The Air / Bay Area
Air quality in San Jose right now
SAN JOSE — The air over San Jose reads 126 on the federal index this evening — unhealthy for sensitive groups.
The pollutants, against the WHO guideline
| Pollutant | Now | WHO 24h | × guideline |
|---|---|---|---|
| PM2.5 µg/m³ | 6.4 | 15 | 0.4× |
| PM10 µg/m³ | 6.9 | 45 | 0.2× |
| Ozone µg/m³ | 164 | 100 | 1.6× |
| NO₂ µg/m³ | 4.4 | 25 | 0.2× |
| SO₂ µg/m³ | 2.3 | 40 | 0.1× |
| CO mg/m³ | 0.2 | 4 | 0.0× |
Source: Open-Meteo (Copernicus CAMS) · WHO 2021 global air quality guidelines · No figure on this page is written by hand.
What this air means
The particles at this level begin to matter for sensitive lungs: children, older adults, and anyone with respiratory or cardiac disease should shorten or lighten outdoor exertion. The mechanism is dose — less time and lower breathing rates mean a smaller entry in the body’s ledger.
The mechanism, briefly
Particles under 2.5 microns — a fortieth the width of a hair — ride air all the way to the alveoli, the one-cell-thick membrane where the lung hands oxygen to the blood. The membrane cannot tell oxygen’s friends from its enemies: within an hour of significant exposure, ultrafine particulate is circulating. That is why the numbers on this page are worth checking — dose is the only variable you control.
From the Air desk
The ocean takes about a third of our carbon dioxide — and pays for it in shells
River Mast
Air pollution is taking lung tissue, not just irritating it — and the pollutant still doing it is ozone
Iris Vale
We invented a government cover-up that does not exist. Here is how the AQI in your phone is actually calculated.
Sol Index
The lid over a heat dome is sinking air, not the stratosphere — and it is what kills the Delta breeze
Cael Frost
Nearby
Fremont · Santa Cruz · Oakland · Berkeley · San Francisco · Salinas
All California cities → · En español → · The Paper · Today’s Edition