Mercury in compact fluorescent tubes (CFLs) is a health hazard and therefore we should not use CFLs....at least that is the false message being spread by many people.
Yes, there is mercury in CFLs (typically less than 5mg), and yes, they need to be recycled correctly to ensure that the mercury (and electronic components) stay out of landfills. The thing is, the benefits of using CFLs and the associated reduction in mercury emissions far outweigh any issues associated with the mercury in a CFL.
So why do CFLs contain mercury? All fluorescent lamps contain mercury (compact fluorescents as well as conventional straight tubes). The mercury is excited by an electrical current which causes the mercury to emit ultraviolet light. The ultraviolet light stimulates phosphor in the tube which produces visible light. Interestingly enough normal fluorescent tubes have escaped the mercury stigma even though they can contain more mercury that a CFL.
What does coal have to do with it? The burning of coal to produce energy is one of the largest sources of mercury from human activity (in South Africa 80% of our energy comes from coal). This mercury enters the atmosphere and eventually lands in our water systems. Mercury entering into aquatic systems can be transformed by microbial action into methylmecury which bioaccumulates in the food chain.
Incandescent bulbs release more mercury into the environment than CFLs. When you take mercury emissions from coal into accout it turns out that a normal incandescent bulb results in more mercury being released into the environment than a CFL, even when a CFL is disposed into a landfill rather than properly recycled. The US EPA estimates that 1.8mg of mercury enters the environment from a dumped CFL while the use of an incandescent bulb results in 5.8mg (for 8000 hours of use). See the Energy Star's mercury fact sheet for their assumptions.
What about CFL breakages in the home? Breakages need to be dealt with carefully, but do not pose a serious hazard. Ventilate and have any people or pets leave the room. Follow the recommended clean–up guidelines in the EPA mercury fact sheet. There is an old and false story about expensive clean–up procedures which came about due to a misunderstanding – snopes.com has the full history of that story, which makes for interesting reading.
What do we need to do? Switch to CFL or LED bulbs wherever and as soon as possible. This reduces both energy consumption and mercury emissions which is good for our well–being. Consider LEDs where suitable – they contain no mercury and have a longer life span than CFLs (although they only available in certain light formats, provide a different type of light, and you need to compare their efficiency to CFLs). Correctly dispose of your CFLs (and LEDs) for recycling, as this keeps the mercury out of the landfills and allows it to be reused in new lights.
Please share this, blog about it, write newspaper articles, tweet (and retweet) it, stumble it, tell your friends, and explain it to anyone who does not know that using CFLs will actually reduce your exposure to mercury. CFLs help us to reduce energy consumption and keep our environment clean – let the world know.
 "Global Atmospheric Mercury Assessment: Sources, Emissions and Transport," UNEP
 UNEP mercury programme
Image courtesy of Energy Star.