Why City-Wide AQI Is Misleading for Your Run
Your city's AQI comes from one station. The air quality along your actual route can be very different.
Quick Answer
City AQI is typically measured at a single monitoring station, then applied to broad areas. Real air quality can vary a lot block by block — a park and a busy road 200 meters apart may show very different readings.
This is general guidance, not medical advice. Consult a healthcare provider if you have respiratory or cardiovascular conditions.
One Number From One Station
When you check your city's AQI on a weather app, you're seeing data from one (or a few) monitoring stations. These are usually placed in representative locations — not on busy highways, not in parks — to give an average reading.
But as a runner, you don't care about the city average. You care about the air on your specific route, at the time you'll be running. And that can be very different from the number on your phone.
How City AQI Monitoring Actually Works
Most cities operate 1–10 official monitoring stations. These are expensive, calibrated instruments that measure PM2.5, PM10, ozone, NO₂, SO₂, and CO.
The stations are sited following government guidelines — at a standard height, away from direct emission sources, in locations chosen to represent the wider area. The reported city AQI is usually the highest reading across all stations.
This works well for policy decisions and health advisories at a population level. But for an individual runner planning a route, it misses the detail that matters.
Micro-Variation: How AQI Changes Block by Block
Air quality is hyperlocal. Field studies often find PM2.5 levels next to busy roads are notably higher than in nearby parks. Key factors driving micro-variation include:
- • Traffic density and vehicle types (diesel trucks produce far more particulates)
- • Wind direction and speed (wind can clear or concentrate pollution)
- • Building canyons (tall buildings trap pollution at street level)
- • Green spaces (trees filter particles and reduce ground-level ozone)
- • Elevation and terrain (valleys trap inversions, hills disperse pollutants)
For a runner doing a 5–10km loop, this means the AQI you breathe can vary dramatically even within a single run.
Check Your Route's Air Quality
See segment-by-segment AQI along your running or cycling route before heading out.
Try Aeriqo FreeTraffic Corridors vs. Green Spaces
The biggest AQI differences often come from traffic. Running alongside a 4-lane road during rush hour can expose you to substantially higher NO₂ and PM2.5 than a quieter parallel street.
Green spaces can help in two ways: trees may filter some particulates, and parks are usually farther from direct emission sources. Being farther from major roads often lowers particulate exposure.
What Route-Level AQI Shows You Instead
Route-level AQI checks air quality at multiple points along your actual path, not just at one monitoring station. This reveals the segments where pollution spikes and where the air is cleanest.
With this information, you can make better decisions: swap a road segment for a park path, start your run from the cleaner end, or pick a different route entirely on high-pollution days.
That's exactly what Aeriqo does — draw a route or upload your GPX, and see AQI for each segment before you head out.
Frequently Asked Questions
How accurate is my city's AQI?
City AQI is accurate for the monitoring station's location, but it's an average that may not reflect conditions at your specific location. The further you are from the station, and the more varied the terrain and traffic, the less representative the number is.
Why does AQI differ between a park and a nearby road?
Roads have direct emission sources (vehicles), while parks usually have less direct traffic and more vegetation. In many studies, PM2.5 near busy intersections is clearly higher than in nearby park areas.
How far from a road should I run for cleaner air?
A few hundred meters from major roads often helps. Even moving one block off a busy street can make a meaningful difference in exposure.
Can two runners in the same city breathe different air?
Absolutely. A runner in a park might experience AQI 35 while someone running along a highway a kilometer away breathes AQI 80+. Same city, same hour, very different exposure.
What is route-level AQI?
Route-level AQI measures air quality at multiple points along a specific path, rather than relying on a single city-wide measurement. This shows you how pollution varies across different segments of your run.
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