Because of the ubiquity of microplastics (MPs) in the environment there are concerns regarding human exposure. In this study, MPs have been determined in three physiological fluids: urine, sputum and bronchoalveolar fluid (BALF)
from 30 adult patients in Iran with respiratory conditions. A total of nine small (20-100 μm) and mainly green and red fibres of polyethylene, polypropylene and polystyrene construction were detected in urine samples of eight participants. By contrast, 358 MPs that were dominated by small, white and transparent fibres, but also included larger (100-500 μm) fibres and fragments and spherules of various sizes, were detected in sputum samples. Here, a broader range of polymers was identified but polyurethane was dominant. In BALF samples, 123 MPs were detected that included a higher proportion of larger fibres, along with fragments and spherules. The colour distribution of these MPs was similar to that of sputum samples but polymer distribution was closer to that of urine samples. These observations suggest that MPs that are inhaled and ingested might be fractionated differently though the body. Further research is required to elucidate how particles larger than theoretical limits (set by filtration mechanisms) are present in physiological fluids, what fractionation processes are present, and whether ingested or inhaled MPs are responsible for acute and chronic health impacts.