Air quality improves in Delhi as rainfall washes away pollutants

For the first time since Diwali, Delhi's air quality was registered in the 'poor' category on Thursday, an improvement from 'very poor' the day before, after rains lashed the city washing away the pollutants.

However, authorities warned that the condition may slip back to the "very poor" range from Saturday.

The overall air quality index (AQI) in the national capital on Thursday was recorded at 213 which falls in the 'poor' category, according to data provided by the Central Pollution Control Board (CPCB).

The EPCA has recommended curbs on non-CNG private vehicles to tackle rising air pollution, but experts say banning all private vehicles without a proper strategy and alternatives "is bound to create issues".

Delhi's air quality has been oscillating between 'very poor' and 'severe' after Diwali, on November 7, due to explosion of firecrackers.

According to pollution watchdog the CPCB, 25 areas in the national capital registered poor air quality and 11 registered moderate air quality on Thursday.

The PM2.5 (particles in the air with a diameter of less than 2.5 micrometres) level was recorded at 95, while the PM10 (particles in the air with a diameter of less than 10 micrometres) was recorded at 177.

An AQI between 0 and 50 is considered 'good', 51 and 100 'satisfactory', 101 and 200 'moderate', 201 and 300 'poor', 301 and 400 'very poor', and 401 and 500 'severe'.

The Centre-run System of Air Quality and Weather Forecasting (SAFAR) said air quality improved significantly following sufficient rainfall on Wednesday night due to wash-away effect.

"Surface wind speed moderately increased but pollution level declined faster than expected. Still weather conditions are not completely favourable except sporadic rain. This implies that the air is lighter and free path increased to allow faster dispersion," it said.

"In addition to cleaning of air by rain, it also tend to suggest that accumulative emission loading is relatively less. Stubble fire is almost negligible. The AQI is likely to remain in the 'poor' range on Friday but slip back to the 'very poor' range thereafter," SAFAR said.

According to the Indian Institute of Tropical Meteorology, PM2.5 concentration will improve in the next two days.

"The air quality index is likely to improve in the next two days. But will still remain in the 'poor' and 'very poor' categories in Delhi-NCR. Also, the impact of biomass burning in northwest India is marginal over Delhi," it said.

Meanwhile, the AIIMS is conducting a study on air pollution exposure among school-going asthmatic children in the national capital, for which wearable sensors would be provided to them which will consistently monitor their exposure to air pollution, both indoor and outdoor.

Assistant professor in the pulmonology department, AIIMS, Dr Karan Madan said these pollution sensors are lightweight, easy to strap around the waist and will generate a comprehensive data on their air pollution exposure throughout the day.

As a part of the study, being conducted in collaboration with IIT-Delhi, University of Edinburgh, Imperial College of London, and Sri Ramachandra University in Chennai, these wearable sensors will be given to the children for a week.

The study is funded by the Department of Biotechnology (DBT), Ministry of Science and Technology, and the Medical Research Centre, the United Kingdom.

The chairman of the Supreme Court-appointed Environment Pollution (Prevention and Control) Authority (EPCA), Bhure Lal, wrote to the CPCB on Wednesday recommending implementation of either the odd-even scheme or a complete ban on non-CNG private vehicles if the air pollution level in Delhi rises again.

However, experts maintained that last time when the odd-even scheme was implemented there was no substantial effect on air quality level, while there was not enough clean public transport to fall back on.

"Banning all diesel vehicles and disincentivising privatised modes of transport has to be done but in a phased, coordinated and systematic manner, with alternative infrastructure availability for maximum public acceptability of the move," said Greenpeace India's senior campaigner Sunil Dahiya.

"The first step in that direction can be stopping registration of new diesel vehicles in polluted geographies," he said.

Aishwarya Sudhir, senior researcher, Climate Trends, said any move to ban or limit vehicles is will be successful only if there are alternate means of transport available.

Lal had said all cities, which have similar emergency plans, such as Paris and Beijing, include restrictions on private vehicles, which is done by either number plate or by fuel type or its age.

He had said vehicles contribute as much as 40 per cent of the total emission load in Delhi and roughly 30 per cent in the region.