A few months ago several US universities and medical schools joined ranks to initiate a study regarding health issues being attributed to LED light. The problems were first recognized from LED exposure from consumer devices such as cellphones, iPods, and TVs. Now Gizmodo and the LA Times have published some of the first articles on one of the heath issues - the reduction in melatonin production due to exposure to LED generated light in the "blue portion of the non-visible spectrum".
It will be interesting - and important - to follow this concern as we move from very low output LEDs in consumer devices to very high output LEDs being promoted for consumer general illumination lighting, automotive and street lights.
Gizmodo - Experts: Kindle Helps You Sleep, iPad Causes Insomnia
LA Times - Reading on iPad before bed can affect sleep habits