Glasgow and Edinburgh are amongst the cleanest cities in the UK for air quality.

While air quality in the UK has improved since the industrial revolution, some parts of the country are far worse than others.

Research from the indoor air quality experts HouseFresh revealed 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.

This meant out of the 25 cities, Glasgow was ranked 24th and Edinburgh 25th.

HouseFresh said that the air quality levels in Glasgow were the equivalent of indirectly smoking 92 cigarettes a year, with Edinburgh following at 87 cigarettes. This is compared to air quality in Northampton - which is equivalent to indirectly smoking 189 cigarettes a year.

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/Norwich - 157 cigarettes

8. Leeds - 155 cigarettes

9. London - 154 ciagarettes

10. Stoke - 149 cigarettes

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

One of the main air pollutants measured is PM2.5, or particles smaller than 2.5 microns.

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.