A team at the University of Toulouse measured microplastics in the size range that can reach deep into the lungs (1–10 micrometres) in the air of homes and car interiors, then estimated daily inhalation.
They estimated that adults breathe in about 68,000 particles a day in the 1–10 micrometre range, plus about 3,200 larger particles (10–300 micrometres). Concentrations were higher in cars than in homes. The totals are roughly 100 times higher than previous estimates, which had mostly counted larger fibres.
The finding matters because indoor air, where people spend most of their time, may be a larger route of exposure than food and drink, and because fine particles are the ones that can lodge in lung tissue.
It is a single study with a modest number of sampling sites; inhalation figures are modelled from air concentrations, not measured in people.