Mobile phone cancer link in rats – Expert Reaction

US research suggests a link between mobile phone radiation and cancer in male rats, but experts have cautioned that the results may not be directly applicable to humans.

Published by the National Toxicology Program (NTP) of the US National Institute of Environmental Health Sciences, the study concluded there was evidence that male rats exposed to high levels of radiation similar to that used in 2G and 3G phones developed cancerous heart tumours. The effect was not found in female rats or in male or female mice.

The US Food and Drug Administration responded to the study by pointing out some unusual findings, including that rats exposed to whole body radiofrequency energy lived longer than the unexposed control group. The FDA concluded that existing safety levels remained acceptable for protecting public health.

The SMC gathered expert comment on the study.

Dr Faraz Hasan, Senior Lecturer (Communication Engineering and Networks), School of Engineering and Advanced Technology, Massey University, comments:

“The NIEHS study is something useful in that it measures the physiological impact of wireless communication on living beings (rats and mice in this case). It seems that the study has considered the worst case scenario in which their considered minimum exposure is actually the maximum allowed by the international standards. The US Food and Drug Administration has suggested a few inconsistencies with the findings of the report. It is necessary to conduct a long term study, 5-10 years, for example, to completely understand the biomedical effects of radiation. However, the technological change is so rapid that by the time a long-term study concludes, we have moved on to something completely different. It is encouraging that the National Toxicology Program is working towards reducing the time needed for evaluating new telecommunication technologies.

“In essence, radiofrequency signals carry energy that gets imparted on human body. What makes them safe (or unsafe), in lay terms, is the amount of power they are transmitted with and the distance that they travel before reaching us. While the NIEHS study has focused mainly on 2/3G networks, New Zealand and other countries will start deploying 5G from 2020 onwards. The 5G network may result in more exposure to radiation because the number of transmitters, their frequency and their proximity to us will all increase quite significantly. Secondly, the NZ government is considering the roll out of three separate 5G networks (one for each network operator) that will drastically, and quite frankly unnecessarily, increase the exposure to 5G transmissions.”

Dr Hasan is the team lead at Massey University’s Telecommunication and Network Engineering Research Group, which is studying whether there could be adverse human health effects from the rollout of 5G networks.

Our colleagues at the Australian and UK SMCs gathered the following comment.

Rodney Croft is former Executive Director of the Australian Centre for Radio Frequency Bioeffects Research and Professor of Health Psychology in the School of Psychology at the University of Wollongong, comments:

“Mobile phones and associated technologies use ‘radiofrequency’ electromagnetic fields to operate. To determine whether these radiofrequency fields might pose a problem for public health, a substantial literature has tested for effects of radiofrequency fields on cancer and cancer-related biological processes. The NTP study is the latest such study, and has many advantages over previous studies in terms of the number of animals tested and the use of exposure over the whole of the animals’ lives. However, consistent with previous research, the NTP study does not provide evidence of a link between radiofrequency fields and cancer, nor any evidence that mobile phone use can adversely affect health.

There are a number of key issues that need to be considered when interpreting the NTP press release and research publications:

1. The animals exposed to radiofrequency fields lived significantly longer than the controls (and cancer risk increases as you get older).

2. The radiofrequency fields are not relevant to mobile phone use (they were strong enough to increase body temperature in the rats by over 0.5 degrees, whereas a mobile phone can’t increase body temperature at all).

3. The results were only reported for male rats, but not female rats, or male or female mice (which makes the relevance of any results to humans questionable).

And most importantly…

4. There is no indication that any of the results are statistically significant (i.e. not merely due to chance).
This is particularly important as sensible patterns were not observed within or across rodent groups, and also because the reported findings are inconsistent with previous research findings. If chance was ruled out using statistical techniques, the reported ‘evidence’ of carcinogenicity would vanish.

The NTP rodent carcinogenicity study does not provide evidence that the radiofrequency fields relevant to mobile telecommunications can cause cancer.”

Rodney Croft has not declared any conflicts of interest.

Bruce Armstrong is a consultant for Cancer Causes and Prevention, and Adjunct Professor in the School of Global and Population Health at the University of Western Australia, comments:

“In a nutshell, the present results serve only to add a little strength to the evidence available following the first report on the rat studies. That report has stood up to very careful scrutiny. The new results from the mice studies serve to strengthen the findings from the rat studies only a little. I remain of the view that IARC classification of ‘possibly carcinogenic to humans’ remains correct for the present.”

Bruce Armstrong has not declared any conflicts of interest.

Prof Kevin McConway, Emeritus Professor of Applied Statistics at The Open University, UK, comments:

“It’s good that the US National Toxicology Program (NTP) has researched these issues. But these findings don’t cause me any real concern about health risks to humans from mobile phone use. There has been much previous research on this topic, most of which has found no evidence of any risk to humans, and some of which has found very limited evidence of a small risk with very heavy phone use. I don’t think that these NTP results have moved us on from that yet, and that’s generally because they were not designed to investigate those risks. They were looking at something else.

“The results are from experiments in which non-human animals (rats and mice) were subjected to radiofrequency radiation for 9 hours a day, every day for their whole lives, starting before birth for the rats and at a very young age for the mice. That’s way more use than most people make of their phones. I’m no physicist, but I understand from information in the reports that the lowest radiation levels used were equal to 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, for instance, are considerably less than those limits). The higher doses for the animals were four times those limits. What’s more, the rats and mice were exposed to the radio waves throughout their bodies, and that’s not much like the radiation exposure to humans when they use their phones, which will be mostly in particular parts of the body near the phone. It’s certainly not yet obvious how these high-dose results in rats and mice might tell us anything about normal levels of human mobile phone use.

“What these studies have told us is that, under these particular conditions which don’t match human phone use, in particular animals that aren’t humans, there is clear evidence that the radio waves led to an increased risk of a particular kind of tumour in the heart, but only in male rats. Evidence for other increased risks as an effect of the radiation, in other parts of the body, or in female rats or in mice of either sex, was either considerably weaker, or non-existent.

“Does this tell us anything useful? Well, it establishes that, under certain conditions radiation of the same kind as produced by some mobile phones, but generally much stronger and much longer lasting, can lead to an increase in a certain type of tumour in certain rats. That’s worth knowing, but it’s a bit like a hypothetical experiment where rats are run over by heavy boulders. That would doubtless establish that heavy boulders have the potential to harm rats, but it doesn’t tell us anything at all about the risk to humans arising from the existence of heavy boulders in the world. To investigate that risk requires a completely different type of research.

“So here we have a study that found evidence, some of which is pretty weak, of effects of mobile phone radiation on tumours in rats, and which tells us pretty well nothing direct about risks of actual phone use in actual humans. I’m not going to stop using my mobile phone in the light of this.”

Prof Kevin McConway is a member of the Advisory Committee of the UK Science Media Centre