I’m grateful for this opportunity to help populate Citizen Cohn with a few blog contributions while Jonathan is away. I’m especially grateful because I want to address some reactions to my last TNR article concerning the potential linkage between cell phones and cancer.

I was gratified to see my column get some attention. Yet when I started to see it pop up on websites such as verizoncustomer.net, and when I started getting emails from other public health researchers, I realized that some clarification and correction were in order.

In my view, anyone considering these questions should keep in mind two apparently discordant insights: First, the absolute cancer risk to a given cell phone user—though imperfectly known—is very small. Cell phone radiation would not make my top-20 list of population health problems. Second, there remains a real specific issue regarding potential links between cell phone use—particularly long-term use—and brain cancers that should be addressed.

My original piece for TNR effectively communicated the first insight. The second, not so much. I was reminded of this by Joel Moskowitz, Director of the Center for Family and Community Health at the University of California, Berkeley School of Public Health. He sent me polite but insistent emails suggesting that I was understating the risk.

Moskowitz is an emphatic industry critic who has sounded the alarm about this issue in the popular media, as well as in scholarly journals. Because he says bluntly that the telecom industry has a vested interest in co-opting researchers and minimizing the risk, it would be easy, but foolish, to dismiss what he’s saying.

I'll start with some preliminaries. As I noted in my last column, Glioblastoma multiforme (GBM) accounts for about 60 percent of the 17,000 primary brain tumors diagnosed in the U.S. The age-adjusted GBM death rate is approximate 4.3 per 100,000 people per year. Because this is a rare outcome, and because heavy and chronic cell phone use is a recent trend, the impact of such use on this deadly cancer is inherently difficult to measure. (This controversy highlights the value of maintaining a strong epidemiological surveillance network to scrutinize these relationships.)

Moskowitz also noted one embarrassing point. I did a back-of-the-envelope calculation which posited that cell phones cause an 18 percent increase in GBM risk. This resulted in a crude extrapolation that cell phones would increase annual GBM fatalities by about 0.8 per 100,000. Had I done this crude back-of-the-envelope extrapolation correctly, I would have used a figure of 24 percent. This doesn't really change things, but it was sloppy.

More important, Moskowitz notes that if one focuses on recent studies of long-term mobile phone users, one starts to find higher numbers. One especially finds higher numbers for “ipsilateral” tumors—those occurring on the same side of the head that one uses to talk on a cell phone. The issue can get a bit complicated. Recall biases raise one issue. Many people use both ears for cell phone calling. If someone develops a brain tumor on the left side, he may be more likely to say that this is the ear he used most often.

Even allowing for such complexities and other inherent uncertainties, a 54 percent proportional increase in the risk of GBM tumors is well within the range of reasonable possibilities. (Indeed, some studies provide even higher estimates for GMB risk, though the available data is pretty limited.) No one can definitively support this estimate, but no one can definitely refute it, either.

So if this larger estimate turned out to be right, what would this do to my basic argument?

At one level, it changes absolutely nothing. A 54 percent increase corresponds to an absolute risk of roughly 0.000023 deaths per year per long-term cell phone user, about 2.3 per 100,000. If we assume that there are 150 million such users, that’s almost 3,500 deaths per year. That remains a small number compared to other glaring threats to population health our society leaves unaddressed. 18,361 Americans were reported murdered in 2009. Similar numbers die of HIV/AIDS. Annual mortality rates in studied groups of street injection drug users often reach 2,000 per 100,000.

In addition, more than 400,000 Americans die annually from tobacco use. The added mortality risk facing the typical 50-year-old male smoker is in the neighborhood of 400 per 100,000. Yet many tobacco control efforts languish due to state and local budget crises. Our society foolishly neglects prevalent risks which we know right now will kill many more people than cell phones ever will.

Yet that’s not the whole story. This column exemplifies the perils and uncertainties of crude calculations. So I’ll do another one. Suppose I were to place the same economic value on avoiding a fatal brain tumor as federal policymakers place on preventing other threats to human life from pollution, occupational injuries, and the like. These policymakers attach a value of $7.9 million to a human life. (To be persnickety, one would be willing to pay $7.90 to reduce one’s risk of death by one in a million.)

By this metric, I would be willing to pay about $15 per month to reduce a posited GBM mortality risk from 2.3 per 100,000 to zero. Some of this $15 might be in cash. Some of it might be in the form of inconvenience or maybe in the form of some dorky additional technology. That’s not huge. Policymakers should spend more time on matters such as HIV prevention, smoking cessation, and even mundane stuff such as highway traffic barriers that can save more lives. Still, $15/month is not so trivial. Neither are the few thousand deaths a year that might occur if cell phones turn out to be more dangerous than we hope they are.

Viewed as a specific public health threat, cell phones deserve special monitoring and care for the simple reason that they permeate our lives. Billions of people will be using them. As individuals, we can make minor lifestyle changes to reduce risk. Device makers and telecommunications firms need to watch this issue closely, and to do things right. So I’m glad public health researchers and activists such as Joel Moskowitz are on the case, keeping the industry, and the rest of us, honest and accurate in our calculations.