There’s a bit of buzz about the WHO characterizing cell phones as “possibly carcinogenic to humans”. This is a pretty detailed explanation of what that means, from Ed Yong (I think; the link that brought me here said so, but I don’t see Ed’s name on the page anywhere)

World Health Organisation verdict on mobile phones and cancer

What does that mean?
It means that there is some evidence linking mobile phones to cancer, but it is too weak to make any strong conclusions. Specifically, IARC’s panel said that the evidence that mobile phones pose a health risk was “limited” for two types of brain tumours – glioma and acoustic neuroma – and “inadequate” when it comes to other types of cancer.

The Chairman of the group, Dr Jonathan Samet, said, “The conclusion means that there could be some risk, and therefore we need to keep a close watch for a link between cell phones and cancer risk.”

The post goes into some detail about why this is really a non-issue: there is still no proposed mechanism, there are obvious flaws in some of the studies and there are a lot of conflicting results. That last part ties into an important point — the underlying reason that researchers are getting conflicting results is because the system being measured is inherently noisy and the effect under scrutiny is small.

The increased risk‚ from one of the studies (remember, there are others that saw no increased risk), is a 40% increase of those two types of brain tumors, which sounds like a lot, except … you need to look at this in context. Even a substantial increase in a small risk still leaves you with a small risk. We’ve seen this before with traffic analysis, and now we have it for cancer analysis. Matthew Herper has already run the numbers

96% of the U.S. population, or about 300 million people, have cellphones. If everyone’s risk of glioma went up 40% as a result of cellphone use, the number of gliomas in the U.S. would increase by 8,000. That’s a one in 40,000 increase in each person’s risk of glioma, which still isn’t very big.

But the study the WHO is citing only showed the 40% increase in the 10% of people who used cellphones most. I don’t know how many people in the U.S. would now fall into this group, but we’d be talking about maybe hundreds of cases spread out over the whole U.S. population.

We can look at this another way. A fair amount of data has not yielded a statistically significant result. Any signal that exists is still buried in the noise, requiring more statistics, but until you get those statistics, you can’t rule out an effect. What you can do is say that the effect is no larger than some amount, and what is probably the worst-case scenario analyzed above — in the unlikely event the study wasn’t an aberration — yields a very small risk. Which is probably why the collective response of scientists has been “meh”