Two comprehensive studies into putative links between mobile phone radiation and cancer, conducted by United States National Toxicology Program (NTP), have found an increased incidence of a range of cancers in rats and mice.
The findings do not, however, mean you should ditch your phone.
The studies, released in draft form ahead of peer review in March, exposed rats and mice to radiofrequency radiation (RFR) – also used in radio and TV broadcasting, pagers and microwaves – at frequencies typically emitted by mobile phones.
The experiment’s other parameters were decidedly more punishing.
The critters were subject to whole body exposure for up to 18 hours a day – ten minutes on, ten minutes off – over two years, at dosages ranging from zilch for sham controls to 15 watts per kilogram of body weight.
By comparison, the Australian standard maximum RFR a user should absorb from a mobile handset, laid down by the Australian Radiation Protection and Nuclear Safety Agency, is two watts per kilo.
The researchers found exposed male mice had an increased incidence of rare skin cancers such as fibrosarcomas, as well as a “positive trend” in the rate of lung cancer. Neither finding, however, reached statistical significance. Exposed female mice had higher rates of the blood cancer lymphoma.
Over in the rat enclosures, dosed-up males had higher rates of a rare heart cancer called schwannoma. Exposed rats of both sexes were also found to have tumours of the brain, pituitary, liver, prostate, adrenal and pancreas – only the latter two at rates that were statistically significant.
The researchers were duly cautious in their conclusions, describing the evidence for carcinogenic activity of mobile phone radiation as ranging from “some”, in the case of schwannoma, to “equivocal” for skin, lung, liver, blood, brain and adrenal tumours.
So what does it mean for the dedicated user of wireless tech? Not enough, perhaps, to lever the device from their iron grip just yet.
For starters, the rodent exposures went way beyond those of the average phone user. Your standard rat lives around 2.5 years, so the experiments lasted the equivalent of about 70 human years.
“The levels and duration of exposure to RFR were much greater than what people experience with even the highest level of cell phone use, and exposed the rodents’ whole bodies,” said NTP senior scientist Dr John Bucher, who contributed to both studies.
The studies also threw up some counterintuitive findings; male rats in the sham control group, who got no RFR, were outlived by their irradiated mates.
According to Sarah Loughran, Research Fellow at the Australian Centre for Electromagnetic Bioeffects at the University of Wollongong, that finding casts doubt on the study’s validity.
“The control group rats had a shorter lifespan and therefore it would be expected that they would also develop fewer tumours, which was indeed the case,” she said.
“An extremely large number of statistical comparisons were performed in the NTP studies, making it difficult to determine whether the results were merely due to chance.”
The issue generated incendiary fallout in 2016 when the ABC pulled an episode of the science program Catalyst, entitled “Wi-fried”, for breaching impartiality guidelines by favouring the “unorthodox” view that mobile phones could cause brain tumours.
In response to the current study, the American Cancer Society (ACS) puts the orthodoxy front and centre.
“The evidence for an association between cell phones and cancer is weak, and so far, we have not seen a higher cancer risk in people,” said ACS Chief Medical Officer Otis Brawley.
The ACS itself notes that, because the level of RFR in mobile phones isn’t enough to damage DNA or heat tissue, it’s not clear how it could cause cancer.
Moreover, it states, most studies show people with brain tumours do not report more phone use, do not develop tumours more on the side they use their phone, and do not get tumours at a rate proportionate to how much they use the phone.
A widely reported 2016 Australian study, led by the University of Sydney’s Simon Chapman, found that despite rapid uptake of mobile phones, rates of brain cancer rose only marginally over a nearly 30-year period, a finding the authors put down to better diagnosis.
Two recent meta-analyses, however, concluded mobile phone use may be linked to a form of brain cancer called glioma.
The ACS sees reason for caution. It notes mobile phone use is increasing, and has only been widespread for around 20 years, which may be shorter than the latency period for some cancers. Phones are also increasingly used by children, whose tissues may be more vulnerable, and whose RFR exposure will be longer.
The take home, it seems, is that the issue must receive careful scientific scrutiny for many years to come.