Southampton has been named among the top 10 worst cities in the UK for air pollution.

Research from the indoor air quality experts HouseFresh revealed that the air quality levels in Southampton were the equivalent of indirectly smoking 162 cigarettes a year.

This meant it ranked fourth on the UK list, with only Northampton, Nottingham and Bristol being worse.

To determine the number of cigarettes people around the world are indirectly smoking due to poor air quality, HouseFresh reviewed data on average PM2.5 concentrations in cities worldwide from AQICN.org.

PM2.5 refers to particulate matter with a diameter of 2.5 micrometres or less, and due to its minute size can get into the lungs and bloodstream.

They then converted it to the equivalent number of cigarettes passively smoked per year in terms of negative health effects using a formula from Berkeley Earth.

On their website, they said: "Berkeley’s Earth describes a rule-of-thumb that compares exposure to PM2.5 particles to cigarettes smoked: one cigarette per day is the rough equivalent of a PM2.5 level of 22 µg/m3.

"We took the average daily median AQI PM2.5 during 2022 as the average AQI PM2.5 in the city. We converted that value to cigarettes as per Berkeley’s Earth rule-of-thumb and multiplied the result by 365 to obtain how many cigarettes you’ve indirectly smoked during a year."

READ MORE: Southampton's air quality set to be improved - here's how

Top 10 worst UK cities for air pollution

1. Northampton - equivalent to indirectly smoking 189 cigarettes a year

2. Nottingham - 181 cigarettes

3. Bristol - 163 cigarettes

4. Southampton - 162 cigarettes

5. Kingston-upon-Hull - 161 cigarettes

6. Cardiff - 160 cigarettes

7. Southend - 157 cigarettes

7= Norwich - 157 cigarettes

8. Leeds - 155 cigarettes

9. London - 154 ciagarettes

10. Stoke - 149 cigarettes

HouseFresh said that in general, the highest concentrations of toxic particulate matter are located in the southeast part of England, while the lowest are in northern England and Scotland.