People driving through smog on Delhi roads
India is the home to 14 of the 15 most polluted cities in the world in terms of PM 2.5 concentrations | PTI
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In research published in a peer-reviewed science journal, Indian experts blame the multiple exemptions granted, including to two-wheelers.

Bengaluru: The Delhi government’s ‘odd-even’ initiative to curb pollution, in fact, led to an increase in vehicular emissions, a new study by Current Science has found.

The traffic plan, closing the roads on alternate days to vehicles with odd and even registration numbers, was first implemented in Delhi for two weeks in January 2016, during the infamous smoggy winter of 2015-16.

Such efforts have proved successful in international hubs like Beijing and Paris.

However, a few days after the experiment, readings of the eight Central Pollution Control Board (CPCB) monitors in Delhi showed no reduction in pollutants in the air. The new research goes a step further and says the plan turned out to be counter-productive.

Delhi is the second most populous city in the world, with over 27 million inhabitants residing in its rapidly developing metropolitan areas in 2017. At 9.3 million, it has the highest number of personal vehicles in India — 2.9 million cars and 6.1 million two-wheelers. With new vehicle registrations climbing each year, the city is increasingly burdened by toxic pollutants and their accompanying negative health effects.

In the past decade, air pollution in the city has exceeded safe limits set by Indian regulatory organisations as well as the UN’s World Health Organisation for large amounts of time. Delhi’s pollution typically worsens in the winter, when people start burning biomass for heat and farmers burn crop residue to prepare their field for the new season.

The main pollutants in Delhi’s air are gases like sulphur dioxide, carbon monoxide, nitrogen oxide, and two types of particulate matter (PM): PM10 are particles that are 10 micrometres in size, while PM2.5 measure 2.5 micrometres and sit in our lungs. The latter is the biggest and deadliest contributor to air pollution and lung cancer.

Exemptions marred the plan

According to the new study, published in Current Science, a peer-reviewed journal, the CPCB monitors could not isolate traffic emissions from the city’s overall pollution levels.

So, a team headed by Vinayak Sinha of the Indian Institute of Science, Education and Research (IISER), Mohali, and including researchers from the ministry of earth sciences, the India Meteorological Department (IMD), Indian Institute of Tropical Meteorology (IITM) as well as IISER, set out to measure vehicular emissions alone.

To do this, the researchers sampled air in glass flasks at the Indian Oil Corporation Limited (IOCL) arterial road thrice a day.

“This is a strategic road which connects the residential colonies of Dwarka, the commercial and business centres of Sadar Bazar in central Delhi, the suburban residential colonies of Palam in southwest Delhi and the New Delhi International Airport,” they wrote in the study.

“A mixed fleet of 35,000–40,000 diesel, petrol and gasoline-powered vehicles have been reported to ply on road during peak traffic hours,” they add.

Air samples were collected during days when the odd-even plan was in place and when it wasn’t. The team isolated 13 chemicals that constitute definitive traces of vehicular exhausts and analysed the samples at the Atmospheric Chemistry Facility, IISER.

Their result: Toxins in the air actually increased on days that the rule was in place. This might seem counter-intuitive, but the study explains the reason why: The multiple exemptions granted under the rule, including for women drivers as well as two-wheelers, public buses, trucks, three-wheelers, taxis, VIP vehicles, hybrids, and CNG-run cars. Furthermore, the rule was in effect from 8 am to 8 pm, and didn’t apply on Sundays.

During the study, the highest amount of particulates was found in air samples taken between 7 am and 8 am. This spike was due to the commuters who evaded odd-even by leaving for work early. Readings during the day increased too. The sales of used cars shot up when the rule was announced, with citizens now having multiple cars.

While the plan was in place, the number of exempt vehicles on the roads shot up. In fact, the paper explains that two-wheelers have higher emissions per unit than cars fitted with latest emission-control technology.

Though the reduction in car traffic did curb congestion, the study concluded that the rule triggered a fleet emission response, where increased exempt-vehicle activity negated the curtailed effects of emissions from non-exempt vehicles.

Why it worked elsewhere

In Beijing and Paris, there are no exceptions, and the rules are fluid, varying with pollution levels. Beijing’s rules leave a buffer to avoid creating a void that would need to be filled in by alternatives: Number plates ending with one and six cannot travel on Mondays, two and seven on Tuesdays, three and eight on Wednesdays, four and nine on Thursdays, and five and zero on Fridays. No vehicle gets an exemption, including the ones that come from outside the city.

Sinha’s team says that to evaluate the efficiency of such a plan in the future, a more elaborate experimental setup would be needed, where tail-pipe emissions are monitored vehicle to vehicle.

This again begs the question of whether combative measures need to be prioritised for personal vehicles over other larger sources of pollutants. According to a 2015 study by IIT-Kanpur, submitted to the Delhi government just before the implementation of odd-even, the largest sources of pollution in the city are construction dust, burning of municipal solid waste, industrial activity, and burning stubble off fields and biomass.

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