That’s why randomized controlled trials (RCTs) often yield fairly clear answers about the effectiveness of treatments compared to other study designs. (Fun fact: Scottish doctor James Lind, a clinical trial pioneer, figured out that citrus fruits seemed to have an effect on scurvy using one of the earliest RCTs.) RCTs can also be used to study whether something, like cellphone radiation, can cause disease.
Using a speaker/personal speakerphone or earplug (not wireless) during conversation - distancing the mobile phone from the user’s body reduces his exposure to the radiowave radiation. Therefore, keep the mobile phone at a distance from the body (do not carry it on the body, such as in the belt, pocket or on a neck strap). Obviously, reducing the amount and duration of calls on the mobile phone is another simple measure to reduce exposure.
Participation bias, which can happen when people who are diagnosed with brain tumors are more likely than healthy people (known as controls) to enroll in a research study. Also, controls who did not or rarely used cell phones were less likely to participate in the Interphone study than controls who used cell phones regularly. For example, the Interphone study reported participation rates of 78% for meningioma patients (range among the individual studies 56–92%), 64% for glioma patients (range 36–92%), and 53% for control subjects (range 42–74%) (6).
Since use of mobile phones by children began at a later stage compared to use by adults, the effects of exposure to mobile phones in this population have not yet been investigated. Considering their health sensitivity, the long life expectancy in the young population (probably involving the accumulation of significant exposure and development of morbidity in the long-run), and ethical issues involved in decision making regarding the population of minors, additional precaution is required in this population. Therefore, the Ministry of Health advises parents to reduce children’s exposure to mobile phones as much as possible, consider the age they start using them, reduce the amount of time mobile phones are used, and in any event, make sure they use earphones (not wireless) or a speaker when using the mobile phone.
The amount of RF energy absorbed from the phone into the user’s body is known as the specific absorption rate (SAR). Different cell phones have different SAR levels. Cell phone makers are required to report the maximum SAR level of their product to the US Federal Communications Commission (FCC). This information can often be found on the manufacturer’s website or in the user manual for the phone. The upper limit of SAR allowed in the United States is 1.6 watts per kilogram (W/kg) of body weight.
The use of "hands-free" was not recommended by the British Consumers' Association in a statement in November 2000, as they believed that exposure was increased.[41] However, measurements for the (then) UK Department of Trade and Industry[42] and others for the French Agence française de sécurité sanitaire environnementale [fr][43] showed substantial reductions. In 2005, Professor Lawrie Challis and others said clipping a ferrite bead onto hands-free kits stops the radio waves travelling up the wire and into the head.[44]
Experts suggest that mobile phone users can take a number of precautions to reduce any possible health risks. Almost all agree that the best step is to keep mobile phone conversations short and to a minimum. Many believe that so-called hands free kits reduce the risks by cutting the amount of electromagnetic radiation entering the brain. They also recommend that users buy phones with external aerials so that it is as far away from the head as possible when in use. Similarly, it is believed that phones with a long talk time are more efficient and produce less powerful emissions. Users are also advised against buying handsets with a high “SAR” value, which means it emits more radiation.

The science is still out on whether the long-term use of cell phones—which emit electromagnetic radiation when they send and receive signals from towers or WiFi devices—can affect human health. But for people who want to reduce their exposure to this type of energy, the California Department of Public Health has published new guidelines on how to do just that.
Every day, we’re swimming in a sea of electromagnetic radiation (EMR) produced by electrical appliances, power lines, wiring in buildings, and a slew of other technologies that are part of modern life. From the dishwasher and microwave oven in the kitchen and the clock radio next to your bed, to the cellular phone you hold to your ear—sometimes for hours each day—exposure to EMR is growing and becoming a serious health threat.
In addition, the findings might be influenced by the fact that the study subjects owned cell phones that were in some cases manufactured two decades ago. The way we use cell phones and the networks they’re operated on have also changed since then. Last, cancer can develop slowly over decades, yet the studies have analyzed data over only about a five- to 20-year span.
EWG met with representatives of Pong Research and fully agrees with its business premise that cell phone cases should decrease, not increase, radiation exposure. Pong hopes to carve out a niche by selling cases that lower the phones’ radiation exposure. We anticipate that as awareness of the potential risks of cell phone radiation grows, Pong and other companies will respond by marketing cell phones and cases that offer users good communication with less radiation.
So of course now that we understand that the cases are not tested and just the material--it makes sense! We measured power density levels all around the case-the shielding material most likely isn't used "all over" because then the phone couldn't receive signal and wouldn't be able to engage in a call.  That's why we did not see even close to a 99% reduction when some cases were on the phone.  In fact, watch the video and you'll see some readings are more than 20% higher with a case on vs the naked phone.
But, dear reader, don’t think we’ve reached a “case closed” moment: Unfortunately, even the best evidence on cellphones and brain tumors is far from ideal. Remember, these cohort studies are still observational research — not experimental studies like RCTs. That means they can’t tell us about causation, and there are still many ways they could be biased.
Says Dr. Carlo: “We also conducted four different epidemiological studies on groups of people who used cell phones, and we did clinical intervention studies. For example, studies of people with implanted cardiac pacemakers were instrumental in our making recommendations to prevent interference between cell phones and pacemakers. In all, we conducted more than fifty studies that were peer-reviewed and published in a number of medical and scientific journals.”
Cellsafe backs its claims by publishing independent test results on its site. These test reports are detailed, complex and confusing, but the results are available for you to interpret. For example, their tests found that an iPhone 4S produced a SAR of 1.069 W/kg on the 3G 2100Mhz frequency without a case, and 0.267 W/kg with a Cellsafe case. But what in the world does that actually mean? Is a SAR of 1 W/kg dangerous? Is a reduction to 0.267 W/kg actually better, or are we just splitting hairs?
The only consistently recognized biological effect of radiofrequency radiation in humans is heating. The ability of microwave ovens to heat food is one example of this effect of radiofrequency radiation. Radiofrequency exposure from cell phone use does cause heating to the area of the body where a cell phone or other device is held (e.g., the ear and head). However, it is not sufficient to measurably increase body temperature. There are no other clearly established effects on the human body from radiofrequency radiation.
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