I disagree about the order of which lights are healthiest, though, based on personal experience. This is the order I would say instead:
* Halogen, LED, incandescent, fluorescent.
Halogen, in my opinion, is by far the healthiest per lumen. It's only a problem if there's very much of it (as in more than one 60 watt equivalent lamp being on at the same time).
Fire light usually isn't bright enough to be of any concern; I don't know what symptoms I would have if it were brighter (other than being hot). It's relaxing.
Sunlight can cause me some issues, but it usually feels good.
Fluorescent light is an issue no matter how bright it is (I don't know why), and no matter how long an isolated exposure (but brighter and longer exposure does cause more issues). Less frequent exposure does make it feel a lot better. Fluorescent light can also give me issues that only begin hours after exposure.
Location: SW Idaho, USA
USDA hardiness zone: 6
Elevation: 2,260 feet Profile post