Particles of Truth - A Science History of the Air we are Breathing
The first time I read about the health effects of air pollution was in April 2023 when I was commissioned by PARI to compile focus and factoids for the report "Health effects of short and long-term air pollution exposure: Evidence from a survey of residents living in rural and urban regions near Kolkata" by Climate Trends. Then in 2024, I studied the course SWE 316 Air Pollution and Control Engineering under the formidably knowledgeable Dr. Balaji Kannan at AEC&RI, TNAU and found myself really liking the subject. Now I'm here at ESED, IIT Bombay and just finished the course ES 635 Air Pollution Science and Engineering so ably and creatively taught by Prof. Srinidhi Balasubramanian and Prof. Harish Phuleria (+ TAs: Kounik Bhaiya and Mirunalan Anna) that I am further piqued by the subject. And Srinidhi Ma'am was kind enough to lend me her book:
Particles of Truth
A Story of Discovery, Controversy and the Fight for Healthy Air
By C. Arden Pope III & Douglas W. Dockery
Imagine grabbing an air pollution textbook or the presentation deck of someone teaching air pollution and extracting the introduction that explains why we are worried about air pollution and since when. Then when you expand it, elaborate it, contextualise it, highlight the progresses, explain the setbacks, and finally recommend what can be done - you get this amazing piece of science history that compels you to understand the science of air pollution. The authors C. Arden Pope III and Douglas W. Dockery are researchers from different fields who converged at the problem of the health effects of air pollution in 1989.
This book is a culmination of the events that led to the recognition of air pollution as a problem, extensive studies by the authors and their colleagues on the association between human health and air pollution, controversies that arose from their research outputs, changes in federal regulations and approaches to improve air quality, all in the format of a engaging firsthand account that could actually be adapted into a movie! The authors, it felt to me, were like buddies who paired up for a very important scientific adventure. Or became buddies during the adventure.
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| Arden Pope and Douglas Dockery with Utah Valley in the background (1995) |
As Gina McCarthy puts it in the Foreword: "Particles of Truth is a real-life account of the ground-breaking science accumulated over the past four decades. It tells the story of the hard work that went into pulling together the body of evidence that has underpinned new policies, regulations, practices, and technologies that have successfully reduced air pollution and saved countless lives. It is also a testament to the ingenuity, creativity, courage, and persistence of Doug, Arden, and the many dedicated research scientists who have strived for decades to understand and document the connection between air pollution and health. These individuals are consummate professionals who have spent their lives gathering and analysing data, testing and retesting new methodologies, and expanding the body of research needed to connect the dots between air pollution and health with the precision that science demands."
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| pc: Douglas Dockery's LinkedIn post |
With that re-said, this is a great read for anyone who breathes. The authors have elegantly organised the book into 12 chapters, or rather 12 questions, which they answer eloquently from multiple vantage points. Now I will go on to list each chapter and highlight what I found most interesting in each of them:
1. What is healthy air, and why does it matter?
The authors introduce us to Ella-Kissi Debrah of London, the nine-year-old who succumbed to air-pollution-triggered asthma attacks in 2013. Had she been alive, she'd be just as old as me.
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| The Ella Roberta Foundation |
Other books mentioned in this chapter:
- Doubt is Their Product: How Industry's Assault on Science Threatens Your Health by David Michaels
- Merchants of Doubt: How a Handful of Scientists Obscured the Truth on Issues from Tobacco Smoke to Global Warming by Naomi Oreskes and Erik Conway.
- Into Thin Air by Jon Krakauer
2. Does air pollution smell like money or disease?
Ironically, a French account of the Meuse Valley fog incident in Belgium in 1930, that killed 60 people, reported that "little was done since air pollution was considered an unavoidable consequence of prosperity". Guess this cry has just shifted to different places and countries like ours now.
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| Nemery, Hoet, Nemmar (2001) The Meuse Valley fog of 1930: an air pollution disaster |
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| Firket (1936) Fog along the Meuse Valley Jean Friket was a Belgian chemist who studied the Meuse valley disaster. He noted: |
"About fifteen autopsies with microscopical examinations of tissues and spectroscopical or spectrographical analyses of blood, and also toxicological analyses of all organs were performed. The histological examinations showed that noxious products had been inhaled in the last hours of life, and had brought on a local and superficial irritation of the mucous membrane of the respiratory ducts exposed to the air inhaled. The microscopical sections of the lungs showed, in addition, the inhalation of fine particles of soot even as far as the pulmonary alveoli."
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| Waterloo Bridge (1903) Claude Monet |
David Bates was a doctor at a London hospital during the smog episode. He examined the lungs of cattle that died during the smog to find "acute inflammation in the small airways of the lungs" that killed them. He went on to become a pioneering respiratory physiologist and air pollution epidemiologist, motivated by being a witness of the 1952 London smog.
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| Dr. David Bates |
The authors conclude this chapter by acknowledging that air pollution smells like both money and disease, but chapters 6 and 11 answer this further.
3. Does regular exposure to air pollution harm human health?
Arden Pope and Douglas emphasise on "natural experiment", which is an observational study where researchers leverage an externally-occurring event to study cause-and-effect relationships. It was a natural experiment that pushed Arden Pope, an economist and statistician initially, towards air pollution research. Hailing from Wyoming and Idaho, he was working at the Brigham Young University in Utah, when he identified the natural experiment that changed his life. Not dropping spoilers here.
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| Arden Pope's "landmark study" |
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| "Steve Lamm is wrong" |
Several prominent figures in air pollution epidemiology are introduced in this chapter and the authors worked with them over decades. Most of them are from the Harvard School of Public Health.
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| I love this part: "Larry Kalkstein (above), a well-respected climatologist, was critical of the early daily time-series mortality studies, arguing that the researchers should use a "synoptic weather modelling approach" that used more meteorological variables and allowed for control of more complex weather conditions. According to him, the initial statistical modelling approaches were inadequate. He predicted that this approach would eliminate or reduce the estimated adjusted daily associations between air pollution and mortality. In January 1995, Doug, Arden, Joel Schwartz, Larry Kalkstein and others made presentations at meetings sponsored by the EPA... Larry and Joel got into a heated debate about which of the two modelling approaches worked better. Arden happened to be sitting between them, mostly keeping his head low. When there was a brief break in the action, Arden asserted that the debate over the best weather model was an empirical question. He had adequate data from the Wasatch Front Area of Utah to try both modeling approaches. He bet Larry a milkshake that the method used by Joel, Doug, and Arden would work better than Larry's approach.... The EPA provided essential funding to conduct the research. Arden flew out to the Centre for Climatic Research at the University of Delaware and worked with Larry to compare the two modeling approaches. Who won the milkshake? It was a toss-up. Both models fit the data equally well... In the end nobody bought milkshakes - but they had a nice dinner together. Consistent with the finding that their models worked equally well, they split the check." |
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| 652 cities! |
There are so many researchers mentioned in this chapter. I tried compiling their work too but the exercise lost purpose at one point.
4. Do long-term exposures increase the risk of disease and death?
Here comes the Harvard Six-Cities Study. It aimed to study the respiratory health effects of PM pollution and SOx on adults and children in six U.S. cities.
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| The results showed that the effect of air pollution on mortality risk was much higher than expected. |
5. Were the cohort studies reproducible - or just "secret science"?
The data of so many people involved in a study was obviously secret and should be kept confidential. But protests were launched against the air pollution researchers demanding data release. The authors call it an attack on the credibility of science.
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| During peak controversy, this review was published in 1997. |
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| Ten years later, the authors published a review in the same journal. |
Outlining many other cohort studies, even using publicly available data, it was found that these studies were consistently reproducible. There's no other way out except accepting the fact that air pollution kills.
6. Environmental justice and air pollution: who pays?
The polluters don't pay. Air pollution smells like money to them. The already disadvantaged communities bear the brunt.
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| An arcgis map showing communities close to legacy waste sites. |
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| Must-read NYT article a day in the life of two kids in Delhi. Arden and Doug served as resources to this study. |
7. Does reducing air pollution improve health and reduce mortality?
Air pollution increases the risk of death and disease. But does the lack of it do the opposite? After multiple extensive studies - YES.
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| Kelly & Clancy (1984) Mortality in a general hospital and urban air pollution |
Another very interesting study was based on the Huai River Policy in China. This 1950s policy subsidised coal for indoor heating above the Huai River but not below it. Bechara north guys were unintentionally tricked.
Then the authors also outline a study on the impact on lung function when children move to and from places with different pollution levels. I suppose I can explain that. I was using the nasal spray prescribed by the ENT doctor for my "dust allergy" nearly every day during my six years in Coimbatore from 2019 to mid-2025. Our apartment is right on a state highway and I commuted everyday to college which was 7 km away. After shifting to the IITB campus (which is so full of trees), I realised that I did not need to use the nasal spray everyday. But to be on the safer side, I consulted with the ENT here and he said that if I feel I don't need it, then I don't need to use it. So happy me halted taking the spray. Then came Diwali and re-introduced me to runny nose, constant sneezing and watery eyes. I also observed that I got these symptoms when I went outside the campus but didn't use the spray before or after. Initially I thought I was overthinking. Now, I don't think I am.
8. If air pollution is lethal, why isn't everyone dead?
I found this chapter a little boring because at this point, the authors were trying to convince critics. But I am not one of them.
In short, everyone isn't dead because the dose-response curve is non-linear.
9. Does epidemiological research on air pollution provide evidence of a causal relationship?
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| This Guardian article explains the working of this industry-backed researcher who wants to convince AI to convince users that air pollution is not the cause of health effects. Why can't this bro do a literature review and convince himself? |
Austin Bradford Hill and Richard Doll initiated a study in 1951, sending questionnaires to British doctors. What they found then is what is played at the beginning of every movie: Smoking causes cancer. Based on this study, the Bradford-Hill criteria for causation in epidemiologic studies was presented. They include nine points: strength, consistency, specificity, temporality, biological gradient, plausibility, coherence, experiment and analogy.
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| Austin Bradford Hill |
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| Richard Doll. Interestingly he said, "I did not expect to find smoking was a major problem… I would have bet on roads and motorcars" |
When I was reading this chapter and the Bradford-Hill criteria paper, I was intrigued by the last few paragraphs in the paper:
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I immediately decided to put this in my review. But later to my surprise, I found the exact same paragraphs at the end of the last chapter in Particles of Truth!10. How does air pollution cause health effects? New word I learned: atherosclerosis. 11. Is pollution control worth the economic cost?I mean, if someone asked that question to me, I'd have gotten really mad. It is synonymous to asking: "Is your health (or rather, life) worth spending so much money on?". But the authors painstakingly tell us the answer: YES. "The costs of public and private efforts to reduce air pollution by meeting Clean Air Act requirements were estimated to total about $65 billion in 2020... The benefit estimate was a whopping total of almost $2 trillion."  This table from a 2022 World Bank report sums it up. The authors also explain economic approaches to tackle air pollution:
The first two won't work. The third is not sufficient. The fourth can, but the fifth is a clearer version. |
12. When will the evidence end the controversy?
Doug and Arden summarise all the previous chapters in a "stylised scientific and public policy debate". They also touch upon climate change: "Speaking of slow emergencies, there are complex but inextricable links between air pollution, human health and climate change."
The stakes are high. But the work is clearly before those who want clean, healthy air for all who breathe.
Thus ends the book Particles of Truth, an unforgettable read because I am literally breathing what they spent decades studying.
