Mobile phone cancer stories are a trend that never goes out of fashion

A $30m (£23m) US government experiment to test whether the radio-frequency radiation – which carries calls made on mobile phones to masts – can cause cancers has concluded it can but with some big caveats.

It found this in rats – just the male ones – and only at intensities way above what any person would be exposed to. Even then, the evidence was only “clear” for some heart cancers, but much less robust for brain and adrenal gland tumours.

The conclusions come from the US National Toxicology Programme which spent a decade investigating the risk in the most robust way it could, exposing lab rodents to a lifetime of powerful mobile phone-like radiation.

It’s easy to understand why this needs rigorous study. Any new technology sparks countless health scares and mobile phones went from being in-car novelties to must-have handsets in a short space of time.

Additionally, radio waves aren’t the strongest source of radiation around – as anyone who grew up searching for phone service in the countryside will attest – their potential to cause cancer is debatable.

The radiation emitted by most mobile phones is weak and typically doesn’t have the ability to cause mutations in DNA that can lead to cancer, according to Cancer Research UK (CRUK).

But when researchers looked for potential health impacts of phones, which were mainly found clamped to the side of the head in decades past, they also found a worrying rise in brain tumour rates.

Between the 1990s and 2016 brain tumour cases have risen 34 per cent but mobile phone use in the same period rocketed 500 per cent.

In this time advances in scanning and diagnostic technologies has markedly improved, CRUK points out, so much of the increase could simply be down to better detection and record-keeping.

But even assuming the rise is bona fide, correlation does not equal causation. Mobile phones’ rise is marked by plenty of other correlational trends like a boom in microwave meals or the decline of Lycra.

Many studies have attempted to look at heavy phone users and cancer rates in humans directly and some have found associations with increased risk in certain types of brain tumour. The World Health Organisation’s cancer research arm even felt there was sufficient evidence in 2011 to reclassify phones as a “possible cause of cancer”.

But no matter how many people they recruit, and how sophisticated the statistical wizardry to control for things like obesity, and smoking, these studies can’t overcome this correlation-causation hurdle.

The best way to do this would be to take a group of people and make them live identical lives, while measuring their phone use and other sources of radiation then track their disease rates and scour their tissues for tumours when they die.

It’s not clear if America’s National Toxicology Programme drew up that proposal for their ethics committee to consider, but its understandable why they focused on rodents and the more basic question of whether radio waves can cause cancer.

The researchers are apparently satisfied that it can – at high doses and in rats – and, while this may suggest increased risk in humans, it doesn’t move the evidence on from where it currently is.

Without that direct link to the phone in your pocket, it’s not time to go back to your landline just yet.