Evidence of Sub‐Micrometric Plastic Release When Heating Food Containers Based on Light Scattering Measurements

A growing body of literature is raising concerns about the spread of nano‐ and microplastics and the hazards they pose to the environment and on human health. There is still a limited understanding of their sources and formation mechanisms, making their release and uptake difficult to track and quantify. Among the obstacles to the progress in this field there is the lack of reliable methods for quantitative studies, leading to a potential underestimation of the extent of their release and the related risks. In this paper, the application of an optical method for studying the release of sub‐micrometric plastics in water by polypropylene containers certified for alimentary use is described. The results show evidence of negligible release when the temperature of the water is kept below the manufacturer's specifications, whereas a rampant increase occurs beyond these conditions, irrespective of the thermal history of the sample. Particles with a diameter distribution that spans one order of magnitude are observed, ranging from ≈200 nm to 2 µm, and their refractive index and shape is characterized with light scattering measurements. This work focuses on particle release and does not assess toxicity or effects on living organisms. Water heated close to 100 °C in food containers causes an appreciable release of plastic particles predominantly smaller than 1 µm. Particle‐by‐particle optical data shows that these particles are spherical in shape and have the same refractive index of the bulk material they detach from. An optical method for characterizing plastic particles at both low and high concentrations is discussed.