How the cigarette comparison works
Fine particulate matter, or PM2.5, is the pollutant most strongly linked to premature death. The particles are small enough to pass from the lungs into the bloodstream. Cigarette smoke is also mostly PM2.5, which makes a comparison possible. In 2015 physicists Richard and Elizabeth Muller of Berkeley Earth compared mortality data from smoking with mortality data from air pollution and arrived at a simple rule of thumb: breathing air with 22 µg/m³ of PM2.5 for 24 hours is roughly as harmful as smoking one cigarette.
This page takes the 24-hour average PM2.5 for your location from the CAMS atmospheric model, divides it by 22, and shows the result. The "right now" pace uses the current hour instead of the daily average. The last seven days and tomorrow's forecast are shown as bars so you can see whether today is unusual.
What the AQI colours mean
| US AQI | Category | PM2.5 (24 h) | ≈ Cigarettes/day |
|---|---|---|---|
| 0–50 | Good | 0–9 µg/m³ | up to 0.4 |
| 51–100 | Moderate | 9–35 µg/m³ | 0.4–1.6 |
| 101–150 | Unhealthy for sensitive groups | 35–55 µg/m³ | 1.6–2.5 |
| 151–200 | Unhealthy | 55–125 µg/m³ | 2.5–5.7 |
| 201–300 | Very unhealthy | 125–225 µg/m³ | 5.7–10 |
| 301+ | Hazardous | 225+ µg/m³ | 10+ |
The World Health Organization's 2021 guideline is far stricter than most national standards: no more than 15 µg/m³ averaged over a day and 5 µg/m³ over a year. By that measure almost every large city in the world exceeds the guideline on most days.
Frequently asked questions
How can air pollution be compared to cigarettes?
Researchers at Berkeley Earth compared the health impact of long-term PM2.5 exposure with the health impact of smoking and found that breathing 22 µg/m³ of PM2.5 for a day causes roughly the same harm as smoking one cigarette. Dividing the day's average PM2.5 by 22 gives the cigarette equivalent.
Where does the air-quality data come from?
From the Copernicus Atmosphere Monitoring Service (CAMS) global model, delivered through the free Open-Meteo API. It combines satellite observations, ground monitors and weather models and is updated hourly. Your browser calls the API directly; nothing passes through our servers.
Why does the number differ from my local monitor or another app?
The model has a resolution of roughly 10-40 km, so it represents the wider area rather than one street. Local sensors near traffic or industry can read higher; parks can read lower. Apps also differ in whether they show the current hour or a 24-hour average and which AQI scale they use.
Is one cigarette equivalent really dangerous?
A single cigarette a day is associated with meaningfully higher risk of heart disease and stroke over a lifetime. The comparison is about chronic exposure: living for years in air worth five cigarettes a day is comparable to being a light smoker, without ever lighting up.
What can I do on a bad air day?
Limit strenuous outdoor exercise, keep windows closed, run an air purifier with a HEPA filter, and wear a well-fitted N95/FFP2 mask outdoors. Children, older adults, pregnant women and people with asthma or heart disease should be most cautious.
Data: Open-Meteo Air Quality API using CAMS (Copernicus) model data, licence CC BY 4.0. Method: Berkeley Earth, "Air Pollution and Cigarette Equivalence" (2015). This page is for general information and is not medical advice.