The L.A. Times had a front page article last Saturday about a proposed California law that would make it mandatory to buy compact fluorescent light bulbs to replace old incandescent bulbs beginning in 2012. The purpose of the new legislation, authored by Assemblyman Lloyd Levine, is to save energy. They compute that the difference in energy costs per year between the incandescent bulb ($9.20) and the CF bulb ($2.50) justifies the switch. If everyone used these new low-energy, long-lasting bulbs, electricity consumption would be slashed by 75% according to the article.
All of this sounds very good but nowhere in the article did it mention the one aspect of artificial lighting that matters most to me, i.e., whether or not the bulbs provide full-spectrum lighting. Until now, I had thought that fluorescent lighting was very bad for your eyes and that you could not get full-spectrum light or "natural light" from a fluorescent tube. I was wrong.
Let me explain what full-spectrum lighting is. The sun provides light in a fairly even distribution over the visible spectrum of electromagnetic waves. This is the light that our eyes evolved to see. We were not meant to spend our lives inside a dark cave (modern office building) coming out only for small periods of sun, or staying awake for very long past sunset. Of course, the sun's spectrum changes with location, the seasons, and time of day, and our eyes were also meant to soak up the sun's rays at various times throughout the day. Sunlight also provides a small amount of mid- and near-UV light.
The best artificial lighting would try to imitate what the sun can do for us. Full spectrum lighting is better not only for our eyes but for our general health as well. How can you tell if you are getting full-spectrum lighting? There are two numbers that will indicate the color temperature and the color rendering of any light source. The Correlated Color Temperature (CCT) is a measure of a light source's apparent "whiteness," yellowness (warmth), or blueness (coolness). This number is given in degrees Kelvin (K). If you use a good camera, you have probably encountered this number already. A flash will give you a cooler, daylight exposure than without flash in low light. Indoor photos taken under incandescent light will be very yellow. In the old days, there were different kinds of film you could use to counteract this. The sun's CCT can vary from 3600K (warm/yellow), to 4870K at noon, to 7100K on an overcast day, or to 25,000K (very cool/blue) in the Northwest sky. 5500K is considered "white" light from the sun.
The Color Rendering Index (CRI) indicates how well the colors of objects are rendered (reflected), using a light source at a specific CCT. Sunlight has a perfect CRI rating of 100. Note that this number cannot be compared with different sources that have different CCT ratings. An incandescent bulb may have a high CRI rating of 95 but still appear yellow because it's CCT is only 2700K. But generally, a light with a CCT of 5000K and a CRI of 80-89 will give excellent color rendering. To qualify as a "full-Spectrum" light, a bulb or fluorescent tube must have a CCT of 5000 to 7500K and a CRI of 90 to 100. Whether or not the artificial light also includes the proper ratio of mid- and near-UV light is another issue and a very thorny one.
OK, now try and find these numbers on the box of bulbs you are considering buying. It's not easy. Phillips assumes you are not interested in these technical details or couldn't understand what they mean if they gave them to you. GE offers a glossary of terms that does explain all this very nicely, but when you go to buy a particular bulb, you can't get the specifics. After much searching on the web, I found a few companies that will give you the full details and this is when I found that you can indeed purchase compact fluorescent bulbs that fit the definition of full-spectrum lighting. These bulbs are very costly, ranging from $10 to $50 for a simple 75W equivalent bulb. They are not available at your local Home Depot, at least not at mine, you must buy them over the Internet adding shipping costs to the total. If you are interested, you can get lots of info and the names of brands to consider from the Bates Method website store.
One major drawback to these fluorescent bulbs is that they contain mercury, although not very much. To dispose of them properly, they should be taken to a hazardous waste site (which I am not sure really solves the problem. It only pushes it on to someone else). And these bulbs don't fit some sockets and cannot be used with a dimmer switch. Currently, I have several lights with full-spectrum bulbs made with neodymium oxide, a rare earth element. These bulbs contain krypton gas and a chrome plated brass base that give them an earth-friendly life of over 3,500 hours. I am very satisfied with the results but may consider the CFLs when they need to be replaced.
But I still wonder if it is good to have the equivalent of noonday sunlight at 10:00 p.m. And what about UV light which is also important for our health? Most fluorescent bulbs have coatings to absorb the UV rays and many health experts think that this is good. But again, we were meant to soak up the UV rays all day long, too. And nature has ways of making sure we do not get too much of a good thing. (See Dr. Michael Eades's blog for Feb. 16, 2007 on the subject of Folate and Fun in the Sun.)
All in all, I think the best solution may be to insist on buildings with windows or skylights and at night to turn off the lights and go to bed early.