Air pollution causes millions of deaths worldwide and costs the world economy $5 trillion per year. Over 90% of the world’s population lives in places where air quality exceeds World Health Organization’s (WHO) guideline limits. Therefore, air pollution has become a major global challenge in the past years. Human activity and natural processes can both generate air pollution. Typical sources of air pollution are e.g. traffic, energy production, manufacturing and chemical industries, fumes from solvents, landfills, forest fires and volcanic activity.