What is LED (light emitting diode) ? LED's disadvantages, problems, and effects on human beings

LED is the most recommended light source nowadays. Apart from light bulbs, it is also used in the background light of electronic display screens, such as your smartphone¹ and computer monitors/screens¹, etc.

As LED is not too hot and energy saving, it is greatly promoted and is used to replace other more traditional light sources, such as fluorescent tubes, curlicue compact fluorescent light bulbs, and incandescent light bulbs.

However, it is exactly because LED lights produce a fair amount of light in the blue spectrum⁴ (or called ‘blue light’), that they are so bright!

There is no free lunch in this world; we may be paying a price⁴ to use LED.

According to a research paper called ‘The Effects of Blue Light On Ocular Health’ ⁵, written by Elaine Kitchel of the American Printing House for the Blind, the wavelength of blue light is ‘near UV’ ^5: 
http://www.tsbvi.edu/instructional-resources/62-family-engagement/3654-effects-of-blue-light

On the other hand, according to another article ‘Blue light has a dark side’ by Harvard Health Publications of the Harvard University, “Those curlicue compact fluorescent light bulbs and LED lights are much more energy-efficient than the old-fashioned incandescent light bulbs we grew up with. But they also tend to produce more blue light” ⁴, please refer to: 
http://www.health.harvard.edu/staying-healthy/blue-light-has-a-dark-side

Concluding from different researches or articles (which are listed in the reference list at the bottom of this blog), “short wavelength LED street lighting ……legitimately raises the question of whether these new light sources are introducing as many problems as those they are claiming to solve” ³, such as blue hazard⁶, light pollution^2,6, night vision² in aging eye³, increase glare^2,3, poses threat to driving safety at night³ (because of the strong spike of light), “disruption of nature’s light cycles on all flora and fauna”², “may contain other hazardous metals such as lead and arsenic” ⁶, blue light even affects our sleep⁴, causes damage to the retina in eyes¹, etc.

So do have a look at the following article 6 and understand what is LED, which you will surely see or use everyday at close distance, and understand its disadvantages, problems, and effects: 
https://en.wikipedia.org/wiki/Light-emitting_diode

References：

1.      A website in Taiwan called '睛睛這一家', article '藍光是什麼？為什麼螢幕有藍光傷害? (2015-7-9)'

2.      Jim Benya editor: Blue light blues.

3.      Deborah Burnett (2009): Driving at night – how light affects the eyes of aging drivers.

4.      Harvard Health Publications (2012): Blue light has a dark side.

5.      Elaine Kitchel: The effects of blue light on ocular health.

6.      Wikipedia(2016): Light-emitting diode.