I guess it all depends on what you consider safe.Fluorescent lightbulbs have been around for quite some time, and although they have improved drastically over time quality-wise, the technology is still pretty much the same.
- The tubes themselves contain mercury vapor, along with a few other gases.
- They also have a phosphor coating (the white powdery stuff on the inside of the glass), which is what gives off the light.
- The mercury vapor actually emits UV light that makes the white powdery stuff glow.
So in normal operation, I suppose the only by-product that one could consider harmful is UV radiation. It's not much, so I wouldn't be worried about it.
- If the lamp itself breaks, sure -- there is mercury inside that could be considered harmful ... but, again, it's not that much.
- I imagine the old-style thermometer the nurses would use when I was in grade school had much more mercury in it than a CFL.
LEDs have come a long way over the last few years and the technology is growing at a very rapid rate.
- My guess is that in another 5 years or so, compact fluorescents will be a thing of the past.
- LEDs are more efficient, will come down in price and will last much longer.
The other thing I'll mention about CFLs is that they're not as great as many people make them out to be. Read the packaging closely some day. Even though it might say in large print on the front of the box that it will last 8,000 hours, in small print somewhere, it will say that you need to leave the lamps on for 3 hours at a time or something crazy like that to reach that level of efficiency. If you turn CFLs on and off frequently, they don't last as long.
For more information:
Also, read David Bergman's "How energy efficient are "Xenon" halogen bulbs in light fixtures?"