Our original light source, the sun, gives off the entire spectrum of visible light in every color of the rainbow. All of these wavelengths combined looks to us like white light. We all know that being outside in the sun feels good, and there are a number of reasons for this; turns out, one of them is the kind of light the sun emits. The full spectrum is protective; I’ll get to this in a bit.
Incandescent light, the kind Thomas Edison invented, consist of an airtight glass container with a gas mixture, usually nitrogen and argon, and a tungsten filament inside of it. Electricity passes through the wire and results in a full spectrum of visible light, just like the sun. The problem is, they’re not very energy-efficient: ninety five percent of that electrical energy gets converted into heat rather than light. Halogen lights are technically incandescent as well, they’re just even less energy-efficient than regular lightbulbs and much more of a fire hazard. This is because the way the bulb is made and the gas inside the bulb (once iodine, now usually bromine) enables them to heat up many times hotter than a regular lightbulb.
The most common alternative to incandescent bulbs in most office and commercial buildings are fluorescent bulbs. The airtight glass tubes of fluorescent bulbs contain mercury vapor (see a problem here? Check out this article on heavy metals), which, when given an AC current (not constant, but subject to very fast pulses) excites photons to emit radiation at UV frequencies. This gets converted to visible light when it strikes a synthetic fluorescent substance called phosphor with which the tube is coated. The spectrum of the light produced depends on the phosphor, and it’s a challenge to attempt to create white light using phosphor. Some fluorescent lights tip toward the blue end of the spectrum and some towards the red end. This is why we all look a little sickly under the fluorescent lights of an office building.
Main problems with fluorescent lights:
- The flickering. This has been associated with migraines and headaches in sensitive people, and eye strain.
- The incomplete spectrum. Blue light suppresses production of melatonin, interfering with sleep. It’s also been implicated in retinal damage and, with long-term exposure, macular degeneration.
- The mercury. Although the U.S. Environmental Protection Agency (EPA) says the mercury in one fluorescent bulb is about 1% that found in a mercury amalgam filling or a glass thermometer, they’ve issued a 21-step set of instructions of what to do if you break one. Why? The mercury levels may be very low, but it’s mercury vapor in there. Highly volatile.
Light-emitting diodes (LED) are used in everything from your computer screens to traffic lights, and they are now becoming a more popular choice for general lighting as well. LEDs are semiconductors; there’s no filament, they’re highly efficient, and they last a very long time. Also: no flickering, and no mercury.
Main problems with LED lights:
- Still not a full spectrum. This is why it can disrupt your sleep to use your computer or your smart phone in the hours before bed. (There’s a program called f.lux you can download for free that will dim the screens, though, shifting light from the blue to the red spectrum.)
- The heavy metals. There might not be mercury vapors inside of LEDs, but the Journal of Environmental Science and Technology found lead and arsenic in LEDs in 2010, among other toxins.
- If you work in cubbyville and can’t get away from the fluorescent lights, make sure you get outside as much as possible. Go outside first thing in the morning and take a walk at lunch if you can. The sunlight will certainly help your circadian rhythm.
- It’s a good idea not to use your computer or phone before bed, but if you must, try f.lux.
- Don’t use fluorescent bulbs in your home. If you can skip the LEDs and use the incandescents despite the extra energy costs, do so.