Roberto Rosal
Professor of Chemical Engineering in the Department of Analytical Chemistry, Physical Chemistry and Chemical Engineering at the University of Alcalá
The article presents a critical reassessment of global microplastic emissions to the atmosphere. The authors use a Lagrangian particle dispersion model driven by previously published emission inventories, including both theoretical bottom-up approaches and earlier top-down estimates based on regional data from the United States. These simulations are compared against an extensive dataset of more than 2,000 real-world observations.
The main conclusion is that earlier estimates dramatically overestimated atmospheric microplastic emissions by two to four orders of magnitude—that is, they predicted between 100 and 10,000 times more plastic than is actually present. The study also challenges the notion that the ocean is a major source of plastic particles to the atmosphere. Instead, the results indicate that oceanic emissions are negligible compared with terrestrial sources, and that the ocean effectively acts as a sink for plastic originating on land.
The issue with inventory-based theoretical estimates lies not so much in their conceptual framework as in the highly inflated input values, which stem from large uncertainties in emission factors. Although the study does not introduce new measurements, its strength lies in confronting theory with global observational evidence, demonstrating that scientific estimates—even those that receive significant media attention—can be subject to massive errors and should therefore be interpreted with caution.