Switzerland’s air drops 219 tons of microplastics a year
Imagine sweeping your patio every morning and finding, invisibly fine among the usual grit, plastic. Not a wrapper or a bottle—dust. Researchers in Switzerland have now counted that dust settling out of the air. Their ledger runs to hundreds of tons a year.
A study by teams at Empa, Eawag and Agroscope reports that approximately 219 metric tons of microplastics fall out of the Swiss atmosphere annually in areas below 2,000 meters in elevation. That is not a spill or a dump; it is ordinary weather, delivering plastic the way it delivers pollen and soot—day after day.
By the numbers: what the air is dropping
| Metric | Value / Share |
|---|---|
| Annual microplastics deposited below 2,000 m | approximately 219 metric tons per year |
| Landing on agricultural land | about 78 metric tons per year |
| Direct to water bodies (atmospheric input) | around 10 metric tons per year |
| From treated wastewater (for comparison) | only about 5 metric tons per year |
| Urban site deposition rate | an average of 881 particles per square meter per day |
| Dry deposition share of total mass | about 60% |
| Microplastics share of total airborne particle mass | between 0.02% and 0.12% |
| Most frequent polymers found | PET 31%, PE 26%, PP 21% |
Scale matters. Two hundred and nineteen metric tons is roughly the mass of three hundred full-grown dairy cows. The study’s estimate that about 78 tons land on agricultural soils frames a practical question: those fields are where we grow food.
Where it lands—and why that’s not just a city problem
At an urban site, the team measured an average of 881 particles per square meter per day. Outside big cities, other Swiss locations showed values ranging from 249 to 331 particles per square meter per day—lower, but in a surprisingly tight band given how different those places are. The researchers interpret this as evidence that airborne microplastics are not confined to urban air.
For water, the atmosphere’s contribution is not trivial: around 10 metric tons a year settle directly into Swiss lakes and rivers. For context, a parallel analysis by Eawag puts the input via treated wastewater at only about 5 metric tons annually.
How it falls: wet versus dry
Microplastics return from air to ground in two ways. Some are washed out by rain or snow; others settle during dry weather. In Switzerland, dry deposition accounts for about 60% of the mass the team tallied, with the remainder arriving in precipitation.
That split matters for mitigation. Measures that reduce resuspension and outdoor abrasion could affect the dry fraction directly, while stormwater management shapes how much of the wet fraction runs off into streams and fields.
What the particles are made of
The fingerprint of polymers is familiar: polyethylene terephthalate (PET) accounted for 31% of identified particles, polyethylene (PE) for 26%, and polypropylene (PP) for 21%. These are among the most common plastics in daily life.
The analysis does not name the exact products shedding these fragments or fibers. The researchers state plainly that the study cannot determine the specific products from which the individual particles originate.
How they counted: a lab built for specks
To sort plastic from non-plastic reliably, the teams used a joint particle laboratory operated by Eawag, Empa and Agroscope. Collected samples were prepared, applied to a filter, and analyzed using imaging infrared microspectroscopy.
Rather than hand-picking suspicious grains, the method scans randomly selected areas on the filter point by point. That automation gives an objective census of which particles are plastic and which polymer family they belong to.
The deeper cut
What “0.02% to 0.12%” actually means
The study estimates that microplastics constitute between 0.02% and 0.12% of the total mass of airborne particles—whose budget is dominated by mineral dust, combustion aerosols, and biological material. For aerosol scientists, that tiny mass fraction is a red flag for analytical bias: a trace component embedded in a complex matrix is the classic setting for false positives from spectral overlap and false negatives from detection limits. Imaging IR microspectroscopy helps by generating spatially resolved spectra across a defined filter area, so the denominator (“all particles scanned”) is known and polymer assignments can be made on spectral libraries rather than morphology. But mass-based percentages hinge on converting counts to mass, typically by associating each classified particle with an areal footprint and thickness to estimate volume and then applying polymer densities. If thickness is assumed rather than measured, mass fractions can shift by factors of a few without changing the particle counts. That is why the count-based metrics—881 particles m−2 day−1 at the urban site and 249–331 at others—are often the more robust comparison across locations, while mass shares are the right unit for source apportionment and risk models tied to load.
One gap the data cannot close yet
Even with polymer IDs in hand, tracing each particle back to a product is out of reach. The researchers emphasize this limitation: their measurements cannot determine the specific products from which the individual particles originate. Policies aimed at sources will need other lines of evidence to pinpoint which uses and activities are shedding most to air.
A small percentage, a large cumulative load
Microplastics make up between 0.02% and 0.12% of airborne particle mass. That sounds negligible until it falls everywhere, every day. Distributed over a country, those fractions sum to approximately 219 tons per year below 2,000 meters—and about 10 tons dropping straight into water bodies.
Seen that way, today’s numbers are both modest and urgent. They are modest compared with the torrent of natural dust and soot, urgent because plastics persist. The study’s ledger tells us where to look first: agricultural land, urban air, and the dry fall that quietly does most of the work.
The paper: Wet and dry atmospheric deposition of microplastics at urban, suburban, rural and mountainous sites in Switzerland (Atmospheric Chemistry and Physics, 2026)
Sources: Microplastics fall across rural Switzerland, adding over 200 tons yearly to land and water (phys.org)
Images: Cover: Stephane Lesbats / Wikimedia Commons (CC BY 4.0); Figure 1: Stephane Lesbats / Wikimedia Commons (CC BY 4.0)
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