Air quality comparison · Iran, 42 km apart
Karaj vs Tehran Air quality index (AQI) today
Tehran has cleaner air than Karaj right now: AQI 73 (Moderate) against 81 (Moderate).
Both sit in the same EPA band, so the health advice is the same for each today. But over the past 7 days, on modeled daily averages, Karaj averaged AQI 56 against 93, and it was the cleaner of the two on 7 of those days. Tehran has more tree cover.
Updated . Lower is better on the US EPA index: 0–50 is Good, above 300 is Hazardous. Measured by Airleaf.
Karaj81Tehran73
Head to head
Karaj vs Tehran at a glance
Tehran is ahead on 4 of 5 measures, and Karaj on 1. The better figure in each row is marked.
| Karaj | Tehran | |
|---|---|---|
| Air quality nowUS AQI. Lower is better. | 81 | 73 (better) |
| PM2.5Fine particles, µg/m³. | 21.4 | 17.4 (better) |
| Past week's averageUS AQI, 7 days. | 56 (better) | 93 |
| Tree coverWithin 2 km of the center. | 7.3% | 7.5% (better) |
| Trees still neededTo reach a healthy canopy. | 71.3K | 70.7K (better) |
Air quality today
What is the air like in Karaj and Tehran right now?
Tehran has cleaner air than Karaj right now: AQI 73 (Moderate) against 81 (Moderate). PM2.5 is setting the index in both.
Karaj's PM2.5 is about 1.4× the WHO's 24-hour guideline of 15 µg/m³. Tehran's PM2.5 is about 1.2× the WHO's 24-hour guideline of 15 µg/m³.
Both readings are model estimates, with no ground station close enough to either.
KarajTehran
Concentrations at the same moment as the index above, for the pollutants both places report. Lower is better. The dark marks on the PM2.5 and PM10 rows show the WHO's 24-hour guidelines (15 and 45 µg/m³).
Karaj: Model estimate · no ground station nearby. Data: Open-Meteo / CAMS, US EPA index.
Tehran: Model estimate · no ground station nearby. Data: Open-Meteo / CAMS, US EPA index.
The past week
Which had cleaner air over the past 7 days?
But over the past 7 days, on modeled daily averages, Karaj averaged AQI 56 against 93, and it was the cleaner of the two on 7 of those days. A single reading can catch a city on a bad afternoon; the week says whether it was the weather or the place.
- Cleaner days
- Karaj7Tehran0
- Average AQI
- Karaj56Tehran93
- Worst day, AQI
- Karaj76Tehran126
The daily numbers (7 days)
| Day | Karaj | Tehran |
|---|---|---|
| Nov 5 | 70 | 97 |
| Nov 6 | 60 | 91 |
| Nov 7 | 51 | 78 |
| Nov 8 | 38 | 64 |
| Nov 9 | 41 | 87 |
| Nov 10 | 57 | 108 |
| Nov 11 | 76 | 126 |
Daily averages from the CAMS atmospheric model for both places, so the week compares like with like. They can differ from today's reading at the top of the page wherever that comes from a ground station.
What it means today
Is it safe to go outside in Karaj and Tehran today?
Unusually sensitive people should consider limiting long outdoor exertion. Both are in the same EPA band today (Moderate), so the advice is the same.
Exercise outdoors
Fine for most people; unusually sensitive people should take long or hard exercise easier.
Windows
Fine to open; close them if you are sensitive to pollution.
Masks
Not needed for most people.
Air purifier
Worth running if you are sensitive.
Against everywhere else
How do Karaj and Tehran compare with the rest of the world?
Right now Karaj's air is cleaner than 30% of the 5,420 places Airleaf tracks, and Tehran's is cleaner than 36%. Within Iran, that is 23% and 29% of its 97 measured places.
Cleaner air than…
- Karaj
- Beats 30%
- Tehran
- Beats 36%
More tree cover than…
- Karaj
- Beats 15%
- Tehran
- Beats 15%
Includes model estimates as well as station readings, so it can differ from our most polluted and cleanest air rankings, which use station readings only.
Satellite timelapses
Watch both change, year by year
A clear satellite photo a year of the land around each city. Press play, turn on the forest cleared since the first year, or drag the before and after.
Karaj
2017: satellite photo from June 2017 of a 5 × 5 km area in the city center.
Tehran
2017: satellite photo from August 2017 of a 5 × 5 km area in the city center.
Trees
Which has more trees, Karaj or Tehran?
Tehran has more tree cover: 7.5% of the land within 2 km of its center against 7.3% around Karaj, or about 23,562 trees against 22,934.
The dark mark is each place's canopy target: 30% of the land, raised where air quality is poor.
| Karaj | Tehran | |
|---|---|---|
| Trees standingEstimated from the canopy area. | 22.9K | 23.6K (better) |
| Trees still neededTo reach the target. Fewer is better. | 71.3K | 70.7K (better) |
| CO₂ absorbed each yearBy the trees already standing. | 505K kg | 518K kg (better) |
Tree cover on the satellite image
The same 2 km radius around each center, with the tree cover the satellite found marked on it.
Reading these numbers
How this comparison is made
Air quality index
The US EPA index, computed from current pollutant concentrations: ground stations where a place has them nearby, and the CAMS atmospheric model everywhere else. It moves hour to hour, so it is a snapshot rather than a verdict on either place. The guideline marks are from the WHO's 2021 air quality guidelines.
Trees and forest
Tree cover is the share of ground under canopy within 2 km of each center, read from Sentinel-2 satellite imagery at 10 m detail. It measures that circle, not the whole municipality, which is what makes the two comparable. Forest loss comes from the University of Maryland's Global Forest Change maps.
More on the method on the About Airleaf page.
Frequently asked
Karaj vs Tehran: your questions answered
Is Tehran cleaner than Karaj?
On air quality, yes, right now: Tehran reads AQI 73 against 81, a gap of 8 points on the US EPA index. This is a live reading rather than an annual average, so it can reverse within a day. But over the past 7 days, on modeled daily averages, Karaj averaged AQI 56 against 93, and it was the cleaner of the two on 7 of those days.
Is it safe to exercise outdoors in Karaj and Tehran today?
The advice is the same for both today. Unusually sensitive people should consider limiting long outdoor exertion. Karaj reads AQI 81 and Tehran reads AQI 73.
Which has more trees, Karaj or Tehran?
Tehran has more tree cover: 7.5% of the land within 2 km of its center against 7.3% around Karaj, or about 23,562 trees against 22,934. Both figures describe the same-sized circle of ground around each center, not the whole municipality.
How many more trees do Karaj and Tehran need?
Karaj needs about 71,314 more to reach its canopy target of 30%, and Tehran about 70,686 to reach 30%. The target starts at 30% of the land and rises where air quality is poor.
Why can two places 42 km apart read differently?
Air changes over short distances with traffic, industry, wind and hills, and each reading comes from the nearest ground stations or, where there are none, from a regional model. A gap of a few points between neighbors is within normal variation, while a gap that crosses an EPA band is worth noticing.
Are Karaj and Tehran measured the same way?
The method is the same: the US EPA index for air, and Sentinel-2 satellite imagery at 10 m detail over an identical radius for trees. Both readings are model estimates, with no ground station close enough to either. Nothing is adjusted for population, city limits or climate.
How often does the Karaj vs Tehran comparison update?
The air readings refresh about once an hour, and each reading's local time is shown at the top of the page. Tree cover comes from the latest clear satellite image of each area (Sep 18, 2026 and Sep 18, 2026), and the forest figures are published yearly.
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