In some of the world's most popular cities, every breath you take is bad for your health. Delhi, Beijing, Varanasi and Agra have some of the world's worst air pollution, many times greater than the level the World Health Organisation regards as safe. Long-term exposure to air pollution carries elevated risks for asthma, chronic obstructive pulmonary disease, cardiovascular disease and lung cancer. According to a study published in British medical journal The Lancet, 5.5 million premature deaths were attributable to air pollution in 2013.
But what if you're just in town taking in the sights for a few days, should you be worried? There's a dearth of clinical research on the effects of such short-term exposure, but according to a study in the Journal of Travel Medicine in 2018, a healthy, non-smoking subject who travelled from New York and spent two weeks in Shanghai suffered no decrease in lung function on her first week in Shanghai, when air pollution readings were similar to those of New York. However in the second week, her lung function deteriorated when the particulate matter reading increased, accompanied by an increase in respiratory symptoms including throat irritation, cough with phlegm, nasal irritation and congestion. Many who have spent time in a city with poor air quality will have noticed similar symptoms.
For concerned travellers, face masks are a partial solution but they vary widely in their effectiveness. Surgical masks and paper masks are the least effective. Tight fit is essential, and those that work best are P2 particulate respirators.