Skip to main content
hpa logo
Topics A-Z:
Search the site:
Home › Topics › Radiation › Understanding Radiation › Understanding Radiation - Topics › Electromagnetic Fields ›Wi-Fi
Printer friendly page (opens in new window)

Wi-Fi

General position

There is no consistent evidence to date that Wi-Fi and WLANs adversely affect the health of the general population. The signals are very low power, typically 0.1 watt (100 milliwatts) in both the computer and the router (access point) and the results so far show exposures are well within internationally accepted (ICNIRP) guidelines. Based on current knowledge and experience, radio frequency (RF) exposures from Wi-Fi are likely to be lower than those from mobile phones. Also, the frequencies used in Wi-Fi are broadly the same as those from traditional RF applications.

On the basis of the studies so far carried out in house, the HPA sees no reason why Wi-Fi should not continue to be used in schools. However with any new technology it is a sensible precautionary approach, as happened with mobile phones, to keep the situation under ongoing review so that parents and others can have as much reassurance as possible. That is why Sir William Stewart, formerly the chairman of the HPA, stated that  it would be timely to carry out further studies as this new technology is rolled out. The HPA continues to discuss this with relevant parties.

Basics

Wi-Fi is a particular type of wireless local area network (WLAN) - ie it is not necessary to plug a computer into a phone network via a cable. There are many types of WLAN but all of them allow two or more computers to form a network using radio frequency (RF) signals. They allow users to access and share data, applications, internet access or other network resources in the same way as wired (cable) systems. For more information, view the Wireless Local Area Networks (WLANs) page.

ICNIRP is the International Commission on Non-Ionizing Radiation Protection. See  the ICNIRP website at http://www.icnirp.org.

Key points

  • There is no consistent evidence to date that exposure to RF signals from Wi-Fi and WLANs adversely affect the health of the general population.
  • The signals from Wi-Fi are very low power, typically 0.1 watt (100 milliwatts) in both the computer and the mast (or router) and resulting exposures should be well within internationally-accepted guidelines.
  • The frequencies used are broadly the same as those from other RF applications such as FM radio, TV and mobile phones.
  • Based on current knowledge, RF exposures from Wi-Fi are likely to be lower than those from mobile phones.
  • On the basis of current scientific information, exposures from Wi-Fi equipment satisfy international guidelines. There is no consistent evidence of health effects from RF exposures below guideline levels and no reason why schools and others should not use Wi-Fi equipment.

Exposure to electromagnetic fields from wireless computer networks (Wi-Fi) - update on project progress

Following the announcement by the Board of HPA on 12 October 2007, a systematic programme of research into WLANs and their use started at the HPA Radiation Protection Division. At the start of the project, comprehensive Wi-Fi test facilities were set up at the HPA Chilton site and a review of technical standards and wireless equipment used in UK schools was carried out.

Due to the popularity of laptops in classrooms and the likelihood that the majority of Wi-Fi exposure would come from these devices because they are generally nearer to children than the access points, it was decided that the experimental measurements would begin with laptops transmitting in the 2.4 GHz frequency band. A total of 15 laptops were chosen from among the most popular models used in the education sector in the UK.

The objective of the laboratory measurements was to establish the radiation pattern (ie the angular distribution of electric field strength around each laptop) during transmission and identify the angles at which the field was a maximum. The electric field strength at these angles was then measured as a function of distance.

The results have so far shown that, for a given position, the field strength fluctuated between 2 (and sometimes 3) distinct levels because of the existence of several transmitting antennas within each laptop. Overall, similar radiation pattern measurements for all 15 laptops have been observed with a minimum in the direction from the front of the laptop (towards the torso of the user). Generally, two angular maxima were observed that were symmetrically opposed across a vertical plane bisecting the screen and keyboard. All 15 laptops tested had electric field strength values indicating they had output powers during transmission in the range 6-20 mW. Taking into account the directional properties, the Equivalent Isotropically Radiated Power (EIRP) calculated for all laptops was in the range 17-57 mW and well below the 100 mW (EIRP) limit set for Europe.

A more detailed description of the project and some early results are presented here  Wi-Fi in schools (PDF, 276 KB). Furthermore, these results have been presented at the Bioelectromagnetics Society (BEMS) and the European BioElectromagnetics Association (EBEA) BioEM2009 conference (June 2009), see paper 9-2 at http://bioem2009.org/session-9/.

These results are consistent with the HPA position that exposures to the radio waves from Wi-Fi equipment are not expected to exceed internationally-accepted guidelines and that they are less than from mobile phones. Further results will be published on the HPA website after they have been finalised.

Further work

The remainder of the laboratory measurements includes the assessment of the electric field strength around access points operating at 2.4 GHz. Measurements will also be carried out on a selection of laptops and access points operating in the 5 GHz band.

Further work will then involve the modelling of Wi-Fi equipment and its internal RF structures (antennas) in order to assess the localised specific energy absorption rates (SARs) in users, including children. In addition, measurements of radiated powers and transmit time proportions in schools are planned.

The experimental results, together with information from other studies on radio signals and health, will then be used as the basis for a wider health risk review.


 

Last reviewed: 26 October 2009