Carcinogen in Delhi’s air, IIT Kanpur’s study finds

New Delhi, December 30

Delhi’s air may be more toxic than previously imagined: a study by IIT Kanpur found traces of a deadly chemical among the pollutants in the city.

Called polycyclic aromatic hydrocarbons (PAH), the toxin is a product of emissions of diesel vehicles that, even in small quantities — such as the ones found — was likely to be carcinogenic and could even harm a foetus, a study submitted by the institute to the Supreme Court found. 

PAH was part of the hazardous PM 2.5 particulate matter found in Delhi’s polluted air. The study identifies road dust (38 per cent), vehicles (20 per cent), domestic fuel burning (12 per cent) and industrial point sources (11 per cent) as sources of PM 2.5.

"PAH are toxic gases and a potent carcinogen, meaning exposure to them can cause cancer. It comes mainly from sources that use diesel as fuel which include diesel-run cars, generator sets, trash burning," Anumita Roychowdhury, head of Centre for Science and Environment (CSE's) clean air campaign, said.

The Central Government has submitted a draft of the study commissioned in 2013 to the Supreme Court, but the findings have yet to be made public.

Experts on air pollution said the findings were alarming: the toxin would make particulate matters such as PM 2.5 and PM 10, already present in large amounts in the city's air, deadly.

"This is because these particles, which can embed themselves deep in the respiratory system, can carry with the toxic gases inside inflicting more harm," Roychowdhury said.

Apart from PM 2.5, the report has identified oxides of Nitrogen (NOx) — whose main sources are industrial estates including power plants (52 per cent), vehicles (36 per cent), diesel generator sets (6 per cent) and domestic sources (3 per cent) — as a concerning pollutant in the city.

The study also found that if aircraft were to be excluded from the list of top sources of pollution, vehicles became No. 1 polluters.

However, there was a difference in sources of pollution during summers and winters: vehicles contributed to 25 per cent of PM 2.5 emissions during winters, while pollution caused by biomass burning were slightly higher at 26 per cent. In summers, however, coal and fly ash made up for 26 per cent of PM 2.5, soil and road dust 27 per cent; biomass burning 12 per cent; and vehicles 9 per cent.

The report of the IIT-K study titled 'Source Apportionment Study of PM2.5 and PM10', which was deliberated upon recently in a meeting attended by its lead investigator, has played a major role behind the recent announcement of a series of anti-pollution measures by the Delhi government.

It also recommends a switch to Euro VI emission compliant petrol and diesel. Incidentally, the city government announced its decision to adopt Euro VI by 2017 after receiving the report.

Euro IV fuels, currently in force in major cities, contain 50 parts per million (ppm) sulphur, while Euro VI stipulates 10 ppm sulphur. BS IV and BS VI are equivalents to the corresponding Euro fuels. — PTI