Talk:Specific absorption rate

Untitled section

Why is the hazards discussed in relation to a pure technical measurement unit? I think that that discussion should be moved to the "Electromagnetic radiation hazard" page.

I will give it a graze period and then remve the hazrd discussion. I do not think that it belongs here either.Mossig 21:22, 25 April 2006 (UTC)

Actually the SAR has primarily been used for measuring RF absorption due to MRI, not cell phones. 1 SAR is defined as 1Watt / kg = 1 Joule / kg s

So why aren't the units sieverts per second? Gene Nygaard (talk) 12:46, 29 November 2007 (UTC)

It could be, but as sievert are mainly used for ionizing radiation SAR from RF-fields are described as measured in W/Kg. I have never seen SAR used as a unit, as proposed above. Mossig (talk) 20:19, 29 November 2007 (UTC)

Thanks. I figured it was something like that, but I'd forgotten how to characterize it. Gene Nygaard 22:57, 30 November 2007 (UTC)

The unit Sievert is only used for ionizing radiation and it includes already a biological weighting factor (for ionizing radiation). — Preceding unsigned comment added by 147.142.107.30 (talk) 10:03, 29 October 2014 (UTC)

SAR Limits

I've just added a bit more detail on European SAR limits. I have quoted directly from IEC-60601-2-33:2002 for the MRI limits, but I don't have access to IEC 62209-1 (handheld devices) - could somebody who has the standard check that 2W/kg is accurate? I have also hidden the reference to the ICNIRP limit -- I don't think this is considered current, but again, I'd like to have someone confirm. Finally, does someone out there know the FCC/FDA SAR limits for MRI? GyroMagician (talk) 16:34, 8 November 2008 (UTC)

Why souldnt the ICNIRP limit be considered current? I will unhide the link to ICNIRP, as this still is the basis for most of the worlds regulations. And I am sceptical about quoting technical standards, such as the MRI standard, direct without the rest of the definitions. It is to little information to be really useful, and to much to give any insight into the matter for the curious reader. Mossig (talk) 00:04, 9 November 2008 (UTC)

Okay, I wasn't sure about the ICNIRP limit, I though IEC standards had superceded it - thanks for correcting. Which definitions do you think are missing from the MRI SAR limits? Maybe I should remove the 1st/2nd controlled level limits and only quote the normal operating limits? Or maybe you would prefer to see the MR limits on the MR page? I would also like to try and give some context to the ICNIRP line - it seems rather 'hanging' at the moment. Input welcome. GyroMagician (talk) 11:45, 10 November 2008 (UTC)

An SAR measurement appears to refer to physical absorption at the time of use (cell phone, MRI), but not cumulative absorption over time. Does the extreme proliferation of radio waves represented by cell-phone use (transmission towers, "hot spot" wi-fi, etc.) increase cumulative retention of some potentially tissue-altering effect? Jimsimple (talk) 13:53, 27 June 2010 (UTC)

Good question. SAR is usually used to give an indication of the amount of heating caused by a device. If you deposit too much heat, you start cooking tissue. But if you stay below some limit, it is generally assumed that the heat will dissipate, and no permanent damage is done. For example, IEC-60601 assumes that if the heating stays under 1°C, no damage is done (you can experience a higher temperature rise with a fever, so this seems reasonable). But SAR by itself only measures energy is deposition, over a given time. In principle it could be used to prescribe limits based on concerns about low-level 'background' EM radiation, with an averaging period of years rather than minutes, although I have never seen it used this way. GyroMagician (talk) 19:22, 27 June 2010 (UTC)

Volume/Mass

Local SAR is commonly measured/calculated over 10g (IEC) or 1g (FDA) of tissue. This is confusing because the integral of (sigma * E^2/ rho) is taken over a volume, not a mass (check the units). In simulation (FDTD and similar) this is done by expanding a volume around the calculation point until it contains the required mass. I've modified the wording of the article to try to capture this - is it better? GyroMagician (talk) 06:57, 29 June 2010 (UTC)

Lab measurements versus practical antenna operation

Hope I'm not off-topic, but these lab measurement don't seem to say anything about the actual compling between the user's hand and head to the emission object, that is the hand-held cell phone. I learned a long time ago after many years as a radio amateur that the coupling to the body is of keen importance at these microwave frequencies. Witness the Iphone 4's bad reputation due to the placement of the feed to two separate antennas in the natural grip point of a right-handed user, which causes a weakening of the emitted field, and dropped calls with resulting bad PR. This coupling effect is included in the calculations of the designers; and must be met if the impedance and emission pattern is to be the desired one. This is not always true for all antenna designs, for example: fractal antennas are often least affected as their feeding impedance is already so low, whereas stub or frame antennas are most affected. See iPhone 4 which uses a frame antenna. Rumors say that their next model will have a metal backplane as one antenna. My point in this all, is that assigning "safe" and "unsafe" gradings are worthless and may be completely incorrect as to the effect on the brain. Secondly, at these frequencies there often occurs hot spot anomolies, which could be much higher than than measured or calculated average over a unit the size of the brain. Witness the unevenness which plagued the first generation of microwave ovens. I would have proposed instead a measuring system based upon a "in-ear" sensor unit with a shielded (coax) cable to the measuring unit. Whether the sensor could be placed in actual human user's ears is another question; but see no reason why not----as we after all are using cellphones meant for intensive consumer use. I perhaps unnecessarily add that I have a degree in EE from NC State University, but claim no expertise in modelling in a lab environment---although have done some practical work but in the 2--30 Mhz range. Thanks for any guidance to a newbie at Wikipedia.

Idealist707 (talk) 21:42, 1 June 2011 (UTC)

Practical difference between US SAR and EU SAR?

Can somebody who knows more than I do about this matter add something about what the difference between the EU SAR measurement and US SAR measurement means in practice. It now explains that one is measured over 1g of tissue and the other over 10g, but says nothing about what that difference is measuring actually means. It is clearly not just a different scale, as the difference between the EU SAR and US SAR on the same phone varies.

If Device A has a higher US SAR rating ccompared to Device B, but a lower EU SAR than Device B, what is the actual difference between the devices for the radiation dose of the user? Does it mean that the "worst 1g spot" on the user's head gets more radiation using Device A, but over a larger mass (10g) the total dose is lower, so the radiation absorbion is more concentrated on a specific spot using Device A but less on total, or what? And if so, how is it possible that some phones have a higher EU SAR rating than US SAR? And how is it possible that some phone have a higher US SAR value than EU SAR value, if the US standards should measure the maximum value over a smaller mass?

--86.50.106.241 (talk) 13:13, 23 April 2012 (UTC)

Mobile phone SAR list

Is this list useful? To be trustworthy every entry needs a reference required and that is clearly impractical. The article is about the definition of SAR not the SAR of every item that people can think of. All that is needed is a single entry saying that the SAR of a mobile phone is in the range of 0.5 - 1.5. — Preceding unsigned comment added by Mtpaley (talk • contribs) 00:12, 16 February 2013 (UTC)

The fact that this table includes the operating system of each devices is damning. — Preceding unsigned comment added by Mtpaley (talk • contribs) 00:15, 16 February 2013 (UTC)

I propose moving the SAR list to a new page. Anyone disagree? Mtpaley (talk) 19:17, 26 February 2013 (UTC)

Done it. There is now a new page called Mobile Phones SAR List Mtpaley (talk) 20:21, 28 February 2013 (UTC)

Put 'Mobile Phones SAR List' on request for deletion. It it a list of numbers without meaning or sensible units. — Preceding unsigned comment added by Mtpaley (talk • contribs) 21:52, 19 March 2013 (UTC)

In Feb 2013 I moved the 'Mobile Phones SAR List' into a new page and a month later I proposed (badly - I accept a procedural messup here) to get this page deleted which it was. The current SAR page is now close to a edit war between ViperSnake151 and Elvey about the value of a list of SAR values for many phones which is a reenactment of what happened in Feb 2013 when I moved this list into a new article. Look at the talk page section 'Mobile phone SAR list' for comments on this. The same debate seems to be coming back between ViperSnake151 and Elvey. I am just commenting on this to point out that there is a history - I intend to keep out of any debate this time. Mtpaley (talk) 23:48, 11 December 2013 (UTC)

As I believe is now obvious to all, the SAR values are verifiable in the FCC database; so one reference to the database suffices. Viper last two edits were both removed the list at least twice. Is this the talk page section you're referring to, or are you referring folks to a deleted page, or what? Link, please. I won't speculate as to what the real reasons some folks oppose the list are, but it seems like a 'see what sticks' approach is being tried. I can't think of a COI that would provide such evidently strong motivation.--Elvey (talk) 00:37, 12 December 2013 (UTC)

The individual SAR's can be listed in their respective infoboxes. I personally think that here, its merely trivia, as it does not discuss the SAR's of any other products. ViperSnake151  Talk  20:31, 22 December 2013 (UTC)

I don't see an argument there, just unsupported opinion. I don't see an offer to merge it to infoboxes either. (I do see the argument that the information is not verifiable, but that's been thoroughly debunked.) I've added some commentary from the FCC, which I think provides some useful context that a bare, stand-alone list doesn't offer. WP:IDONTLIKEIT isn't policy and you shouldn't be making that argument in this or any deletion discussion. --Elvey (talk) 23:40, 22 December 2013 (UTC)

It looks like the stand-alone list that was just deleted per AfD is being recreated in this article, and the issues with criteria for inclusion have not been resolved. I agree with Mtpaley's observation above that the section should mention the FCC & other agencies' limits for mobile phone radiation, and maybe a few examples, but not an exhaustive list of every phone ever rated. I'm also concerned that only Android devices are listed, and devices running other operating systems have been scrubbed through various revisions - this looks like POV pushing. It's not relevant in this article whether the phone is supported by a free OS or if it is available unlocked. Ivanvector (talk) 16:59, 30 December 2013 (UTC)

Ivan, you're wrong, in that the list was created here first. It was then sneakily deleted, out of process. For a role in which, IIRC, Mtpaley apologized. I don't think the OS is POV pushing; I think it's an artifact of the delete any such list; throw every excuse we can come up with POV pushing. But we agree, there's no need for that column. --Elvey (talk) 22:04, 2 January 2014 (UTC)

I see that it was created here first. I shouldn't have said that it was being "recreated" here; that implies an end-run around AfD, and that wasn't my intent. My POV concern was that only unlocked Android phones were listed, and there was a WP:WEASELy blurb that seemed to be pushing Replicant, but that has all been resolved by adding more phones and removing the two columns. I don't object to the OS being indicated, I was just concerned that there was only one. Ivanvector (talk) 23:06, 2 January 2014 (UTC)

If there is going to be a list of SAR values then I would support one entry for phones specifying about 1 W/Kg but it should also include some other non ionizing sources of energy to make this number meaningful. A quick back of the envelope calculation gives tropical sunshine at 1.0, WIFI at 2m is 0.008. If pressed I will calculate the numbers for a audio speaker, ultrasound scan, cell phone base station at 10m and a few more. But agreeing with Ivanvector the current list is even worse than the one that I got rid of a year ago. I mentioned that the OS of a phone is irrelevant but if it can be unlocked is even more irrelevant and just serves to discredit this article. Mtpaley (talk) 19:47, 30 December 2013 (UTC)

I don't understand what it is that you would support. A list that has just one entry for all phones, with 1 W/Kg as the combined/averaged SAR for that entry? With what as the RS? --Elvey (talk) 22:04, 2 January 2014 (UTC)

Obviously, we couldn't include a "back-of-the-envelope" calculation but ideally there are tests published for other types of devices. I'm not an expert in this, I don't know where to look. Ivanvector (talk) 23:09, 2 January 2014 (UTC)

I have proposed deletion of the category Low-radiation smartphones, for the same reasons discussed in the AfD List of low-radiation smartphones. This seems like the most appropriate place to post a notice since the "main page" was already deleted. Please head to the CfD section to comment. Thanks! Ivanvector (talk) 18:50, 31 December 2013 (UTC)

Ivan, I'm disappointed that you re-raise the idea that we don't have a RS, as the FCC was provided as an RS for the SAR values, and updated list of 20 lowest radiation cellphones was provided by Enric Naval as a list of the 20 lowest radiation cellphones. The idea seems discredited to me. No? --Elvey (talk) 22:04, 2 January 2014 (UTC)

Criticism - removed

I have just removed the following:

SAR limits don't consider that the human body is particularly sensitive to the frequencies responsible the microwave hearing effect, which occurs with exposures well below SAR limits and perhaps is particularly sensitive to other frequencies or signal patterns that could explain other reported physiological effects.

There is no conflict between SAR and the uw hearing effect - you simply have to average over a small enough volume. The heating involved is tiny in terms of energy (and temperature change, according to the linked WP page) - so in terms of safety, there is no concern. Unless I'm missing something? GyroMagician (talk) 21:14, 25 June 2013 (UTC)

What about resonance?

I think the intention is a broad criticism of using just thermal heating as the safety metric. If some people can sense MHE at low power levels, then there may be other problems that may be triggered in fine structures (and countering the notion that a bulk measure is appropriate). I'm ignorant of the field, but here's a firefighter's organization objecting to collocating cell towers with fire stations:

http://www.iaff.org/hs/Facts/CellTowerFinal.asp

I cannot speak the cited references weight, but there are plenty. For example, footnote 9: "Drs. Henry Lai and N. P. Singh of the University of Washington in Seattle have reported both single- and double-strand DNA breaks in the brains of rats exposed to radiofrequency electromagnetic radiation at an SAR of 1.2 W/Kg. DNA is the carrier of the genetic information in all living cells. Cumulated DNA strand breaks in brain cells can lead to cancer or neurodegenerative diseases."

Glrx (talk) 23:56, 25 June 2013 (UTC)

Gyro confabulates SAR limits set by law, which are for specified volumes and SAR limits of the measurer's choice of volume. I'm restoring the text, but adding "set by law" to clarify:

SAR limits set by law don't consider that the human body is particularly sensitive to the frequencies responsible the microwave hearing effect, which occurs with exposures well below SAR limits set by law and perhaps is particularly sensitive to other frequencies or signal patterns that could explain other reported physiological effects.--Elvey (talk) 22:54, 15 August 2013 (UTC)

And I am re-reverting. I usually try to be more gentle about reverts, but the proposed paragraph is pseudo-scientific nonsense, without any supporting evidence. The addition of "set by law" does not make the disputed paragraph any more acceptable. — GyroMagician — continues after insertion below

It's relevant to your comment, "you simply have to average over a small enough volume" - you can't do that given the "set by law" clarification, which is why I added it. --Elvey (talk) 01:48, 12 December 2013 (UTC)

Let's start at the beginning. SAR measures energy absorbed by tissue under some sort of excitation, usually but not exclusively electromagnetic RF. SAR is only intended to measure heating, and assumes no cooling effects (tissue perfusion, etc). SAR does not attempt to quantify any ill-defined damaging effects caused by undetermined mechanisms.

The microwave hearing effect page says the following (in the lede): "The generally accepted mechanism is the rapid (but minuscule, in the range of 10⁻⁵ °C) heating of the brain". Heating in the range of 10^-5°C is certainly not large enough to be a safety concern. You see a far larger change in temperature when you step outside each morning. Most standards (IEC, FDA, etc) assume energy deposition causing a temperature rise of approximately 1°C to be the safe limit. That is around 10,000 times the heating caused by the MHE. That the human body can sense such small changes is remarkable - which is why the MHE page remarks upon it. As I understand it, there is nothing special about the frequency range involved, in terms of absorption by the human body. But also note that frequency dependence is included in the definition of SAR, via tissue conductivity, which is most certainly a function of frequency.

Further, SAR is about heating caused by energy deposition. As such, the integral of energy deposited over some time period is interesting. The actual waveform, or signal pattern, is not relevant.

I do not understand what kind of resonance you think may be relevant here. But I also point you back to the tissue conductivity, which may show sharp peaks at some frequencies.

Of course, SAR has limitations as a safety metric - I am often in the position of arguing against it. See, for example, some of the work from Tommy Vaughan at the University of Minnesota. He argues, fairly convincingly, that we really need to be looking at tissue temperature, and that this correlates badly with SAR - but SAR always over-estimates heating, becuase it does not account for cooling or diffusion effects. GyroMagician (talk) 00:15, 17 August 2013 (UTC)

I'm all about not advocating pseudoscience. I'm not an advocate of closed-mindedness. Your argument is circular: the FDA assumes heating is the only issue, and the heating is not significant, so there's no issue. Do you accept that that there's strong evidence that the microwave hearing effect exists? What is it dependent on, if not the frequencies or signal patterns that you dismiss with your circular argument?--Elvey (talk) 01:48, 12 December 2013 (UTC)

For reference, this is the current text being discussed:

SAR limits set by law don't consider that the human body is particularly sensitive to the frequencies responsible the microwave hearing effect, which occurs with exposures well below SAR limits (as set by government regulations) and perhaps is particularly sensitive to other frequencies or signal patterns that could explain other reported physiological effects.<ref name="frey" />

Sure, the MHE exists. Do you accept that the mechanism causing it is understood, and that because the heating involved is so small, it does not present a safety concern? GyroMagician (talk) 00:29, 16 December 2013 (UTC)

I'm not aware that the mechanism causing it is understood, and if you are, why didn't you answer when I asked what it is? Competing theories explain the results of interferometric holography tests differently, per http://www.sciencemag.org/content/209/4461/1144.extract?sid=f514230e-1373-4da5-ad36-3689f428e21b . As to your section question, 'it' is MHE? I understand what non-ionizing radiation is. I also understand that there's quite a large body of evidence (and a bunch of nonsense too) indicating that there are adverse health effects. I think Larry Lessig's review correlating cell phone safety research funding and results is impressive, but inconclusive.--Elvey (talk) 20:12, 22 December 2013 (UTC)

CfD nomination of Category:Low-radiation smartphones

Category:Low-radiation smartphones has been nominated for deletion, merging, or renaming. You are encouraged to join the discussion on the Categories for discussion page.

I decided to add the proper notice here too. Please comment on the CfD page. Ivanvector (talk) 18:52, 31 December 2013 (UTC)

Improvements and deletions to the Mobile phone SAR list section

I have made the following changes: (1) removed the Phonearea.com text: it is not shown as a reliable source and it is not relevant that it offers a list for sale. Direct links to clearly reliable sources like the FCC are available and in fact are provided for the listing; (2) Removed the health disclaimer that was below the text. It is not relevant to a listing, and the disclaimer is not made by any regulatory body assessing SAR like the FCC; (3) That mobile phones can use a free OS is not relevant to a SAR listing; I have removed the text and will begin removing it from the listing itself (help appreciated); (4) A phone's status as locked or unlocked is not relevant to a SAR listing; I will begin removing it from the listing itself (help appreciated); (5) I think the "Original shipping mobile phone operating system and TUI" column should also be deleted, as I do not see the relevance to a SAR listing, except to identify a particular phone to readers . Is that necessary information? Comments invited; (6) I have improved the remaining text. --papageno (talk) 22:17, 1 January 2014 (UTC)

I have removed the "free OS" and "unlocked" columns from the table, as they are not relevant in the context of this article. The "model number" is probably not useful here (readers will know phones by their common name or model name), and I'm not sure that the "ID" and "link ID" columns are necessarily useful. I'm also skeptical that the TUI is necessary to list for Android devices, unless it affects the SAR measurement, but it's reasonable to think a reader would want to sort by OS so let's keep that. Also, I'm not familiar with all of the specific measurements listed (product specific use, etc.) but if they are to be included, it should say somewhere in the article how the measurements are derived or why the particular measurement is important. CENELEC measurements for EU market should be added as well, if they are reasonably accessible.

Since it's conceivable that any editor could come along and add any phone to this list, we should set a limit to inclusion. It's hard to say what the criteria should be, but I suggest perhaps a phone that was tested more than some number of years ago would be deleted from the list, in order to keep it to a manageable size. Is two years reasonable? Ivanvector (talk) 04:30, 2 January 2014 (UTC)

Note: a user has moved the entire list to a standalone article (again), as of this edit called Comparison of specific absorption rate for devices but changing frequently as before. Please continue discussion on that talk page. Ivanvector (talk) 14:25, 2 January 2014 (UTC)

Instead of struggling to decide on inclusion criteria for a list, then keeping a list up to date, let's avoid the problem all together by providing good information for readers on how they can look up the information themselves. We could write it generically ("Search your national regulatory authority…One should look for these things…Here are some explanatory notes…Two sources one might consider are the FCC and EU…caveat that models may be different in your jurisdiction…etc.") This still runs into issues about how to include a reasonable number of regulatory authorities in the main places in the world, but at least we could start with the FCC and EU, and perhaps a few other major English-speaking countries. --papageno (talk) 16:18, 2 January 2014 (UTC)

The only rating authorities mentioned in the article are the FCC (US) and CENELEC (EU). India uses FCC ratings but has other non-SAR criteria for rating, so I think at this point just including the FCC and CENELEC values is fine. Do we know how to look up CENELEC tests? I'm not opposed to the list - our inclusion criteria is "phones that are rated" which seems fine to me. If it gets too big we could revisit in the future. I'd like to see some CENELEC numbers though. Ivanvector (talk) 22:37, 15 January 2014 (UTC)

Comparision

I found unhelpful this article without the comparision between several devices (cell phones, WiFi, incandescent light bulb, power lines, etc.) and natural ocurrence (like solar radiation). But I only found the SAR for cell phones, and W/m² for the others. If anyone can get the data I'd appreciate it.

Eloy (talk) 07:15, 28 March 2014 (UTC)

SAR and eyeglasses

User JIA329 has made a few edits talking about SAR and eyeglasses. The reference provided is not accessible, so I have added a {{Verify source}} template. I can find this article online, which is perhaps the source. However, the article is poorly written, is a computer simulation without experimental confirmation (and so preliminary), and is not indexed in PubMed. Without more solid confirmation, the paragraph should be removed. --papageno (talk) 22:01, 15 April 2015 (UTC)

No comment about the quality or verifiability of the reference, but even if it is legit, it definitely does not belong in the header of the SAR article where it is currently placed. If the reference is verified and deemed to be relevant, I would suggest changing the "Criticisms" section to "Criticism and Limitations" or something similar and include it there. --EvilTwinSelf (talk) 11:14, 28 May 2015 (UTC)

Not just humans

Article: "Specific absorption rate (SAR) is a measure of the rate at which energy is absorbed by the human body..."

... except when it's absorbed by mice and rats in experiments. The calculations differ for these creatures (unfortunately, in a way that I do not have the expertise to edit into the article). 92.3.210.192 (talk) 16:18, 15 July 2018 (UTC)

Better inclusion of time averaging

SAR values are averaged over time. I do not believe this is adequately mentioned in the text. A footnote to the MRI table does mention six minute averaging, but there should be mention made in the lede, and in the mobile phone section. I believe the time averaging period is six minutes for mobile phones as well, per ICNIRP 1998 (reference is in the article). I also know that the time average period is six minutes in Canada. --papageno (talk) 21:48, 13 October 2018 (UTC)

EU regulatory landscape

I'm not an expert but my understanding is that CENELEC doesn't set the exposure limits--it sets standards for testing. My understanding is that the European Council sets the limit in the EU (i.e. 1999/519/EC, which EUR-Lex says is still in force), based on recommendations by the ICNIRP. My understanding is also that CENELEC sets standardization of methods of the measurement of SAR, not the limits. The publicly available 1999/519/EC document could serve as a reference for these two points: The introduction and conclusion discuss the fact that the document is based on the recommendation of the ICNRP and point (12) discusses the role of CENELEC. Thanks MyIpIsLocalhost (talk) 21:19, 28 February 2024 (UTC)