How many cigarettes you’re indirectly smoking due to pollution levels

Every day, the average adult inhales approximately 11,000 liters 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. Airborne pollutants are one of the greatest sources of toxic exposure known to humankind and according to one estimate from the World Health Organization, air pollution contributes to seven million premature deaths worldwide every year.

Of special concern is fine particulate matter (PM2.5) — airborne particles from engines and other emissions that are less than 0.033 the diameter of a human hair. These particles make their way to the deepest parts of your lungs and can get into your bloodstream. Cigarettes emit ten times more PM2.5 matter than diesel car exhausts, according to a controlled experiment reported by Tobacco Control. But while quitting smoking reduces exposure to toxins and improves overall health, it is harder to avoid the toxins that pollute the indoor and outdoor air.

Air quality varies significantly around the globe, and in many parts of the world, the negative health effects of poor air quality are equivalent to smoking hundreds of cigarettes a year. To better communicate the health risks of air pollution, we used the latest data to calculate the number of cigarettes people around the world are indirectly smoking due to poor air quality.

Key findings

Breathing Delhi air is like smoking 1,797 cigarettes per year

The level of air pollution in the Indian capital is equivalent to smoking 35 cigarettes a week.

First, we sourced the average PM2.5 levels for every major city worldwide in 2024. These are measured in µg/m3 or micrograms per cubic meter of air. The 20 cities with the worst air all breathe the equivalent of at least 15 cigarettes per week. The worst air of all is India’s capital, Delhi, where average PM2.5 levels of 108.3 µg/m3 equate to 35 cigarettes per week or 1,797 per year.

Eighteen of the top 20 capital cities with the worst air are in Asia, and the other two are in Africa

To get a comprehensive global view, we narrowed our focus to the world’s capital cities.

Delhi has leaped to the top of the table in 2025 with more than twice the PM2.5 levels than in our 2024 report. Researchers have found that local humidity levels may have obscured the true level of particulate matter in Delhi’s air in previous years.

The only non-Asian or -African capital city among the 30 capitals with the worst air is Sarajevo, Bosnia and Herzegovina, where the pollution is equivalent to smoking 511 cigarettes yearly. UNICEF reports that the effects of air pollution cost “over 21.5 percent of BiH’s GDP through lost work and school days, and healthcare costs.” The U.N. Environment Programme attributes Sarajevo’s poor air to “heavy traffic, poor spatial planning, solid-fuel based heating and natural factors are to blame for the poor air quality.”

Boise, Idaho, is America’s most air-polluted major city

And for some Californians, breathing local air is like smoking 169 cigarettes annually.

Next, we looked at the average levels of fine particulate matter in the air of America’s major cities.

Two of the three cities with the worst air are in California. Just 6.0% of adults smoke tobacco in California, but in Fresno, residents indirectly smoke the equivalent of 169 cigarettes per year, and in Los Angeles, that figure is 168. Local emissions policies have reduced the amount of fine particulate matter that Californians inhale by 65% in 25 years. However, an increase in the number and spread of wildfires has significantly reduced local tree cover, releasing carbon dioxide into the air and inhibiting the natural cooling of the local environment.

We found that the city with the highest PM2.5 level is Boise, Idaho, where an average density of 10.3 µg/m3 means the equivalent of smoking 171 cigarettes per year for Boise residents.

The city is reeling from one of the worst wildfire seasons of recent years. On July 23, 2024, the city’s Air Quality Index (AQI) score reached 227 AQI, the first time it has crossed into the “very unhealthy” category in a quarter century.

“Unfortunately we’re downwind from a lot of the California and Oregon fires, so smoke not only gets funneled here, but it can get trapped in the valley.”

— Brittany Brand, director of Boise State University’s Hazard and Climate Resilience Institute

Liverpool’s air is like smoking 171 cigarettes per year

The Merseyside capital is UK’s worst city for PM2.5, but southern coastal cities also suffer.

Finally, we looked at the air pollution in every UK city to determine the 20 cities with the worst air.

Along with traditionally industrial cities with dense urban centers, such as Manchester and Liverpool, there are a number of southern coastal cities, such as Worthing, Bristol and Bournemouth. In Bristol alone, where PM2.5 levels are equivalent to smoking 124 cigarettes per year, five people die each week as a result of air pollution, according to the Alan Turing Institute.

Some of these coastal towns are impacted by an influx of tourist vehicles in the summer months, and the air quality is also affected by salt particles from the sea and the industrial emissions of ports. They may also have been overlooked for reforestation programs.

In Bournemouth, motor vehicles are one of the biggest contributors to urban air pollution, compounded by a dense road network, outdated buses, and a lack of investment; a clean air zone has been proposed, but there are concerns over the economic trade-off.

The number of cigarettes in your local city’s air

Use our interactive table to check the pollution levels in over 700 global cities.

The decline in smoking over the past two decades has been one of the great public health achievements of the 21st century, but worsening air pollution has offset many of the expected gains in general respiratory health. An increase in wildfires, rising vehicle and industrial emissions and domestic wood-burning appliances make living in some of the world’s most populous cities the equivalent of smoking hundreds of cigarettes a year.

Many cities with the worst air pollution are in fast-growing, developing economies, while the cities with the cleanest air are wealthier in service-oriented economies. But the air quality in some of the most developed major cities also decreases the local life expectancy, much like smoking. You can use the interactive table below to search for your city and see the number of cigarettes you effectively smoke each year due to air pollution.

Air pollution is one of the greatest threats to human health in the world and kills more people each year than tobacco, car accidents or diabetes. Respiratory health has become a major focus in public health since the COVID-19 pandemic, and smoking rates have fallen considerably over the past several decades.

For a complete picture of health, however, it is essential to know the respiratory impacts of the air we breathe daily. Do you know how many cigarettes you are indirectly smoking due to air pollution?