A new report detailing an increase in tumours in male rats exposed to cell phone radiation has been widely reported in international media.
The study, undertaken by the US National Toxicology Program, reports ‘low incidence’ of two types of tumors in the brains and hearts of male rats exposed to cell phone radiation. The research has been published on the preprint server bioRXiv, and is accompanied by peer review comments, but only reports partial results of a number of studies.
Our colleagues at the Australian SMC collected the following expert commentary.
Dr Rodney Croft is Director of the Australian Centre for Electromagnetic Bioeffects Research, an NHMRC Centre of Research Excellence at the University of Wollongong. He comments:
“The National Toxicology Program (NTP) study addressed a range of important health-related endpoints in rats and mice and is an important contribution to the radiofrequency (RF) emission health debate.
“Unfortunately there is not sufficient detail in the present report to evaluate it fully, particularly given a number of criticisms by the reviewers (and described in Appendix G of the report). Of particular note is that the rats treated with RF lived longer than the controls (which is counter intuitive given that the increased tumour rates normally lead to reduced lifespan), the controls did not have ‘any’ tumours (which is also not what is normally found), and the lack of clear dose-response relationships raises the possibility that the results may merely be ‘false positives’ (particularly given the large number of statistical comparisons, the one significant result would appear consistent with chance).
“It is also noteworthy that the results do not appear consistent with the cancer rates within the human population, nor with the majority of other experimental research, even at the very high exposure levels, which are many times higher than humans are exposed to.
“The NTP study will thus need to be fully evaluated once further details become available, and considered within the context of RF emissions science as a whole. At present though, and particularly given a range of uncertainties regarding its results, the NTP report does not provide reason to move from the current scientific consensus that mobile phone-like exposure does not impact health.”
From the UK SMC:
Professor Malcolm Sperrin, Director of Medical Physics at Royal Berkshire Hospital, said:
“This is a very interesting and well-designed study of the incidence of two types of tumour in rats. The conclusions suggest that there is a small additional risk from exposure to RF similar to that used in mobile phones, although the increase is very small. That being said, the paper correctly points out that given the large number of phone users, even a small increase in risk could lead to a measureable increase in the observed population of developed tumours.
“However, the exposures given to the rats is high, the rats are clearly not human equivalent and perversely, the life expectancy of the rats exposed to the RF is marginally greater than the control. This report is a forerunner of a more comprehensive study but does lend credibility to the cautions necessary in very long RF exposures. It also suggests that the original categorisation of RF as ‘possibly causing cancer’ was correct. It should be borne in mind that the hypothesis of cancer genesis is not postulated and certainly does not reveal a link between normal domestic use of RF devices and health detriment, but does suggest that further studies are warranted.”
Prof Kevin McConway, Emeritus Professor of Applied Statistics at The Open University, said:
“It’s good that the US National Toxicology Program (NTP) is researching these issues. But these partial findings don’t cause me any real concern about health risks from mobile phone use. There has been much previous research on this topic, some of which has found no evidence of any risk, and some of which has found limited evidence of a small risk with heavy phone use. I don’t think that these NTP results have moved us on from that yet.
“First, these are only some of the findings from the NTP research. Other potentially important information from the studies is not yet available, or it has not yet gone through the full scientific review process. Looking at only part of a picture can produce distortions.
“The results are from an experiment in which non-human animals (rats) were subjected to radiofrequency radiation for 9 hours a day, every day for their whole lives, starting before birth. That’s way more use than most people make of their phones. I’m no physicist, but I understand from information in the report that the lowest radiation levels used were somewhere around the safety limits imposed on mobile phone manufacturers, for the radiation when one is actually using the phone (and the stated radiation values for my own phone are considerably less than those limits). The higher doses for the rats would thus be well above those limits. It’s certainly not yet obvious how these high-dose results in rats might tell us anything about normal levels of human mobile phone use.
“The study is statistically underpowered. That means that not enough animals were used to allow the researchers to have a good chance of detecting a risk from radiofrequency radiation of the size one might plausibly expect, on the basis of previous findings. Ninety animals per group sounds like quite a lot, but the key point is the number of tumours one would expect to see, and these tumours are relatively rare. So random variation can be important, and in this study the ‘control’ rats (who received no radiation) seem to have been slightly unusual, in that they lived shorter lives and had fewer tumours than the average for rats in similar studies. Also it may seem odd to worry about a low chance of detecting a risk, when in fact they did detect a statistical risk. The concern here is that risks and effects that are detected in underpowered experiments often turn out to be exaggerated – they may or may not still be real effects, but further study shows them to be smaller than the original research indicated. It’s too soon to tell if that will be the case here.
“So here we have a study that found fairly weak evidence of small effects of mobile phone radiation on tumours in rats, where it’s plausible that the effects are even smaller than what was found, and where it’s not (yet) clear how far any such results are applicable to humans. I’m not going to stop using my mobile phone in the light of this.”