Air pollution in Delhi

This item appears on page 19 of the January 2020 issue.

Air pollution in Delhi, India, reached “severe” levels on multiple days in November. On the Air Quality Index (AQI), which measures the levels of particulate matter smaller than 2.5 micrometers in diameter within a cubic meter of air, measurements regularly exceeded 500, the lower limit of “severe,” according to the World Health Organization. In some areas of Delhi, levels of 999 were measured, the highest possible on the AQI.

Due to the extreme air pollution, schools were closed on multiple occasions and more than five million masks were distributed to students. Delhi’s thick smog was also responsible for multiple flight cancellations.

Dangerous levels of air pollution are an annual occurrence in Delhi in the autumn months due to a combination of weather patterns, city pollutants (from cars and construction), and farmers in outlying areas burning their fields to prepare them for replanting in the spring. Steps to limit pollution, such as restrictions on driving and cooking fires, typically have little effect until winds pick up again in winter to blow the smoke away.