‘Like Clockwork, and Not Getting Any Better’.
At the beginning of November, smog in Delhi was so thick that flights were cancelled, schools were closed, doctors warned that breathing the air for a day was as harmful as smoking 50 cigarettes, and Delhi Chief Minister Arvind Kejriwal declared a public health emergency—again.
“Right around Diwali, for four of the last five years these major events have occurred like clockwork, and unfortunately they’re not getting any better,” says Kevin Lane (SPH’14), assistant professor of environmental health. “The air pollution levels are staying the same—or potentially getting worse.”
Lane says “potentially” because, during these smog events, the machines that monitor concentrations of particles in the air actually max out at 999 micrograms of particulate matter size 2.5 (PM2.5) per cubic meter of air. Small enough to get deep into a person’s lungs and even into their blood, PM2.5 causes millions of deaths from cardiovascular and respiratory issues around the world each year.
The PM2.5 levels during these smog events in Delhi are likely as high higher than in the Great Smog of London in 1952 and the 1948 smog event in Donora, Pa., in 1948, “events we know to have been catastrophic when it comes to mortality and morbidity,” Lane says.
Delhi has taken some steps, including banning fireworks and firecrackers traditionally set off during Diwali, and alternating days when only cars with even- or odd-numbered license plates are allowed on the roads. That (and favorable weather) may have helped bring smog down to the city’s usual—but still unhealthy—levels a week into November this year, but Lane says much more will need to happen at a national and even international level.
Lane discussed why these smog events keep happening, what they mean for the health of people in Delhi, and what he and his colleagues are doing to help.
First of all, why does Delhi keep having these smog crises around the same time each year?
You’re having the Diwali festival, but also there’s agricultural burning at this time of season in northern India, as well as in surrounding countries like Pakistan, and changes in meteorology and cooler temperatures at this time of season lead to atmospheric inversions that decrease particle dispersion and keep those air pollutants from circulating out of Delhi.
In addition to that, traffic has been increasing, and you have solid fuel-burning from industrial sources and home heating and cooking.
When you don’t have the wind patterns and rain to push and clean out the air pollution naturally, you get these buildups that can become very toxic and dangerous for the population in Delhi.
What level of PM2.5 is safe?
The guidelines from the World Health Organization say a safe level would be 10 micrograms per cubic meter as an average exposure on an annual scale, and on a daily basis 25 micrograms per cubic meter. In this case, in Delhi, what we’re seeing is levels that are registering as 999, so we’re talking orders of magnitude higher and potentially much more dangerous.
I was in Delhi this summer for an air pollution meeting, and on one of the days PM2.5 was above 300 micrograms per cubic meter. Coming from Boston, where on a daily basis we might be exposed to 10-30 micrograms per cubic meter of particulate matter, what I was seeing was ten times that. It was actually something that you could feel physiologically affecting you, having trouble breathing and coughing a lot. Without being exposed to these levels it is difficult to imagine what it’s like during these major events where the levels are two to three times higher.
How will climate change affect this issue?
Delhi has a number of major environmental issues, not just air pollution, and with increasing temperatures from climate change you have year-round exposures that are putting vulnerable populations at risk.
In the summertime, you have heatwaves in excess of 40 degrees Celsius [104 degrees Fahrenheit] and even hitting 45 degrees Celsius [113 degrees Fahrenheit], so you have huge heat impacts, and then that’s followed by a monsoon season where you have flooding. Then, in the fall, you have what are becoming yearly major air pollution events. There is less time for these communities to fully recover—especially those who are homeless and suffering the most.
What needs to happen to reduce air pollution in Delhi and across India?
Exposures come from a lot of the same sources that we see here in the United States, such as traffic—so, increasing public transportation, less burning of solid fuels, and reducing industrial sources, but this requires national and state policy actions.
A solution to mitigate personal exposure is to increase building filtration through HEPA air filtration. What a lot of people are doing is buying small, room-based air filtration—however, there is a social equity issue, because only certain segments of the population are able to afford it. The most vulnerable populations, who are homeless and/or live in slums, are really feeling the brunt of these exposures and negative health outcomes.
Larger-scale solutions need to be done at a state or national scale, especially when you’re talking about major sources that are even beyond state or national boundaries, such as crop burning at this time of year in surrounding states and countries. There’s no one solution that will fix everything, but at some point we have to realize that this is just going to happen again and again.
What are you currently working on around this issue?
I’m part of a group of researchers (including Greg Wellenius, incoming director of the SPH Program on Climate and Health) at Boston University, Harvard, the Karolinska Institute, the India Institute of Technology, Sri Ramachandra University, and the Public Health Foundation of India. We’re building a high-resolution nationwide air pollution model, so that researchers with the health information on the ground can do the same kinds of health studies that were done in North America and in Europe to provide the epidemiological evidence for air pollution standards.