Are electromagnetic fields harmful?

Listener Don got in touch via The Naked Scientists forum. Chris Smith asked technology journalist Tim Revell to reveal the truth about EMFs.

Tim - Well it's a very long and detailed question and the short answer is no you don't need to be worried about these. And that you shouldn't get yourself in a bit of a state thinking about them because electromagnetic fields are in so many different things. You see them in mobile phones they come off microwave ovens they come off Wi-Fi routers, computers, the sun. So if they were this terrible conspiracy against us we would have spotted them by now because they are all over the place.

So what actually is an electromagnetic field? Well it's a sort of combined word of an electric field and a magnetic field and you can think of them as just regions of influence. An electric field for example, will manipulate an electric charge, a particle that is electrically charged, and a magnetic field will manipulate something that is magnetic. And the way that we think of these in terms of whether they're harmful or not for us is in terms of how powerful they are and what they might actually do to you.

So the majority of electromagnetic fields that you come into contact with are what's called no- ionizing so these are like your Wi-Fi routers or your mobile phones and things like power lines as well, are all non-ionizing. And that means they won't do any damage to you. And there have been study after study after study that has looked at this and you are absolutely fine. Now there are some electromagnetic fields that are actually bad for us, think things like ultraviolet rays from the sun. We know that if you stand outside in the sun for too long you get sunburnt and that is because ultraviolet rays are not very good for you and also x-rays in medicine are also not very good for you. So if you limit your exposure you're absolutely fine. But if you had too much of them then you could be in trouble.

Chris - Very comprehensive, thank you Tim. I will use my phone with impunity on that basis. I think the answer is that we're doing a massive experiment on the scale of the whole world aren't we? There are more smartphones and mobile devices now than people on the planet. So everyone's using them at some point pretty much and we have got really good exposure data because we know, because most of these devices are phones,  how long people are spending on them. And so we actually know roughly what people's doses are. And so people are beginning to relate any health outcome with exposure and looking for a relationship and am I right in saying I don't think yet we've seen one.

Tim - Yeah, absolutely. Every now and again a study surfaces that says oh there's a big issue with mobile phones or mobile phone towers. But when you look into it they are very, very small samples that you can't really make many conclusions from, especially when you compare them to the fact that there are hundreds of studies that have huge samples and huge amounts of data that say otherwise. So if we're going to find that they turn out to have a bad effect it will be from one of these big studies not a tiny, little one you find on a Facebook group on a strange corner of the internet.