Cell phones and cancer - end of story? Nope

The headlines last week trumpeted the latest finding on the cell-phone and cancer front. "Study sees no cancer link," our AP story announced. "Don't worry: Your device is probably safe."

The Danish study found no discrepancy in cancer rates among 360,000 people that appeared linked to cell-phone use. On the other hand, as this New York Times blog points out, the study had some methodological shortcomings, leaving its authors unwilling to rule out the possibility of "a small to moderate increase in risk of cancer among heavy users of cellphones for 10 to 15 years or longer." Tara Parker-Pope wrote:

The Danish study is important because it matches data from a national cancer registry with mobile phone contracts beginning in 1982, the year the phones were introduced in Denmark, until 1995. Because it used a computerized cohort that was tracked through registries and digitized subscriber data, it avoided the need to contact individuals and thus eliminated problems related to selection and recall bias common in other studies.

However, the major weakness of the study is that it counted cellphone subscriptions rather than actual use by individuals, and failed to count people who had corporate subscriptions or who used cellphones without a long-term contract. Those small details could have diluted any association between cellphone use and cancer risk, the investigators conceded.

Another glaring weakness is the time frame itself, which ends in 1995 - well before the huge climb in cell-phone use that occurred over the last decade as devices improved and prices fell.

In 1996, according to data from CTIA-The Wireless Association, about 38 million U.S. subscribers spent an average of a little more than 3 minutes on their cell phones. Today's users average nearly 19 minutes - and presumably well more, since CTIA's denominator is  328 million "wireless subscriber connections," well more than one per every man, woman and child in the country. Some people are on their phones constantly - a fact I know firsthand because I've sat near them on the train.

It's not worth being alarmist about the possible cancer risks from wireless phones. As many others have pointed out, the devices are much riskier to motorists and pedestrians because of drivers who use them incessantly to talk or text when they should be paying full attention to the road. But it's worth paying at least momentary heed to what public health experts call "the precautionary principle" - as Time.com did this summer in an excellent package of stories  after the last "latest report" suggested that maybe there really is a risk.  Bryan Walsh wrote:

The truth is that for most technologies, we don't wait around to see what the long-term effects will be. We don't put cell phones on the shelf for a decade or so while epidemiologists carry out controlled studies on their potential carcinogenicity. Most of us — Americans especially, as native early adopters — want the new, and we worry about the potential consequences later.

That's true widely, not just for technology. Take industrial chemicals. Though thousands of new chemicals are introduced into the marketplace each year, the Environmental Protection Agency investigates only a handful of them, at most. (Regulations handcuff the agency.) Generally, the government depends on safety studies completed and submitted by the companies themselves. And if it turns out that something might be harmful — as may be the case with the endocrine disruptor BPA — any investigations take place after the exposure. We're the guinea pigs.

Of course, not every product is treated as innocent until proven guilty (with a very high standard for guilt). Drugs have to go through several layers of testing before they're released to the public — guilty until proven innocent, like a Soviet court case. But they're the exception, not the rule. When it comes to cell phones, as the environmental epidemiologist and activist Devra Davis argues, "we've been conducting a global experiment on our children and ourselves."

Is there any other way? There's the precautionary principle, which is just a fancy way of saying a new technology is guilty until proven innocent. We don't use it much in the U.S. — although it comes up repeatedly in Europe, especially in regard to genetically modified food — in part because we love the new. And that's the deal we've struck, even if not all of us are on board or are even aware of it. We value the benefits of new technologies more than the precaution of ensuring they are absolutely safe.

The good news for the cell phone question in all of this is that we really can have both. Cell phones have made an incredible difference for the world, mostly positive. Cell phones are not cigarettes — they are not purely toxic products — and they can be employed in ways that minimize whatever risks exist. (By the way, it is absolutely true that the riskiest thing you can do with a cell phone is text on it while you're driving, but that has zero bearing on any cancer risk.) We can have precaution and technology in this case. But that question is one that will turn up again and again in the future — and we'll all need to choose our level of perceived risk.

So use a headset, keep the phone out of your pocket, and cut out the texting from behind the wheel.  (Remember that it's your shifting mental focus, not simply the dialing or texting, that's the real culprit in distracted-driving casualties, so don't count on Apple's new Siri personal assistant to save you from the risks.)

And have a little humility about the limitations of human knowledge. What we don't know about a new chemical or technology can hurt is. It may just take many years to find out.