Salt from Afghanistan pushing up PM2.5 levels, claims study

NEW DELHI: 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. Nitrate aerosol

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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 from west Asia.

The scientists then took the help of a trajectory model called ‘Hybrid Single Particle Lagrangian Integrated Trajectory’ developed by US agency National Oceanic and Atmospheric Administration.

“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 a massive dust storm in Iraq, Kuwait and Saudi Arabia.