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Delhi air pollution: Salt from Afghanistan pushing up PM2.5 levels, says study

During the months of winter, Delhi usually gets winds from the north and north-west coming all the way from west Asia. CPCB report says air-borne salt particles originating from large salt pans in Afghanistan are pushing up pollution levels in Delhi.

delhi Updated: Dec 20, 2017 10:13 IST
Joydeep Thakur
Joydeep Thakur
Hindustan Times
Delhi air pollution,Delhi air quality,Delhi smog
PM2.5 particles are one of the primary and most dangerous pollutants as they can penetrate deep inside the lungs.(PTI FILE)

Minute air-borne salt particles originating from large salt pans in Afghanistan are pushing up pollution levels in Delhi, mostly during the winter months when westerly and northwesterly winds flow, a study conducted by experts from the Central Pollution Control Board (CPCB) and Indian Institute of Technology-Delhi has found.

Even though these salt particles don’t harm humans directly when inhaled, experts say they are pushing up levels of PM2.5 in the city. PM2.5 particles are one of the primary and most dangerous pollutants as they can penetrate deep inside the lungs. These salts comprise at least 11% of PM2.5 concentrations in Delhi’s air, the CPCB’s report said.

“Initially, we thought that it could be sea salts, coming in from either the Bay of Bengal or the Arabian Sea. But then we realised that it was not possible as the study was done in the month of February, which falls in winter. In winter, Delhi doesn’t receive any winds which originate in the sea,” said a senior CPCB official.

During the months of winter, Delhi usually gets winds from the north and northwest. These winds come all the way from west Asia. The scientists then took the help of a trajectory model called ‘Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT)’ developed by US scientific agency National Oceanic and Atmospheric Administration (NOAA).

“The trajectory model revealed that the air mass was coming in from Afghanistan. As there are large salt pans in Afghanistan, the high-altitude winds could be carrying salt from these pans and transporting them to India. Delhi receives a portion of these trans-boundary pollutants,” said D Saha, head of the air quality laboratory at CPCB.

Trans-boundary pollutants have earlier also been found to be pushing up pollution levels in Delhi.

In November, when pollution in Delhi breached emergency levels, scientists had blamed it on dust storms in west Asia. Strong high-altitude winds were bringing in pollutants from Iraq, Kuwait and Saudi Arabia where a dust storm had played havoc.

The team also found sudden spikes in the levels of chromium and copper in the city’s air, when the westerly and northwesterly winds were blowing. Experts said that these metals in the air could be coming from the electroplating industries located in Haryana close to Delhi’s border.

“As the metals or salts are usually not monitored and no standards have been developed for them anywhere in the world, we can’t say they are above the permissible standards,” said Saha.

CPCB has already urged the Indian Meteorological Department to develop an early warning smog-alert system so that such trans-boundary movements of pollutants could be detected beforehand. This would give the authorities some head space to take precautions.

First Published: Dec 20, 2017 10:13 IST