DECT phone health risks

[matt]

The claimed health risks of using a DECT cordless phone seem remarkably unheard of. Just wondering if anyone here was aware of the claimed dangers?

Google "dect phone health risk"...

 

[Tarkin]

It's generally accepted (at least in publications and journals that I read) that em radiation in the micrometer and above range passing though your body, especially head, does *some* damage. However, unless you're on the phone all day every day, I wuldn t think a dect would do al that much. Hairdryers on the orher hand can actually have a surprising cumulitive effect on killing braincells, a huge em field mere cm form your brain...not one that you'd normally think about.

 

[matt]

It's generally accepted (at least in publications and journals that I read) that em radiation in the micrometer and above range passing though your body, especially head, does *some* damage. However, unless you're on the phone all day every day, I wuldn t think a dect would do al that much. Hairdryers on the orher hand can actually have a surprising cumulitive effect on killing braincells, a huge em field mere cm form your brain...not one that you'd normally think about.

I'd be inclined to agree was it not for the fact that I've read that the base unit for the DECT phone (essentially a mobile phone mast) is "always on" and emits higher levels than a mobile phone mast.

The articles also point out that "mobile" phones boost their emissions during calls but drop back to a negligable level when not in use.

We've currently reverted to using plain old corded phones.

 

[PowerTool]

We've currently reverted to using plain old corded phones.

I've never actually got past that stage

Andrew

 

[Tarkin]

I'd be inclined to agree was it not for the fact that I've read that the base unit for the DECT phone (essentially a mobile phone mast) is "always on" and emits higher levels than a mobile phone mast.

The articles also point out that "mobile" phones boost their emissions during calls but drop back to a negligable level when not in use.

Where did you read that a DECT base station produces a stronger em field than a mobile phone mast? Its is true that a base station is always on but generally it will operate at lower power than when a call is being made (it only really transmits its identity to any handsets in range), but I sereously doubt that it has a higher power output that a mobile phone mast. Think of it in terms of ranges, a dect system has a range of a couple of hundred feet, at best. A mobile phone system has a range measured in 10's of miles. Even taking into account the greater sensitivity and driectionality of a mobile pohne system, a dect system would be far less powerfull. of couse this is all relative, as em fields decrease in strength with distance, althoguh in slightly different ways in this case as i believie mobile phoine masts have a directional mast system. So if you live 20 miles form a mobile phone mast, and have a dect basestation on top of your head, then in that case the dect base station will be the dominating field. But overall, dect systems are low power. All modern equipment produces em fields, and you cant help but be surrounded by em fields. Thigs like electrtic ovens, heaters, hairdyers etc produce the highest fields, and compared to them things like mobiles and dects have small output powers.

That said, there is the issue of frequency succeptability, that is, which frequencies is the human body most succeptable to. Of the top of my head I have no idea. What I do know is that there is alot of study in this field, trying to find out just how bad em radiationis for you, and what frequencies have the most effect. However there are alot of contradictory findings, and many meangless studys with poor conclusions. So this is something to which there is no absolute definate answer. Nobody, so far as I know, has produced satisfactory clinical results to show that these things are really bad for you. I suspecty you've been reading the doomsday 'mobile phones are killing us all' daily mail headline type websites on this, feel free to correct me if I'm wrong! Therss notihng worng with them, sometimes they are right, but often they are unnesessarily over dramatic, sensationalist and exaggerate everytihng, someitmes using poor scientific studys to justify their content, which are often totally incorrect.

All I will say is that the jury really is still out on this one as to whether or not these thingfs are really dangerous for you. Personally, I think that it will be found that certain em frequencies are harmfull to the human body, but that very high signal strengths or prolonged exposure in the extrteme is required to cause the effects to show. This kind of technology has been around now for over 20 years, and there are virtually no *confirmed* cases of people suffering illeffects (althgouh I grant you its perfectly possible that some may have gone unnoticed).

Anyway, i'll appologise for this mini rant before i get shoutred at...

 

[Shady]

Dect Phone info:

Cordless phones and their base stations have output powers much too low for exposures to exceed internationally accepted guidelines and HPA ( The UK Health Protection Agency) does not consider there are particular safety issues with their use.

All cordless phones have average output powers of around 10 milliwatts (10 mW, one hundredth of a watt) during conversations, although the instantaneous output power can vary over time due to the structure of the signal.

The signals from older analogue cordless phones are at a constant level of 10 mW, whereas the signals from modern digital cordless phones are in the form of 100 bursts every second, each of around 0.4 millisecond (ms) duration. The bursts are at a peak power level of 250 mW, but on average the phone only transmits for 1/25 of the time and so the average power is 10 mW.

The average output power of mobile phones can be up to 250 mW, but unlike cordless phones, mobile phones have adaptive power control and can reduce their output power in a series of steps to as low as around a mW, or even lower in the case of 3G phones. Hence, in circumstances where there is a very good communications link to the base station, e.g. when a mobile phone is right next to it, the instantaneous power from a mobile phone could actually be lower than from a cordless phone. However, recent research suggests that, in more typical call circumstances, mobile phones spend a large proportion of the time at their highest power levels and so average powers of mobile phones are appreciably higher than from cordless phones.

Cordless phones are held to the head like mobile phones and some of the radio waves they produce are incident on the head. The radio waves carry energy and, as with mobile phones, some of this energy is absorbed in the head and could produce temperature rises if too much were absorbed too quickly.

The energy absorption is measured in the quantity ‘specific energy absorption rate' (SAR) which has the unit watt per kilogram (W kg -1) . SAR is closely related to the electric field strength produced inside the body tissues, but electric field strength outside the body, while more easily measured, is of less relevance.

Many expert groups and advisory bodies have reviewed the scientific information relating to health effects that might arise due to absorption of radio waves in the head. The former NRPB (now the HPA Radiation Protection Division) completed a formal review process in 2004 and advised that the exposure restrictions of the International Commission on Non-ionizing Radiation Protection (ICNIRP) should be adopted in the UK . These restrictions advise that SAR should not exceed 2 W kg -1 when averaged over any 10 g of tissue in the head and any 6 minute period for the general public.

Frequency of the radio waves is an important factor in determining the depth to which they penetrate the head. Higher frequency radio waves penetrate less distance into the head. The frequencies used by digital cordless phones are around 1900 MHz (megahertz), which is similar to those used by mobile phones (900, 1800 and 2100 MHz). Older cordless phone handsets used in the UK radiate at a lower frequency than mobile phones, either around 47 MHz or 39 MHz, depending on the system, meaning that there is greater penetration into the head.

However, SAR is the quantity of interest in evaluating exposures. On a theoretical basis, radio transmitters producing an average power of 20 mW or less cannot exceed the guideline exposure limit value (2 W kg -1), irrespective of how they are used. Hence, as all cordless phones have output powers around 10 mW, they should not be able to cause exposures above guidelines however they are used.

Measurements of the SAR values from cordless phones are not generally available, however it is possible to scale the range of typical values reported for mobile phones operating at full power (0.2–1.4 W kg -1). Assuming physical factors (such as the antenna types and positions in relation to the head) are similar to those with mobile phones, this suggests that DECT cordless phone SAR values would be expected to be in the range 0.008–0.06 W kg -1 , at least 30 times below the ICNIRP guidelines.

Just as digital cordless phones send radio signals to the base station (one of the charger units) during calls, so the base station transmits radio signals back to the phones. The base station frequencies, signal structures and power levels are the same as those of phone handsets when a call is being made.

The base station is not located immediately adjacent to the head and consequently exposure levels produced are much lower than with the phones. One situation where a user may be particularly close to a base station would be if the main charger unit were placed on a bedside table. If such a base station were 30 cm from the head, this would be at least ten times further away than a phone handset and SAR values would be at least a hundred times lower, and thus thousands of times below the ICNIRP guidelines. Often the cordless phones in bedrooms are secondary units with a charger, and the main base station/charger is somewhere else in the house.

When no calls are being made, DECT base stations emit 0.08 ms pulses once every 10 ms at a peak power level of 250 mW. This implies the average output power is 2 mW which is five times lower than when a call is being made. SAR values would also be five times lower.
Summary

Summary: No appreciable danger that has produced measurable effects in humans, according to a non-partisan international body. (ICNRP) The handset rates 30 times lower than threshold values, the base station 'thousands' of times lower, unless you tape it to your head...

Mobile Phone masts:

The power of each base station transmitter is set to a level that allows a mobile phone to be used within the area for which the base station is designed to provide coverage, but not outside the coverage area. Higher powers are needed to cover larger cells and also to cover cells with difficult ground terrain. Typical maximum powers for individual macro-cellular base station transmitters are around 5-10 W, although the total radiated power from an antenna could be up to around 100 W with multiple transmitters present.

Assuming the maximal value of 250 mW for a Dect base-station, mobile masts (more properly, the antennae mounted on them) are radiating at around 20 to 400 times higher power... Not remotely similar.

I really wouldn't worry. It's a bit like deciding that you won't live in Cornwall because of all that evil radon gas giving you cancer... Theoretically possible, but statistically insignificant...

 

[Tarkin]

Assuming the maximal value of 250 mW for a Dect base-station, mobile masts (more properly, the antennae mounted on them) are radiating at around 20 to 400 times higher power... Not remotely similar.

Nice one Shady, i spent ages trying to find the output power range for a dect base station, without much luck.