Air pollution, which surpasses tobacco, car accidents and diabetes in lethality, remains one of the most serious global health threats. To illustrate its impact, HouseFresh, an air quality research group, conducted a study that translates PM2.5 pollution levels into the number of cigarettes a person would indirectly smoke in a year. Their findings, published on 23 July 2025, are based on 2024 data from 700 cities around the world.
The study uses Berkeley Earth’s guideline that one cigarette is equivalent to 22 micrograms per cubic metre of PM2.5 concentration. By applying this calculation, HouseFresh was able to estimate the annual cigarette equivalent for residents in each city. G. John Cole of HouseFresh explained the intent: “Every day, the average adult inhales approximately 11,000 litres of air. But while getting outside and breathing in fresh air has numerous health benefits, the reality is that not all air is good for you.”
In Delhi, India, residents breathe air equivalent to smoking 1,797 cigarettes annually, which is nearly five cigarettes per day. This makes Delhi the most polluted capital city by this measure. N’Djamena in Chad follows with 1,523 cigarettes per year, Dhaka in Bangladesh registers 1,294, and Kinshasa in the Democratic Republic of Congo records 966. These figures reflect significant health risks in rapidly expanding urban areas, particularly across Southeast Asia and Africa.
Top 5 capital cities for indirect cigarette exposure
- Delhi, India – 1,797 cigarettes per year
- N’Djamena, Chad – 1,523 cigarettes per year
- Dhaka, Bangladesh – 1,294 cigarettes per year
- Kinshasa, Democratic Republic of Congo – 966 cigarettes per year
- Sarajevo, Bosnia and Herzegovina – 511 cigarettes per year
The study also includes rankings of cities in the United Kingdom and the United States. In the UK, Liverpool tops the list with an air pollution level equivalent to 171 cigarettes annually. This is followed by Worthing at 166, Northampton at 158 and Manchester at 149. London ranks ninth, with residents inhaling air equal to 154 cigarettes a year, despite pollution control efforts such as the Ultra Low Emission Zone.
In the United States, Fresno in California stands out with 169 cigarettes annually. Los Angeles closely follows at 168. This is particularly notable given California’s low adult smoking rate of 6.0 percent.
HouseFresh based its calculations on 2024 PM2.5 data from IQAir.com. The process involved dividing the average daily PM2.5 concentration by 22 and multiplying the result by 365 to obtain the yearly cigarette equivalent. This method was chosen to make the threat of air pollution more relatable and easier to understand.
The World Health Organization estimates that air pollution contributes to seven million premature deaths each year. The study draws attention to how pollution in developing regions is often exacerbated by industrial expansion and weak regulatory enforcement. Economies in the Middle East, Southeast Asia and Africa consistently recorded the worst pollution levels. In contrast, cleaner air is found in cities like Bern in Switzerland, where residents are exposed to pollution equivalent to just 11 cigarettes per year.
Even within the UK, some cities exceed the World Health Organization’s recommended limit for PM2.5. Swansea, which ties with Cardiff as the most polluted city in Wales, records PM2.5 levels of 10.3 micrograms per cubic metre. This is more than double the WHO’s guideline of 5 micrograms and equates to 131 cigarettes per year. Swansea Council monitors a range of pollutants under the Air Quality Wales Regulations 2000, although the HouseFresh study focuses solely on PM2.5 for consistency in its comparison.
Air pollution is known to increase the risk of lung cancer, heart disease and respiratory conditions, in a similar manner to the effects of smoking. To make the data more accessible, the study features an interactive map that allows users to explore the air quality in their own cities.
