Can Delhi’s odd-even policy help in preventing health issues?

Context- While there is some evidence that an odd-even vehicle policy reduces pollutant levels, experts say the available data lacks consistency, and the reduction achieved may not be sufficient to address health-related impacts.

“It is not even a band-aid,” said Dr Sagnik Dey, professor and coordinator, Centre of Excellence for Research in Clean Air at the Indian Institute of Technology-Delhi.

Can odd-even prevent health issues?

  • Explaining why odd-even is not a long-term solution, Dr Dey said: “With several exceptions, odd-even doesn’t really cut the number of vehicles plying on the roads by 50%.
  • More importantly, the reduction in emissions doesn’t always mean a reduction in the pollutant concentration in the air, as that depends on meteorological factors like wind speed. The evidence so far shows an uneven impact — while some areas have seen reductions, others have not, or the reduction has been only for a few hours.”
  • Dr Dey added that there is no study to show whether this small reduction in air pollution levels impacts people’s health.
  • Dr Karan Madan, additional professor of pulmonary, critical care, and sleep medicine at AIIMS, Delhi, agreed: “When the PM2.5 levels are over 500, a 20% decrease would mean a drop to only 400. That is still very harmful.”
  • Long-term exposure to pollution is associated with increased risk of hypertension, diabetes, and cardiovascular diseases like heart attacks and strokes. It is known to increase the risk of chronic lung diseases, cancers, lower immunity, and also leads to depression.

What do studies say?

  • Several studies have shown a decrease in the level of particulate matter when the odd-even scheme is in effect in Delhi. This reduction, however, has only been around 5 to 10%.
  • A study of the 2016 implementation of odd-even using satellite data, by Dr Dey and Dr SN Tripathi of IIT Kanpur, found a 2 to 3% decrease in PM2.5 concentration in most of Delhi, barring three pockets where it went down by 8 to 10%. Another study from Delhi Technical University found a 5.73% reduction in PM2.5 levels on average and 4.70 % in PM1.
  • The studies said that the lower PM levels could be because of fewer cars, and also because of traffic moving faster on decongested roads and engines idling less.The studies noted that the sharpest drop in PM levels was observed during midday and not early morning, when the cold temperatures keep the pollutants suspended close to the ground.
  • Another study by scholars from IIT Delhi and two UK colleges compared PM levels in 2016, when odd-even was implemented, with the same period the previous year. It found that PM2.5 ranged from -2 to -44 % from the previous year during odd–even hours, but was higher by 2–127% during non–odd–even hours.

Why is reduction of NO2 important?

  • There could be one important benefit from the odd-even scheme. With fewer vehicles on the road and less congestion, Dr Dey said, it stands to reason that gaseous pollutants such as nitrogen dioxide, primarily coming from vehicular emissions, would also reduce.
  • This is significant, because a recent AIIMs study found that emergency room visits increased more with an increase in NO2 levels, than with PM2.5. Short-term exposure to nitrogen dioxide led to a 53% increase in the number of patients who visited the hospital’s emergency room up to a week later.

So what needs to be done, then?

  • The measures are to kick in after Diwali, and hence won’t help with the pollution caused by crackers. Doctors suggested people stay away from crackers.
  • As for long-term solutions, Dr Dey said measures such as phasing out BS-IV vehicles and bringing in more electric vehicles are likely to show results in the coming years. Measures like odd-even should be implemented in a regional manner and not in Delhi alone
  • Dr Madan also called for the use of air purifiers in schools.

Conclusion- With pollution levels reaching severe category in and around areas of Delhi NCR emergency measures become need of the hour. However, knee jerk reactions cannot constitute the entirety of our response. There needs to be a comprehensive pollution management strategy and its effective implementation.

Syllabus- GS-3; Environment

Source- Indian Express


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