LED lights that appear to give off white light are still giving off blue light. The sun also gives off blue light.
Blue light has a higher frequency that affects the body in different ways than red or orange light. It wouldn't be harmful at all if the only source we had was the sun. But since it's everywhere it has become a health hazard.
One effect of blue light is that it destroys melatonin in your eyes. That's why turning on a light at night will wake you up if you were tired.