In December 1952, London was enveloped in a fog so thick that visibility was down to under one metre, barely enough to see the end of your arm. Dense fogs—pea-soupers—were not unusual. They happened most winters and were only a worse example of the pollution that hung in the air year-round. This story will sound familiar to anyone living in the Gangetic plains, and especially in Delhi.
The severity of the 1952 fog caused a rethink. By various measurements, between 4,000 and 12,000 people died, a daily mortality rate higher than the peak of Covid in the UK. Thankfully, it did not last long. The winds changed, the air cleared and the government and people more broadly got some perspective on how deadly the pollution was.
Four years later a novel Clean Air Act was passed. High-sulphur coal which caused the highest toxicity was banned first. Over time coal heating was replaced by gas. Power plants and polluting factories in the city were cleaned up or closed and production moved further away. With North Sea gas becoming abundant, coal was replaced almost entirely.
As medical evidence piled up, sulphur scrubbing and unleaded petrol came in during the 1980s. In the 1990s, a clean diesel programme was launched to reduce particulate matter. Diesel as a fuel was promoted for its fuel efficiency before that policy started reversing around 2010. Euro emission standards started in the 1990s with the latest Euro VI standards mandating emissions that are less than a tenth of the Euro I standards.
More recently, London has promoted clean air zones. At a local level, these are about speed restrictions, banning vehicles from idling and other such actions. These are focused on schools, hospitals and similar facilities where local pollution levels are a concern. More broadly, all of London has been covered by a policy of Low Emission Zones since 2009 that restricts polluting heavy vehicles. And an Ultra-Low Emission Zone restricting all polluting vehicles has been applied in central London since 2019 and expanded in phases to cover all of London. Besides these, all other sources of pollution, such as wood fires, are being tackled through action plans.
Alongside these, the substantial investment in public transport has meant fewer vehicles on the road. Although not aimed at air quality, a better public transport system has a good collateral benefit.
The result is that the air is cleaner and the pea-soupers are a distant memory. Although London still does not meet WHO guidelines on air quality, the worst air quality days in the city are better than the best days in Delhi.
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Overwhelming medical evidence
And that is where the nub of policymaking comes in. The science has evolved and policy has to evolve with it. The science, as it stands now, is clear: air pollution is deadly. Indeed far deadlier than previously imagined, so much so that there is only one safe level of air pollution – a big zero.
Data and academic research linking air pollution to pulmonary disorders are abundant. More recently research has also established links to other health issues that cause longer-term mortality – heart diseases and strokes, autoimmune disorders as well as neurological issues.
It is this sort of evidence that has led policymaking, including the very substantial reversal of policies to encourage diesel vehicles. Policies such as these are not easy but when the evidence is clear, inaction isn’t an option. Collection and dissemination of the evidence is a clear step in building a body of support for the tough policies that are needed to make a difference.
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What is different in India?
The evidence base in India is more sketchy but clear enough to warrant serious action. An estimated 1.6 million people die due to air pollution every year. That figure is thrice the official toll from Covid. So where is the Covid-like urgency to act on this?
Actions in the UK and elsewhere provide some pointers for what needs to be done in India but there are significant points of departure as well. Despite the loud debate on crop burning or Diwali crackers, it is road dust that accounts for half the suspended particulate matter around the year. It is an insignificant issue in London so it needs a different sort of response in cleaning roads, not by sprinkling water or sweeping but by vacuuming away dust and stopping mud from being carried onto roads.
It is only once we get past road dust that all other pollutants come into play. Within the remaining half the leading constituent is still vehicular pollution. Although studies in India do not make a distinction between tailpipe emissions and tyre and brake wear and tear, evidence from other countries suggests that nearly half the particulate emissions are not from the tailpipe. The experience in India may lead more toward the tailpipe because of the types of vehicles and their maintenance but it is still the case that even if we moved to an entirely electric fleet we would still have the bulk of the emissions.
Pollution in the Gangetic plains, not just from crop burning but all types, is easily transported around making the entire area a gas chamber. This, again, is a point of departure from the experience in London. It is similar to the debate in the 1990s, when the northeast of the USA complained about transported pollutants from midwestern power plants. It led to a significant cleaning up of power plants. The more acute nature of transported pollutants in the Gangetic plains means that we need collective action. Political point-scoring between states or between the Centre and states will not get us very far.
At its core, the challenge in Delhi and elsewhere is crying out for a better public transport solution. As it turns out, it is the answer to many other problems as well.
Fewer and cleaner vehicles driving on cleaner roads have the potential to fix a substantial source of the problem. The actions Delhi is taking on restricting BS III vehicles have similar outcomes to London’s Ultra Low Emission Zone and are commendable but it is only one step in many that are yet to be taken and even this needs to be emulated more widely outside Delhi.
We need to act on crop burning and fireworks as well, not least because they happen at a time of year when there is more ambient and persistent pollution. But let it not take away from action on the primary source of pollution.
When the weather changes and the severe pollution abates, attention will drift away. But as the 1952 pea-souper in London showed, it is only concerted, continuous action afterwards that can clean up the air. Short-term actions of the kind in Delhi’s Graded Response Action Plan are good for dealing with the emergency but do little to address the long-term issues.
If 1.6 million deaths per year is not enough to focus the mind, then nothing else can.
Shashi Verma is Chief Technology Officer at Transport for London. Views are personal.
(Edited by Theres Sudeep)