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Occurrence and characteristics of atmospheric microplastics in Mexico City
Summary
Researchers conducted the first study of atmospheric microplastics in Mexico City, sampling air at seven monitoring stations across urban, residential, and industrial areas during dry and wet seasons. Microplastics were found in every sample, with higher concentrations near industrial and urban centers and during the dry season. The predominant type was blue fibers, and many particles were small enough to be inhaled, raising concerns about airborne microplastic exposure in densely populated cities.
While atmospheric microplastics have attracted scientific attention as a significant source of microplastic contamination in the environment, studies in large population centers remain sparse. Here we present the first report on the occurrence and distribution of atmospheric microplastics in Mexico City (Latin America's second most densely populated city), collected using PM and PM active samplers at seven monitoring stations (urban, residential, and industrial) during the dry and wet seasons of 2020. The results showed that microplastics were detected in all of the samples examined, with mean microplastic concentrations (items m) of 0.205 ± 0.061 and 0.110 ± 0.055 in PM and PM, respectively. The spatial distribution of microplastics showed seasonal variation, with greater abundances in locations closer to industrial and urban centers. There was also a significant difference in microplastic concentrations in PM and PM between the dry and wet seasons. The mean PM/PM ratio was 0.576, implying that microplastics were partitioned more towards PM than PM in Mexico City. Fibers were the most prominent shape (>75 %), and blue was the most common color (>60 %). The size characteristics indicated microplastics of varying lengths, ranging from 39 to 5000 μm, with 66 % being <500 μm. Metal contaminants such as aluminum, iron, and titanium were detected using SEM-EDX on randomly selected microplastics. The microplastics were identified as cellophane, polyethylene, polyethylene terephthalate, polyamide, and cellulose (rayon) using ATR-FTIR spectral analysis. Our findings unravel the extent and characteristics of atmospheric microplastics in the Mexico City metropolitan area, which will aid future research to better understand their fate, transport, and potential health risks, demanding more investigations and close monitoring.