Air conditioner filters become sinks and sources of indoor microplastics fibers

Indoor airborne microplastics fibers (MPFs) are emerging contaminants of growing concern. Nowadays, air conditioners (ACs) are widely used in indoor environments. However, little is known about their impact on the distribution of indoor MPFs. In this study, we first disclosed the prevalence of MPF contamination in filters for indoor split ACs used in living rooms, dormitories, and offices. The average density of microfibers was 1.47-21.4 × 10² items/cm², and a total 27.7-35.0% of fibers were MPFs. Of these fibers, the majority were polyester (45.3%), rayon (27.8%), and cellophane (20.1%). We further tracked the long-term accumulation of MPFs on AC filters in three types of rooms, and demonstrated that dormitories showed relatively heavy accumulation especially after running for 35-42 days. Furthermore, we found that simulative AC filters which had been lined with PET MPFs could effectively release those MPFs into indoor air, propelling them away from the ACs at varying distances. Statistical analysis showed that the estimated daily intake of MPFs (5-5000 μm length) from AC filters would increase gradually with their usage, with the intake volume reaching up to 11.2 ± 2.2-44.0 ± 8.9 items/kg-BW/day by the 70th day, although this number varied among people of different ages. Altogether, these findings suggest that AC filters can act as both a sink and a source of microplastics fibers. Therefore, AC filters should be evaluated not only for their substantial impact on the distribution of indoor airborne MPFs, but also for their role in the prevalence of the related health risks.

Perfluoroalkyl substances (PFASs) in air-conditioner filter dust of indoor microenvironments in Greece: Implications for exposure

The occurrence of perfluoroalkyl substances (PFASs) was for the first time investigated in various working microenvironments (internet cafes, electronics shops, coffee shops, restaurants, etc.) in Thessaloniki, Greece, using the dust trapped by central air conditioner (A/C) filters. Perfluorooctane sulfonic acid (PFOS) was found in the range from 16 to 227 ng g^-1, however it was detectable in only 30% of samples. On the contrary, perfluorohexanoic acid (PFHxA) was found in 85% of samples in the range from 3.6 to 72.5 ng g^-1, while 90-95% of samples exhibited perfluorooctanoic acid (PFOA), perfluorodecanoic acid (PFDcA) and perfluorododecanoic acid (PFDoDA) in the range from 10-653 ng g^-1, 3.2-7.4 ng g^-1 and 3.8-13.1 ng g^-1, respectively. The PFAS profile varied largely among the different microenvironment categories suggesting different sources. Estimated daily intakes through dust ingestion were calculated.