Not just winter, bad air troubles Delhi, neighbouring cities round the year

Delhi and its neighbouring cities – Noida, Ghaziabad, Gurugram and Faridabad – were among the most polluted cities in the world round the year in 2018, a Hindustan Times analysis with data from airvisual.com shows.

Delhi was the most polluted city in the world on Sunday, according to global air quality monitoring website airvisual.com, as a blanket of dense smog covered the city-state throughout the day.

Commuters on the Delhi-Gurugram Expressway amid heavy smog, in Gurugram, on Tuesday, November 5, 2019. (Yogendra Kumar/HT PHOTO)

Air pollution levels increase in Delhi and other regions in northern India in winter season every year. But what often remains underestimated is that Delhi’s air pollution problem is not winter-specific.

Delhi and its neighbouring cities – Noida, Ghaziabad, Gurugram and Faridabad – were among the most polluted cities in the world round the year in 2018, a Hindustan Times analysis with data from airvisual.com shows.

The website ranked these five cities among the world’s 11 most polluted cities in the year 2018. Gurugram and Ghaziabad topped the list.

The ranking is based on the annual average concentration of fine particulate matter PM 2.5, a hazardous pollutant able to penetrate deep into human respiratory system and from there to the entire body. Three other Indian cities – Bhiwadi, Patna and Lucknow – were also among these 11 cities. (See chart 1)

The website gives monthly average of PM 2.5 levels for all 12 months of 2018 for 2612 cities in the world. An analysis of this data shows that at least Delhi or one of its four neighbouring cities was among the eight most polluted cities in the world every month.

Average PM 2.5 level of these five cities was less than or slightly more than 50 micrograms per cubic meter (µg/m³) – normally considered safe for human life – in only three months – July, August and September. (See chart 2)

But even in these months, Delhi and its neighbouring cities were among the most polluted worldwide. For instance, Faridabad ranked seventh in July, third in August and first in September even as its average PM 2.5 level was less than 75 µg/m³ in this period.

Except in July and August, all these five cities have ranked among 33 most polluted cities in the world. (See chart 3)

These figures suggest that even as air pollution levels in Delhi and its neighbouring region peaks only in winter season, it is a significant problem throughout the year.