Microwave irradiation resulted in thinner cell walls, smaller chloroplasts and mitochondria, and enhanced emissions of volatile compounds, in particular, monoterpenes and green leaf volatiles (GLV). These effects were stronger for WLAN-frequency microwaves. Essential oil content was enhanced by GSM-frequency microwaves, but the effect of WLAN-frequency microwaves was inhibitory. There was a direct relationship between microwave-induced structural and chemical modifications of the three plant species studied.
The highest typical daily exposure, according to a study of 2009, came from cellphone base stations, cellphones and DECT cordless phones, with the highest exposure locations in trains, airports and buses. The typical background power of electromagnetic fields in the home can vary from zero to 5 milliwatts per meter squared. Long-term effects of these electromagnetic fields on human and animal health are still unknown.
It should be noted that the given values of SAR were normalized to 1 W peak antenna power output, while typically a WLAN antenna radiates about 10 mW; therefore, for a real world operating system, maximum SAR of 0.37 × 10−3 and 0.18 × 10−3 (W/kg) is expected for 2 and 1 active antennas, respectively, which are 104 times lower than the European safety limit (2 W/kg) [IEEE Standard for Safety Levels with Respect to Humans, 2005].
We investigated the long-term effects of radiofrequency radiation (RFR) emitted from Wi-Fi systems on hearing. Sixteen Wistar albino rats were divided equally into two groups: sham control and exposure groups. The rats in the experimental group were exposed to 2.4 GHz RFR emitted from a Wi-Fi generator for 24 h/day for one year. The same procedure was applied to the rats in the sham group, except that the Wi-Fi generator was turned off. All groups were kept in Faraday cages during the 12 months to eliminate external electromagnetic fields. The distance between the Wi-Fi generator antenna and the exposure cages was 50 cm. Pre-exposure distortion product otoacoustic emissions (DPOAE) of all rats were measured at the beginning, 6th and 12th months of the study. The DPOAE values of the sham, baseline and exposure groups were compared statistically. For the 6000 Hz hearing frequency, the DPOAE values in the exposure group were lower than those in the sham group (p < 0.05). Similarly, the 6000 Hz hearing frequency values obtained at the end of the 12th month were also lower than the baseline and 6-month values in the exposure group (p < 0.05). In contrast, the DPOAE values at the 6th and 12th months of exposure for the 2000 Hz hearing frequency were higher than the baseline value (p < 0.05). These results indicated that 12 months of RFR (24 h/day) at 50 cm from a 2.4 GHz Wi-Fi source can affect hearing. However, further studies are necessary.
These studies are not definitive. Much more research is needed. But they raise serious questions that cast doubt on the adequacy of the FCC rules to safeguard public health. The FCC emissions cap allows 20 times more radiation to reach the head than the body as a whole, does not account for risks to children’s developing brains and smaller bodies and considers only short-term cell phone use, not frequent calling patterns over decades.
Radiofrequency radiation from cell phones is non-ionizing and is not powerful enough to cause cancer. Ionizing radiation, including x-rays and ultraviolet light, produces molecules called ions that have either too many or too few electrons. Ions are known to damage DNA and cause cancer. Cell phone radiation, like radio, TV, and visible light radiation, is non-ionizing and lacks sufficient energy to add or remove electrons from molecules, and therefore it cannot ionize and cause cancer.  According to the authors of a 2005 peer-reviewed study of 3.7 million Swedish residents, a "biologic mechanism that could explain any possible carcinogenic effect from radiofrequency radiation has not been identified." 
We’re living in a wireless technology age, but there’s some evidence that exposure to electromagnetic radiation from cell phones and wireless devices could increase your risk of certain cancers and tumors. However, more research is needed. In the meantime, I recommend practicing the precautionary principle. Some great cell phone safety tips include:
Whether you call them cell phones, smart phones or mobile devices, it seems like everyone has one. According to the wireless telecommunications industry, the U.S. now has an estimated 300 million mobile subscribers, compared to 110 million subscribers a decade ago. The increase in cell phone use has generated concern about possible health risks related to radiofrequency electromagnetic fields from this technology, and a market for shields as possible protection against the radio waves the phones emit. The Federal Trade Commission (FTC), the nation's consumer protection agency, has some practical tips to help you avoid scams and limit your exposure to electromagnetic emissions from your cell phone.
A 2005 study in the International Journal of Cardiology found that mobile phones may have "adverse effects" on pacemaker functions under certain conditions.  According to the US Food and Drug Administration (FDA), radiofrequency energy from cell phones can create electromagnetic interference (EMI) that may disrupt the functioning of pacemakers, especially if the cell phone is placed close to the heart.  The American Heart Association includes cell phones on its list of "devices that may interfere with pacemakers." 
“There are 25,000 brain tumor cases in India’s Andhra Pradesh and Telangana states, and most of them are attributed to excessive use of cell phones, as per a recent medical survey”. Girish Kumar said that World Health Organization warned of increasing risk of cell phone brain tumor and cancer cases caused by the use of cell phones and location of cell towers in residential areas.