LRI ECO67: Understanding the relationship between plastic-based fabricated article composition, article degradation processes, and the generation of microplastics under relevant environmental conditions

Background

There is an increasing concern related to potential environmental and human risks associated with microplastics. The environmental risk of microplastics is dictated both by bioavailability and toxicity (i.e., hazard), as well as the likelihood of exposure to microplastics in the environment. Thus, the processes through which end-use articles manufactured from plastics degrade into microplastics under environmentally relevant conditions are important for determining microplastic exposure and risk in the environment. Gaining a robust understanding of these degradation processes is critical to improve the understanding of the lifetime/timescale of plastics in the environment and their consequent interactions with biota.

Plastic-based fabricated articles such as packaging (e.g., films, pouches, bags, bottles, plastic-ware), agricultural film (e.g., silage, mulch, greenhouse), and durable goods (fishing nets, ropes, boating equipment, etc.), are found in the terrestrial and aquatic environment either as part of their in-service function, or as waste.  These articles slowly degrade as a function of time and environmental factors (light, heat, pressure, abrasion, biological activity, etc.). These degradation processes can result in the formation of microparticles in the environment. Plastic characteristics, including but not limited to chemical composition and structure (e.g., crystallinity, molecular weight), impact degradation processes. Moreover, plastic-based products (i.e., fabricated articles) are seldom made from a single plastic but rather are often engineered from several materials including more than one plastic type, different polymers and/or non-polymeric materials (e.g. additive, fillers).  The formulation and design of the final plastic product is based on the specific end-use application(s) to deliver the required performance and function. These diverse  materials, used to generate the final plastic product, can all influence degradation and introduce significant variability into degradation processes across different end-use plastic products.  In addition, the fabrication conditions used to produce the finished plastic article and any transition the fabricated article might have undergone during its use could potentially influencing the degradation processes, thus must be taken into consideration to both accurately assess environmental and human health risk and find solutions to address that risk.  Many of these factors were not considered in prior microplastic studies. Especially, the impact of product formulation on the degradation of plastics in the environment is under studied.

Environmental conditions also play an important role in the degradation of plastic-based fabricated articles.  Natural environments are complex systems consisting of multiple potential degradation processes, including but not limited to photodegradation by UV radiation, chemical degradation by oxygen, mechanical degradation by natural forces, and microbial degradation by microorganisms. There is currently a knowledge gap regarding the cumulative impacts of multiple environmentally relevant stressors on the degradation of fabricated plastic articles to macro-fragments, microparticles, and nanoparticles.

To address the gaps of our understanding on degradation of plastics in the environment, Cefic LRI is currently sponsoring a project to develop a mechanistic model of micro and nanoplastic fragmentation in the environment (Cefic LRI ECO59). The 2^nd ICCA MARII Workshop,  held in June 2023, had a dedicated session on degradation processes of microplastics. One of the research priorities identified from this session is the need for quality data linking fabricated article product formulation to plastics degradation processes and the generation of micro- and naoplastics, under relevant environmental conditions, which can then be used to build robust predictive models.

Therefore, proposals are requested to build an understanding of how plastic-based fabricated article formulation impacts plastics degradation and micro- and nanoplastics generation, under environmentally relevant conditions.