COVID-19, Air Pollution and Health: Lessons for India
Pallavi Pant and Katherine Walker
This commentary is part of a CCAPC series on Communicating air pollution-linked risks in India in light of COVID-19. CCAPC/2020/04 | September 2020 | Edited by Santosh Harish | Posted: September 1, 2020
As a result of the COVID-19 pandemic, the world has witnessed large-scale shutdowns of economies across much of the globe including unprecedented restrictions on travel and industrial activities. The shutdowns have led to significant, albeit temporary, reductions in air pollutant emissions and air quality in regions around the world. In many Indian cities, residents have experienced blue skies and relatively clean air during the lockdown for the first time in many years or even decades. The blue sky vistas have made possible what no data can do – to showcase what’s possible if air pollutant emissions are controlled. They have created a timely opportunity to engage communities in action on air pollution in India, and already, public air quality campaigns are using blue sky images to demand action on air pollution (see #SaalBhar60).
What are the implications of the pandemic and the lockdown for air pollution research and regulation in India? What kind of rigorous research do we need to convincingly demonstrate the links between actions taken during the shutdowns, air quality and health, and in particular, how our chronic exposures to air pollution over the past several years have affected our susceptibility to the effects of COVID-19? Amidst a flurry of new analyses, we reflect on the emerging evidence, its potential lessons, and urge caution on the work yet to be done to understand the causal linkages between the pandemic, air pollution and health. We are still in the early stages of the pandemic, and every day, we continue to learn new aspects of the disease and its relationship with other factors. Below, we highlight three key lessons for India with respect to COVID-19 and air pollution:
One, the scientific questions about relationship between air pollution and COVID-19 susceptibility and mortality have particular importance for India. The pandemic and shutdowns create important opportunities to study the relationships between the duration and level of exposure to air pollution and susceptibility to infection (i.e. higher incidence rates) or poorer clinical outcomes for patients (e.g., more serious infections, higher case fatality rates). Even before the pandemic hit, India carried a heavy burden of chronic respiratory and other diseases; in fact, India accounts for 26% of global DALYs (Disability Adjusted Life Years) attributable to air pollution although it only represents 18% of the world’s population. India has also experienced high exposures for a long time, having ranked among the countries with the highest levels of outdoor PM2.5 exposure worldwide for the last decade or more. Exposures to air pollution have been shown to affect the human body’s immune defense making an individual more susceptible to respiratory infections such as pneumonia. Published evidence also suggests that air pollution exposures increase susceptibility to infectious diseases such as tuberculosis and severe acute respiratory syndrome (SARS); they have also been linked with a range of adverse health outcomes, including diabetes and cardiovascular, respiratory, and neurological diseases – all of which contribute to poorer outcomes in patients infected with the virus. In fact, data reported so far suggest that individuals with pre-existing co-morbidities (e.g. diabetes, heart and lung diseases) may be susceptible to more severe infections and be at higher risk of mortality from COVID-19. Considering the strong body of evidence on the effects of air pollution on the development of these co-morbidities, it is possible that exposure to air pollution is linked to more adverse outcomes from COVID-19. However, we must note that despite a large number of media reports on the topic, there is, as yet, limited direct evidence.
Two, thoughtful, well-designed approaches towards understanding the impact of the lockdowns on air quality may provide informative templates for estimating air quality changes resulting from specific policy interventions under NCAP and other policies. Globally, several studies have estimated the potential health and economic benefits of these short-term air quality improvements. It is true that the COVID-19 related shutdowns have created vast “natural experiments” for study. Natural experiments – which include both planned and unplanned actions not directed at air quality (e.g. abrupt closure of industrial facilities due to a labor strike) – have been used effectively in other settings to answer policy-relevant questions about the effects of the event on emissions, on subsequent air quality, human exposure and ultimately, on public health. How much do the changes in emissions translate into changes in air quality? Do changes in air quality lead to measurable changes in health? Studies that effectively demonstrate the linkages between each of the steps from emissions to health provide important causal evidence to support more intentional actions. However, substantial scientific experience with such studies advises that that they can be complex to design and conduct, requiring high quality datasets and thoughtful, rigorous statistical designs to make sure that the changes in air quality observed in the study are truly explained by the intervention (e.g. not by short-term or seasonal meteorological changes) and similarly that observed changes in health are not explainable by other factors (changes in behavior, economic status, or in access to medical care).
Study of the COVID -19 related shutdowns in India and elsewhere face a number of similar challenges that need to be better addressed – lockdowns were enforced in several stages and on multiple sources, making it more difficult to link specific actions or sources to changes in air quality. Similarly, the shutdowns led to vast changes in population behaviors that could also affect exposures and health. Another important factor to consider in interpreting the results of shutdown-related studies is that the air quality changes are short-term. While they may provide immediate relief and improve some measures of population health, these effects are also short-term. They may tell us little about the benefits of long-term reductions in air pollution that have been typically far larger and more influential in driving public policy on air pollution.
Three, data from the shutdown period can be used to build a case for multi-sectoral, multi-pollutant governance. In India, several studies have reported significant reductions in outdoor concentrations of PM2.5 and nitrogen oxides, including NO2. At the same time, there has been some evidence for an increase in outdoor ozone concentrations. This observation isn’t unexpected – and indeed is well known prior to the COVID-19 shutdowns – given the role that nitrogen oxides play in scavenging and thus reducing ozone concentrations. Other reports suggest that the restrictions have led to increases in exposure to household air pollution as more people stay home. So far in India, most actions on air pollution, including the National Clean Air Programme (NCAP), are primarily focused on regulation of particulate matter (PM10 and PM2.5). These divergent trends hold an important air quality management lesson; management of pollutants individually may not yield the same air quality and health benefits in the long term as a targeted multi-pollutant approach.
The unprecedented circumstances created by COVID-19 offer several opportunities for India- a moment to realign the economic and policy objectives to provide clean air, and to improve our scientific understanding of the interplay between air pollution, chronic diseases and infectious diseases such as COVID-19. However, if studies are to inform effective public policy decisions, it is critical to proceed expeditiously, but cautiously and not to compromise on the rigorous statistical designs, data quality, and independent peer review that will provide reliable evidence we need.
Pallavi Pant and Katherine Walker are affiliated with the Health Effects Institute, USA.
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