LAUSR

Humans spend 70-90% of their time indoors, however, there is a significant lack of knowledge regarding human exposure to microplastic particles and fibers (MPs) within the indoor environment. Fibers make up more than 90% of household settled dust worldwide and have been found in indoor air. Studies have identified MPs larger than 50 micrometers in indoor dust, but these are unlikely to be respirable and little information is available regarding smaller airborne particles. It is evident that humans are inhaling these particles as they have been found in excised diseased and healthy human lung tissues. We have developed methods to identify plastic particles in settled household dust larger than one micrometer in diameter by distinguishing plastic from cellulosic, proteinaceous, and inorganic materials using two different stains, Nile Red for plastics, and Trypan Blue for cellulosic materials. Proteinaceous and inorganic materials remain unstained. Household settled dust is collected onto silicon nitride nanomembranes where in situ analysis of particles can be characterized. The innovative use of nanomembranes allow for particle capture and multiple analyses to take place on the same substrate. Particle analysis via colorimetric staining and imaging is followed by polymer identification via Raman spectroscopy and subsequently characterized via scanning electron microscopy for size and surface morphology. Using this innovative approach, microplastic particles larger than one micrometer in diameter have been identified in all settled dust samples.