It's a plot worthy of Hollywood - a fatal radioactive poison, secret documents, suppressed information, and drugs.
But this isn't fiction. This is the story of the tobacco industry's knowledge, policy and inaction around radioactive material in cigarette smoke. And how it took a painstaking search through thousands of court-ordered documents to uncover exactly why tobacco firms are unwilling to remove this deadly radioactivity, despite knowing how for more than 30 years.
By their own admission, "creating doubt about the health charge without actually denying it" is a strategy the tobacco industry has used effectively for decades, using smoke and mirrors to deflect mounting evidence of the deadly harm caused by their products.
As politicians and the public debate the merits of putting cigarettes in plain packaging to deter new young smokers, this particular story should serve as a timely reminder of how Big Tobacco operates when faced with the possibility of falling profits.
Setting the scene: radioactivity and cancer
But before delving into the main plot of this real life drama, it's worth taking a step back to understand some of the basics about radioactivity and cancer.
For many, the word 'radioactive' is likely to conjure up emotive images of nuclear power plant catastrophes and mushroom clouds. But it's not all the stuff of disaster movies. Low-level background radiation is constantly present in the natural environment, both from cosmic rays from outer space and from radioactive material found throughout nature - in the soil we tread on, the water we drink, and the air we breathe.
Low levels of radiation are safe. Even some of the essential elements that make up our own bodies - such as potassium and carbon - have radioactive versions, which add to our background radiation dose.
But higher, concentrated doses of radiation can be dangerous. And long-term exposure to above-normal levels of radiation can be deadly. It's no coincidence that Marie Curie - who coined the phrase 'radioactivity' - died from aplastic anaemia, a disease of the bone marrow that's now known to be linked to radiation poisoning. She did much of her work in a shed with absolutely no safety measures, and she even carried radioactive material around in her pockets.
One of the earliest links between radioactivity and cancer was made in a small US town called Orange in the 1920s. Women working in a watch factory in the New Jersey town painted the dials with glow-in-the-dark radioactive paint. They frequently licked the tips of the brushes, and inadvertently took in the radioactive element in the paint - radium. Many of these women later developed cancer of the jawbone or mouth, and the use of the deadly radioactive paint was stopped.
Puffing on polonium
Step forward 40 years from the time of these 'radium girls' to the swinging sixties - a time when more than 50% of men and 40% of women in the UK smoked and tobacco advertising was still seen on TV.
In 1964, two scientists from the Harvard School of Public Health published a landmark study that revealed that a radioactive element called polonium in cigarettes could be "significant" in the development of lung cancer.
But how does this radioactive chemical get into tobacco in the first place?
There are two main routes. Some tobacco plants are grown using fertilisers that contain apatite, a group of minerals that becomes contaminated with radioactive lead phosphate, the 'parent' of polonium. The plants absorb this radioactivity from the fertiliser.
Tobacco plants also absorb tiny dust particles from the air that are loaded with small amounts of radioactive material, including polonium and other radioactive elements that eventually decay into it. These radioactive dust particles clump onto the sticky, hair-like projections (called trichomes) that thickly cover both sides of tobacco leaves.
Cigarettes deliver dangerously concentrated doses of radioactivity directly into the lungs. When smokers inhale, the radioactive particles damage lung tissue, creating 'hot spots' of damage.
Other chemicals in cigarette smoke damage the lung's cleaning systems, which would normally get rid of gunk in our airways. So the particles build up over time. These localised build-ups lead to far greater and longer exposures to radiation than people would usually get from natural sources.
Autopsies of smokers have shown that cancer often develops where these polonium-induced hot spots of damage occur.
The evidence for the cancer-causing effects of radioactive polonium in tobacco smoke is strong. But instead of addressing these findings in public, the tobacco industry turned to denial and cover-ups.
A deadly cover-up
Take another step forward to the 1990s, when over half a century's worth of internal tobacco company documents began to be posted online after a 1998 US court order.
Academics have spent years trawling through these 13 million documents to learn about the industry's scientific research and policy around tobacco. A few years ago we wrote about a report showing the tobacco industry knew about the danger of polonium in cigarette smoke for over 40 years, but suppressed publication of their research to avoid heightening the public's awareness of the issue.
This and other studies also found that the industry adamantly resisted efforts to remove polonium from tobacco leaves, and repressed publications about radioactivity in tobacco smoke. Polonium might be only one of many cancer-causing substances in tobacco, but why on earth would the tobacco industry resist the chance to remove one of the deadly poisons in their product?
Professor Hraye Karagueuzian and colleagues at the University of California wanted to find out, and their recent study seems to have the answer.
The plot thickens
Professor Karagueuzian's team looked in detail at previously unanalysed documents to find out why an industry that makes more than Coca Cola, McDonald's and Microsoft combined - around £3,500 for every person killed by smoking - is reticent to make its product less deadly.
They were surprised by what they found.
First, the industry was aware of the presence of higher than background levels of radioactivity in tobacco five years before the wider scientific community had published any research on the topic. In 1959, a Canadian health official - by a quirk of fate called Mr Ash - wrote to tobacco company Philip Morris to ask whether tobacco should be regulated as a "radioactive substance", and suggested a way to remove up to a third of the radioactive dose from cigarettes.
But this letter was "summarily dismissed" by the tobacco company, according to Professor Karagueuzian.
Second, in the 1960s the industry went on to build an in-depth knowledge about the effects of polonium on smokers. They not only knew of potential cancerous growth in the lungs of regular smokers, but even accurately calculated how much radiation a long-term smoker would take in.
And despite knowing how to remove the deadly radioactivity for several decades, the industry was "unshakable and adamant with respect to its policy of silence, denial, obfuscation, and rebuttal to any and all from of news about tobacco radioactivity".
The reason? Professor Karagueuzian is convinced profit underpinned this silence and denial.
The final twist: nicotine free-basing
Over 30 years ago, scientists discovered that a process called acid washing removes almost all of the polonium from tobacco. But the tobacco industry refused to use it to remove the radioactive material from their products.
Officially, they said the process would cost too much and might have a negative impact on tobacco farmers and on the environment. Karagueuzian says accepting this logic is "tantamount to accepting that inhalation of radionuclides by smokers is the safest way to dispose of excess tobacco radiation".
The newly studied documents reveal a potentially more plausible reason why the industry avoided acid washing - the process alters the nicotine in tobacco leaves and makes it less able to deliver the instant nicotine rush smokers craved.
The chemical ammonia is added during the processing of tobacco leaves, which ensures most of the nicotine in cigarettes is in a 'free base' form that is more quickly and easily delivered to the brain. Crucially, the acid wash process counteracts this 'free-basing' effect. It adds a positive charge to nicotine molecules, which are then delivered more slowly to the brain, depriving smokers of the full effect of the drug.
The term free-basing has more commonly been associated with cocaine addiction, where users seeking a more intense effect from the drug convert it from its normal form to its more intense free-base form.
Free-basing is about giving addicts a drug 'kick' as quickly and efficiently as possible. It's not hard to imagine why an industry that relies on addicts being hooked on their deadly products would resist a process that reduces the effect of their key drug.
Smoking kills - so we need to stop people starting
Let's be crystal clear: polonium isn't the only killer in tobacco. There are more than 70 cancer-causing chemicals - including arsenic and formaldehyde - and hundreds of other poisons in a single cigarette.
Tobacco will kill one billion people in the 21st century if trends continue, one sixth of the current world population. That's one person dying every six seconds.
And those incomprehensible numbers don't speak of the countless family members and friends who have to cope watching their loved one die, and then carry on with life after they have gone.
Despite some legislative successes in the UK aimed at reducing the number of smokers, tobacco is clearly still a colossal health problem.
The best protection from tobacco is not to smoke it in the first place. And if we're to beat cancer, then stopping as many new smokers entering the market as possible is clearly a route we must follow, and campaigning for plain packaging of cigarettes could help. Although it won't stop current smokers, it will help give millions of kids one less reason to start. Quite simply, it will help to save lives.
But it will also damage tobacco industry profits. The story of polonium highlights the twists and turns made by an industry that puts profits above health, and continues to push a product that kills half of all its long-term users.
Make a stand
This story should serve as a stark reminder to those who hear the tobacco industry's counter arguments about the effects of plain packaging of their product.
Perhaps the following quote will help to explain not just why removing radioactivity has been refused by the tobacco industry, but also more broadly why they resist efforts to make their product less appealing:
"Tobacco products, uniquely, contain and deliver nicotine, a potent drug with a variety of physiological effects... if we meekly accept allegations of our critics and move toward reduction or elimination of nicotine from our products, then we shall eventually liquidate our business. If we intend to remain in business and our business is the manufacturer and sale of dosage forms of nicotine, then at some point we must make a stand."
Claude E Teague Jr, Assistant Director of Research at R.J. Reynolds Tobacco Company, 1972
Our business is beating cancer. So we must make the strongest stand possible against the industry that is responsible for millions of deaths from this disease.
If you want to join us, please sign our petition.
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