Studies have shown an association between cell phone use and a decreased risk of certain brain tumors. According to a peer-reviewed Dec. 2006 study of 420,095 cell phone users in Denmark, the results showed a "reduced brain tumor risk" among long-term subscribers. [1] Two other peer-reviewed studies also found that cell phone users had a slightly decreased risk of developing brain tumors. A July 20, 2005 Danish study [41] found a "decreased risk for high-grade glioma," a malignant brain tumor, and a 2005 Swedish study [42] also found a "decreased odds ratio" for developing glioma as well as meningioma, another type of brain tumor.

With that in mind, several school districts in the U.S. and other countries have tried to reduce exposure in the classroom to RF radiation from devices. The Maryland State Department of Education, for example, recommended in 2016 that school districts use wired networks instead of WiFi whenever possible, turn off routers when not being used, and keep routers as far away from students as possible. In France, WiFi is banned from nursery schools.

20. Remember to focus on driving. “Don’t look up phone numbers, don’t take notes or play with your PDA (personal digital assistant) while driving. These activities prohibit you from watching where you are going. Of course, you shouldn’t read the paper, apply eye make-up or write notes while driving either! Driving is serious business.” – How to Hear in a Hands-Free World: Mobile and Cell Phone Safety Tips, AudiologyOnline; Twitter: @audiologyonline
There was a negative correlation between the cell phone usage duration and the total sperm count (r = −0.064, p = 0.04). Similarly, there was also a negative correlation between the wireless internet usage duration and the total sperm count (r = −0.089, p = 0.019). Otherwise there were no significant correlations among the other four main question branches (cell phone usage time, cell phone carriage habits, wireless internet usage time. and internet connection type) and sperm parameters.
CONCLUSION: The available literature on the effect of RF-EMFs on plants to date observed the significant trend of radiofrequency radiation influence on plants. Hence, this study provides new evidence supporting our hypothesis. Nonetheless, this endorses the need for more experiments to observe the effects of RF-EMFs, especially for the longer exposure durations, using the whole organisms. The above observation agrees with our earlier study, in that it supported that it is not a well-grounded method to characterize biological effects without considering the exposure duration. Nevertheless, none of these findings can be directly associated with human; however, on the other hand, this cannot be excluded, as it can impact the human welfare and health, either directly or indirectly, due to their complexity and varied effects (calcium metabolism, stress proteins, etc.). This study should be useful as a reference for researchers conducting epidemiological studies and the long-term experiments, using whole organisms, to observe the effects of RF-EMFs.

Because of this physical law, even if  holding a Wi-Fi router directly against your forehead was very dangerous (and, we assure you, it is not) working in your home office 45 feet away from the Wi-Fi router would not be dangerous simply because the microwave radiation of the already minuscule 1 watt Wi-Fi router would have radically decreased in intensity. When you factor in that the Wi-Fi radiation is already harmless, you see that there is no situation in which the Wi-Fi signal from your router, your laptop, your media center, or any other Wi-Fi device in your home could possibly hurt you.
This study analyzed cellular stress levels in rat thymus after exposure to a 2.45 GHz radio frequency (RF) using an experimental diathermic model in a Gigahertz Transverse Electromagnetic (GTEM) chamber. The thymus tissue presented several morphological changes, including increased distribution of blood vessels along with the appearance of red blood cells and hemorrhagic reticuloepithelial cells, while the glucocorticoid receptors presented greater immunomarking on the thymic cortex in exposed animals. These results indicate that non-ionizing sub-thermal radiation causes changes in the endothelial permeability and vascularization of the thymus, and is a tissue-modulating agent for Hsp90 and GR.
The study was an attempt to draw attention towards the adverse effects of non-ionizing electromagnetic radiations (NI-EMR) in the frequency that is used widely in the field of telecommunication. Many studies have captured the impact of the 900 MHz and 1800 MHz frequencies, however the frequency of radiation in Wi-Fi range has not been much explored. Along with the use of cell phones there is a growing concern with the use of Wi-Fi devices which continuously emit radiations in the frequency of 2.4 GHz. Hence we thought it prudent to investigate the impact of radiation of the frequency of 2.45 GHz. It can be concluded that the exposure to non-ionizing radiation of 2.45 GHz caused detrimental changes in rat brain leading to learning and memory decline and expression of anxiety behavior along with fall in brain antioxidants. The exposure triggered the gene expression of caspase 3 which plays a major role in the apoptotic pathway. The chronic impact of non-ionizing radiation needs to be thoroughly evaluated in humans so that combative steps can be taken.
Nevertheless, a group of scientists got together in the mid-2000s, calling themselves the BioInitiative Working Group. This group, which largely consisted of wireless radiation researchers, has written a harsh reply as feedback to the reports claiming that posed no health risks.  The reply lists a wide range of health effects scientists at the European Commission have unfortunately either ignored or dismissed.