Here is how crackers make Diwali air fouler

Climatic conditions in the Indo-Gangetic plains during Diwali do not allow a quick dispersal of pollutants although crackers are burst for just a few hours on the festive night, according to experts who think fireworks are a key, although not the only factor that plays a part in poor air quality levels in winter northern India.

Low wind quality, typical of winter months in northern India, prevents the thinning out of pollutants, says a recently published paper on the impact of fireworks on air quality in rural Haryana’s Palwal during Diwali.

The study by Kirk R Smith, professor of global environmental health at the University of California, Berkeley, finds that PM 2.5 levels remain elevated even after Diwali and sulphates and potassium levels show substantial rise.

PM 2.5 (particulate matter that have a diameter of less than 2.5 micrometers) are tiny particles which are so fine that they can enter the bloodstream and lodge deep into the lungs. Other compounds used in crackers such as barium and antimony are toxic, depending on exposure levels.

Study warns that pollution on Diwali and the day after could trigger health hazards that might require medical attention even among rural population.

In Diwali 2015, the study measured the PM2.5 concentration level in Palwal at 296 micrograms per cubic metre, which is five times higher than the Indian safe standard and 12 times higher than the World Health Organization guideline. The concentrations of sulphate, potassium, aluminium, sodium, ammonium and barium were found to be 4.30 , 3 , 3.11 , 3.19 , 86.6 and 1.93 times higher, respectively, than that on a usual day.

“The background pollution levels are already high before Diwali. The atmosphere is also stable during this season. So dispersal is difficult...So it’s important to reduce emissions during this season and not add more pollutants from firecrackers,” says Sagnik Dey, associate professor at the Center for Atmospheric Sciences, IIT Delhi.

The burning of crop stubble is considered one of the primary reasons in air pollution in northern India in early- and mid-October, when air quality deteriorates in Delhi. With wind speed dropping and temperature dipping, stubble fires shoot particulate matter and other pollutants into the air. There have already been 6,000 crop fires in October in Punjab and Haryana, according to the data by US space agency NASA. This is half the number of fires reported last year in the same period. Lucknow, Agra, Kanpur, Varanasi and Gwalior, have already started recording “very poor” air quality.

A study published by the University of Minnesota and the National Institute of Public Finance and Policy says “... Winter months see some of the worst air pollution levels in Delhi. ..”

This year, Diwali, which falls on November 7, will coincide with the stubble burning season that might continue till November 15.

BP Yadav, the deputy director general at IMD, says minimum temperatures start falling in November in north India. Weather conditions can be calm, bringing the boundary layer closer to the Earth’s surface and trapping pollutants near the breathing zone, he says.

First Published: Oct 24, 2018 07:18 IST