The impacts of plastic products on air pollution - A simulation study for advanced life cycle inventories of plastics covering secondary microplastic production

A framework, SecµPlast, to include secondary microplastic (MP) formation due to photooxidation into current Life Cycle Assessments (LCA) from cradle-to-grave of products. The framework details how to incorporate secondary MP formation into the plastic's life cycle as related to the plastic's use phase, and location specific waste treatment and how to connect the impacts with current life cycle impact assessment methodologies (LCIA). Plastics, now ubiquitous in the environment are a potential source of emerging pollution and have been shown to have negative effects of various species. Thus, the framework consist of 1) a degradation module, which accounts for micro- and nano- plastic formation with dynamic degradation of microparticles, 2) an emissions module accounts for the potential of the plastic particles to be emitted to air, and 3) an impacts module which connects the various emissions to existing LCIA methods. The framework allows for quantification of secondary microplastic in an LCA context and for further characterization of the impacts at endpoints in terms of human health, and allows for a high level of regionalization, both in terms of input data and characterization of impact damages. SecµPlast was tested on a case study of mulch film which showed that the per kg contribution to particulate matter (PM) and other impacts is low. The impacts vary largely depending on the degradation rate and ranged from 9.24×10−6 to 0.00043 kg PM equivalents per kg of mulch film, depending on either a slow or fast degradation rate, respectively. The impact came mostly from the littered fraction, which was estimated to be 10% of the products weight after the use phase, in Europe. The degradation rates due to UV degradation were low, 0.034 µg/year for a slow degradation rate, compared to values derived from the literature, 0.345 µg/year for a fast degradation rate during littering, that included other sources of degradation, such as abrasion. However, when these impacts are scaled up to the European consumption of plastics and monetized, it is evident that even small increases of PM are costly for society and could potentially amount to millions of dollars per year in human health damages. Further research efforts should focus on filling data gaps, such as microplastic losses during production, recycling and potentially incineration, as well as degradation kinetics including other degradation factors such as freeze/thawing, wet/drying in combination with UV degradation.