Air-borne particles from the salt mines of Afghanistan are pushing up the levels of air pollutants in Delhi, a team of scientists has found.
Initially, the Central Pollution Control Board (CPCB) team had thought that the wind might be carrying sea salt from either the Bay of Bengal or the Arabian Sea. Subsequently, the source of the pollutants was traced to Afghanistan.
A study by the CPCB scientists, including its air laboratory chief Dipankar Saha, has found that about 11 per cent of PM2.5 in Delhi are salt particles.
However, since the study was undertaken during the winter months, the scientists ruled out the possibility of the particles being carried from the sea as the wind direction was generally from the north or north-west during this period.
"We undertook a study, using the trajectory models of the US government's National Oceanic and Atmospheric Administration. That is when we found that the salt particles were coming from those areas of Afghanistan, which have large salt pans," Saha said.
The scientists also found the presence of metals such as chromium and copper in the city's air, which Saha said were being emitted by the electroplating industries in Haryana.
There were no safe standards for these metals yet, Saha said, adding that exposure to chromium could trigger health complications.
PM2.5, which are essentially ultrafine particulates 30 times finer than the human hair, are mainly composed of sulphates, nitrates, ammonia, sodium chloride, black carbon, mineral dust and water, according to the World Health Organisation (WHO).
The study once again establishes the role of external sources in the city's air being toxic.
Last month, the Centre-run pollution monitoring agency, SAFAR, had identified a West Asian dust-storm as the chief trigger behind the recent smog episode in Delhi-NCR.
On November 8, the contribution of the dust-storm to the city's air pollutants was 40 per cent, eclipsing the emissions from stubble-burning, which stood at 25 per cent, the Pune- based System of Air Quality And Weather Forecasting and Research (SAFAR) had said.
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