Particulate Matter (PM10) atmospheric samples (<10 µm) collected from 8 different locations across the United Kingdom were quantitatively characterized for seven selected plastics using Pyrolysis Gas Chromatography Mass Spectrometry (Pyr-GC-MS-MS). Plastics were ubiquitously detected with concentrations of total plastics (∑7 Plastics) ranging 0.9 to 6.9 µg/m3, with a mean concentration of 2.6 µg/m3. The most abundant plastics were polyethylene terephthalate (412 – 3,883 mg/m3) and polyvinyl chloride (412 – 3,014 mg/m3), followed by polystyrene (1 - 19 mg/m3), polymethyl methacrylate (<1 - 20 mg/m3) and polycarbonate (<0.81 - 6.9 mg/m3). Polyethylene and polypropylene were not detected at any site. The ∑7 Plastics concentration (µg/m3) showed a weak relationship with population density (r2= 0.41). Daily exposure estimates were calculated from the atmospheric concentrations, with the average adult within the United Kingdom exposed to between 15 and 109 ng/day (mean 35 ng/day, 13 µg/per annum) of plastic in PM10. This study provides the first mass-based quantification of microplastics in the respirable fraction of ambient air and demonstrates their ubiquity in this important size fraction.