JUNE 12, 2018
NEW DELHI – A sudden haze descended upon Delhi and its neighboring areas on Tuesday as the air quality plummeted into the severely polluted category, bringing back memories of November when the city’s air reached dangerous levels of pollution.
Tuesday’s pollution was driven by dust particles classified as PM10, which are roughly a fifth of the width of a human hair. From 138 at 6pm on Sunday evening, the PM10 concentration index shot up to 433 at 8pm on Tuesday, a trend that experts attributed to a switch of wind direction.
In November 2017, the air quality index (AQI) remained over 400 for around a fortnight, due to pollution from farm fires. At that time, the main pollutant was PM2.5, which is linked to more fatal health conditions than PM10.
The safe limit for PM10 is 100ug/m3, and readings above 430ug/m3 are considered severe.
“Strong westerly winds are blowing across Delhi with a speed of 35-40 km per hour since Monday. An anti-cyclonic flow over northwest India is channelising these winds towards Delhi, which is why a lot of dust is coming in from across Rajasthan, Haryana and Punjab,” said Kuldeep Srivastava, a senior scientist with the Regional Weather Forecasting Centre (RWFC) in New Delhi.
Another expert said the strong winds are also kicking up local dust pollution.
“Unlike in winter, it was only PM10 which shot up on Tuesday. The level of PM2.5 didn’t rise. This denotes that it was mainly atmospheric dust pollution which shot up. This can happen when there are strong surface winds blowing over a long time,” said Mohan P George, who heads the Delhi Pollution Control Committee’s air quality division.
Air pollutants such as particulate matter trigger allergies, cough, lung infections, heart disease and even irreversible lung damage.
Dust pollution has been uncharacteristically high this summer, which has recorded several storms.
“There was nearly 30 – 40% increase in the number of patients with asthma and COPD (Chronic Obstructive Pulmonary Disease) coming to the clinics the day after the dust storms. The proportion seems high because anyway we get very few respiratory cases in the summers,” said Dr Vikas Maurya, head of the department of pulmonology and sleep disorders at Fortis hospital, Shalimar Bagh.
At the Indira Gandhi International (IGI) Airport, visibility dropped from 3.5km in the morning to around 1.5km by Tuesday evening. “This is the worst visibility we have encountered at the airport in recent times on a normal day when there are no dust storms,” said RK Jenamani, head of the aviation meteorology services of Delhi region and IGI Airport.
Delhi is not the only city to be affected. The AQI shot up in Gurugram, Noida and Ghaziabad. While in Ghaziabad the 24-hour average AQI was recorded to be 333, in Noida and Gurugram it was 342 and 308 respectively.
Earlier this year, the World Health Organisation labelled Delhi as the world’s most polluted city. Greater Cairo in Egypt was listed as second, followed by the Bangladesh capital, Dhaka. Beijing ranked fifth.