Breathing air in a place like India or Bangladesh is almost equivalent to smoking. In high-income countries (where pollution is lower), the effect of smoking is worse than pollution. Obviously this will vary based on the situation. If you smoke more than average, the effect of smoking will be worse. If you live in Delhi or Dhaka, where pollution is higher than the average in South Asia, the effect of pollution goes up to about two years.
Click here to read more on the measuring method and the original studies: https://smartairfilters.com/en/blog/is-being-in-a-high-pollution-city-like-delhi-india-really-like-smoking-a-pack-a-day-healthwise/