Anyone who has stepped off an airplane in one of the major cities of the developing world has encountered profound and noxious air pollution. In New Delhi, Jakarta, Accra, Kathmandu and many other cities, diesel exhaust and burning garbage foul the air. The most serious concern is particulate matter (PM) – microscopic particles, much smaller than a human hair, usually produced when chemicals from fuel combustion react in the atmosphere. Once these particles form, winds can transport them over long distances.
Exposure to particulate matter causes nearly six million premature deaths every year. Most of these deaths occur when PM exposure causes heart attacks, strokes or lung disease, so many people do not realize that air pollution is the underlying cause. As a result, many people view air pollution as a quality of life issue, not as a global health concern.
At my laboratory we study how air pollution affects public health. We recently analyzed how effectively several types of face masks – including versions widely used in heavily polluted cities – protect users from hazardous levels of PM. Our results showed that no mask is 100 percent effective, and the cheap cloth masks that many people in developing nations use sometimes provide very little protection. These findings highlight the need to reduce air pollution in communities, and to provide better protection strategies by educating people about ways to avoid exposure.
Cloth versus paper
Across the developing world millions of people are moving to cities, where they are exposed daily to dangerous levels of air pollution. According to the World Health Organization, 98 percent of cities in low- and middle-income countries fail to meet the agency’s guidelines for air quality, compared to 56 percent in high-income countries. On a bad day in New Delhi hourly PM levels may spike as high 350 micrograms per cubic meter of air, compared to highs of roughly 20 micrograms per cubic meter on a polluted day in Houston.