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Tom Kosatsky
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Tom Kosatsky
2015-06-18 16:43
You know, anyway, that smoking causes lung cancer in smokers. You probably also know that to a degree it causes lung cancer in people who live with smokers. I won't really talk about either of those things, but if you can get to the slide that's marked “Lung Cancer in Lifelong Non-Smokers”, you'll see that there is a new thing that's been described only over the last, about, 10 years, which is lung cancer in lifelong non-smokers, something which, before this committee invited me to speak with you, I didn't know much about. It turns out that it's a whole other disease. It has some similarities to smokers' lung cancer but some very important differences.
The geography is different. It's a huge phenomenon in Asia and in Asians in Canada. It has a female predominance, so there are far more lung cancers in female non-smokers than in male non-smokers. The age distribution is different, so it tends to present itself at a much younger age than smokers' lung cancers do. The cell types, the cancer types are different. The typical small cell squamous lung cancer that you see in smokers, you don't get in non-smokers. You get a whole different cell type and cell shape. The genetics are different, so there is some family relationship. It's not very strong, but there's a very strong genetic relationship based on genetic analysis. You can almost predict who's going to get it, which is a really important thing. Further, it tends to be much more symptomatic at diagnosis than is lung cancer in smokers. The five-year survival, oddly, is better, even though it presents later, for non-smokers' lung cancer than for smokers' lung cancer. In many ways it's a different disease.
Radon-related lung cancer is somewhere intermediate, because, as I'm going to say, most radon-related lung cancers occur in smokers. The question of whether it is more cost-efficient to stop smoking was right on the mark.
The next one is called “Principal risk factors (excluding occupational exposure)”, only because you asked. There are a number of conditions, including radon exposure, that are associated with non-smokers' lung cancer, like the history in your family. It's associated with hormone use in women. It's associated with environmental tobacco smoke. It's associated, to a degree, with air pollution. It's associated with cooking-oil fumes, so indoor cooking over a long period of time. It's associated in Asia and Africa with domestic heating by wood and wood products in the home. Those are also associated with lung cancer. Something that I didn't know much about before is that it's associated with lung infections like tuberculosis and other lung infections over a long period of time. It's also, like so many of the other bad things in life, associated with being poor. Getting lung cancer is associated with being poor, even if you eliminate all the other stuff. To a degree it's mitigated or prevented by a diet high in fruits and vegetables, so eat your leafy greens, eat your fruit, and you're less likely to get lung cancer no matter what else you do.
The next one is an American slide. It has a little American flag, and it looks at the attributable percentage of lung cancer by cause. For active smoking, it's 90%. For radon exposure in the U.S., it is between 9% and 15%, and in Canada it's estimated at 15%. For workplace carcinogen exposure, it's 10%. For air pollution, it's 1% to 2%. That adds up to more than 100% because, as you'll see, some of those causes add to or multiply each other. If you're exposed to radon, don't smoke. If you smoke, don't be exposed to radon.
Non-smokers' lung cancer is a really important cause of lung cancer. It's about number six in terms of all the causes. Radon-related lung cancer—this is U.S. data but for Canada it would be the same—is number eight. How could that be? It could be because smoking and radon exposure are interactive, so one multiplies or adds to the effect of the other. That leads, in any case, to non-smokers' lung cancer being a very bad issue.
Any radon exposure is bad news, not just at over 200. An artificial limit, no matter what it is, is not very useful for lowering the whole population's exposure. It would be better if we were all exposed to less radon rather than picking one area, maybe for convenience, or one level. It may be good for convenience, but it's not a really useful population health measure. For the whole population, it would be better if we were all exposed to less radon. It's a linear relationship. The more radon you're exposed to and the longer you're exposed, the more likely you are to get lung cancer.
The other thing is that, as I was saying, the more you smoke the more it interacts. On the last slide, which I made up using Canadian data, most radon-associated lung cancers occur in smokers. If you've never smoked, as you get up to high levels, like interior B.C. levels, of radon about 36 people out of 1,000 exposed to those levels would get lung cancer. On the other hand if there was no radon exposure and you did smoke, about 100 people would get lung cancer. If you add the two together, you're exposed to a high level of radon and you smoke, 270 people exposed to those two for their whole lives, smoking and radon, will get lung cancer. It's 270 out of 1,000 people; that's tremendous.
How can you lower it? The number one way to lower it is to stop smoking or to never have smoked. The number two way to lower it is to lower your radon exposure, and you'll do that for everybody in the population. The less smoking there is, the less radon there is, the less lung cancer there will be, to the point that as we lower the level of smoking exposure, radon will become a more important cause of lung cancer. But there will be a lot less lung cancer. If we eliminate smoking, there will be less lung cancer in general, but all of these other causes other than smoking will increase in focus. The big issue is the interaction, the doubling, tripling, quadrupling, or really octupling effect, because it's an eight-time effect, of smoking and radon will go away.
What's been the Canadian public health stance on radon? Before the year 2007, it was pretty passive and largely seen as a private issue. Health Canada was helpful. They gave advice when people asked for it. That was at the time of the 800 becquerels per metre cubed, or 800 disintegrations per second per metre cubed level, which is what a becquerel is. Then when the level was lowered a more active stance was taken. Health Canada was involved with large-scale testing across the country to establish a radon profile across the country so that we knew what our levels were likely to be. They were much more active in terms of giving advice, and with this lower guideline, they promoted it and they encouraged “test and remediate”. Test and remediate to me is not the way to go. The way to go is to build it out in the first place.
If you look at this complicated Ontario slide, Ontario looked at levels of radon across the province and how many cases of lung cancer could be saved by doing something for those above 200 becquerels per metre cubed, by adopting 100 becquerels per metre cubed, by adopting 50 becquerels per metre cubed—all of which are attainable—or by going to as low a level possible and getting close to outdoor air levels, which are relatively benign. At 200 becquerels per metre cubed, if every Ontario resident got their house from that point down to outdoor levels, 2% of all the lung cancers in Ontario would be averted. If you got down from current levels above 200, if everybody tested and remediated and they successfully got their house down to background or no radon, it would avert 2% of all lung cancers. If all houses in Ontario with any level of radon in them could get down to outdoor levels, we'd get rid of 13% of all Ontario lung cancer deaths. If there were a way to do it, why not do that? Why not get it down lower?
The next slide looks at the change in levels of radon over time. This is Dutch data. Canada would be the same. Yes, as we've made our buildings tighter, radon levels have increased. This is even more reason to look at the joint effects of building changes on radon.
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