First, you must have a proper meter. To check for magnetic field emissions, an AC Gaussmeter will work. Most AC gaussmeters will have an internal probe. Simply position the gaussmeter on the phone. Note carefully where the meter is positioned. Make a call and watch the readings. Notice the highest and lowest readings, and make a mental note of the "average" reading. Now, insert the magnetic shield, and repeat.
This 2017 review, published in Neurological Sciences, looked at case-control studies on cellphone use, focusing on glioma, meningioma, and acoustic neuromas. This review was interesting because the researchers divided the studies by quality, and higher-quality studies — which tended to be funded by the government and not the cellphone industry — showed a trend toward an increased risk of brain tumors, while lower-quality studies did not. Overall, though, their meta-analysis found an increased risk of brain cancers (mostly gliomas) among people who were using cellphones for 10 or more years, and no increase in the risk of acoustic neuroma.
Of course, scientific seesawing like that doesn’t provide a lot of clarity or confidence for the 90 percent of American adults and roughly 80 percent of teens who report having a cell phone. So how concerned should you be about cell-phone radiation? Consumer Reports’ health and safety experts conducted a thorough review of the research and offer some guidance.

Studies in people: Another type of study looks at cancer rates in different groups of people. Such a study might compare the cancer rate in a group exposed to something like cell phone use to the rate in a group not exposed to it, or compare it to what the expected cancer rate would be in the general population. But sometimes it can be hard to know what the results of these studies mean, because many other factors that might affect the results are hard to account for.
Great article. I learned several things that I will put into use with my electronic technology. Thank you. There are numerous EMF/EMR blockers that you can stick on your cell phones, computers, (even microwave ovens for people who still use these). Each brand I’ve researched has the same goal but they’re all different. Are some brands more effective than others? If you can recommend some good brands, I would appreciate your advice. What are good features to look for when selecting the EMF blockers?

I just received this pouch today and it seems to be well-made. I did slide my phone into it (Droid Ultra) and it is snug, but fits. I think my son will also be able to put his ipod in the pouch which is helpful. I mostly bought this because my son puts his phone and ipod in his pocket all the time and I am concerned about the long-term effects of radiation exposure especially so close to his reproductive parts. Hopefully this will provide him with some protection from those elements.

Initially leaked in 2016, results from that $25-million study provided the most compelling evidence yet that RF energy may be linked to cancer in lab rodents. The strongest finding connected RF with heart schwannomas in male rats, but the researchers also reported elevated rates of lymphoma as well as cancers affecting the prostate, skin, lung, liver and brain in the exposed animals. Rates for those cancers increased as the doses got higher but the evidence linking them with cell phone radiation specifically was weak by comparison, and the researchers could not rule out that they might have increased for reasons other than RF exposure. Paradoxically, the radiation-treated animals also lived longer than the nonexposed controls. The study results were reviewed by a panel of outside experts during a three-day meeting that ended on March 28. They concluded there was "clear evidence" linking RF radiation with heart schwannomas and "some evidence" linking it to gliomas of the brain. It is now up to the NTP to either accept or reject the reviewer's conclusions. A final report is expected within several months.
Let’s be honest, we’re addicted to our smartphones. According to an ABC news report, the average person checks their phone 150 times per day, not to mention the other 15 hours per day it sits in your pocket. It’s also nothing new that cell phones emit Electromagnetic Fields/Radiation (EMF/EMR) when it’s glued to the side of our head more than 22 times per day. 
The frequency of radiofrequency electromagnetic radiation ranges from 30 kilohertz (30 kHz, or 30,000 Hz) to 300 gigahertz (300 GHz, or 300 billion Hz). Electromagnetic fields in the radiofrequency range are used for telecommunications applications, including cell phones, televisions, and radio transmissions. The human body absorbs energy from devices that emit radiofrequency electromagnetic radiation. The dose of the absorbed energy is estimated using a measure called the specific absorption rate (SAR), which is expressed in watts per kilogram of body weight.