In February 2015, journalist Kate Dawson was browsing the Getty Images website when she stumbled upon an enigmatic black and white photo of a woman with four strings of pearls around her neck and a chiffon scarf around her nose and mouth. The woman was surrounded by an ominous gray haze. “I was just struck by the photo,” Dawson tells The Verge.

That image was taken in December 1952, when London was trapped in a deadly cloud of fog and pollution for five days. At the time, the city ran on cheap coal for everything from generating power to heating homes. So when an anticyclone caused cold air to stagnate over London, the sulfur dioxide, carbon dioxide, and smoke particles mounted — and ended up choking as many as 12,000 people to death.

When Dawson realized no books about the Great Smog of 1952 had been written, she decided to pick up the project. But as she researched newspaper clips from the time, she saw that another killer dominated the headlines: a man who had murdered at least six women, stashing their corpses under the floorboards and into the cupboards of his apartment in Notting Hill. “It was just this deluge, it was incredible,” Dawson says. “I couldn’t get around it and I couldn’t find anything about the smog.”

Eventually, Dawson decided to weave the two stories together, in a new book called Death in the Air. The parallels are “bizarre,” Dawson says, if not eerie: both the Great Smog and the serial killer, called John Reginald Christie, asphyxiated innocent people to death, and both spurred the passage of historic legislation. The deadly smog prompted the British government — after much denying any connection between the deaths and pollution — to pass the world’s first Clean Air Act. Christie’s horror story, on the other hand, led to the abolition of the death penalty years later. A neighbor of Christie, named Tim Evans, was accused of killing his own wife and child and executed before Christie confessed to the murders — a wrongful conviction that riled the public.

“It was just this deluge, it was incredible.”

For Dawson, the way the media — and the public — reacted to both stories at the time is very telling of how the world still works to this day. Outlandish tweets and headline-grabbing news often get the most attention, sometimes overshadowing more important stories, she says. “All of this to me just resonated in our time period, and so I thought the juxtaposition was really important,” Dawson says.

With air pollution still making headlines today, The Verge spoke with Dawson about wrongful convictions, why Londoners didn’t freak out about the deadly fog, and whether the Great Smog could still happen today.

The interview has been edited for brevity and clarity.

In the book, you mention a very well-known incident: the smog that killed 20 people and sickened thousands more in Donora, Pennsylvania in 1948. I don’t remember ever reading about London’s Great Smog of 1952 in history books, though. Why is that?

It is interesting the reaction between the two, and I think it’s very telling about both societies. In 1948, the reaction of the small town was [similar to the one you’d expect for] a natural disaster: they set up a triage center in the community center. It was a concerted effort from everyone in the town to try to get through this. And they recognized it as a deadly disaster. It’s not what happened in the Great Smog of 1952. Really, it was yet another smog, it just lasted a lot longer. And the panic didn’t even come until months later when the death tolls came out and they realized that thousands of people died. And even then there wasn’t panic. So in Donora, there’s a museum dedicated to the event, and there’s nothing like that in London. So you’re talking about two drastically different reactions. So right, in the history books one is represented and one isn’t.

Why didn’t Londoners react with panic?

There are a couple reasons. Number one, we’re talking about 300 years of smog like this. Because of the weather system, this turned into an extraordinarily long and extraordinarily deadly smog but these weather systems, these anticyclones, had come every year; they were always there. They lasted two or three days, usually two, and then they’d be blown away by a wind and all the pollution would float to the atmosphere. That’s just not what happened [in 1952]. It stayed around for five days.

There were people who died in their bed, died in the hospital rooms, and because there were no central computerized systems for the hospitals, there was no data that connected all of the deaths. It was anecdotal evidence. But even the doctors in the hospital said, “You know, we just thought we had a really rough few days.” It didn’t occur to people that this happened across the city. The media didn’t connect it.

The Great Smog eventually spurred the passage of the Clean Air Act of 1956 in the UK. What influence did it have on clean-air legislation in the US and around the world?

UK’s Clean Air Act was really the first sort of overarching federal legislation in the world where you had a government, not just local government or state government, that placed some pretty restrictive rules on industry and on local citizens, and provided subsidies so that Londoners could begin to convert from coal-burning fireplaces to smokeless fuel, which is very expensive. It really was a blueprint for other nations to follow.

It was the pioneer effort that was really only brought about because of Norman Dodds and many people from the Labour Party, who pushed the issue so far and forced the British government to finally act. This was a systemic problem that no one really took seriously in the government because it was just something that was always there and the government was bankrupt.

The book is filled with vividly painted characters that lived through the Great Smog. How did you find those people?

I had to think to myself: Who actually would have been in the smog? Who was a lifesaver, who were the helpers? So of course I thought of doctors, nurses, ambulance drivers, and police officers. So I found the national retirement associations for each of these groups, and I emailed the head of each of these associations and said, “Listen, I know you all have an email database, can you blast an email on my behalf to all of your members and say, I’m a journalist who’s writing a book about the Great Smog of 1952, she’s looking for people who worked in the Great Smog. Would you respond if you’re interested in being interviewed?” So I got a huge amount of responses. They were very interested in telling the story.

Even then, when I spoke to all of these people who survived the smog, even Rosemary Sergeant, who had lost her father and it was this incredibly heartbreaking story, they all had the same mantra: this was just part of life in London. It was the most overpopulated and industrialized city in the world. And it became something of, well, this is just a byproduct of living in the city. That’s why it was important for me to include Rosemary, as a 13-year-old girl, because she had no decision in this. She didn’t buy coal. Eighty percent of the public smoked, she didn’t smoke. She didn’t choose to live in London. She was truly an innocent victim, with no culpability at all.

What surprised you the most about this time period?

One, I thought London recovered from World War II much more quickly than, in fact, it did. I was surprised that in 1952, seven years after the war, London was still in dire straits. The government was still in dire straits. And then, of course, all the repercussions that come from that: the poverty, the crime, the small police budgets.

What surprised me about John Christie’s case, besides the incredible media attention that it received, [is that] there was a lot of controversy. Christie had a neighbor who was eventually hanged partly because of Christie’s testimony. The man had been convicted of killing his wife and child, and later it was found that Christie had confessed and that Christie was really guilty and the man was posthumously exonerated. And so I went into this case really feeling like I was going to find the same evidence and come to the same conclusion, and really didn’t come to the same conclusion. And that was surprising to me.

I fell into the trap that a lot of people do, which is just assuming that history and conventional wisdom is right. After looking at all the evidence, I don’t think Christie’s confession was right and I think the right man was hanged for killing the wife and the child. I think people really just did not want to believe that two people could be living in the same house at the same time, and both be killers and not know each other or work together. And I believe it’s absolutely feasible.

What evidence did you find that convinced you of this?

Speaking to the police officer, Len Trevallion, who helped investigate the case, we talked about how the crime wasn’t feasible the way John Christie laid it out. I looked at the pathologist’s report, which to me was the most interesting. The wife, who was Beryl Evans, there were many photographs of her before they buried her. And the pathologist, buried deep in his report, said that she had been hit in the mouth so hard that her lip was touching her nose. That’s very hard. And the way the blood clotted, he estimated that she had been hit 20 minutes before she died.

“The truth lies with both of them who are dead.”

I gave that photo to present-day pathologists, two of them, and they agreed: yeah, it looks like she was hit 20 minutes before. Now, in what world is a woman going to let a neighbor hit her, sit around for 20 minutes, and then strangle her? It doesn’t make any sense. No one heard her scream. But her husband was abusive and hit her all the time. So to me, what makes sense is that the husband hit her and they fought and then he killed her later. When John Christie confessed to killing his neighbor’s wife and child, I think it was just taken as gospel. Christie was confessing to killing everybody under the Sun because he wanted to escape the death penalty [by appearing insane]. So he had what he called the-more-the-merrier defense. And I didn’t believe any bit of his confessions. Of course, the truth lies with both of them who are dead.

This book is also a story of what happens when there are no regulations about pollution. I'm wondering what it says about our current political climate, where we have an administration that's gutting the Environmental Protection Agency.

I think that our current situation is distressing and troubling. Of course it’s unlikely something like [the Great Smog of 1952] is going to happen in our country. Pollution is horrible but not to that extent in such a closed area. But I think that what’s happening with the EPA, defunding certain programs, reducing the staff, and the current political climate of leaning more towards the industrialists and less towards clean air, is distressing and in some cases irreversible.

This should be a cautionary tale. And I think that very few people in power are listening. Just because you don’t have the Great Smog of 1952, with the yellow clouds and the air that smells like rotten eggs, doesn't mean that the air you breathe is not destroying your health, and every research shows it is. And I just think we take it for granted.