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Making sense of cancer mythsCan mobile phones cause cancer? What about air pollution, or deodorants? These are just a few of the very many cancer myths that constantly do the rounds, in both the press and in people’s minds.

I suspect we’ll spend a lot of time on this blog addressing common myths. And for good reason too – they can actually be quite dangerous.

They can distract people from proven links between lifestyle and cancer and hinder their chances of making healthy and informed choices. And by promoting the belief that ‘everything causes cancer’ or actively refuting sound advice, they can lead people to make decisions that are actually bad for their health.

To understand the impact of these myths, it’s important to measure how widely believed they are. Our transatlantic counterparts at the American Cancer Society have recently run a survey to do just that. They interviewed almost 1,000 adults by phone and asked them whether they agreed with 12 statements about cancer.

Now, obviously these results are from the States, so we need to be careful before generalising them to the UK. But in many cases, the survey’s findings tally with what we see in this country, so it’s instructive to look at what the prevailing myths are over there too.

Let’s go each myth in turn and look at the truth behind them.

Myth: The risk of dying from cancer in the United States is increasing

68% of people agreed with this statement, and it’s a bit of a tricky one. Technically, the statement is false, since the death rate for all cancers combined in the States has been falling over the last 30 years. However, some people may have been basing their answer on the absolute number of cancer deaths, which has steadily risen because of the US’s ageing population.

Myth: Living in a polluted city is a greater risk for lung cancer than smoking a pack of cigarettes a day.

Air pollution is a much weaker cancer risk factor than smokingThis is quite a shocking result – 39% of people agreed with this statement. This myth seems to be particularly widespread, and about half of the people who’ve taken our smoking quiz also believe it.

It is, of course, completely false. The evidence says that air pollution does cause some cases of lung cancer, but its effects pale into comparison to smoking. While tobacco causes about 90% of lung cancer (as well as a dozen other types), air pollution causes about 3% at most. And it may be that most of these cases occur in people like lorry drivers exposed to large amounts of diesel exhaust as part of their jobs.

The fact that so many people believe this highlights the fact that people tend to underestimate health risks associated with their own choices (such as smoking). At the same time, they tend to overestimate risks associated with external factors beyond their control (such as pollution).

Myth: Some injuries can cause cancer later in life.

37% of people agree with this. This particular myth probably dates back to the 1800s,. It’s probably survived because an injury directs people’s attention to an existing tumour. A few studies have linked certain types of injury such as head trauma to a slightly higher risks of some cancer, but it’s clear that if these links are real, they’re very, very small.

Myth: Electronic devices, like cell phones can cause cancer in the people who use them.

Mobile phones don't cause cancer. Given how common this myth is, it’s no surprise that 30% of people agreed with it. The evidence, on the other hand, does not. The vast majority of studies have found that mobile phones don’t increase the risk of brain cancer or any other types.

While it’s still unclear if there is a risk for long-term users, the largest study so far found that even using mobiles for 10 years doesn’t increase your risk of cancer. And there’s not really any reason why it should – the radiation that mobiles give out is very weak and doesn’t have enough energy to damage DNA or cause cancer.

Myth: What someone does as a young adult has little effect on their chance of getting cancer later in life.

A quarter of people believed this to be true, probably because cancer is (quite rightly) seen as a disease of old age. But that doesn’t mean that our actions as young adults have no bearing on our later risk. For example, smokers have higher risks of cancer the more years they spend smoking. So unless they quit, the cigarettes they smoke in early life will add to their risk later on.

And in many cases, risky behaviours in early life can lead to risky behaviours in later life – smoking is infamously addictive, and studies have shown that people who are obese as teenagers find it difficult to shift the extra weight later in life.

Myth: Long-time smokers cannot reduce their cancer risk by quitting smoking.

It’s good that only 16% of people believed this myth. It’s never too late to quit smoking and studies have found that even people in their 50s or 60s can improve their health if they quit (although the earlier you quit, the better).

Myth: People who smoke low-tar cigarettes have less chance of developing lung cancer than people who smoke regular cigarettes.

Despite the marketing tactics of the tobacco industry, most Americans do seem to be aware that low-tar cigarettes as just as bad for you as normal brands, and only 15% believed this myth.

Smokers breathe in more deeply to compensate for the lower nicotine doses so they get the same amounts of cancer-causing chemicals, if not more. In the UK, our own campaign helped to raise awareness of the truth behind this myth.

Deodorants don't cause breast cancerMyth: Personal hygiene products, like shampoo, deodorant, and antiperspirants, can cause cancer.

Once very common, this myth seems to be dying out with only 14% of people agreeing with it. Which is a good thing because it’s based on no scientific evidence. The link between deodorants and cancer started with an hoax email several years back, riddled with scientific errors. Since then, the studies which assessed this link found no risk. Brits seem to be a bit more clued up about this myth – in our own Reduce the Risk survey in 2004, only 9% of people believed that deodorants caused cancer.

Myth: Getting a mammogram, or using a special X-ray machine to detect breast cancer, can cause cancer of the breast.

It’s good to see that only 10% of people believed this. Mammography does expose women to radiation, but the doses are very low. For women within the screening age range, the small risks are completely outweighed by the benefits of detecting breast cancer.

Myth: Getting a base tan or base coat at a tanning salon will provide protection from skin cancer when you go outside in the sun.

Our SunSmart campaign has been saying for years that pre-existing tans aren’t enough to protect you from the sun. It seems that most Americans are aware of that, with only 8% agreeing with this myth. A tan provides, at best, the equivalent protection of a factor 3 sunscreen. It’s no substitute for seeking shade, covering up or factor 15 sunscreen.

Myth: Underwire bras can cause breast cancer.

This is another myth spawned by internet and email rumours. The idea was that bras cause breast cancer by restricting the lymphatic system, but there is no scientific basis for this claim whatsoever. It seems that people realise this, as only 6% agreed with this myth.

Sunbeds can cause skin cancer just as regular sun exposure can. Myth: You cannot get skin cancer from using a tanning booth.

Only 6% agreed with this claim, which is promising given that you most certainly can get skin cancer from tanning booths and sunbeds. While these are often marketed as ways of getting a ‘safe tan’, the International Agency for Research into Cancer recently said concluded that they increased the risk of melanoma by 75%, especially in young people.

In the UK, our own surveys have found that 8% of people felt that sunbeds were ‘not very important’ or ‘not at all important’ in terms of skin cancer risk.

Conclusions

At least in the US, progress is being made at dispelling unhelpful myths. It’s promising to see that very few people still believe that deodorants or underwired bras can cause cancer, or that sunbeds are risk-free.

However, this survey shows that there’s still a lot of work to be done. The myth around mobile phones and pollution need to be addressed and the latter one, in particular, could put smokers off trying to quit.

The researchers also found that people were most likely to agree with these myths if they belonged to ethnic minorities or lower socioeconomic groups, or had lower educational backgrounds. It’s these same groups who bear the greatest burden of cancer and are most likely to make lifestyle choices that will actually increase their risk.

It just goes to show how important it is to target accurate information about cancer risk factors continues at these groups.

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Comments

Kat August 23, 2007

Either way, it’s quite useful to get a story like this out in the media, to highlight the myths that exist, and the fact that they are incorrect. You’d be surprised how often the same old stories come up when we talk to supporters, or from the letters from the public we receive every week.

As a Science Info officer I spend a lot of time writing responses to people who are quite convinced that, say, shampoo is more of a cancer risk than smoking (it isn’t). While you can argue that some of the myths are actually perpetuated by certain sections of the media, on the web, it’s reassuring to see that “mythbusting” can still make the headlines.

Simon August 21, 2007

That’s a good point Ed, on the possible effect the other way. Also, I suspect that this may have been (to some extent) a survey conducted for PR purposes, rather than to learn anything new. As we know, the media love to hang a story on a good survey (or even a bad one!).

Simon August 20, 2007

Correct me if I’m wrong, but isn’t there a major flaw with the methodology of this survey? The survey only asked people to comment on false statements – in the words of the report, “each statement was framed to be contrary to the available scientific evidence”. Suppose that I (prior to the survey) believed two of the statements to be true, and ten of them to be false. Having mostly answered “not true” to the questions, I would probably be more likely to say “not true” to those I had previously believed to be true, influenced by a (possibly subconscious) awareness that the survey is likely to be only dealing with myths.

The corrolary of this, given that the majority of answers overall were “not true”, is that the questions presented later in the survey are likely to have been skewed towards “not true”. It’s impossible to know whether this is indeed the case, as the methodology of the survey does not make it clear what order the questions were asked in. This effect could easily have been eliminated, by rephrasing some of the questions to have “true” answers (e.g. “You can get skin cancer from using a tanning booth”). I would also think that it would make the results more robust if the survey questions were asked in a random order to each participant.

The scary thing is that if I’m right about this, the effect would be to shift the bulk of the results towards “not true”. In other words, it’s possible that even more people believe these myths than the survey suggests. Either way, I’d be fascinated to know what a similar survey in the UK would throw up. My instinct is that it wouldn’t be much different.

Ed August 20, 2007

That’s a good point Simon. However, there could be all sorts of hidden effects at work. People may also, for example, think “There have been a lot of myths here, some of these are bound to be true”, which would skew the later answers towards more agreements than usual. I agree that a randomised order would have been helpful in accounting for these effects, and like you say, it’s impossible to know whether this was actually done.

I think the results of the survey would be very similar in the UK – certainly, the myths we have data for (e.g. sunbeds, deodorants) match up quite well.

In particular, what I’d like to see is a study of whether believing in myths makes it more likely that people will disregard advice on proven risk factors.