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Comment by topspin | Hacker News Reader

Please provide a reference for that 1.4W/kg figure. 4.5kg human head would need 6.3W to see 1.4W/kg. A cell phone such as a pixel 6 is 2W and that power isn't all pointed directly at the head.

I've found a FCC limit of 1.6W/kg. That's a limit, not what is actually experienced.

Ok, so here is a list of mobile device figures: https://emfadvice.com/sar-ratings-radiation-levels-smartphon...

Highest listed is One plus 7t Pro at 1.394W/kg.

That's in the same order of magnitude as these as these NIH results. Perhaps if you need to use a mobile device for most of your waking hours try to keep it away from your head. Otherwise it's probably not a concern.

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Reference:

https://support.google.com/pixelphone/answer/10937646?hl=en

SAR is sort of a "maximum power density" measurement. It's not claiming to expose your entire head to that power density, just a small ~10 g measurement portion.

That's in the same order of magnitude as these as these NIH results.

Yes. This is worrisome. The FCC limit is 1.6W/Kg.[1] Neural damage was observed in mice at 4W/Kg. Several high-end smartphones from Apple and Google get above 1W/Kg.

Those are worst-case numbers for smartphones, says the FCC. Average values are lower. Worst case for cumulative transmit energy would probably be sustained heavy upload traffic, such as streaming outgoing HD video. Transmit power is highest when near the range limit for a cell tower, since the handset increases power when more range is needed.

[1] https://www.fcc.gov/general/specific-absorption-rate-sar-cel...

check out the works cited of TFA, many of them involve 1.4-1.6W/kg SAR

>Transmit power is highest when near the range limit for a cell tower, since the handset increases power when more range is needed.

Yeah, in addition to the inverse square law, devices also have a higher noise floor from adjacent devices broadcasting at higher power.

This is why banning microcells to "stop the dangers of 4G from harming our children" just increases the Tx power and SAR by orders of magnitude. But you can't argue with these people.

You can't divide by 4.5kg as the distribution of power into the human head is not homogeneous. It's going to be much much higher adjacent to the ear.

In any case this is burst power during very high bitrate use such as 4k video, loading webpages, or pulling app/os updates. No ones phone is going to push a watt during voice calls. More like a few mW.

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