Are Blue LEDs bad for peoples eyes?

Blue LEDs are bad for you
Hello,
We have just nearly won a contract to supply color changing LED lamps to the local park.
However, the local council have said that since blue is one of the colors…..we must first prove to them that the brightness of the blue phase is not enough to damage peoples eyes. They want us to provide a math calculation showing the nearest possible distance to someone’s eyes, and then prove that our lamp will always keep the blue phase dim enough not to damage peoples eyes. It seems ridiculous. Surely Blue Light isn’t any more of a danger to eyes than any other color?
All you can find on the web is trash stories like this…
https://metro.co.uk/2013/12/09/led-lights-should-we-worry-about-damage-to-our-eyes-4220937/

They may be overly cautious because blue wavelength is close to ultraviolet light. Maybe they had (or heard about) an incident of blue lamps sending UV light. Arc welders who expose their eyes to flashes of UV light later feel a headache sensation behind the eyes.

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The 'eye-ache' also happens to beachgoers who see sunlit objects all day.

Can cause cataracts.

LED lights are (reasonably) monochromatic; I do not think any blue LED will emit any detectable amount of UV.

Human eye is less sensitive to blue; even if you turn up the intensity, people will not notice the difference.

Eye damage (say cataract) is mainly caused by UV (and partly visible) light - but do not forget that for most it takes 50-60 years before it shows up. Your LED lights perhaps will stay for a max of 5-10 years.

The main cause is damage to proteins (in the eye) and is caused by UV light in the range of 240-260nm (there are many other factors)

If you are using sunglasses (that claim to block UV), the outside world looks more bluish.

To be effective, the blue phase must be very bright else it will appear very dim (because of our eye response curve).

As far as I know, laser safety regulations (e.g. IEC 60825) basically apply also to LED lights. There are some formal requirements of luminance density to be kept. The limit values are wave length dependent, I'm not aware now if the spectral range of blue LEDs has different limits than e.g. green or red.

Without collimating optics, luminance density of LED chips is much lower than lasers, despite of a quite high optical power. There shouldn't be a safety problem except on short distance.

What's the problem of doing the calculations?

What's the problem of doing the calculations?

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The problem is that there isnt an official, universally accepted calculation.

There is the argument that shorter wavelength light carries more energy but that makes assumptions about the original power delivered to and emitted from the source. In reality, if you are making decorative lights with a reasonably well balanced 'perceived' color range and not intending to dazzle anyone with brightness, there is no danger whatsoever. To argue that blue light is dangerous would be like warning people not to look at the sky.

If you have to put together a risk analysis, I would include the spectral distribution curves for the LEDs to demonstrate that insignificant harmful radiation is emitted.

You could point out that they are almost certainly changing street lighting to white LEDs which emit just as much and possibly quite a bit more blue and UV light.

UV itself certainly is dangerous and ironically, most 'super bright' LEDS of any color use a UV source to stimulate a phosphor to produce their light. I use UV here to sterilize my incoming water supply but with a 40W mercury vapor lamp and it is well shielded in a metal casing.

Brian.

In the last few years, optometrists are urging people to get glasses with blue tinted lenses to reduce the damage to the retina from ultra violet and blue light, especially from LED lighting.

https://www.macular.org/ultra-violet-and-blue-light

During my recent visit to my eye doc, he just returned from an international seminar where this issue was discussed and apparently agreed upon.

E-design said:

In the last few years, optometrists are urging people to get glasses with blue tinted lenses to reduce the damage to the retina from ultra violet and blue light, especially from LED lighting...

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LED lighting is relatively recent and very few (perhaps none) studies (most of them are relatively long term studies) are reported in peer reviewed journal. I simply looked up in scopus- you can also see in pub-med.

it can cuse damage to our eyes. it is because of the colour temperature emitted bye blue led light. Our Eye ratin can resist upto 3000K colour temperature but the blue led exceed this value and is upto 4000K colour temperature which is no doubt harmful to our ratinal cell.

Long term, blue LEDs are likely to have issues. In terms of acute exposure, this is unlikely. People can look at the sun and not have immediate harm.

I would suggest proposing a different metric. For example, comparing the blue exposure of the LED at normal viewing distances and durations to the equivalent blue levels in common monitors/tablets or various lightbulbs. This could allow you to claim the blue leds are no worse than short-term exposure to normal monitors or lightbulbs.

This is not entirely ideal due to the difference in pupil dilation in natural lighting vs other cases.

MD_SHAHRUKH said:

it is because of the colour temperature emitted bye blue led light.

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Color temp of monochromatic light is a meaningless idea;

Our Eye ratin can resist upto 3000K colour temperature but the blue led exceed this value and is upto 4000K colour temperature.

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What is the color temp of normal daylight?

As everyone knows, sun light at sea level still includes UV A and UV B, in other words spectral components below 400 nm. Blue leds with 430 nm center wavelength have also some UV A below 400 nm, leds with 465 nm center wavelength don't. In any case the radiation is less aggressive than sun light.

The approach I would follow, in addition to all the other great suggestions above, is to obtain (from the vendor) the spectral output of the proposed LED.

As others will have correctly noted, the amount of UV A emitted by the LED will be a minute fraction of total light output. For UV B (the real concern) with its shorter wavelength, the total emission may be negligible.

In any case, I suspect that LEDs with blue-tinted lenses will absorb the vast majority of spurious UV emissions. Think of it as a low pass filter.

schmitt trigger said:

The approach I would follow, in addition to all the other great suggestions above, is to obtain (from the vendor) the spectral output of the proposed LED.

As others will have correctly noted, the amount of UV A emitted by the LED will be a minute fraction of total light output. For UV B (the real concern) with its shorter wavelength, the total emission may be negligible.

In any case, I suspect that LEDs with blue-tinted lenses will absorb the vast majority of spurious UV emissions. Think of it as a low pass filter.

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Most blue LED sources do not emit any detectable UV; I just have one article right now https://www.advancedaquarist.com/2012/3/aafeature but you can find many more.

I consider them practically monochromatic- comparable to using a color filter- but anyway it is best to refer to the published datasheet from the manufacturers. But there are violet LEDs too and they are much closer to UV.