“We are at the mouth of the cave when it comes to understanding PM1”

India suffers from some of the worst air anywhere in the world. While reports have confirmed this over recent years, the impacts of toxic air in several crowded metros of the country and evidence of the rapidly increasing public health burden have catapulted air pollution into the realm of public imagination and have started to create political pressure points. As this process has unfolded, particulate matter (PM) has become a part of common parlance. As air pollution monitors churned out data in terms of concentration of the different sizes of particles suspended in the air, PM levels provided an easily comprehendible idea of just how bad or good the air was at any given time. Over the years PM10 and PM2.5, having particle sizes less than 10 and 2 microns respectively (for reference, a strand of human hair is about 70microns thick), have not only gained popularity as a reliable metric for air quality but have also been studied extensively for their impacts on human health. Now a new preliminary analysis, conducted jointly by researchers from IIT-Delhi, JNU and Delhi University, has thrown up some worrying findings on the pervasiveness of new category of even smaller particle which measure less than 1 micron.

The analysis, which looks at air quality in the Delhi-NCR region of the Indo-Gangetic Plain, warns of serious implications of these ultra-small particles as carry much higher potential to penetrate deeper into human tissue and the bloodstream than their bigger counterparts. Carbon Copy speaks to Dr. Palak Balyan from the Centre for Atmospheric Sciences in IIT-Delhi and one of the authors of the recent PM1 analysis. Balyan is a researcher working on the Indo-UK project DAPHNE (Delhi Air Pollution: Health And Effects), funded by the Indian government’s Department of Biotechnology.

What is PM1 and why is it important to study it

Just like PM10 and PM2.5, PM1 is also a category of particulate matter suspended in air. PM1 particulate matter though have sizes below 1 micron (µ) which is much smaller than PM10 and even PM2.5. The crucial link between PM2.5 and health studies when looking at the impacts of air pollution has already been established and given the smaller size of PM1, the potential harm from them is greater as they can enter into the blood stream and reach vital organs with more serious ramifications.

What are the safe limits for PM1 and how well is it monitored?

Monitoring and tracking of PM10 and PM2.5 has now become standard and the terms have been popularised because the extent of pollution and tracking are becoming well known. Unfortunately, there is no such data available on PM1 and neither is it being monitored. The technology to monitor and study these extremely small particles is still not calibrated or operated at scale. And so, there is very little in terms of concrete evidence beyond preliminary observations and correlations of the effect of PM1 on human health. Since there is little to no data available, there are no prescribed safe limits in India or internationally. From an Indian perspective, there is definitely a need to develop indigenous standards that incorporate background levels which are heavily dependent on local geographic, environmental and meteorological factors, not just for PM1 but also for PM2.5 and PM10. But we are still very much at the mouth of the cave when it comes to knowing the extent and impact of PM1 pollution.

Your analysis throws some light on the extent of PM1 pollution in the Delhi-NCR region. What can you tell us about it?

The initial idea for the analysis was to try and develop an estimate of the extent and flux in PM1 levels in the pre- and post-Diwali period. This would not only give us a peek into how firecrackers contributed to the scenario and also some insight into how the levels changed along the winter season which brings the worst air days of the year for the region.

We deployed and tracked 100 sensors in the Indo-Gangetic Plain (IGP) area to monitor PM10, PM2.5 and PM1 levels and found high levels, peaking at over 300 µg/m³ around Diwali. Worryingly, the levels were between 100 and 200 µg/m³ about a month before Diwali. This is way above even the prescribed safe limits for PM2.5 of 40-60m µg/m³!

However, it is important to note that the sensors we have used to monitor PM have not been validated and certified for PM1 size particles. So even though the data offers us an indication of what the scenario is like, confirmation can only happen after the data is calibrated with a reference grade monitor which is incredibly expensive. This is a major bottleneck in PM1 research in India at the moment.

Does the analysis offer any insights into the sources or seasonality of PM1 concentration?

Interestingly, the levels of PM1 also seem to correlate with PM2.5 and PM10 over this period of time. We know that sunlight plays a big role in how these particles rise in the atmosphere, interact with water droplets, and come together to form larger PM. There is also a good chance that all particulate matter share the same sources. But beyond this, we need much more research into the composition of PM1 particles and the specific contributions of different kinds of particles to this category. Composition is just as important as size. For instance, depending on whether the particle is a volatile organic compound (VOC), a Polycyclic aromatic hydrocarbon (PAH) or a heavy metal, PM1 can carry different health risks including cancers and neuro-degenerative diseases such as Alzheimer’s Disease and Parkinson’s disease. PM1 exposure can also have severe impacts on physical and mental development in children.

Worryingly, preliminary data suggests hazardous levels of PM1 pollution irrespective of season. While simplistically it can be expected that PM1 levels will reduce as solar radiation reaches its peak during the summer, this might also go in the opposite direction since moisture levels are much lower. So it might be that PM1 levels actually increase during summers, but this needs to be confirmed in the coming years.

What are the next steps in studying PM1 levels and establishing links with human health?

Over the years monitoring of particulate matter has grown by leaps and bounds. First it was PM100 that came into focus, then PM10 and PM2.5 monitoring expanded rapidly. PM1 will likely become the next category of pollutants to shape how we look at air pollution. While monitoring of PM1 levels needs to be improved, environmental studies that can track the particles penetration into the blood stream and genetic material also need to be conducted with the help of biomarkers. This is easier said than done though as it involves some ethical implications if conducted on live subjects.

Where are we in terms of incorporating health concerns in India’s air pollution control policy? How soon can we expect PM1 to be integrated in the National Clean Air Programme (NCAP)?

Health is nowhere in India’s air quality improvement policy, it is not even mentioned in the NCAP. This speaks of the major gap between science and policy when it comes to the effects of air pollution. Science often takes years to be translated into policy, by which time science has progressed further. Given the lack of data surrounding PM1 and its health effects, I wouldn’t be surprised if it takes years to garner any attention at the policy or political level.

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