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Wireless Health Concerns: Busted, Plausible, or Confirmed?

Over the past few years there have been several news articles based mostly out of Canada claiming adverse health effects of exposure to indoor wireless networks. These constantly seem to come up when schools put RFPs out for wireless systems. A few of the articles can be found here:

http://www.cbc.ca/news/canada/british-columbia/story/2011/10/14/bc-wireless-vancouver-schools.html

http://www.cbc.ca/news/canada/toronto/story/2010/08/15/ontario-wifi.html

http://educhatter.wordpress.com/2010/10/08/wireless-schools-and-student-health-whats-causing-the-headaches/

The first step towards understanding the differences between cellular wireless and 802.11 wireless is examining the output power of a cell phone handset and a typical indoor 802.11 access point.

Let’s first examine a typical cellular device.  The radio waves emitted by a GSM handset can have a peak power of 2 watts.

As an example, the iPhone 4 from AT&T has a radiation rating of 1.17 W/kg. The user manual states “keep iPhone at least 15 mm (5/8 inch) away from the body, and only use carrying cases, belt clips, or holders that do not have metal parts and that maintain at least 15 mm (5/8 inch) separation between iPhone and the body.”

To contrast, the maximum output power of an indoor 802.11 wireless access point is 100 milliwats, and 1 milliwatt is equal to 0.001 watt. To put it another way, an indoor access point operating at its maximum output power is 11 times less powerful than the power output of a typical cell phone handset. Today’s indoor wireless designs do not call for the access points to operate at the maximum output power. It is more common for them to be operating with an output power of 25mW. An indoor access point operating at its recommended output power of 25mW is 46.8 times less powerful than a typical cell phone handset.

Ultimately can we say that the risks are plausible, confirmed, or busted? No. The World Health Organization has classified RF transmissions as a carcinogen concern but let’s face it, is there ANYTHING out there today that doesn’t get that classification?

Stay tuned for a podcast episode soon discussing this very matter and how Wireless VARs are combating these claims!

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Blake Krone

Blake Krone

Cisco CCIE #31229 (Wireless) and CWNE #152, all around tech junkie, code poet. Connecting people with cans and strings.

8 Comments

  1. July 2, 2012 at 7:24 pm — Reply

    One milliwatt is a one thousandth of a Watt. That would be .001 watts.

    I think you meant to say that an AP broadcasting at 100mw is the same as 1/10th of a watt.

    Not to mention, one meter away from the AP is about -40dB down, so if you get no closer than a meter from the AP the actual wattage is .0000001 watts… (move the decimal point four spaces to the left for -40db at 1 meter)

    Compare that to the cellphone that you put directly next to your head!

    People who use cell phones, but are afraid of Wi-Fi are “math challenged”, and probably are the same folks that buy lottery tickets, thinking the math is in their favor there too.

    Keith

    • July 2, 2012 at 10:00 pm — Reply

      Thanks Keith for the math check, both Jen and I looked it over and that slipped past us!

  2. July 28, 2012 at 5:55 am — Reply

    Hello,

    Beside the Specific Absorption Rate (SAR), which needs to be measured in a LAB environment (W/kg), you need also take in account the EMF or RFE (depends on how you like to call it) measurements, these measurements can be done onsite with a specific measuring device (Narda 3006).

    The values are in V/m (volt per meter) for the electric field strength and A/m (amperes per meter) for the magnetic field strength.

    Procedures to measure these values originate from the cellular world, measuring electromagnetic fields generated from cell towers.

    The procedure how to measure WiFi exposure is another discussion so don’t shoot me, but basically in most cases it is somehow the same procedure as the cellular one, which in the case of WiFi the measurements will be done with no clients on the WLAN, just measuring the access points beacons on certain locations afterwards some math is used on the results to get the “worst case scenario” and so on. This procedure is not my favorite, its still a mathematical estimation and try to find a measuring window with no clients on the WLAN after deployment.

    We recommend to do direct measurements on the WLAN under a high duty cycle (lots of clients downloading and uploading), in this case you will measure the “worst case scenario” which is what you want to know anyway.

    Regarding the measurement results, I have been involved in more then 600+ measurements in Europe, all results were far below the EU legislation (61V/m & 0,16A/m), although some european country’s have more stricter legislations towards EMF exposure to public safety, the most strictest value was 4,34V/m & 0,05W/m, big gap between these values if you ask me.

    Anyway when the measurements are done 20cm below the access point, with 2 radios enabled and a duty cycle around 90% in both frequencies the values can exceed the strictest safety threshold!
    When you measure further away (30cm) from access point you’re back in the safe zone.

    In my opinion this discussion is far from ended because we are talking here about values that create “tissue heating” regarding long term exposure nobody knows.

    But the world we are living in is already an electromagnetic soup without WiFi and cellular phones, at the end we will know 😉

    What you don’t want to do or see is putting the access point on the desk close to the person working on that desk with both radios enabled and lot of traffic on both radios, believe me sometimes you see those scenarios, so while you are surveying onsite make sure you choose the access points locations wisely.

    Cheers
    Joeri De Winter

    • August 7, 2012 at 12:19 pm — Reply

      Thanks for the comment Joeri, some good points there. I tend to take into consideration someones desk as I think most of us do when placing APs. No one wants an AP above their head regardless of the possible health risks.

    • August 7, 2012 at 2:54 pm — Reply

      I wonder when the last time someone mounted an enterprise-class AP within 20cm of someone’s head…

      2.4GHz RF looses about 40bB – or 10,000 times its power in just one meter… of course if you get inside that 1m limit…

      Point learned – don’t place an AP within 1m of either humans or other Wi-Fi devices!

      • August 10, 2012 at 1:07 am — Reply

        Hello Keith,

        We did the “20cm measurements” as worst case scenario for that customer, their building had some areas (corridors) which were 2m20cm of height, and cisco recommended to the customer that the minimum distance between humans and access points needed to be 20cm.
        Their union representative demanded to do the measurements at 20cm from the access point, I guess they had some tall dudes working there…..

  3. October 5, 2012 at 11:15 am — Reply

    Hi All,

    I realise this post is a few months out of date but something just hit me about your above points. You are talking about not being 20cm or closer to an access point, which I doubt anyone ever is, but the station device is often 20cm or closer to a person?

    I know my phone often is or my tablet, in fact even as I type this at work my laptop must be 30cm away.

    Presumably then the power of the station is considerably less than the access point? It can’t be that far off because they are both communicating to each other?

    Forgive my wireless ignorance but I just thought I’d post this and see if I get your point of view

    Tom

    • October 18, 2012 at 3:35 pm — Reply

      Hey Tom,
      You’re right on the 20cm distance, although i’ve been in some places were the access points are installed real close to the human body, Anyway the “20cm measurements” were on specific request of the customer in case of the low ceiling corridors.

      Regarding the EMF exposure coming from wireless clients, this is extreme low in relation towards the (in my case) EU legislation. TX power has very low impact on the EMF exposure level, the parameters which has the highest impact is duty cycle and distance so the highest EMF values you will find close to a very busy access point operating in the 2.4GHz and 5GHz band.

      With the “30cm distance from the access point” rule you will always be in the safe zone, at least for 802.11agn access points, 802.11ac could be a different ball game!

      and having an inquiring mind is not a sign of being ignorant 😉

      Cheers
      Joeri

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