Airborne microplastics: Occurrence, sources, fate, risks and mitigation

This paper serves to enhance the current knowledge base of airborne microplastics which is significantly smaller than that of microplastics in marine, freshwater and terrestrial environments. It systematically presents the prevalence, sources, fate, risks and mitigations of airborne microplastics through the review of >140 scientific papers published mainly in the last 10 years. Unlike the extant review, it places an emphasis on the indoor microplastics, the risks of air-borne microplastics on animals and plants and their mitigations. The outdoor microplastics are mostly generated by the wear and tear of tires, brake pads, waste incineration and industrial activities. They have been detected in many regions worldwide at concentrations ranging from 0.3 particles/m3 to 154,000 particles/L of air even in the Pyrenees Mountains and the Arctic. As for indoor microplastics, the reported concentrations range from 1 piece/m3 to 9900 pieces/m2/day, and are frequently higher than those of the outdoor microplastics. They come from the wear and tear of walls and ceilings, synthetic textiles and furniture finishings. Airborne microplastics could be suspended and resuspended, entrapped, settle under gravity as well as interact with chemicals, microorganisms and other microplastic particles. In the outdoors, they could also interact with sunlight and be carried by the wind over long distance. Air-borne microplastics could adversely affect plants, animals and humans, leading to reduced photosynthetic rate, re-tarded growth, oxidative stress, inflammatory responses and increased cancer risks in humans. They could be mitigated indirectly through filters attached to air-conditioning system and directly through source reduction, regula-tion and biodegradable substitutes.

Automated summary

This paper systematically presents the prevalence, sources, fate, risks, and mitigations of airborne microplastics through the review of >140 scientific papers. It emphasizes the indoor microplastics and their risks on animals, plants, and humans. Outdoor microplastics are mainly generated by various activities and have been detected worldwide, while indoor microplastics come from wear and tear and have higher concentrations. Airborne microplastics can interact with chemicals, microorganisms, and other particles, and can adversely affect organisms and humans. Indirect and direct mitigations can be achieved through filtration systems and source reduction, regulation, and biodegradable substitutes.