As the air pollution in Delhi worsens, scientists and experts have pointed out that the issue needs to be looked at a chronic level. The air quality in Delhi dipped to the severe category Wednesday morning after a slight improvement a day earlier.

The situation has worsened in Mumbai too since it debuted as among the world's most polluted cities last weekend.

A blanket of toxic smog covers Delhi and surrounding cities with schools being shut. The stricter odd-even rule is set to make a comeback after four years.

Speaking to The Citizen, social activist and chemical scientist Dunu Roy said that it is important to not just look at the issue from the outside.

“Unfortunately, our judges, experts and media are just concerned about the spikes. In technical terms what we are talking about is chronic toxicity versus acute toxicity. To simply explain, chronic toxicity is like a daily dose, so the effect may not be immediately visible. Acute toxicity is when you are getting a very high dose at one time and so the immediate effect can be seen or felt,” Roy said.

He further said that if one has to see the impact health wise then acute toxicity is less dangerous than chronic toxicity. “It is because the latter accumulates over time and that is very dangerous because once it gets into your lungs these particles don’t come out. You can’t wash out the lungs,” he added.

Many people who The Citizen spoke to said that they had to stop going on early morning walks as it became difficult for them to breathe. “My eyes burnt and looking at the smog I preferred to stay at home,” Ritika Roy, a resident of Greater Kailash said.

Shikha, a resident of Delhi said that she has stopped her children from going out of the house. “We can not afford children to fall sick, which happens fairly regularly when this season comes. Schools are also shut down. It is sad that this is the reason why children are not allowed to enjoy their childhood,” she said.

Meanwhile, Delhi Environment Minister Gopal Rai on Monday announced that the odd-even car rationing scheme will be implemented in the city from November 13 to November 20 in view of the worsening air quality.

He further said that schools of all classes, excluding 10 and 12, will remain shut till November 10. Earlier, classes from 6 to 12 were "given the option" of going online, even as primary classes were ordered to stay closed till November 10.

Rai said that the earlier ban on BS3 petrol and BS4 diesel cars in Delhi will continue, and there will be no construction-related works in the city.

The odd-even scheme curbs the usage of vehicles based on the last digits of their licence plates. Under it, vehicles with licence plate numbers ending in odd digits (1,3,5,7 and 9) are permitted to ply on roads on odd dates, while those ending in even digits (0,2,4,6 and 8) can run on even dates.

For Aftab Ali, who is a heart patient, going on a walk in the morning was risky. “It is so annoying to deal with this every morning. My doctors have also told me to avoid working out at the moment,” he said.

Speaking to The Citizen, Dr Neetu Jain, Senior consultant pulmonology critical care at PSRI Hospital said that one should avoid outside physical activities at all cost.

“It is a grim situation, especially for people who have asthma or other respiratory diseases. This also includes heart disease. They are suffering and the hospital visits have also increased, while their medications have also increased. Some people are even on steroids and lots of people are getting hospitalised including in the Intensive Care Unit,” she said.

She emphasised that it is better to be inside the home than outside at the moment. “Inside the home the air is the same with little differences in the AQI,” she added.

An Air Quality Index (AQI) is a number used by government agencies to measure the air pollution levels and communicate it to the population. As the AQI increases, it means that a large percentage of the population will experience severe adverse health effects.

The measurement of the AQI requires an air monitor and an air pollutant concentration over a specified averaging period. The results are grouped into ranges, and each range is assigned a descriptor, a color code and a standardized public health advisory.

The AQI has six range categories (Good, Satisfactory, Moderately Polluted, Poor, Very Poor, and Severe) and checks the associated health impacts.

The situation is so dire that the and an embarrassment for the Indian government, the ongoing world cup was affected when experts raised concerns over Bangladesh-Sri Lanka World Cup match.

While the face-off did happen in Delhi, asthmatic players were forced to skip practice after doctors raised concerns.

Meanwhile, in a loop that has happens every year when the issue of air pollution arises, the Supreme Court on Tuesday pulled up the Punjab government over stubble burning while thick clouds of smog shrouded parts of Delhi as the air quality across the national capital continued to remain in the 'severe' category.

It also observed that there can't be a political battle all the time. “We want it (stubble burning) stopped. We don't know how you do it, it’s your job. But it must be stopped. Something has to be done immediately,” the Supreme Court told the Punjab government.

A Bench of justices Sanjay Kishan Kaul and Sudhanshu Dhulia, hearing air pollution matters, directed Punjab, Delhi, Uttar Pradesh and Rajasthan to stop stubble burning "forthwith", making chief secretaries and director general of police concerned responsible for overseeing the implementation of the court order. Justice Kaul observed that while travelling through Punjab over the weekend, he saw widespread fires on both sides of the road.

The court also put the onus on the Centre, suggesting it should stop supporting minimum support price (MSP) for paddy in Punjab and should rather find ways to make farmers shift to alternative crops.

"The government has been propagating millets. Why not promote it?" the court said.

However, Roy said that putting all the blame on stubble burning is problematic and diverts attention from the issue as a whole. He further explained that even if there was no stubble burning happening the “time curve” is the same.

Roy was attributing the data towards the “Time series data” also referred to as time-stamped data, which is a sequence of data points indexed in time order. These data points typically consist of successive measurements made from the same source over a fixed time interval and are used to track change over time.

“Nothing is happening to that curve. That curve remains going up. This is because winter is the inversion time. It is the time when all the pollutants settle down because of the inversion factor. That is the cold air above traps the pollutants below. There's no way where the pollutants can go.

“Stubble burning takes place in Punjab and Haryana. Now, logic would have it say that it is the wind that blows these pollutants to Delhi. Now, Delhi is not a terminus on the line. Delhi is only one of the stations along the line. Why does it stop at Delhi? Logically, if the wind is blowing, it should keep blowing right down the energetic plane. It should not stop at Delhi and just pool here,” he said.

“If the wind is blowing, then okay, it pools here. It can't go here. It has to keep going. By that logic, the pollution from Delhi will also go down the street, downwind. It'll go and affect Lucknow and Kanpur and Banaras and Hawra and so on.

“If the wind is not blowing, then logically, the pollutants from Punjab wouldn't come to Delhi. They would pool in Punjab and Haryana itself,” the scientist who has been working on the issue for years and has written various research papers, added.

The Punjab government has, however, claimed that there is a 70% decrease in stubble burning cases in Punjab in the last two years.

The ruling Aam Aadmi Party (AAP) Punjab also responded to the Supreme Court’s statement and said that the Mann government is “constantly taking steps to stop stubble burning in the state”.

The AAP said that the Supreme Court has hinted that only Punjab farmers are not responsible for the dire pollution situation of Delhi as the hon'ble court has also asked the governments of UP, Haryana, Rajasthan and Central Government to take necessary measures to curb this problem.

Addressing a press conference at the party office in Chandigarh, AAP Punjab chief spokesperson Malvinder Singh Kang, said that stubble burning has been a compulsion of farmers but the government provided alternatives such as biofuel factories which buy paddy stubble from farmers.

“It helps farmers as they don't have to burn the stubble and they get good money for it too. Kang said that only farmers are not responsible for the pollution that Delhi is facing today, so the central government must own up to its responsibility and take steps to curb all kinds of pollution in the national capital,” he said.

Roy further said that farmers can not be blamed for stubble burning.

Meanwhile, the political blame has again sparked in the national Capital and other regions affected by it. While Delhi BJP president Virendra Sachdeva slammed Kejriwal for indulging in "political tourism" in poll-bound states during the crisis, Gopal Rai trained guns on the BJP governments in Haryana, Uttar Pradesh and at the Centre.

Addressing a press conference, Rai on Friday said that Union Environment Minister Bhupender Yadav should become "active" in addressing the air pollution problem, emphasising that it's not just the national capital, but the people in northern India were breathing polluted air.

He said the BJP was blaming Kejriwal for the air pollution problem in Delhi and asserted that he was not responsible for the poor air quality in Uttar Pradesh and Haryana.

"There are two smog towers in Delhi. One is in Anand Vihar, which is run by the Central government while the other is in Connaught Place, which is run by the Delhi government. The DPCC's chairman Ashwani Kumar joined in December. His payment has been stopped by IIT Bombay and for the past eight months, the smog tower has been closed. We are tired of saying it again and again. But he's not ready to open it," Rai said.

"Though it is the decision of the Cabinet and it's the order of the Supreme Court, they have still closed it. These conditions are against us. If other states like Haryana and Uttar Pradesh were active, like Delhi, then the situation could improve," he added.

Rai also hit out at Uttar Pradesh Chief Minister Adityanath and said, "He does not see the pollution in Greater Noida being caused by buses and construction activities while speaking about the stubble burning in Punjab. He blames Punjab because the AAP is in power in Punjab, where we have managed to reduce stubble burning by 50 per cent."

Meanwhile, addressing the media, Adityanath said when he landed in Ghaziabad on his way to Delhi, he felt a burning sensation in his eyes when he stepped out of the plane.

"I realised it was due to smog. When I checked NASA satellite images to see areas affected by stubble burning and industrial pollution, it was found that the whole of Punjab and northern parts of Haryana were indicated in 'red' (indicating stubble burning). When air from these states travelled, Delhi was covered in darkness," he said.

Roy who has also been part of groups who have suggested solutions to the government to tackle the situation said that there are two possible solutions, according to him, that needs to be done.

“First is that there needs to be a change in agricultural policy. The growing of Basmati and paddy or even wheat in Punjab is not something that farmers did. It was promoted by government policy. So, it is pointless blaming farmers for it,” he said.

He further said that there needs to be done something about the public transport. “I don’t mean metro here because all metros require paratransit. You get off a metro but have to take another vehicle to reach the destination, you can’t walk by and large. This means that paratransit needs to be put into place, which is on a large scale,” he said.

Dr Jain, meanwhile, recommended people to leave Delhi for a couple of months as the situation escalates. “Punjab or Haryana are no better so people will either have to go South or further up. We are worried about the number of increases in patients and I feel the work needs to be done on the policy level regarding this,” she added.

The overall air quality index (AQI) in Delhi was recorded at 418 Wednesday morning. Some of the worst-affected areas were Punjabi Bagh (460), Narela (448), Bawana (462), Anand Vihar (452), and Rohini (451). The situation isn't any better in Noida, Gurugram and other surrounding cities. Noida's average AQI in the morning was 409, Gurugram 370, Faridabad (396) and Ghaziabad (382).

Mumbai recorded an AQI of 165 this morning. A hospital has set up a special Intensive Respiratory Care Unit to attend to patients with respiratory issues in the city, fearing a rise in health issues due to pollution.

This is despite the city's geographical advantage of being located on the coast and being surrounded by water on three sides, which leads to strong winds blowing away most of the pollutants in the air.

Meanwhile, Stage-4 of the Graded Response Action Plan (GRAP), a set of anti-pollution guidelines, has been invoked and diesel trucks and construction activities have been banned in the national capital.

The GRAP is a set of emergency measures that kick in to prevent further deterioration of air quality once it reaches a certain threshold in the Delhi-NCR region. Approved by the Supreme Court in 2016 and notified in 2017, the plan was formulated after several meetings that the Environment Pollution (Prevention and Control) Authority (EPCA) held with state government representatives and experts. It was after this that a plan was institutionalised with measures to be taken when air quality deteriorates.

According to the order, the state governments in the NCR may decide to discontinue physical classes for classes 6 to 9 and class 11, and conduct lessons online. Moreover, the governments may also decide on whether to allow public, private, and municipal offices to work on 50% strength while the rest of the employees work from home.

State governments may also consider other emergency measures like closure of colleges and other educational institutions, and closure of non-emergency commercial activities, permitting vehicles to run on an odd-even basis. The central government may make an appropriate decision on permitting work from home for employees working in central government offices.