Proving a negative in science is really, really hard — and that may well be the task that researchers trying to evaluate the potentially carcinogenic effects of cell phone use may have before them.
To wit: in a new study published in the BMJ, European researchers — looking at more than 300,000 Danes who had used cell phones — concluded that there was no evidence to suggest that using a cell phone increased the chance of developing a brain tumor. That was true even for people who had used cell phones for more than a decade, and the BMJ study is the biggest so far to look at cell phone radiation and cancer. As the study authors themselves wrote in the conclusion:
In this update of a large nationwide cohort study of mobile phone use, there were no increased risks of tumours of the central nervous system, providing little evidence for a causal association.
Case closed, right? That all depends on your perspective. Other researchers and activists were quick to criticize the study, arguing that it was still not broad enough to fully exonerate cell phones. Devra Davis, an expert in the environmental causes of illness and the president of the Environmental Health Trust, said in a statement:
From the way it was set up originally, this deeply flawed study was designed to fail to find an increased risk of brain tumors tied with cellphone use. In order for any study of a relatively rare disease like brain tumors to find a change in risk, millions must be followed for decades.
Indeed, that’s what makes it so hard to design a study that can give us a definitive answer on the potential risks — if any — posed by cell phones. Brain tumors are extremely rare and strike for mostly unknown reasons, and they can take decades to develop. Cell phones have only been used heavily for the past decade or so, which means that enough time may not have yet passed for the potential impacts of cell phone use to show up in brain cancer statistics.
At the same time, cell phones have become virtually ubiquitous. There are more than 5 billion cell phone subscriptions in the world, which means it’s becoming nearly impossible for scientists to find a control group that hasn’t used mobile phones.
Perhaps it’s not surprising then that the results of research into cell phones have been so confusing and contradictory. Less than six months ago the International Agency for Research on Cancer called cell phones “possibly carcinogenic,” the first official statement that mobiles could indeed pose some danger. (Earlier assessments by the World Health Organization and national public health agencies had mostly concluded that cell phones were safe.) But “possibly carcinogenic” is a long way from definitely cancer-causing — coffee and pickles, among other common things, are also classified as “possibly carcinogenic.”
The multiyear, multinational Interphone study, which was supposed to lay the question to rest, mostly exonerated cell phones when the results were released last year, but that research was so muddled that it was hard for either side to make heads or tails of it.
The reality is that where you stand on cell phone risks likely has a lot more to do with your individual biases than it has to do with hard science. Skeptics of the cell phone-cancer connection point to the fact that mobile handsets emit very low levels of nonionizing radiation — too weak to damage DNA, which is the way that X-rays and other stronger forms of radiation can cause cancer.
But believers in the connection note that the radiation may impact cells in another way, and that there has yet to be a well-designed, long-term study that accurately tracks how we use cell phones today — which is to say, nearly all the time.
If you’re suspicious of cell phones, however, it’s going to be nearly impossible to create a study that would answer all of your fears. After all, it’s difficult to prove a negative, especially given how long it takes brain tumors to form. The good thing is that you don’t need to stop using cell phones if you’re worried; there are simple steps, including the use of a wired handset, that can greatly reduce your exposure to any radiation. That’s a better bet than waiting for scientists and activists to answer the question for good.