I realized there are a couple of other things to mention, but so much of what I’ve been hearing relates to the health claims that I want to address that today and let the other things spill over into next week.
When the full-spectrum term was coined in the 1960′s it referred to both visible light and the invisible ultraviolet (UV) light. The health claims of full-spectrum lighting mostly revolve around the UV end of the range. All fluorescent light emits UV radiation, since it is the UV rays created by the mercury vapor striking the phosphor coating which makes a fluorescent light work. Full-spectrum lamps just emit more UV radiation than normal lamps.
The typical recommendation is to avoid as much UV exposure as possible. UV exposure has been linked to sunburn and skin cancers as well as cataracts in the eye. UV exposure also cause the degradation of textiles, paints, and architectural materials. Museums typically require all wavelengths shorter than 400nm to be filtered out of artificial lights.
- Technical info, you may ignore: Visible light is 760 nm to 380 nm, UVA is light wavelengths between 400 nm and 315 nm, UVB is light wavelengths between 315 nm and 280 nm, UVC is light wavelengths between 280 nm and 100 nm. Visible light is broken down as red from 760 to 610 nm, orange from 610 to 591 nm, yellow from 591 to 570 nm, green from 570 to 500 nm, blue from 500 to 450 nm, and purple from 450 to 360 nm. These are defined by the International Organization for Standardization in ISO 21348:2007.
Full-spectrum lighting to treat SAD (seasonal affective disorder): Using full-spectrum lighting does not fit into the standard treatment of SAD, which involves exposure of the eye to a white light source in a light box. The light box typically generates 10,000 lux and it is used for about 30 minutes. Lower intensities might be used for longer periods. At 10,000 lux, any light source will be effective to treat SAD. Most importantly, these light boxes shield out UV rays, which is the opposite of using full-spectrum lighting. Using full-spectrum lamps in normal overhead lighting will have no effect upon SAD treatment.
Full-spectrum lighting and vitamin D production: Vitamin D is important, but the production is stimulated by the UVB band (315 to 280 nm) of light. Full-spectrum lamps typically use phosphors to generate UVA radiation (400 to 315 nm), and they typically peak around 355 nm. You are better off eating fish and dairy products and–if you’re really worried–taking supplements. Various studies have been done showing exposure to full-spectrum lighting for vitamin D production is impractical. For example, to spike vitamin D production in your body you may need 30 hours continuous exposure to a full-spectrum lamp to get the same affect as 22 minutes of mid-day sunlight. Or, 8 hours of full-spectrum office lighting has about the same UVB exposure as 1 minute of direct sunlight.
Also, the UVB rays that are generated by full-spectrum lamps often don’t bounce off surfaces. That means that if you are hoping to increase your UVB exposure you will only get it when in direct line of sight from the lamp to your skin. Everything else is absorbed by the materials and clothing around you. That also increases the deterioration of those materials.
In summary, there really are no serious health benefits to using full-spectrum lighting.
