May 09 2016

Still No Association of Cell Phones and Brain Cancer

cell.phone.giI have been following the scientific research looking into any possible association between cell phones and brain cancer. A new study coming out of Australia adds to this literature and argues against any association.

The question is obviously an important one, and has drawn some public attention. However, scientists argue about whether or not a causal relationship between cell phones and cancer is impossible or just really low. I fall into the really low camp, but the distinction is minor.

Plausibility

The key fact to understand about cell phones is that they produce non-ionizing radiation. By definition, ionizing radiation is powerful enough to break chemical bonds. This is a health concern because breaking such bonds could cause mutations in DNA, and some of those mutations may turn a healthy cell into a cancerous cell. This is the primary reason that radiation causes cancer.

Non-ionizing radiation, however, is too low energy to directly break chemical bonds, therefore they cannot cause mutations or cancer. Physicists in particular like this physics argument and conclude that non-ionizing radiation is of no possible health risk.

Physicians, however, coming from a biological point of view sometimes argue that biology is complex and we cannot always anticipate all the possible indirect mechanisms of harm. Non-ionizing radiation, for example, may heat tissue causing some indirect harmful effect. Even this mechanism, however, is questionable as the local heating caused by cell phone use is probably insignificant compared to other daily factors.

Everyone agrees, however, (except for some outliers) that the risk from cell phone use is tiny at worst.

The Clinical Evidence

Despite the low plausibility of harm, cell phone use has become rapidly near ubiquitous and so it is reasonable to look for any possible correlation with a negative outcome. Fortunately, that evidence has been very reassuring.

The scientific evidence does not point to any cancer or other health risk from cell phone use (unless you text while driving). The International Agency for Research on Cancer, American Cancer Society, National Institute for Environmental Health Sciences, the FDA, CDC, and FCC have all concluded that there is no clear evidence of any risk, although the IARC considers non-ionizing radiation a “possible” carcinogen.

There have been some dubious or preliminary studies showing a possible correlation, but the bulk of the research shows no correlation between cell phone use and any type of cancer. It is also particularly reassuring that brain cancer incidence overall has not been increasing in the last 30 years. In fact, the incidence has been decreasing by about 0.2% per year.

If there were any causal effect between cell phone use and cancer, we should have seen a spike in the last 10-20 years at least (assuming a 10-20 year lag between exposure and cancer). Of course, you can always argue that longer term exposure is necessary. This argument, while possible, is rarely compelling – you can say that about every single negative health study, that the dose or duration of treatment/exposure was not sufficient.

A better way to look at it is this – the longer experience we have the longer we can say cell phone use is safe. Right now we can say that 20 years of frequent exposure to cell phones is of no detectable health risk. In 20 years (assuming this is the case) we will be able to say that 40 years of exposure is of no risk.

While not impossible, it does seem unlikely that after 30 years of use we would not be seeing some clearly detectable effect, at least among heavy cell phone users, if cell phones were a risk.

One other way to look at it is this; while we can never prove zero risk from anything, at some point the possible remaining risk is too low to worry about. It’s below the risk from just living your life day-to-day. Driving to work is more likely to kill you.

The Australian Study

The new study from Australia takes an ecological approach, which means they look at population data. They simply tracked the incidence of brain cancer by sex and age over the last 30 years, since the widespread introduction of cell phones. They then compared this to what we would expect to see if cell phones did indeed represent a risk factor for brain cancer.

“Using national cancer registration data, we examined age and gender specific incidence rates of 19,858 male and 14,222 females diagnosed with brain cancer in Australia between 1982 and 2012, and mobile phone usage data from 1987 to 2012.”

They found that brain cancer incidence has been stable in women over the last 30 years, but slightly increased in men. They also found that the incidence has been stable in every age group, except for those over 70 where there was a small increase. However, this increase began in 1982, before cell phone use, but after the introduction of CT scan and MRI scan which allow for better diagnosis.

They compared these numbers to the expected number of cases if cell phones increased brain cancer risk by 1.5 and by 2.5, with a 10 year lag in incidence, and they found that the actual numbers matched no increased risk, even among heavy users.

Conclusion

No one study is every definitive, but the Australian study, which spanned 30 years of data and thousands of cases, adds significantly to the data showing no correlation between cell phone use and brain cancer.

Again – we can never prove a zero risk. Scientific data can only set a statistical upper limit on possible risk. Given all the current data, any possible increased risk of cancer from cell phone use, even frequent use over more than a decade, is tiny at worst. It is far less than many other risks we accept without question, like driving.

In fact, texting or speaking on a phone while driving is a proven risk. That is what you should avoid.

Not only is the risk of cell phones tiny to zero, but we have to consider the risk of not using a cell phone, which is another way of saying the benefits of using a cell phone. I don’t know of any data, but it seems plausible that cell phones come in handy during possible emergency situations.

Therefore, avoiding cell phone use because of a possible risk of cancer is probably more likely to cause you harm than good. That is often an unintended consequence of worrying about risks that are tiny. I think we can comfortably put cell phones in that category.

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