If you have a BS IV-compliant diesel car and usually ride alone, you can reduce your per capita particulate (PM) emissions per kilometre by at least 40 times by using a CNG bus instead. And if you have been driving a diesel SUV, then the benefit could be to the tune of 80 times, an analysis by Centre for Science and Environment (CSE) has revealed.

CSE researchers on Thursday released a report showing how each car user can help improve air quality by shifting to public transport. The driver of a single-occupancy BS-IV petrol car can reduce per capita PM emission per km by two times by using a CNG bus. Car-pooling will naturally reduce per capita emission of each car user by about four times. "The programme will allow enormous fuel savings and mitigation of heat-trapping carbon dioxide emissions. Per capita CO2 emissions from a single-occupancy petrol car can reduce by 15 times with shift to buses," the CSE statement said.

CSE researchers further said the fortnight long odd-even strategy that kickstarts on Friday is justified because the air quality this winter has been far worse than 2014. Last December, for instance, at least 3% of the days were in "good' category. The analysis of data from Delhi Pollution Control Committee's (DPCC) real-time air quality monitoring also showed that there were 11 "smog episodes" this winter when on three consecutive days air quality was in the "severe" category.

Another reason why the odd-even strategy could have health benefits is because more than 55% of Delhi's population lives within 500 metres from some roadside and, therefore, within the direct influence of toxic vehicular pollution. Their exposure can reduce considerably through the exercise.

CSE quoted another study by University of California, Berkeley, which has shown that in Delhi people's exposure to vehicle exhaust is three to four times higher than the world average. "Vehicular emissions contain some of the deadliest toxins like polycyclic aromatic hydrocarbons and benzene. These are more in diesel emissions," CSE added.

Source: December 31, 2015, The Times of India