Micro- and nanoplastics (MNPs) are gaining increasing attention currently. (1−9) Since the first evidence of microplastics (MPs) in human feces in 2019, (10) they have been found in various human biological samples such as saliva, sputum, liver, breastmilk, lung, and blood. (11−16) This suggests that MPs can be transported throughout the body via circulation. In vitro experiments suggest that MNP toxicity to human cells may result from membrane damage, oxidative stress, immune response, and genotoxicity. (17−20) Monomers and additives (e.g., stabilizers and plasticizers) may leach from the MNPs inside the organism, exposing the tissues to hazardous chemicals such as phthalates and bisphenol A. (21) Furthermore, due to their large specific surface area and strong sorption capacities, MNPs contribute to a Trojan horse effect that toxic pollutants (e.g., heavy metals and pathogens) can be carried by MNPs and released inside the organism, (22) thereby exerting synergistic toxicological effects. (23) These findings have raised concerns about the actual human exposure to MNPs.

Several studies have estimated the MP intake from different sources, such as air, water, and food, concluding that airborne MPs (AMPs) contribute significantly to the overall human uptake of MPs. (1,24−27) However, the magnitude, variability, and uncertainty of AMP exposure and intake rates globally remain little known. Previous estimations of human exposure to AMPs were almost in a deterministic manner, irrespective of the uncertainties in the data sets used. Due to the differences in analytical techniques, the reported MP abundances in different studies can vary by several orders of magnitude, resulting in a predicament of incomparability for the current MP research. Additionally, their estimations failed to estimate AMPs from the full MP continuum (1–5000 μm). (28) Furthermore, single exposure estimates based on average rates may not well represent the distribution of global AMP intake. A previous study presented an efficient probabilistic method to calculate the MP intake for children and adults. (24) However, their estimation was based on a limited data set and did not differentiate between indoor and outdoor air, potentially leading to an underestimation of AMP intake through inhalation...

Figure 1. Distribution of power-law exponents for AMPs and the fitted Gaussian mixture curve with two Gaussian distribution components (μ1 = −2.248, μ2 = −1.717, σ1 = 0.452, σ2 = 0.323; w1 = 0.313, w2 = 0.687).

Figure 4. Number and mass inhalation of indoor and outdoor airborne NPs for children (a) and adults (b).