Experts and politicians now worry that the arrival of pollution season could pose a double threat, putting people at higher risk of severe infection, while increasing the strain on public health services.

"The combination of air pollution along with Covid-19, and especially as this is going to happen during the winter months, is something we need to be really concerned about and take adequate measures, so that we don't let a huge spike occur in the number of cases," said Dr. Randeep Guleria, director of the All India Institute of Medical Sciences (AIIMS).

India's pollution problem

India has long faced this annual pollution problem; 21 of the 30 cities with the worst air pollution in the world are in India, according to IQAir AirVisual's 2019 World Air Quality Report.

New Delhi residents could live an extra 10.2 years if the air was clean enough to meet WHO standards for particulate concentrations, according to the University of Chicago's Air Quality Life Index.

But the breath of fresh air didn't last long, with the country reopening by early summer. This Tuesday, New Delhi's air quality index reached its worst level since February last winter.

A double threat during Covid-19

Residents and medical workers are now bracing for the double public health threat.

"With the Covid pandemic prevailing worldwide and pollution level spiking simultaneously, there is definitely an increased risk of higher numbers and severity of Covid-19 infection increasing," said Dr. Suranjit Chatterjee, Senior Consultant of Internal Medicine in Delhi's Indraprastha Apollo Hospital.

New Delhi is only beginning to enter pollution season, with more crop burning and the Diwali festivities ahead in the coming months. Meanwhile, though Covid-19 infections in India are slowly on the decline, there are still anywhere from 45,000 to 70,000 new cases a day -- and global health officials are warning that winter could bring another wave.

"Because of the cold air, the virus can survive in the environment for a much longer time and therefore, be more infectious," said AIIMS' Guleria. There are other factors that raise the danger of infection, he said -- when it's cold, people stay indoors more often and keep their windows closed, which creates poor ventilation.

"Many of the pre-existing conditions that increase the risk of death in those with Covid-19 are the same diseases that are affected by long-term exposure to air pollution," said the study.

Chatterjee warned of this link as well -- air pollution can inflame or damage your cells, causing heart disease, stroke, asthma, diabetes and other comorbidities that can make increase the risk of death in Covid-19 patients, he said.

However, it's not just people with pre-existing conditions at risk, he added -- because air pollution in general damages your immune system, "even normal people (in India) are more predisposed to infections in the setting of higher pollution."

There is one ray of hope: citizens may be better prepared this winter since they're already wearing masks and taking precautions, which could better protect them from both pollution and Covid-19.

But India's public health infrastructure, already fragile and strained, might not be able to handle the weight of two severe respiratory threats, especially in populous cities like Delhi and Mumbai.

"The last three years, we did not have enough beds in our ICUs or there weren't enough ventilators in Delhi's hospitals because of air pollution crisis in the month of November," said Vimlendu Jha, an environmental and social activist based in Delhi.

"So, imagine a hospital that anyway is struggling right now because of Covid. Plus the patients, the new patients, elderly and children who are going to (hospital) because of respiratory issues or new cases of pneumonia because of air pollution. It's going to be a huge, huge crisis," he added.

What authorities are doing

Officials are now scrambling to respond to both dangers; in Delhi, Chief Minister of Delhi Arvind Kejriwal has announced a "battle against pollution."

"Especially this year with corona, for our children, for our families, we have to reduce pollution," he said on October 5. "(The) lungs are the most affected by corona, so pollution can be life-taking in such a disease."

As part of the anti-pollution campaign, Delhi authorities have set up a "war room" to monitor pollution control measures. They also launched a mobile app for citizens to register complaints, measures to reduce construction dust, and a ban on diesel generator sets.

The Delhi government has also allocated 200 million rupees (about $2.73 million) to build two smog towers, which act as giant air purifiers. The two towers won't be completed for another 10 months -- but if they prove successful, the city could build several more, said Kejriwal.

National leaders also announced new anti-pollution measures in October, like closing several power plants and banning the use of furnace oil in certain industries.

But some experts and activists are skeptical these will create the lasting change needed to fix India's pollution crisis.

"Every year, we look at these short-term, stop-gap, band-aid solutions to really mitigate a crisis which is so huge," said Jha, the activist. Instead, he said, authorities need to make changes on a much bigger scale -- considering the ways that cities are urbanizing, the types of energy we consume and produce, and the specific industries that are responsible for the highest amount of pollution.

"Is cleaning our environment possible? Yes, it is possible but for that you need to really look at a different kind of a start," he added.

"We cannot be doing business as usual and expect things to get better because if our tree transplantation policy, our construction policy, our public transport policy, our energy regime -- if all of that remains the same and we expect the air to get better, things aren't going to happen."