Wednesday, April 23, 2008

Radon & lung cancer

This is the first of several posts that I will make on lung cancer. They are related to my work on cigarette smoking.

I am interested in the fact that the incidence of lung cancer was very low prior to cigarette smoking but that, these days, around 10-15% of lung cancers seem to be unrelated to cigarette smoking. What is the source of these new lung cancers*? In part the finding could be related to early non-recognition of lung cancers but other factors seem to bear on the higher incidence of non-smoking related cancers that has emerged recently.

In the US the second largest cause of lung cancer is exposure to the element radon – most usually as it seeps through the floor of the family home. Radon kills 15,000-22,000 people in the US annually and is responsible for 12% of all lung cancer deaths. Services are available for testing and reducing radon levels in the family home . There is concern if radon levels exceed 4 pico Curies per litre (4pCi/L).

Puzzling recent findings suggest that radon at low concentrations in the home is hermetic for lung cancer – at low enough dosage levels radiation might help repair damaged DNA. These claims don’t challenge the 4pCi/L standard but the fact is that most households are below that level in any event.

By the way, radon concentrations in Australian homes are low – for most households they are marginally above concentrations in the atmosphere. There is however evidence of heightened health risks from radon in the Australian uranium mining industry.

*Of course passive smoking, asbestos and air pollution also cause lung cancers but their effects seem less important than radon exposure. Smoking and radon exposure are however probably synergistic in promoting lung cancers.

12 comments:

derrida derider said...

I'd have thought that average radon exposure in US homes would be higher than in in Australian homes simply because most US homes have basements. Plus most of our populated areas have got sedimentary rocks rather than granite.

Simon said...

Passive smoking causes lung cancer ?
Have you got a link for a credible study ?

hc said...

Simon, Try here.

conrad said...

Looking at the current smog in Melbourne, I'm surprised radon is beating general air pollution. Given the lag between exposure and cancer, it would be interesting to know what the future rates of lung cancer are likely to be, rather than the current ones, where presumably what is being measured are people that inhaled cleaner air.

Simon said...

Harry

Thanks for the link -

I'm not quite convinced - don't these 2 paragraphs contradict each other ?

"The results of this study, which have been completely misrepresented in recent news reports, are very much in line with the results of similar studies both in Europe and elsewhere: passive smoking causes lung cancer in non-smokers.

The study found that there was an estimated 16% increased risk of lung cancer among non-smoking spouses of smokers. For workplace exposure the estimated increase in risk was 17%. However, due to small sample size, neither increased risk was statistically significant. Although, the study points towards a decreasing risk after cessation of exposure."

Aren't they saying - "we did a study which showed a big increase in risk. Of course because we had such a small sample size it wasn't statistically significant.But that doesn't matter - we know what we know"

Isn't it simply the case that the survey showed nothing because the increase in risk wasn't statistically significant.

hc said...

Simon, I think there is no doubt that passive smoking causes increased mortality overall although there arec questions about whether it specifically increases lung cancer.

These latter doubts seem to me unjustified. This famous study of the wives of Japanese male smokers showed that their risk of lung cancer more than doubled when their spouse was a heavy smoker.

What you could argue is that the doubling of risk is from a low base. Buit the risk does apparently increase.

Spiros said...

Another reason non smokers may be getting lung cancer is that people are living longer generally, thanks to anti biotics and other health improvements. But nobody lives forever, so eventually you are going to contract something that kills you. And that might be lung cancer.

So in the old days a lot of people didn't live long enough to get lung cancer. Now they do.

hc said...

Spiros, That's a simple suggestion that may well be spot on. If you look here Tables 3 and 4 you see that most lung cancer deaths occur post age 65. As life expectancies in the US and Australia have grown about 20 years in the last 80 years people have only recently started to move into these categories in large numbers.

This might explain part of the growth in the lung cancer total and the fact that more cancers are occurring that are unrelated to smoking.

Andrew said...

Are you sure Radon is the 2nd largest cause of cancer in the US? The numbers you give would be just under 1% of US mortality. Not trivial but not huge either.

hc said...

Andrew, As was clear from the following sentence, the second largest cause of 'lung cancer'. Word 'lung' inserted again.

Francis Xavier Holden said...

Many cancers are to some extent a disease of ageing. If you cark it at 45 , like Aboriginals, cancer rates aren't l that high.

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