Quote:
Originally Posted by [M]
I think it is free of any harmful chemicals.
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White LEDs consist of a blue diode (usually InGaN) with a coating of synthetic garnet (Yttrium-Aluminum-Garnet) over the diodes in that absorbs some of the naturally blue light coming out of the diode and emits it at a lower energy state (longer wavelength, yellowish specifically). The combination of these wavelengths appears white to our eyes.
The coating, in and of itself, isn't toxic (and it's encased in epoxy besides). It's the massive quantity of acid and mercury that is used in the mining/extraction of Yttrium that cc700 is referring to. Mining in general is a very dirty business, mining for rare earth elements is an order of magnitude worse.
The ironic thing is, "cool white" LEDs use less Yttrium than "warm white" LEDs, and as such, are better for the environment.