The use of mobile devices has increased exponentially since the introduction of smartphones. With mobile phone subscriptions hitting close to 7 billion globally , our exposure to radiofrequency electromagnetic fields (RF-EMF) is higher than ever. This has raised concerns regarding the effect of RF-EMF on humans, particularly their risk for cancer. The International Agency for Research on Cancer (IARC) has classified RF-EMF as possibly carcinogenic because of a higher risk for gliomas, a type of brain cancer.  While these statistics indicate possible dangers of RF-EMF, fully understanding how it affects a person’s health needs further research and study.
Daily Exposure to RF-EMF
Radiofrequency is emitted by all hand-held electronic devices, such as mobile phones, tablets, and laptops. In occupations where people work with broadcast antennas, cellular towers, and medical equipment, the exposure to RF-EMF is higher. The RF energy from these devices appears to affect some people more than others. Because the body sends information through the nervous system by sending electrical impulses to the brain, it can be surmised that RF-EMF has an effect on human cells and tissue, no matter how small. 
Dindic, et. al.’s review published in 2013 detailed how RF-EMF could potentially damage cells. While the National Cancer Institute states that RF-EMF only heats cells, not damages DNA (which is needed for carcinogenesis),  Dindic et. al. begs to differ. According to their review, cells exposed to RF-EMF experience high levels of oxidative stress. Because of this, free radicals become present in the blood, one of which is peroxynitrite, a very aggressive free radical that can break single-strand DNA – which can ultimately cause cancer. 
Three-fold Increase in Cancer Risk
Hardell and Carlberg published one of the most troubling recent studies explaining the risk of RF-EMF in the latter half of 2014.  They analyzed the long-term effects of mobile and cordless phone use on the risk for gliomas. They based their study on previous research by the IARC in 2011, where RF-EMF was classified as possibly carcinogenic.  Since the IARC study only covered a short latency period of 10 years, Hardell and Carlberg extended their study to include a 25-year latency period.
The study used two case-control studies, with patient diagnoses made between 1997-2003 and 2007-2009 in six Swedish oncology centers. The respondents were 20 to 80 years and 18-75 years for each group. Diagnosed patients were mailed questionnaires that assessed their exposure. Hardell and Carlberg’s results were conclusive – use of mobile and cordless phones was directly associated with increased risk for glioma, with the chance increasing as the latency period and cumulative use of the devices increased. The group with greater than 25 years of mobile and cordless phone use had a three-fold increased risk compared to users with less than 12 months of exposure to the same devices.
While the study has directly associated cell phone use with cancer risk, the risk, in actuality, is very small. When put into perspective – Sweden is one of the countries with the lowest annual mortality rates for cancer (less than 150 per 100,000 population in 2010).  The rates for brain cancer are even smaller. With the risk at roughly 0.15 percent, it is still quite small even when tripled. Still, the study's results are significant enough to shed light on how dangerous RF-EMF can be.