Evidence of meeting #68 for Health in the 41st Parliament, 2nd Session. (The original version is on Parliament’s site, as are the minutes.) The winning word was home.
A recording is available from Parliament.
4:35 p.m.
Conservative
4:35 p.m.
Voices
Oh, oh!
4:35 p.m.
Conservative
The Chair Conservative Ben Lobb
Unless you have an announcement to make, that's it.
That concludes our first round. We'll suspend for a minute and bring up our next panel.
Thank you for your time.
4:35 p.m.
Conservative
The Chair Conservative Ben Lobb
Let's begin. We are on a very tight timeline here.
First up is Tom Kosatsky, scientific director from the National Collaborating Centre for Environmental Health.
Go ahead, sir.
4:35 p.m.
Dr. Tom Kosatsky Scientific Director, National Collaborating Centre for Environmental Health
Thank you.
I am Tom Kosatsky, as introduced. Thank you so much for having me and my colleagues Sarah Henderson and Anne-Marie Nicol.
The National Collaborating Centre for Environmental Health is one of six such centres funded by the Public Health Agency to increase the game, to up the game of public health practice across the country. We do it by letting people know about what's new, about what's effective, and by working with public health practitioners across Canada to do that. We're housed at the British Columbia Centre for Disease Control, where I'm also the medical director for environmental health. Radon is one of my interests.
I'll speak to lung cancer—not to smoking, although, as you've heard, it will come into the conversation—and radon in terms of public health policy for Canada. If you can follow the slides, you'll see that the first one looks at the importance of lung cancer across the country. It's the second leading cause of cancer in men, third in women, but the leading cause of death from cancer in both men and women. I'm not sure everybody knows that. It's far more important as a cause of death than breast cancer, as an example, in women, and far more important than rectal cancer, colon cancer, or prostate cancer in men.
The next slide looks at some of the historic evidence linking smoking, which everyone now knows is linked with lung cancer. Even when I was born, around when those studies were done, this was something that was denied. You remember those ads: your doctor smokes Marlboro.
It was found through studies of doctors that they demonstrated that smokers had 25 times the lifetime risk of lung cancer—
4:35 p.m.
Conservative
Lawrence Toet Conservative Elmwood—Transcona, MB
Dr. Kosatsky seems to be referring to a slide deck that I don't seem to have.
I think many of my colleagues are scrambling to find it too.
4:35 p.m.
Conservative
The Chair Conservative Ben Lobb
It was the motivation of our committee to be paperless. I think that perhaps is why many members do have it, but just not on paper.
4:35 p.m.
Scientific Director, National Collaborating Centre for Environmental Health
I think members have it now, from what I can see.
4:35 p.m.
Conservative
4:35 p.m.
Scientific Director, National Collaborating Centre for Environmental Health
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.
4:50 p.m.
Conservative
The Chair Conservative Ben Lobb
Mr. Kosatsky, we're a bit over time. I'm just wondering if you could wrap it up.
Thank you.
4:50 p.m.
Scientific Director, National Collaborating Centre for Environmental Health
I can finish in one minute.
Even if everybody tested, and everybody whose house was over 200 did remediation, we'd only touch lung cancer in Canada in a minor way. So what should we do? We should and we can build radon out. The new building code, the guidance levels, and provincial adoption help but only in a minor way. It would really help if we installed fans along with this dead-end piece of plastic that's part of the new building code, vent the radon out, and have very low levels in people's houses. People wouldn't tamper with it. You'd live in a low radon house. You wouldn't have to label it. You would know it when you moved in.
It will take years before every new house in Canada has a low radon level, but at least our children and grandchildren won't have this scourge. It's much more cost-effective to do that than it is to mitigate. The cost is much lower per house, and it will have long-lasting effects on the house itself.
What should we do? We should adopt a population approach, look at the whole population and not just the people who have a lot of radon in their houses. We should question the current guideline and lower it to as low as reasonably possible. We should legislate radon-resilient building stock, so we could build radon out of new buildings. People who live in existing houses will say, “How come my neighbour has this house? I want that too.” That would be the best encouragement for people themselves to test and remediate.
We should use provincial authorities for day care centres, schools, and workplaces to emulate what goes on there in our own houses, and we should integrate the anti-smoking and radon-lowering messages, because if we have no smoking and no radon, we will have almost no lung cancer, the number one cause of cancer deaths in this country.
That's the message. Thank you for hearing me.
4:55 p.m.
Conservative
The Chair Conservative Ben Lobb
Okay. Thanks very much.
Next up from the BC Centre for Disease Control is Sarah Henderson.
4:55 p.m.
Dr. Sarah Henderson Senior Scientist, Environmental Health Services, BC Centre for Disease Control
Good afternoon.
There is a slide deck for me as well. The first page of that slide deck should say, “Radon risk areas and lung cancer mortality trends in British Columbia”. I hope that you all have it. I will try to speak to the slides as I go along for those who don't have them.
I want to start by saying thank you so much for inviting me to be here. It's a real honour.
My title at the BC Centre for Disease Control is senior scientist, and I'm really a research scientist. The mandate of my role is to conduct applied public health research in support of good environmental health policy for the province, and that's how I first became interested in radon in British Columbia.
I'm going to show you some real, hard numbers today that come directly from the population data for British Columbia, and that's a bit different from what everybody else has been talking about so far.
If you move to the first slide, it's just a recap of the current guideline values for radon in Canada. We've heard about the number 200 all day, and any concentration lower than that is below the Health Canada guideline. Then if you measure your home and the concentration is between 200 and 600 becquerels per metre cubed, Health Canada currently recommends that you try to remediate that within the next couple of years, whereas if your measurement if over 600 becquerels per metre cubed, they really recommend that you remediate right away. That is the high-danger area for radon.
We've used these values in British Columbia to sort of break up the province into areas that we consider to be low, moderate, and high radon areas. If you are not seeing this in colour, the darkest areas there are coloured in red, and those are the high radon areas.
We're very lucky right now in British Columbia. We have a database of over 4,000 residential radon measurements, including measurements from Health Canada national surveys as well as from a bunch of surveys that have happened in the province, so we were really able to use the data that we have observed in the province to break things up this way. These geographic regions are called local health areas. They're the smallest health geographic unit that we use in British Columbia. We are able to look at deaths that have occurred in this province at this geographic scale, which is why we've used this geographic scale.
We did something quite simple, but I hope you'll agree, also quite effective. We looked at the province by those regions, and over the course of 25 years we summed up all of the deaths attributed to lung cancer in the low, moderate and high regions, and all deaths attributed to all natural causes, and then we divided the number of lung cancer deaths by the number of deaths from all natural causes, and in general, we expect about 7% of all deaths in B.C. to be attributed to lung cancer, which is probably true for most of Canada.
Slide number 4 shows the hypothetical situation. If there were no lung carcinogens in the world other than radon, we would expect lung cancer to be high and steady in the higher radon areas, somewhat lower and steady over time in the moderate radon areas, and then lower still and steady over time in the low radon areas. That's the framework I want you to think about when we go to this next slide.
When we looked at all deaths in British Columbia, we saw something quite different from what one would expect to see under that hypothetical scenario. The bottom line there shows the low radon areas. You might not be able to see that if you're not looking at it in colour. The middle line, which is just a little bit higher than the bottom line, shows the moderate radon areas. Then that line that is sloping upward over time and is quite distinct from the low and moderate lines is the lung cancer mortality proportion that we see in high radon areas over the past 25 years in British Columbia.
We don't have a lot of data about these people. We're doing this with only administrative data. We don't know whether or not they smoked. We don't know whether or not they lived their entire lives in those high radon areas. There are a whole lot of limitations here that we simply can't speak to.
When we split up these data by the higher and lower smoking regions of the province—we know that smoking rates can be up to 30% in some areas and down to 12% in some areas of B.C.—we still see these same persistent trends. It does seem to be that radon is an important factor here.
Another important distinction, and I think it's probably why I was asked to be here today, is what we see when we look at the trends for men versus women.
To look at men, the low line shown on the slide is the low radon areas, the middle line is the moderate radon areas, and the top line is the high radon areas. There's not as big a difference among those three lines as there was when we were looking at everybody together. In general, the lung cancer rates are going down. That's what we expect as the population stops smoking. When we go ahead and look at women, as shown on the next slide, we see the low and moderate lines towards the bottom there, and then the line for women is just taking off and is quite divergent from the other regions.
We're seeing a pretty big difference with respect to the two sexes here when we split up these data. Speaking anecdotally, it's not very scientific, but those of us who are interested in radon in British Columbia hear so many stories from people who say, “My wife died of lung cancer and she never smoked a day in her life.” This matches up with what we hear anecdotally, although that's not very scientific.
Somebody asked about the burden of radon-related lung cancer in high- and low-risk areas according to the current Health Canada guidelines. On this next slide, what we see is from data published by Jing Chen from Health Canada. There's an estimate of 6% of the housing stock currently being over the 200 becquerels value, and that's related to 28% of lung cancers in Canada, versus 94% of the housing stock being under the guideline value and 72% of all radon-related lung cancers being attributable to homes in that range. The bulk of the burden really remains below what we're currently talking about in terms of the Health Canada guideline.
This very point is something that we've addressed in a new paper. I want to make it clear that this work has not been published yet. It's currently under review, but it's not in the scientific literature and it has not been peer-reviewed. We looked at a bunch of different threshold values. It's really just a line in the sand that we're drawing when we say that 200 is the level or 100 is the level. We took that line in the sand and drew it at 600, 500, 400, 200, 100, and 50 becquerels to see whether or not we could still see a clear distinction between high and low radon areas in B.C. with respect to lung cancer mortality trends when we drew that line in the sand in different places.
Indeed, if you look at the far right-hand side, that top plot shows you lung cancer mortality trends in men and in women at a threshold value of 50 becquerels per metre cubed, and you can see that the trends are still distinct from one another. We still see that sharp increase in lung cancer mortality in women in the high radon areas.
In the final slide, the key message again is that these are very limited administrative data. This is something we've done as a surveillance exercise. It was really an exercise we undertook because a lot of the evidence we use in Canada to build our policy comes from places other than Canada. We're pulling together studies that have happened in Europe, the U.S., and elsewhere. We really wanted to show some hard-hitting data from the Canadian context.
Again, most radon-related lung cancers in Canada happen below the current guideline of 200 becquerels per metre cubed. We see clear temporal trends by radon risk areas of British Columbia. We have not repeated similar analyses elsewhere in Canada, but I wouldn't be surprised to see similar results. The trends that we see at 200 becquerels per metre cubed persist when we drop that threshold to 50 becquerels per metre cubed. This is really supportive of that idea of ALARA, or “as low as reasonably achievable”. As Tom said, the way to pursue ALARA in Canada is really through widespread changes to our national building code to protect the population into the future.
We have estimated that it would take about 75 years to turn over the entire residential building stock in Canada, or most of it, but at the end of that 75 years, you would have a radon-resistant building stock and a population that was well protected.
Finally, there does appear to be a difference between men and women in terms of risk.
Thank you very much for your time.
5:05 p.m.
Conservative
June 18th, 2015 / 5:05 p.m.
Professor Anne-Marie Nicol Assistant Professor, Faculty of Health Sciences, Simon Fraser University, As an Individual
You should also have a slide deck from me. It says “Radon and Lung Cancer” on it. I recognize I am the very last person, and I appreciate your persistence. Luckily many people have also spoken to a number of the points that I wish to discuss, so I will go very quickly over the first few slides.
I am an assistant professor at Simon Fraser University in British Columbia. I also work at the National Collaborating Centre with Tom and Sarah, and I also run CAREX Canada, which is the carcinogen surveillance system funded by the Canadian Partnership Against Cancer. I am here because we prioritized Canadians' exposure to environmental carcinogens and the leading causes of cancer-related deaths from environmental exposures, and radon gas was by far the most significant carcinogen. I admit that when I started my research at CAREX, I had never heard of radon gas either. When I went back into the literature, I realized that over time Canada has actually played a very important role in understanding radon and lung cancer.
The data from many of the studies that were done on uranium miners, at Eldorado and even here in Ontario, has been used to determine the relationship between exposure and lung cancer. We've actually been on the forefront of this issue but very much in an academic context rather than in a public health context.
We've already discussed the fact that the WHO notes that this is a significant carcinogen. I would also like to point out that agencies around the world are coming to the conclusion that radon is more dangerous than they had previously thought. In 1993 we had a certain understanding about the relationship between radon gas and lung cancer. That's doubled. The slope that Tom was talking about used to go like this and now it goes like this. Radon is now known to be much more dangerous than we had originally thought. The reason for that is that radon is actually an alpha-particle emitter.
We are a uranium-rich country. Uranium is in the soil and as it breaks down there is a point at which it becomes a gas. That means it becomes movable within the soil. That gas itself gives off alpha radiation, which is a very dangerous form of radiation that can damage DNA. On the next slide you'll see both direct and indirect damage to DNA. This information is compliments of Dr. Aaron Goodarzi. We actually have a Canada research chair studying this at the moment in Alberta.
The next slide, on radiation and DNA damage, shows that alpha radiation is powerful. It doesn't penetrate very far, so if it hits our skin, it doesn't do as much damage as it does if it gets into our lungs. Our lungs are very sensitive. The lining of our lungs is sensitive and when the cells in them are irradiated, they get damaged. Alpha particles are very destructive. The damage is akin to having a cannon go through DNA. That kind of damage is hard to repair, and as a result the probability of genetic mutations and cancer goes up.
The next slide is on strategies for reducing risk. Just to recap, the kind of damage done by the radiation emitted from radon is significant. The damage is difficult for the body to repair once radon is in the lungs.
The next slide is on education and priority setting. Radon does exist across the country. People have developed radon-potential maps. This one is compliments of Radon Environmental where they've looked at where uranium exists and where the potential for higher-breakdown products is, although we do recognize that every home is different. Also there's a map of the United States to show that we are not alone in this and that the states that are on the border have a similar kind of radon profile to that found in Canada. We know that under our current Canadian strategies, we need to educate not just the public but ourselves. Most public health professionals have never heard of radon. When we do work out in public health units, environmental health inspectors, public health inspectors, and medical health officers are still unaware that radon is dangerous. Many bureaucrats and ministries of health are unaware that radon is dangerous.
Also health researchers are only really beginning to do work in this area across the country. In order to have building codes changed, people need to know why you're changing them. We need testing and remediation training. People need to understand why they're actually doing this kind of work.
Kelley Bush alluded to the fact that they've been tracking awareness among the population. This is done by Statistics Canada. The next slide shows a representative Canadian sample. It's been done since 2007 actually, but these are results for 2009 onward. You can see that about 10% of the population were aware of radon. That's gone up to about 30%. This is the number of people who know what radon is and can accurately describe it. We're still at around 30% of the population who know that radon can cause lung cancer.
Health Canada does recommend that everybody test their homes. The next slide, which is also using data collected by Statistics Canada, clearly shows that very few people have tested their homes. Less than 10% of Canadians across the country have tested their homes. We have had a radon awareness program since 2007, so why aren't people testing? We don't have regulatory requirements, as Kathleen Cooper stated earlier. People need to be aware and motivated to change. It's up to the consumer. We have left it up to the consumer to test their own home.
I believe things like denial, the invisible nature of the gas, and people simply being unaware contribute to this. Test kits are still not that readily available across the country. You can phone and ask where you can find them, but they're not always there. In rural regions it's much harder for people to get access to test kits. People then fear the downstream costs of remediating—i.e., I don't want to go in there because I don't know how much it's going to cost me to fix my basement. In some cases the costs can be somewhat considerable, depending on the structure of the home.
Turning to the next slide, I believe to reduce the lung cancer risk from radon gas we need more leadership. The government can legitimate this as a risk. It's something that people don't know about, and we need to take a stronger role in getting people more engaged in this topic. It's not just Health Canada; it's all levels of government—ministries of health, provinces, municipalities. We need to be training people in the trades so they know what they're doing when they're building those radon-resistant homes, and why. Why is that pipe important? Why is that fan important? Again, we need to build radon out, going forward.
Other countries have shown that providing financial assistance works. People will energy-retrofit their home because they get a rebate, but the energy retrofit does increase radon levels. There is clear evidence that this exists. The tighter your home, the more the radon gas remains in your home. In Manitoba they're doing research to look at that at the moment. In Manitoba, though, you can also now get a rebate through Manitoba Hydro to do radon remediation. Some parts of the country are starting, but we need to be offering some kind of incentive for citizens to do this.
I would also like to put in a plug for workplace exposure, because I do study workplace exposure and radon. There are places in the country where people work underground, or in basements and even ground-level buildings, where radon levels are high. Some of these are federal government workers. We need more testing and remediation for workplaces.
That's it. Thank you.
5:10 p.m.
NDP
Mike Sullivan NDP York South—Weston, ON
Thank you, sir. Thank you to the witnesses.
This is amazing information. If I take this home and talk to the folks in my riding, they'll get more scared than they already are. We've been fighting for the past 10 years to reduce the level of exposure to diesel exhaust, which the WHO has reclassified as a class A or class 1 carcinogen.
How does this compare with 464 diesel trains a day going past your house in terms of danger to the individual? Is this something we can wait on, or is it something we should be acting on immediately in a riding such as mine?
5:10 p.m.
Scientific Director, National Collaborating Centre for Environmental Health
Diesel exhaust has a number of important health effects, primarily cardiovascular and respiratory. It increases the burden of emphysema. It makes you more likely to have heart disease. It makes you more likely to have a heart attack if you do have heart disease. It also can cause lung cancer. Radon only causes lung cancer. Effectively, it doesn't do anything else.
In terms of the impact, I don't know what the concentrations of diesel are by people's houses, but you don't live next to a locomotive or with a locomotive. I grew up in a basement in Winnipeg that had high levels of radon. And I don't blame my mother for that.
5:10 p.m.
Voices
Oh, oh!
5:10 p.m.
Scientific Director, National Collaborating Centre for Environmental Health
In any case, the intimacy of exposure to radon is more important than the intimacy or the regularity of exposure to diesel fumes. Between the two, in terms of the contribution to the population burden of lung cancer itself, radon would be far more important. Diesel fumes should be gotten rid of as much as possible as well.
5:15 p.m.
NDP
Mike Sullivan NDP York South—Weston, ON
I agree.
The charts and graphs you showed us had two striking pieces to them. One, this seems to affect women more than men. I'll jump to the conclusion that maybe it's because their lungs are smaller; I don't know. Second, this seems to be on the increase since 1985, yet people lived in homes with radon many more years prior to that.
What is driving those two things? Are there any guesses from the panel?
5:15 p.m.
Senior Scientist, Environmental Health Services, BC Centre for Disease Control
Everything would be speculation at this point. There does seem to be a bigger effect on women. We do know that if you took a population of non-smoking women and a population of non-smoking men, there would be more lung cancer in the non-smoking women. It might be that being female is, in and of itself, a risk factor for developing lung cancer, and that might be a genetic thing. There are lots of different ways that could go.
Also you have to think about this in the context of what the temporal trends were in smoking over the period of the analyses. Men took up smoking earlier and stopped smoking earlier on sort of a population scale. Women took it up later and stopped smoking later, so we're definitely seeing some of that interaction between smoking and radon in that upward trend. We do hope that over time it will plateau and start to come down again, and we'll keep paying attention in B.C. to evaluate whether or not that happens.
There's also the question of other environmental lung carcinogens. What is the interaction between radon and diesel exhaust? We don't know. What is the interaction between radon and something like asbestos or another lung carcinogen? We just don't know. There are all of these things happening in the environment and your lungs are the first things that the environment comes in contact with, so it's quite possibly interaction between radon and other stuff as well.
