In 98% of cities with populations greater than 100 000 in low- and middle-income countries, people are breathing air with pollution levels that exceed World Health Organization (WHO) safety limits, according to the latest WHO Global Urban Ambient Air Pollution Database (http://bit.ly/1XrMGm1).
From 2008 to 2013, the WHO compared air quality readings from 795 cities in 67 countries for levels of small and fine particulate matter, which includes sulfates, nitrates, and black carbon. These pollutants penetrate deep within the lungs and the cardiovascular system, increasing the risk of stroke, heart disease, lung cancer, and chronic and acute respiratory diseases such as asthma. Over this 5-year period, global urban air pollution levels increased by 8%, despite regional improvements. Urban air pollution levels generally decreased during this period in high-income countries in the Americas and Europe, but increased in the Eastern Mediterranean and South-East Asia regions.
Friedrich MJ. Air Pollution Highest in World’s Poorest Cities. JAMA. 2016;316(3):259. doi:10.1001/jama.2016.8300