Ron Melnick PhD Commentary on the National Toxicology Program Radiofrequency and Cancer Study
“The Recommendation To Take Precautionary Measures Especially for Children Is Not Scaremongering – It Is Common Sense.”
Ron Melnick PhD, Jackson Hole News and Guide September 2016
Ron Melnick PhD Responds to Skepticism on the Importance of the National Toxicology Program Study of Cell Phone Radiation.
Contrary to what Bob Culver asserts in his commentary in the Jackson Hole News&Guide on Sept. 21 (“Phones haven’t been proven to cause cancer”), there is a substantial and growing body of independent scientific evidence indicating that non-ionizing microwave radiation from cellphones — RFR — can be damaging to human health.
In 2011 the International Agency for Research on Cancer carried out an extensive review of the world’s literature and classified RFR as a “possible human carcinogen” (published in volume 102 of the IARC Monographs on the Evaluation of Carcinogenic Risks to Humans: Non-Ionizing Radiation, Part II: Radiofrequency Electromagnetic Fields, 2013). The section on cancer in humans lists more than 130 references.
As a senior scientist with the National Toxicology Program, I was one of 22 experts who participated in that IARC evaluation five years ago. At that time we classified cellphone radiation as possibly carcinogenic to humans based on positive associations that had been observed between cellphone radiation and malignant brain tumors and tumors of Schwann cells that surround the auditory nerve leading from the inner ear to the brain (acoustic neuroma). A causal relationship was considered to be credible, and deemed by the IARC as “limited evidence of carcinogenicity.”
However, our working group did not conclude then that there was “sufficient evidence of carcinogenicity” (i.e., causal relationship had been firmly established), because recall bias in the case-control studies could not be fully ruled out as a possible contributing factor. The IARC working group noted that brain cancer risks were increased significantly after 10 years of use, and risk levels were greatest on the side of the head on which users held their cellphones.
More recent evidence on health effects of cellphone radiation has strengthened the case for concluding that this radiation poses a cancer risk. The U.S. National Toxicology Program recently reported results from a study in which rats and mice were exposed to cellphone RFR for two years at exposure intensities in the range of cellphone emissions and that did not cause measurable increases in body temperature.
Carcinogenicity studies in rodents are important for several reasons: 1) Animals and humans exhibit similarities in biological processes of disease induction (that is why animal models are used in preclinical trials of new pharmaceutical agents); 2) It is unethical to intentionally expose humans to hazardous agents; 3) Every agent that is known to cause cancer in humans is carcinogenic in animals when adequately tested (IARC, preamble); and 4) Almost one-third of human carcinogens were identified after carcinogenic effects were found in well-conducted animal studies (Huff, 1993, Chemicals and cancer in humans: first evidence in experimental animals, Environmental Health Perspectives 100:201-210).
The findings of highly malignant and quite rare brain tumors and malignant Schwann cell tumors of the heart in the NTP study present a major public health concern because some of these same types of tumors had been reported in epidemiological studies of adult cellphone users. In addition the NTP reported DNA damage was induced in brain cells of exposed animals. While Mr. Culver is correct that RFR is a type of non-ionizing radiation, the findings of tumors and DNA damage in exposed animals demonstrate that such radiation can adversely affect “living tissue.” For children cancer risks may be greater than that for adults because of greater penetration and absorption of cellphone radiation in the brains of children and because the developing nervous system of children is more susceptible to tissue- damaging agents.
It is a tragedy when any individual dies of a preventable disease. The death of Keith Phillips from brain cancer might well have not happened if he had been aware of evidence linking cellphone radiation with cancer. In light of the accumulating evidence of increased cancer risk from cellphone RFR, precautionary measures should be implemented rather than waiting for the absolute proof that Mr. Culver seems to require before he would offer any caution to his family or friends. If we insist on definitive proof of human harm we are effectively treating ourselves and our families as lab rats in an experiment without any controls and without our consent.
Ronald Melnick, Ph.D, was a senior toxicologist in the Environmental Toxicology Program at the National Institute of Environmental Health Sciences when he led the design of the NTP studies on cellphone RFR. He is now retired and serves as senior scientific advisor to the Environmental Health Trust.
After this post was published two commenters asked more questions and Dr. Melnick gave the following technical response.
Response to Tom Whitney and Bob Culver
In their responses to my commentary on cell phones and brain cancer, Tom Whitney and Bob Culver raise several issues related to human exposures to radiofrequency radiation (RFR) from cell phones and the exposures of rats in the NTP carcinogenicity study. Therefore, I provide here some clarification on the study design and tissue dosimetry that should help them and others understand the fact that the exposures of the brain in the NTP study were not very different from human exposures associated with use of cell phones. Mr. Whitney rightfully noted that the Federal Communications Commission (FCC) limit for exposure of the general population to RFR is 0.08 W/kg averaged over the whole body, but neglected to note the localized exposure limit is 1.6 W/kg averaged over any one gram of tissue. In Europe, the localized exposure limit is 2 W/kg averaged over 10 grams of tissue. These exposure values, which are referred to as specific absorption rates (SAR), are measures of the rate of RF energy absorbed per unit mass of tissue. When an individual uses a cell phone and holds it next to his or her head, exposure to the brain will be much higher than exposures to other parts of the body. Body tissues located nearest to the cell phone antenna receive much higher exposures than tissues located distant from the antenna. Therefore, when considering organ-specific risk (e.g., risk to the brain), the important measure of exposure is the 1.6 W/kg value in any gram of tissue in that organ.
Individual manufacturers and the FCC provide SAR values for cell phone emissions. While some cell phones emit lower radiation levels, other phones emit radiation that can produce an SAR dose near or above 1.5 W/kg. In the carefully designed NTP exposure system in which animals were exposed in reverberation chambers, whole body SAR values were 1.5, 3, and 6.0 W/kg and SAR values in the brain were within 10% of the whole body exposure levels. The statement that the whole body exposures in the NTP study were 75 times higher than the FCC limit for human exposures is true; however, with respect to exposures to the brain, SAR values in rats were similar to or slightly higher than human exposures from cell phones held next to the head.
Mr. Whitney expressed surprise that only “a sub-population [of rats] was affected.” Experimental carcinogenicity studies are generally conducted in small groups of rodents (50 to 100 per exposure or control group), and incidence values of adverse effects are used to assess risk to potentially millions of exposed people. While an increased incidence of 1% in an experimental study would not be statistically significant, such an increase or even an increase in brain cancer risk of 0.001% in the general population would be dreadful. Thus, to identify a hazardous agent, exposure levels in animal studies are often much higher than human exposures, while lower doses are included for analyses of dose-response relationships. In the case of RFR, exposures much greater than 6 W/kg could not be used because thermal effects in exposed animals might alter the outcome of such a study. A preliminary study by the NTP showed that body temperatures of rats exposed to 6 W/kg were maintained within 1 OC of the body temperature of controls.
The NTP study was designed to test whether cell phone RFR could produce adverse health effects at exposure intensities that do not cause a measurable increase in body temperature, and to provide dose-response information to assess human risk for any identified effect. Because GSM and CDMA were the major types of modulations used in cell phone communications, both of those were tested. While inclusion of control groups exposed to unmodulated RFR would have addressed the impact of modulation on observed responses, comparisons of effects to those groups would not influence the analysis of human cancer risk from modulated RFR. To challenge the no-effect hypothesis, and because exposure intensities were limited to 6 W/kg, daily exposures were extended to 18 hours with a continuous cycling of 10 minutes on and 10 minutes off. While this pattern is not typical for most or all cell phone users, cancer risk estimates for the general population would be based on the response rate (i.e., incidence) as a function of tissue dosimetry (absorbed power x hours per day of exposure) over the comparable fraction of exposed lifespan. Thus, cancer risk estimates can be made for any pattern of cell phone use; actual risks would be related to cell phone SAR values and distance from the body that the phone is held.
At this time there is no evidence to support a threshold-type response and there is no data on potential human differences in genetic susceptibility to RFR. It is likely that health risks would be higher for children because of greater penetration and absorption of cell phone radiation in the brains of children and because of increased susceptibility of the developing nervous system. It is also important to note that actively used cell phones are not the exclusive source of exposure to RFR, other sources of daily exposures include cell phones powered on even when not communicating, Wi-Fi devices, cordless phones, cell towers, etc.
The finding of even small increases in brain tumors (gliomas) and heart tumors (schwannomas) in the NTP rat studies raises a public health concern because associations between cell phone use and both gliomas and acoustic neuromas (Schwann cell tumors) formed the basis for the International Agency for Research on Cancer to classify RFR as a “possible human carcinogen.” Because of the large number of cell phone users in the US and worldwide, this apparent consistency between the animal and human cancer data should not be arbitrarily ignored.
While the current cancer findings will not eliminate the use of cell phones, manufacturers should continue to work on providing communication devices with much lower emission levels. In light of the accumulating evidence of adverse health effects of RFR, the recommendation to take precautionary measures especially for children is not scaremongering – it is common sense.
Ronald Melnick, Ph.D.