In the Air We Breathe: Dr. Siddhartha Mandal’s Fight Against India’s Invisible Health Crisis
By Arunima Rajan
Dr. Siddhartha Mandal is an environmental epidemiologist and public health researcher working to understand the health effects of air pollution and climate change in India. Over the last 10 years, he has been carrying out research to understand air pollution exposures and their health effects in the Indian population. His work at Centre for Chronic Disease Control in collaboration with Harvard University, Emory University and Karolinska Institute has led to generation of significant and novel evidence linking air pollution with cardiovascular health in India. In addition, he has trained a large number of medical and public health professionals in environmental health research across the country. He has published more than 35 research articles in international peer-reviewed journals and 2 book chapters.
In an interview with Arunima Rajan he explains that air pollution, particularly fine particulate matter has far-reaching health impacts beyond just the lungs.
Siddartha, you’ve spent years studying air pollution in India. What first drew you to this field, and how has your understanding of the problem evolved over time?
My research in air pollution and health was not a planned venture. During my doctoral and postdoctoral research, I was involved in research involving development and application of statistical methods in health problems. My involvement with air pollution research started by being recruited in the Geohealth hub project, with very little knowledge about exposure assessment and air pollution epidemiology in general. The challenge of tackling a difficult problem that had serious implications on public health was the main attraction. In 2016 there was a massive air pollution episode which further strengthened my resolve to carry out this research despite several limitations in terms of resource and data.
Over these 8 years, I have developed a better understanding of the science behind the pollution problem but more importantly the clinical significance of the issue. I have become more aware of the biological mechanisms by which our health is affected by the pollutants. Finally, I have realised how multi-sectoral this problem is and that knee-jerk reactions are not going to provide long-term solutions.
Mapping PM 2.5 levels across India must have been a monumental task. Can you break down how your team achieved this and what role satellite technology played in filling the gaps left by limited ground monitoring?
We leveraged our experience from a similar modeling exercise at a much smaller scale focusing on two cities (Delhi and Chennai). The biggest challenge to develop a national model was collating all the data from various domains including ground monitoring data and all the predictors that would be used to develop the model. It took massive teamwork as well as collaboration with academic partners to obtain whatever data was available. Next, the processing of all these data in different formats to get it into a usable form and then developing the model took quite a lot of computation time and coding expertise. So, it was careful planning and execution with cross-institutional collaboration that helped us carry out this task.
Among all the data sources, satellite data of various types were crucial to a) get information on several predictors of PM2.5 and b) to arrive at the 1kmx1km spatial resolution for the predictions. Satellite observations provide different types of information, for example, aerosol optical depth to estimate light extinction, fire counts and fire intensity, nighttime light intensity and vegetation, to name a few. These are predictors that provide useful information, that would otherwise be difficult to obtain, to assess PM2.5 at a fine spatiotemporal resolution.
Most of us think of air pollution as something that harms our lungs. But your research shows it impacts much more—our hearts, our brains, even our metabolism. Could you explain these less obvious effects to us?
Fine particulate matter due to its extremely small size can enter the bloodstream via the lungs. Once it enters circulation, it has access to several organs and not just the lungs. Hence the impact on the cardiac, metabolic and cognitive health. Based on current scientific evidence, one of the major mechanisms by which PM2.5 affects health is by
inducing inflammation and oxidative stress and it is well known that systemic low-grade inflammation plays a role in multiple diseases. As a more specific example, PM2.5 exposure triggers an imbalance in the autonomic nervous system, which regulates involuntary functions like cardiac rhythms, which can subsequently affect heart health. As more studies are conducted globally, we expect to gain more insights into these mechanisms in various populations.
Despite the recurring headlines, many still don’t see air pollution as a year-round health crisis. Why do you think public awareness is still stuck in the “winter smog” narrative?
I think it is more tangible in the winter months when we see the haze or smog combined with the media attention. The narrative revolves around acute effects such as respiratory distress. The media attention is also heightened in the winter months, especially focused on the National Capital Region.
We need to do more in engaging communities across the country to spread awareness about how pollution is generated and how it affects health. It is important to show via multiple avenues, how even low and moderate levels of exposure are related to chronic diseases. There may be a false sense of security in cities with low levels of pollution but there is lot of global and national evidence showing harmful effects of low or moderate levels of long-term exposure. Further, given the slow progression of chronic diseases, we often tend to overlook it leading to disastrous consequences.
Clinicians and healthcare providers can play an important role here by informing those seeking healthcare about how the environment can affect their conditions. Given the multifactorial nature of these diseases, we need to bring pollution into the narrative alongside diet, lifestyle, and physical activity to reduce the disease burden.
Research like yours is crucial for policymaking. Have you seen tangible results from your work? Can you share a specific moment when the data you generated influenced action at the government level?
Policymaking in my opinion is a slow and deliberative process. Specially in the air pollution domain, policymakers need to gather a large body of evidence before action. We have seen progress over the last few years with more monitoring across regions as well as prompt actions during the high pollution season. As scientists, we are ready to assist the policymakers in whatever way we can. We are engaging with several governmental agencies to generate, collate and provide evidence. Hopefully, this will translate into development of solutions to mitigate the effects of air pollution and climate change.
Crop stubble burning is a recurring villain in this story. While there’s talk of transitioning to sustainable alternatives, the problem persists. What’s preventing these solutions from being widely adopted?
I am not an expert in this area, but it looks like the solutions are not often co-created with the larger communities that the solutions are for. Also, there might not be one solution to solve it all. So, I feel there needs to be multi-stakeholder engagements with a focus on designing and deploying multiple solutions, testing their acceptability, efficacies, and potential for scalability.
Globally, some cities have tackled air pollution with great success. Are there lessons from their approaches that we can adapt to the Indian context, or are our challenges too unique?
Each location is unique in terms of the sources of pollution, community composition, socioeconomic status and of course, cultural differences. Hence one size may not fit all. However, we can look at examples of Barcelona, London or San Francisco to see how they have tackled pollution. Then we can try co-creating and adapting a few solutions and test whether these are effective in reducing the levels. Several of these cities have invested in public transportation and efficient urban planning to tackle high air pollution levels. In India's case, these strategies need to be adapted while being mindful of the community requirements, such as last-mile connectivity and frequency of public transport. Most importantly, such solutions should be co-created with all stakeholders, possibly in a few areas to start with, and evaluated before deployment in larger scale. We already have a smart cities program under which we could incentivize reduction of air pollution levels and come up with some model cities who achieve the standards.
You’ve spent years observing the problem up close. How do you personally cope with living in Gurugram during Delhi’s pollution emergencies? Does it ever feel overwhelming to work on something so critical yet so persistent?
It is challenging throughout the year especially given the kind of evidence we constantly deal with. The seasonal episodes seem almost inevitable each year with the entire region being engulfed in pollution. We try to take personal measures, for example, using N95 masks whenever possible, to avoid exposure to pollutants. On the other hand, we also try to ensure that we are not contributing to the problem, by adhering to the prescribed guidelines and restrictions. But it does get a bit worrying because these exposures are often not under individual control like modulating diet or lifestyle.
Air pollution often feels like an invisible enemy—out of sight, out of mind for much of the year. How do we shift the narrative to make people see it as a constant and pressing public health issue?
We do not want to create an environment of panic but being unaware does not help either. I think over the last decade; air pollution has indeed found place in public consciousness, at least in the urban areas. If you see the lessons we learnt from the pandemic, it is evident that we can fight back quite well. It's a matter of concerted effort from all sectors.
If you had a magic wand to solve one part of India’s air pollution crisis, where would you use it? And what role do you think ordinary citizens can play in this larger battle?
I would use it to bolster a clean, punctual, and secure public transport system and reform our freight vehicles to reduce our reliance and dependence on cars and diesel-powered goods transport system. This would both reduce vehicular pollution as well as make sustainable and accessible urban and rural communities.
Citizens of this country are critical to make changes to this scenario. We can't push all the responsibility on the governments and wash out hands off. We should raise our voices for sustainable long-term solutions, opt for cleaner alternatives wherever available and educate ourselves on the myriad effects of pollution. It is also imperative that the scientific community collaborates across disciplines and communicates effectively with the public and policymakers.