MTE Explains: Can Monitors Really Hurt You?

As far back as the 1970s, there was a distinct group of people who had concerns regarding the safety of screens. Fast forward to 2014, and screens are absolutely everywhere we walk. They are in bars, in hotels, at the DMV, and basically anywhere where they are useful as boredom deterrents. In the average person’s home, you’ll find one or two TV sets and an active monitor somewhere. The growing presence of screens in our lives has transformed their safety into an issue that some are taking so seriously, they are calling it a crisis. Whenever people are concerned, it is probably useful to help them understand what they are concerned about. And this is what we’re going to do!

How Monitors Vary In Safety

First of all, let’s explain why people are concerned: Monitors, like any other electronic device, emit non-ionizing radiation. While most of this type of radiation (we’ll call it “NI” radiation) isn’t going to give you instant cancer, long-term consistent exposure to some forms of it will damage your retina and might even go so far as to damage neurons.

Of course, I would be a little bit too optimistic by saying that no monitor will emit ionizing radiation. Cathode ray tube (box-like) monitors emit X-rays.

LED/LCD monitors do not suffer from this issue since they don’t use tubes to emit light with electron guns. Instead, they just emit light through diodes (small surfaces that react to electricity by transforming it into light) and change the color of each pixel through transistors and liquid crystals.

Why The CRT Concern Isn’t That Much of a Big Deal

monitorsafety-xray

It might sound like I’m minimizing the whole argument that X-rays are harmful, but I’m going to start off by saying that they are indeed extremely harmful and volatile. But the danger isn’t much of a concern with any device — television or not — that emits X-rays through cathode ray tubes. Here’s why:

  • The U.S. Food and Drug Administration (FDA) has issued a code that prevents manufacturers from creating television sets (and this also applies to computer monitors) that emit more than 0.5 milliroentgens of radiation per hour at a staring distance of 5 centimeters. That means that if your face is roughly two inches (the length of your thumb) away from the screen, you’ll get a very microscopic and negligible dose of X-ray radiation.
  • Today, the vast majority of CRT manufacturers don’t even touch the 0.5 milliroentgen limit. Their need to be energy efficient has significantly reduced the amount of radiation emitted to far below the already-harmless threshold described earlier.

Why You Should Still Be Concerned

The radiation emitted by your monitor is negligible. That’s awesome. But that doesn’t mean that the danger is clear. People still report getting headaches and pain in their eyes when using monitors for extended periods. If radiation isn’t the culprit, then what could possibly be causing these symptoms? These people simply can’t be imagining the pain!

The refresh rate of CRT monitors causes a constant flicker. If that flicker is more noticeable, it will cause the eyes to strain while trying to retain their focus on the image. To some extent, cheaper LED/LCD monitors also have this issue and it can really have a negative effect on the eyes.

monitorsafety-flicker

Your eyes are best used to look at objects that move fluidly throughout the world. Any strobe effect, no matter how small, can ruin your focus, forcing your muscles to strain. The long term effects of this condition haven’t been studied extensively yet, but it’s safe to assume that you might end up damaging your eyes in the long run.

Modern high-end monitors are able to retain their capacitor charge throughout the refresh cycle and do not flicker when refreshing. I highly suggest you invest some money in them if you’re concerned. My left-hand 27-inch monitor cost me $250 and that was about two years ago.

Conclusion

Let’s recapitulate on what we’ve covered so far:

  • All monitors emit radiation.
  • Some forms of radiation are less harmful than others.
  • The radiation that monitors emit is generally harmless.
  • Despite the low radiation levels, people can still suffer long-term damage or short-term headaches due to excessive exposure to flickering screens.
  • Higher-end monitors mostly eliminate the flicker effect, causing them to be easier on the eyes.

Even if you have a high-end monitor that is virtually flicker-less, I still suggest taking breaks once in awhile. You’re still staring at a bright artificial light source. Take a breather every hour or so.

If you have more helpful advice, or more questions, be sure to leave a comment below! We can all help each other!

10 comments

  1. Also you have to be mindful of the brightness setting of the monitor, and the surrounding ambient brightness, don’t let the difference be too large.

  2. Stop using white page backgrounds. Install tools (stylish, bookmarklets, user scripts etc) and configure the OS and the browser to show a black screen with white or gray text by default. (other combinations like white on blue work too)

    Because your eyes have to adjust to different light intensity the white light reduces vision outside the monitor. The large white area around the google search box is even more blinding than the average site. It has this interesting serenity to it when you gaze at it. The mechanism is simple, but I think most web designers dont know how it works precisely, all they know is that statistically people are more focused on the webpage or they are just imitating popular websites.

    After talking about it with some offenders I’m starting to think there is an addictive component to it as well. I imagine not seeing the piles of work on your desk or the many [unfinished] tasks around the house can be quite liberating. ha-ha

    Oddly enough I don’t know any games using bright white light to keep the user focused on the screen, maybe the user is already focused enough. It could also be the amount of time people spend playing games, eye strain would not be beneficial in the design.

  3. Human brain notices any CRT refresh rate lower than 60 cycles (hz) per second as flicker. It is the flicker that induces headaches. The lower the rate, the more flicker, the more headache. Most, if not all, CRT monitors have an adjustable refresh rate. All video cards, except for the really cheaply made ones, can handle different refresh rates. As the refresh rate is increased, the flicker becomes faster and less noticable. At 72 hz most people’s brains cease to notice it. If you are still using a CRT monitor, set the refresh rate to 72 hz or 75 hz and the vast majority of headaches will be eliminated.

    As gaby de wilde says, if you want to reduce eye strain, do not use high contrast on your screen. That goes for CRTs, LCDs and LEDs. Gray or pastel backgrounds are optimum. Also do not use your monitors in a completely dark room. Have some kind of an indirect light on any time you use a monitor.

    1. Very helpful comment! If I may, I would like to add to this by saying that I forgot to include a little word of advice that works for me:

      – Keep your monitor far from you, about a meter (3 feet) from your face. This allows the light from the monitor to scatter out and less of it is hitting your retina.

      I have a high-contrast super-bright 27-inch LED monitor with 3DTV capabilities. A second monitor sits next to it (21.5 Inch) that has almost as much brightness. I recommend sitting far from these, but not too far so as to strain your eye while trying to read.

      On some low-end monitors, turning the brightness down might actually minimize capacitor voltage to a point that they can’t keep up with the next frame. This causes a little flickering. Keep the brightness at an acceptable level, but not too low.

      Even though over-60-hz frequencies are easier on the eyes, you’ll sometimes catch a barely-noticeable flicker once in awhile due to the electron gun cycling at the same time your eye is still processing the image. As you said, 72+ hz solves this on CRTs. On LEDs, a better LED monitor solves this problem (60 hz is generally all most LEDs do, so just get a higher-end monitor that can keep its capacitors loaded correctly).

  4. From an actuarial standpoint, I think the risk of a monitor falling on your head is greater than the risk from the radiation.

    1. And that’s even with the monitor sitting below you. Someone could shout “fus ro dah” at the monitor, and that would be more likely than getting harmed by radiation.

  5. If the length of your thumb is only 2 inches, how did you type this story? (should say Width)

    1. 2 inches is roughly ever-so-slightly smaller than the average thumb length, starting from the hilt knuckle (the joint where the thumb starts). OK, I just measured mine for curiosity. It’s 2 inches + 5/8 of an inch. I wasn’t off by too much, but I’d say there’s a bit of a difference. :D

    2. If your thumb is 2 inches wide, you might want to get that looked at.

  6. When I used CRT monitors, I quickly learned that having the refresh rate set at 72 hz or 75 hz, was vitally important. I would get less headaches and eye strain, using those refresh rates. Now, that I have been using an LCD monitor, for the past several years, for me 60 hz is the best refresh rate. Plus, the settings for the refresh rate, is pretty well standard, for each resolution you prefer.

    I do know one thing, the picture is so much clearer on a LCD monitor, than on a CRT monitor. I have also, gotten use to the Widescreen monitors. The Regular square monitors just plain annoy me, now. I sit about 2 feet, from my monitor and for me, I do fine. Of course, my vision needs glasses, so, I have to sit in the optimal spot, to see well. :)

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