How Clean Is the Air Your Portfolio Breathes?

Ask a Swiss fund manager where their portfolio stands on energy, and you will get a number. Ask where it stands on the air its tenants breathe, and until recently there was no number to give. There is one now. The median Swiss building sits at 10 micrograms of nitrogen dioxide per cubic metre of air, exactly the guideline the World Health Organization set in 2021. The median Swiss institutional portfolio sits at 13.2, about a third higher. This post explains where that gap comes from and what you can do with it. The same update also puts national soil measurements under every building, and they answer a different question entirely: not how pleasant an address is to live at, but what it will cost to build on.

What is new

The Quanthome platform now carries Switzerland's official air-pollution maps, sampled at the location of every building in the country. The source is the Federal Office for the Environment's PolluMap model, built by Meteotest, which estimates annual mean concentrations of two regulated pollutants: nitrogen dioxide (NO2), the classic signal of traffic and combustion, and fine particulate matter (PM2.5). The 2024 annual means are available today for 3.22 million buildings, which is more than 99.9 percent of the national stock.

Air is only half of the addition. The same update brings the national topsoil maps from the Federal Office for the Environment and Agroscope, so every building and every parcel now carries background concentrations of arsenic, cadmium and mercury in the soil beneath it.

Because the platform already links buildings to the vehicles that own them, the new data arrives aggregated as well: every listed fund, unlisted fund, investment foundation, real estate company and benchmark index carries an area-weighted average of each measure across its portfolio. The question "how does my fund compare" has an answer out of the box, on the same official ruler for everyone.

Why you can trust these figures

Every number here comes from federal sources, applied uniformly to the whole country: PolluMap annual means for air, and a soil atlas built from 1,201 field samples interpolated to a one-kilometre national grid. That method carries an honest limitation worth stating plainly: the soil figures describe the diffuse background of an area, not a laboratory diagnosis of one parcel, and the air figures are annual means, not rush-hour peaks. What the data is very good at is comparison. When every building in Switzerland is measured the same way, differences between locations and portfolios mean something.

What the data shows

The two halves of this release measure different kinds of risk. Air is a flow: tenants breathe it every day, no work on the building changes it, and its meaning is quality of life. Soil is a stock: it troubles nobody while the building stands, and it converts into cost on the day a project breaks ground. The observations below follow that split.

Most of Switzerland already meets the strictest air guideline in circulation. Sixty-two percent of Swiss buildings sit at or below the WHO 2021 annual NO2 guideline of 10 µg/m³, and 99.6 percent sit at or below 20. The Swiss legal limit of 30 is exceeded at barely 0.01 percent of buildings. On PM2.5, the pollutant epidemiologists worry about most, the picture reverses: 85 percent of buildings sit above the WHO guideline of 5 µg/m³, though less than one percent exceed the Swiss limit of 10.

Institutional portfolios sit visibly above the building stock, and their tenants breathe the difference. Of the 149 vehicles on the platform, 146 have a value, and their median area-weighted average is 13.2 µg/m³ of NO2, roughly the level of the median building in Basel-Stadt or Geneva. Exactly one vehicle averages within the WHO guideline. The gap is not an artifact of averaging, since a portfolio holding every Swiss building equally would average just under 10. Institutional real estate is urban by design, and the urban tilt now has a number. It is also the one attribute no owner can renovate: the only way to change a portfolio's air is to buy and sell. One caution keeps the comparison honest: a portfolio figure is a single area-weighted average, while the national figure describes individual buildings, so treat this as a ruler, not as a claim about any single asset.

The wrapper tells you almost nothing; the location tells you nearly everything. The four legal forms, from listed funds to investment foundations, post median averages within 0.35 µg/m³ of one another, while cantonal medians run from 6 in Graubünden to 13 in Basel-Stadt, Geneva and Ticino. Ninety-three percent of Geneva's buildings sit above the WHO line, against 1 percent in Appenzell Innerrhoden. All eleven Swiss real estate benchmarks on the platform average above the national building median.

Today's rulebook sorts nobody; tomorrow's might sort almost everyone. No vehicle is anywhere near the current Swiss annual limit: the most exposed portfolio averages 18.4 against a limit of 30. But the Federal Commission for Air Hygiene recommended in 2023 that Switzerland lower its limits to the WHO 2021 values, and on that ruler 145 of 146 vehicles would sit above the NO2 guideline. These are not compliance statuses, since Swiss air limits bind cantons and emitters rather than property owners. They are a signal of where the ruler may move, and of whose tenants would be counted first.

Standing still, Swiss soil is quiet. In place, soil is governed by the soil protection ordinance's guide values, and the country sits comfortably inside them. Not a single building in Switzerland has a mercury background above the guide value of 0.5 mg/kg, and fewer than four buildings in a hundred exceed the cadmium guide value of 0.8. Portfolios are calmer still: the highest cadmium average across all 146 vehicles is 0.41, the highest mercury average 0.17, and unlike air there is no urban premium, because metals in topsoil follow geology rather than traffic. If soil never moved, this dataset would be a footnote.

The moment you dig, the same ground changes legal status. Swiss planning law pushes development inward, and densification means excavation: deeper foundations, underground parking, new basements. Excavated material is waste under the federal Waste Ordinance, and it may only be reused freely if it stays below limit values, including 15 mg/kg for arsenic. More than one Swiss building in five stands on ground whose natural background already exceeds that arsenic line. The ordinance does excuse exceedances of natural origin, but the excuse is not automatic: it has to be demonstrated, sample by sample, and until it is, every cubic metre is priced as if it were polluted. That is the shape of the soil risk: not a health hazard for tenants, but sampling, classification, disposal routes and delay for whoever builds. A due diligence that knows the background before the permit stage budgets it; one that does not, discovers it.

The arsenic map is a geology map, and it matches nothing else you know. In the canton of Jura, 94 percent of buildings stand on ground above the excavation threshold; in Basel-Landschaft, 81 percent; in Neuchâtel, 70. In Fribourg and Geneva, essentially none. Geneva is the sharpest illustration: the country's most exposed air on its most ordinary ground. Across the 146 vehicles, the air and arsenic rankings are uncorrelated, so knowing a portfolio's air tells you nothing about its ground. The country's cleanest-air portfolio makes the point: an alpine vehicle averaging 4.3 µg/m³ of NO2 stands on ground above the arsenic threshold, near the top of the arsenic ranking. Two risk maps, two decisions, one lookup.

What you can now analyse

For the portfolio and its tenants:

• Place your portfolio's air average against the 146-vehicle universe, the benchmarks, and the national building stock, on one official ruler.
• Screen every building in your book against the WHO 2021 guidelines, so you know your exposure before the rulebook moves rather than after.
• Compare peer vehicles on air quality the way you already compare them on yield or vacancy.

For the next project:

• Check the soil background under any building or parcel before pricing a densification, and flag where excavated material may need the natural-origin demonstration.
• Rank acquisition targets on ground risk alongside price and rent, from canton down to the individual address.
• Extend environmental due diligence beyond energy, with a first soil screen that no longer requires a specialist report.

Where to start

The Swiss debate on air-quality limits is moving toward the WHO values, and when it arrives your investors' first question will be a number. Your development team's question is already here, sitting under the next densification project. Both answers are on the platform: sign in to Quanthome, open any portfolio, and read its air and its ground in the same five minutes.