Characteristics of the application and its use
Wi-Fi is the term now commonly used to designate a Wireless Local Area Network (WLAN), which is used to exchange data between electronic devices and to wirelessly connect, for example, personal computers, tablets or smart-phones to each other and to the internet. The main wavebands used by Wi-Fi networks are in the high frequency (HF) range of the electromagnetic spectrum (several GHz).
Wi-Fi network routers (or Wireless Access Points – WAPs) are often set up at homes and in public buildings such as airports and stations, hotels and restaurants, hospitals, schools, and offices, to provide Internet access to all devices connected to them wirelessly. Outdoor Wi-Fi nets are provided in cities around the world; in this case the coverage for a large area will require a number of wireless access points.
Personal exposure to HF from Wi-Fi presents the same general characteristics as the exposure from base stations (far field) and mobile phones (near field). Whereas the near field exposure from devices connected to the router is mostly limited in time and is highest for body parts closest to the device, the far field exposure due to the router is a whole-body exposure, which is of lower intensity but for longer times as the HF emissions continue regardless of whether a device is operating or not.
HF effects on the body and health implications
HF fields have the ability to penetrate into the body (the higher the frequency, the lower the penetration depth), with the main effect of this being a temperature rise in the exposed tissue. The body can accommodate a small increase in temperature, in a similar way excess body heat is dissipated when performing sporting activity. This is because the human body can regulate its internal temperature. However, above a certain level (referred to as the threshold), which depends on the exposure duration, HF exposure and the accompanying temperature rise can provoke serious health effects, such as tissue damage (burns) and heatstroke. In the case of exposure to HF from Wi-Fi, the level of exposure is below this threshold so that body temperature is not affected.
A large number of studies have been undertaken on both acute and long-term effects from HF exposure, such as Wi-Fi, without showing any conclusive evidence of adverse health effects. Much of this research is inferred from the mobile phone and base station literature, as it refers to a similar exposure.
Among all of this research, the risk of tumors in close proximity to the ear where the phone is held, e.g. brain tumors, has been the focus of numerous epidemiological studies. A few of these epidemiological studies have reported a small increase in risk of some brain tumors for the small group of long-term and heavy mobile phone users (read more). These findings may be explained by reporting biases and weaknesses identified in the studies. Several studies have not reported any increase in brain tumors with mobile phone use. Also, experimental studies on animals and cells have failed to confirm the epidemiological studies, and there is no biophysical mechanism that could explain carcinogenicity at such low exposure levels. In addition, the increased risk observed in some of the epidemiological studies is inconsistent with the stable frequency of occurrence of these tumors in the population. That is an important consideration, given the widespread and significant increase in the use of mobile phones in the general population during the last few decades.
In particular, a considerable amount of research has now been conducted on the relationship between HF fields and outcomes such as headaches, concentration difficulty, sleep quality, cognitive function, cardiovascular effects, etc. To date, this research has not shown any such health effects. The only consistently observed finding is a small effect on brain activity measured by electroencephalography (EEG). The biological implication of these small changes is, however, unclear. For example, they have not been shown to affect sleep quality or to be associated with any other adverse health effects.
The overall evaluation of all the research on HF fields leads to the conclusion that HF exposure below the thermal threshold is unlikely to be associated with adverse health effects.
In general, to avoid health hazards from HF exposure, the temperature rise in the body and in the head must be restricted. Thus, ICNIRP recommends that the absorption of HF energy in the head and body, expressed in terms of the Specific Absorption Rate (SAR) that is related to the temperature rise, should be limited. Distinct SAR values apply to whole-body exposure, as typical of the Wi-Fi network router and for the head as mostly relevant for the devices connected to the Wi-Fi, such as mobile phones.
ICNIRP follows up the HF related scientific research and any new information relevant to health. A revision of the current ICNIRP guidelines on HF used in conjunction with Wi-Fi is underway.