Summer in Delhi is hot and oppressive. But rarely is the city’s air laden with toxic amounts of particulate matter. This year, however, Delhi has recorded only one good air day since May. The city’s pollution levels worsened after a dust storm on June 12. On June 14, PM 10 in the city’s air skyrocketed to 938 microgrammes per cubic metre (ug/m3), significantly higher than the year’s next highest of 650 ug/m3 on January 10 — the safe limit for PM10 is 100ug/m3. With the Delhi government pressing in emergency measures, including a ban on construction activity, the city’s air quality has improved somewhat. However, the city’s PM 10 levels are still in the “severe” category.
More worryingly, the June 12 dust storm has also spiked pollution levels in several cities of Punjab and Haryana, including Amritsar, Ropar, Ludhiana and Gururgram, to their worst in 10 years. This is different from the localised storm that is a regular feature of the summer in most parts of North India. Storms such as the one on June 12 are caused by prolonged dry spells and westerly winds blowing at high speeds. The haze they whip up is different from the winter pollution when lack of wind and low temperatures trap pollution inside Delhi.
The dust carried by the June 12 storm was a mixture of particles released by the natural erosion of soil, pollen and microscopic organisms. This cocktail is, ipso facto, not hazardous. But the mixture carried by the storm was unhealthy because it had accumulated toxic substances from combustion sources in the wind’s route — pollution from vehicles, industry and biomass. This means that local emergency measures, such as those instituted in Delhi, can, at best, mitigate the haze to a limited extent.
The most important lesson of Delhi’s latest pollution problem is that the city will need a year-round strategy to ensure that its air remains healthy. Pollution control agencies will have to scale up their coordination with the India Meteorological Department. Winds are a way of nature, but they will not bring in toxic material if pollution control agencies in Delhi, Rajasthan, Uttar Pradesh, Haryana and Punjab act in a concerted manner. Such action, as the problem of crop-burning has repeatedly shown, remains the Achilles heel of North India’s pollution control endeavours. Their response to the haze last week shows that pollution control agencies in the region have not learned their lessons.