspensions. Physical interactions were determined in algae growth studies leading to reduction of cell growth (lowest LOEC 10 mg/L). Daphnid immobility was observed with exposure to particulate chitosan (LOEC 100 mg/L). In zebrafish embryos, predominantly Emwaxy® Jel 100 affected the expression of genes involved in metabolic and catabolic processes (607 up- and 1002 down-regulated genes). Overall, polymer filtrates usually had no significant impact within the concentration range.