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Radar systems in cars - health hazard?

  1. Sep 7, 2014 #1
    Many modern cars now employ radar systems for intelligent cruise control as well as blind spot monitoring. Can the radar waves that are reflected back to the vehicle for these applications pose a health hazard to the vehicle occupants?
     
  2. jcsd
  3. Sep 7, 2014 #2

    jedishrfu

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  4. Sep 7, 2014 #3

    Drakkith

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    As Jedi said, no. The only way radio and microwaves can harm you is by transferring enough energy over a short enough period of time to burn you. This requires very high power outputs, much higher than the radar in a car puts out. For example, a car radar requires about 10 milliwatts of power to detect a man-sized object at 200 meters. These 10 mW's are not concentrated, but spread out over the entired area that the radar covers. In comparison, my microwave concentrates 1,000 watts of power (1,000,000 milliwatts) into a small volume to cook food. So you'd need about 10,000 to 100,000 times more power output from a car radar to pose a threat to a person.

    http://www.path.berkeley.edu/sites/default/files/publications/PRR-97-19.pdf (Page 15)
     
  5. Sep 7, 2014 #4
    The FCC regulates the radiation emission limits of vehicular radar, and the FCC rules are based, in part, on the max permissible human exposure to RF radiation. But isn't there continuing research and debate about the low-level effects of RF radiation? I am far from an expert on this topic. It's why I posed the question to the forum. Was wondering whether anyone with specific knowledge could address whether the current exposure limits set by the FCC might be too high. I have the option of including a radar based automatic braking system on a new car that I'm considering. I love the idea of additional safety on the roads. But not at the expense of possible health damage from the excess RF radiation. Just not sure what to do here. Thanks.
     
  6. Sep 7, 2014 #5

    Vanadium 50

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    You do realize the same FCC limits govern the four radio transmitters in your tires, don't you?
     
  7. Sep 7, 2014 #6

    Dale

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    There is debate about the risk of RF exposure. There is not debate about the risk of automobile accidents. It makes sense to accept a risk which is so small that it may not even exist in order to mitigate one of the largest risks of modern life. That holds even if you take a very alarmist stance on the risks of RF.
     
  8. Sep 7, 2014 #7
    From a physics standpoint, there is absolutely no reason to believe that the low frequency EM waves in radar will hurt a person except the way that Drakkith mentioned. The frequency determines the energy per photon and low energy photons cannot do the sort of tissue damage that causes cancer.

    It is possible, since human beings are such strange, complicated collections of particles that maybe certain groups of cells behave in a way that we can't model with our current understanding of the human body. There is no reason to think that this would be true, but you can't really 100% be sure that it is false. The only way to test this is to get very large samples and see if there is a correlation between more low frequency EM waves and cancer or other health issues.

    So far, studies using large samples regularly conclude that there is no risk. There have been some recent studies that have said increased cancer risk couldn't be ruled out. I only know about one and it had a small sample size. My recollection (I could be completely wrong about this, check it if you are interested) of the recent study that caused the WHO to change its wording is that they were concerned with cell phones increasing the growth rate of tumors for people who already had a tumor.

    So, to the question do radio frequency (specifically cell phone frequency, even though that's not your question, it has been studied a lot) EM waves negatively impact your health:

    Physics says "not in anyway that we can imagine"

    Medical research say "not in most of the ways that we have tested, but maybe a little bit. Plus we will never be done testing all of the possible ways"

    Personally, I am much more worried about dying in a car accident.
     
  9. Sep 7, 2014 #8

    Drakkith

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    Not really. The debate is mostly from people who claim that a few studies show a link between RF radiation and health risks. The problem is that these studies are typically ambiguous in their findings and narrowing down a health risk to a specific cause is extraordinarily difficult. There's simply too many variables. Still, it's always possible that RF radiation is having an effect, so the FCC regulations are necessarily well on the conservative side.
     
  10. Sep 7, 2014 #9
    DrewD, thank you in particular for your detailed response. Quick follow-up, seeing that you raised the issue of cell phones. If you know, how does the radiated energy levels compare between a cell phone and the energy or reflected energy of a car based radar system, all of which operate in the 76-77 ghz band?
     
  11. Sep 7, 2014 #10

    davenn

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    Drew

    76GHz isn't exactly low freq :wink:
    Cancer isn't the main risk from non-ionising radiation such as RF
    Tissue heating is much more of a concern. Also some parts of the body, eg. the eyes, are
    quite susceptible to low but concentrated power levels eg. from the end of a waveguide

    I have had personal and a painful lesson with that

    but that said earlier posts answered the original question adequately
    The resulting few microWatts from a widely dispersed signal isn't going to be of any concern

    Dave
     
  12. Sep 7, 2014 #11

    Drakkith

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    A cell phone typically transmits from 100 milliwatts up to a few watts. I'd guess that the reflected signal from a car radar is going to be in the micro to nanowatt range.
     
  13. Sep 7, 2014 #12
    FYI - The FCC rules allow for a peak power density of 279 µW/cm² at 3 meters (peak EIRP of 55
    dBm) for vehicular radar systems regardless of the direction of illumination. Davenn (and others), I'm assuming that your answer would be the same with this specific power information.
     
  14. Sep 7, 2014 #13

    Dale

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    You are completely missing the most important point.

    All of life is risky. There is nothing that you do that does not carry some risk, including doing nothing. The question is to evaluate the risks compared to the rewards. Here we are comparing between the risks of increased RF exposure and rewards of decreased automobile accident exposure. That comparison is so extraordinarily one sided that the conclusion is obvious.
     
    Last edited: Sep 7, 2014
  15. Sep 7, 2014 #14

    davenn

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    couldn't agree more !

    Dave
     
  16. Sep 8, 2014 #15
    *lower frequency than the EM radiation being emitted by a cat
     
  17. Sep 8, 2014 #16
    And it is possible that one of those risks doesn't even exist.
     
  18. Sep 8, 2014 #17

    A.T.

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    Has this been shown already?
     
  19. Sep 8, 2014 #18

    davenn

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    HUH ???

    have no idea what that is even supposed to mean ??
     
  20. Sep 8, 2014 #19

    jbriggs444

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    Presumably infrared radiation in the neighborhood of 30 Thz.
     
  21. Sep 8, 2014 #20
    Also less dangerous than owning a dog? Ok, ok, I get it.

    All kidding aside, because the radar emanates horizontally from the front and rear bumpers of the car, wouldn't only a tiny fraction of that energy make it back to the car anyway, with the majority of it being dispersed in other directions at the speed of light? If so, the theoretical RF risk is to those outside of the car rather than inside of the car anyway. Is this an accurate description of the way radar waves propagate and are reflected?
     
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