Toward a Framework for Environmental Fate and Exposure Assessment of Polymers

Abstract

Development of risk-assessment methodologies for polymers is an emerging regulatory priority to prevent negative environmental impacts; however, the diversity and complexity of polymers require adaptation of existing environmental risk-assessment approaches. The present review discusses the challenges and opportunities for the fate and exposure assessment of polymers in the context of regulatory environmental risk assessment of chemicals. The review discusses the applicability and adequacy for polymers of existing fate parameters used for nonpolymeric compounds and proposes additional parameters that could inform the fate of polymers. The significance of these parameters in various stages of an exposure-assessment framework is highlighted, with classification of polymers as solid or dissolved being key for identification of those parameters most relevant to environmental fate. Considerations to address the key limitations and knowledge gaps are then identified and discussed, specifically the complexity of polymer identification, with the need for characterization of the most significant parameters for polymer grouping and prioritization; the complexity of polymer degradation in the environment, with the need to incorporate the fate and hazards of degradation products into risk assessment; the requirement for development and standardization of analytical methods for characterization of polymer fate properties and degradation products; and the need to develop exposure modeling approaches for polymers.

Water-Soluble Synthetic Polymers: Their Environmental Emission Relevant Usage, Transport and Transformation, Persistence, and Toxicity

“…Degradation data for some WSPs have been summarized in several studies. ,,, However, several issues remain of note. For example, these polymers cover only a small fraction of the types of polymers currently in use, which are mainly in cosmetics and/or household cleaning products.…”

“…Understanding such information is critical to accurately assessing their environmental exposures and ecosystem impacts. After release into the environment, WSPs may typically undergo a variety of transformations, which can be described as physical transformations (e.g., flocculation and adsorption) and chemical transformation processes (e.g., aging and degradation). − These processes and the mobility of WSPs in compartments such as natural soils and water bodies are significantly influenced by water chemistry (e.g., pH, ionic strength, natural organic content) and soil/aquifer sediments (e.g., composition), as well as by polymer properties (e.g., water solubility, reactive functional groups (RFG), charge, molecular weight (MW), and molecular weight distribution (MWD)). ,, …”

“…15−17 These processes and the mobility of WSPs in compartments such as natural soils and water bodies are significantly influenced by water chemistry (e.g., pH, ionic strength, natural organic content) and soil/aquifer sediments (e.g., composition), as well as by polymer properties (e.g., water solubility, reactive functional groups (RFG), charge, molecular weight (MW), and molecular weight distribution (MWD)). 6,18,19 Reviews on the environmental occurrence, fate, and toxicity of WSPs are extremely limited, and relevant investigations concentrate primarily on polymer types in cleaning products and cosmetics. The recent environmental risk assessment of polycarboxylate polymers such as acrylic acid homopolymers and acrylic acid−maleic acid copolymers used in cleaning products in the United States was conducted by DeLeo et al 10 Duis et al 6 evaluated the environmental fate and impact data for PEGs, acrylic polymers, and cationic PQs in cosmetic products.…”

Assessing and managing environmental hazards of polymers: historical development, science advances and policy options

“…For instance, the ISO 4611:2010-12 standard allows measuring the changes in plastics' mass, size and color as a result of exposure to damp heat, water spray and salt mist, and similar ISO methods are available to look at weathering caused by exposure to sunlight (ISO 4892 part 1–3 (2013–2016), ISO 877-1:2009-06). For microbial degradation, tests such as those envisaged by Brunning et al (2022) 40 could be employed to benchmark the biodegradation of polymers, with the caveat that transformation products formed by primary biodegradation may not themselves be biodegradable. 10 Importantly, rather than using such tests to simply record the changes occurring in a polymer, a possibility to couple them to diverse (eco)toxicity tests performed on the “end-products” of weathering should be actively explored and developed as a standardized addition.…”

“…For the needs of hazard and risk assessment, Brunning and colleagues suggested three basic categories: bulk solid, dissolved, and low-MW polymers. 40 While these three categories provide a useful starting point, dividing the "bulk solid" category into further subsets may prove useful when estimating the exposure potential (see Section 3.2). Furthermore, a signicant subset of polymers may meet the criteria for two or three of these categories, as the proposed category boundaries are blurry (e.g., having a solubility or melting temperature near a threshold), because in the environment, these properties can be affected by specic environmental conditions such as presence of salts and dissolved organic matter.…”