Do Cellphones Cause Cancer? Probably, but it's Complicated (Drs, Portier & Melnick)
The following article on the NTP study was written by Christopher Portier, PhD, a senior collaborating scientist with the Environmental Defense Fund. Until 2013, Dr. Portier was the Director of the National Center for Environmental Health at the Centers for Disease Control and Prevention and the Director of the Agency for Toxic Substances and Disease Registry. Prior to CDC, Dr. Portier was with the National Institute of Environmental Health Sciences where he served as the NIEHS Associate Director, Director of the Environmental Toxicology Program, and Associate Director of the National Toxicology Program (NTP), and Senior Scientific Advisor to the Director. During his 32 years at NIEHS, Dr. Portier maintained his own research laboratory focused on the impact of the environment on human health.
In 2011, Dr. Portier was one of 31 scientists who served on the expert working group formed by the WHO International Agency for Research on Cancer (IARC) that classified radiofrequency radiation "possibly carcinogenic" in humans (Group 2B). Dr. Portier's comments below suggest that IARC should review the research from the past five years and classify radiofrequency radiation "probably carcinogenic" in humans (Group 2A).
- male rats: frontal cortex, hippocampus, liver, blood
- male mice: frontal cortex
- female rats: frontal cortex
- female mice: liver, blood
Do Cellphones Cause Cancer? Probably, but it's ComplicatedThe degree of risk almost certainly depends on the length and strength of exposure—but we still don't know how significant the actual danger is
By Christopher J. Portier, Wendy L. Leonard, Scientific American Blog, June 13, 2016
The National Toxicology Program (NTP) just concluded a massive 2-year study investigating the potential health hazards of cellphone use on rats and mice – most notably including the specific radio frequencies and modulations (RF-EMF) currently used in our U.S. telecommunications industry.
The NTP have chosen to publish their preliminary findings in rats, rather than wait. This study found that cellphone exposure increases the incidence of malignant gliomas of the brain, i.e., brain cancer, and schwannomas (also called neuromas) of the heart in the male rats. While schwannomas are not cancers, they are tumors and can profoundly impact the protective sheathing of the peripheral nerves, which can lead to severe pain and disability.
The increases were small (3-4 percent over controls), but since these are rare tumors, the findings are still significant. What make these studies even more significant are the findings of similar tumors in humans.
Human Studies: Pre and Post 2010
In humans, there have been numerous case-control studies of cancer and exposure to RF-EMF. The case-control studies (studies that compare exposure to cellphones of people who have glioma (case) with those who don’t (control)) conducted prior to 2010 were all negative—meaning, no increases in tumors were found. However, those findings could easily be due to a lack of sufficient time for cancers to develop, or perhaps the sample size was too small.
Three case-control studies conducted since 2010 have all been positive (an increase in gliomas were found) in the highest exposure groups. Two studies found that the tumors occurred on the same side as phone use. These studies are subject to recall bias –people were asked about their cellphone usage and those with the tumor could have exaggerated their usage.
One study had high relative risks (comparing an exposed group to a non-exposed group) that would suggest we should be seeing an increase in gliomas in the general population. This has been examined in several countries with mixed, and often controversial, results.
Cohort studies, which follow people who don’t have tumors, to see if cellphone use results increases cancer risk, have also been conducted; the results were all negative. One of these studies had serious exposure misclassification (i.e., many of the people listed as unexposed actually used cellphones), and the other studies suffered from short follow-up times.
After evaluating these data, an International Agency for Research on Cancer (IARC) working group concluded these data show limited evidence of a glioma increase in humans. This means an association exists, but the data is not sufficient to be able to say they were certain the cellphones were the cause.
There have also been several case-control studies that specifically examined the risk of developing acoustic neuromas (a schwannoma of the acoustic nerve). As with the gliomas, the earlier studies were all negative, and most of the studies since 2010 have shown a positive risk ratio in the highest exposure categories.
So, why is this NTP study a potential game changer?
Back to the Rats
The NTP study is a long-term cancer bioassay in a specific strain of rats. There have been other long-term cancer bioassays in rats, all of which have been negative. Here’s the thing: In all of the previous studies, the length of exposure and/or the magnitude of exposure was much less than what was used in the NTP study. For example, one study used almost the same magnitude of exposure used by the NTP (1.5-4 Watts/kilogram), but only two hours per day (the NTP exposed the rats for 9 hours per day). Another used 21 hours per day of exposure, but with a magnitude 10 to 20 fold less than the NTP. Finally, some of these studies used different rat strains, and it’s well known that different rat strains don’t always respond the same way to environmental exposures.
The new NTP rodent study is not without its critics. For both the gliomas and the schwannomas, there were no tumors in the control (unexposed) animals. Critics argue this inflates the chances of a false positive finding (that a certain result seems to have occurred, but really didn’t). However, 50% or more of the recent (historical) NTP control groups have resulted in no tumors; thus, it’s not an unusual finding. The significant findings remain positive if you compare the exposed rats to the historical control data. Another criticism is that there were no positive findings in the female rats for either tumor—again suggesting this was a false positive finding. However, male and female rats having the same tumor increase in the same site only occurs about 65 percent of the time.
In our opinion, the exposure to RF-EMF caused the tumors seen in the male rats in the NTP study. With the positive case-control studies seen in humans and a similar positive finding in a well-conducted laboratory study in rats, the evidence that call phones can cause cancer has strengthened.
Do we think cellphones cause cancer in humans? Probably. But proximity matters, as does duration, and level of exposure. Think of it this way: sitting around a campfire is a fine thing, but sitting in the flames yields a very different outcome.
Steps You Can Take
1) With mobile phones, distance is definitely your friend. Exposure decreases as an inverse function of distance from the head to the second power. This means that if you double the distance between your head and the phone, exposure is four times less. If you put it on the table, maybe about 50 times the usual distance from your head, the exposure would be 2500 times less. Thus, using a wired headset (or the speakerphone) with the phone on the table would yield a huge reduction in exposure.
Before you ask, studies on Bluetooth headsets have yet to be conducted.
3) Carrying your cellphone in your purse or backpack rather than in a pocket or close to your body will also greatly reduce exposure.
4) Modern cellphones don’t always emit the same amount of RF-EMF when in use. The better the reception, the less exposure from the phone. So limiting the use of your cellphone in areas of poor reception would also reduce exposure.
5) Turn it off if you are not using it.
6) If you feel grave concern over this issue, then don’t use a cellphone. You might also want to prevent or limit the amount of time your children use a cellphone—since they will have much longer exposure over their lifetime.
Cellphones probably cause cancer if the exposure is close enough, long enough, and in sufficient magnitude. We don’t yet know the risk for a given level of exposure in humans. We need more data in this area, not only for cellphones, but for bluetooth devices, wifi and all the other RF-EMF devices out there. Until then, reduce your exposure whenever possible.
National Toxicology Program: Not the First Government Study to Find Wireless Radiation Can Cause Cancer in Lab Rats
Center for Family and Community Health
School of Public Health
University of California, Berkeley
Electromagnetic Radiation Safety
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