The antennas contained in mobile phones, including smartphones, emit radiofrequency (RF) radiation (non-ionizing "radio waves" such as microwaves); the parts of the head or body nearest to the antenna can absorb this energy and convert it to heat. Since at least the 1990s, scientists have researched whether the now-ubiquitous radiation associated with mobile phone antennas or cell phone towers is affecting human health. Mobile phone networks use various bands of RF radiation, some of which overlap with the microwave range. Other digital wireless systems, such as data communication networks, produce similar radiation. In response to public concern, the World Health Organization (WHO) established the International EMF (Electric and Magnetic Fields) Project in 1996 to assess the scientific evidence of possible health effects of EMF in the frequency range from 0 to 300 GHz. They have stated that although extensive research has been conducted into possible health effects of exposure to many parts of the frequency spectrum, all reviews conducted so far have indicated that, as long as exposures are below the limits recommended in the ICNIRP (1998) EMF guidelines, which cover the full frequency range from 0–300 GHz, such exposures do not produce any known adverse health effect. In 2011, International Agency for Research on Cancer (IARC), an agency of the WHO, classified wireless radiation as Group 2B – possibly carcinogenic. That means that there "could be some risk" of carcinogenicity, so additional research into the long-term, heavy use of wireless devices needs to be conducted. The WHO states that "A large number of studies have been performed over the last two decades to assess whether mobile phones pose a potential health risk. To date, no adverse health effects have been established as being caused by mobile phone use." International guidelines on exposure levels to microwave frequency EMFs such as ICNIRP limit the power levels of wireless devices and it is uncommon for wireless devices to exceed the guidelines. These guidelines only take into account thermal effects, as non-thermal effects have not been conclusively demonstrated. The official stance of the British Health Protection Agency (HPA) is that "[T]here is no consistent evidence to date that Wi-Fi and WLANs adversely affect the health of the general population", but also that "... it is a sensible precautionary approach ... to keep the situation under ongoing review ...". In a 2018 statement, the FDA said that "the current safety limits are set to