Simulating human exposure to indoor airborne microplastics using a Breathing Thermal Manikin

Abstract

Humans are potentially exposed to microplastics through food, drink, and air. The first two pathways have received quite some scientific attention, while little is known about the latter. We address the exposure of humans to indoor airborne microplastics using a Breathing Thermal Manikin. Three apartments were investigated, and samples analysed through FPA-µFTIR-Imaging spectroscopy followed by automatic analyses down to 11 µm particle size. All samples were contaminated with microplastics, with concentrations between 1.7 and 16.2 particles m^-3. Synthetic fragments and fibres accounted, on average, for 4% of the total identified particles, while nonsynthetic particles of protein and cellulose constituted 91% and 4%, respectively. Polyester was the predominant synthetic polymer in all samples (81%), followed by polyethylene (5%), and nylon (3%). Microplastics were typically of smaller size than nonsynthetic particles. As the identified microplastics can be inhaled, these results highlight the potential direct human exposure to microplastic contamination via indoor air.

Figure 1

(a) Visual stitched image of a sample (L3S3) and (b) corresponding MPhunter map. Each polymer group is highlighted by a different colour. Cellulose and protein-based fragments and fibres are shown in grey colours.

Figure 2

(a) Microplastic particle exposure; (b) Total particle exposure (MP and nonsynthetic particles) (light grey column – protein-based particles; dark grey column – cellulose-based particles; blue column – MP).

Figure 3

Relative polymer distribution. The category “Other polymers” groups the polymers present in lower percentages (polystyrene - PS, acrylic/acrylates polymers, polyurethane/polyether-urethane - PU, ethylene-propylene-diene-monomer - EPDM, polyvinyl acetate - PVAC, ethylene vinyl acetate - EVA, epoxy resin, phenoxy resin, cellulose acetate and triacetate, polylactic acid - PLA, polycarbonate - PC, acrylic paints, polyurethane paints, alkyd).

Figure 4

(a) MP minor dimension vs major dimension scatter plot. The black dashed line indicates the threshold for fibre classification (length to width ratio of 3); the vertical and horizontal red dashed lines indicate the limit of detection concerning size for major (11 µm) and minor (5.5 µm) dimension (2 × 1 pixels). (b) Percentage of MP fibres and fragments for the total analysed samples.

Figure 5

Size distribution for the total amount of MP (a,c) and nonsynthetic particles (b,d) identified in all analysed samples for major dimension (a,b) and minor dimension (c,d). Bin intervals were selected as 0.1 on a logarithmic scale. Light and dark grey bars on histograms indicate abundance; the red dotted line is the relative cumulative frequency (secondary axis).

Figure 6

Sampling device setup: (a) manikin in seated position ready for sampling; (b) twin adjustable pistons connected to the motor to simulate breathing in and out; (c) sampling setup diagram; (d) Illustration of human boundary layer flow.