Why do fluorescent light bulbs contain dangerous amounts of Mercury and why should people avoid at all cost breaking one?

Mercury in the form of a low pressure vapor is used in fluorescent light bulbs. The mercury vapor is excited by electricity supplied to the bulb and emits short wave-length ultraviolet radiation, which is contained within the bulb and converted to visible light by the fluorescent materials with which the inside of the bulb is coated. Even in older bulbs that used relatively large amounts of mercury by today's standards, a single bulb did not contain "dangerous" amounts of mercury. However, the mercury from numerous bulbs, all released in the same place, could result in contamination of a space or landfill, or development of airborne vapor levels greater than permitted by various exposure standards. This is why low-mercury bulbs were developed. Unfortunately, compact fluorescent bulbs, which are now replacing incandescent bulbs, require greater amounts of mercury than conventional low mercury bulbs do. Many people are concerned about releasing any amount of mercury, no matter how miniscule. As a result, mercury is often described in popular literature as "dangerous Mercury" and any amount is thought to be immediately dangerous. This is not the case. This viewpoint, however, also leads people to think that breaking a fluorescent bulb should be "avoided at all cost." "At all cost" can be a very high cost should not be applied lightly. Breaking a single bulb in a home or office is not a disaster and does not require a HazMat Team to respond for clean up. Simply sweep it up carefully using brush or broom, to avoid being cut, place the waste in an appropriately closed container and discard in a way that will prevent others handling the waste from being cut. Some of the fluorescent materials coating the inside of some bulbs can interfere severely with the healing of a glass cut, and this is actually the most important immediate hazard associated with a broken fluorescent bulb. Where numerous bulbs are being broken, as in recycling operations, the potential hazard from the total mercury present is real and should be addressed through the proper design of the facility, through application of proper ventilation and cleanliness procedures, and perhaps through the use of respiratory protection and professional exposure assessment and control.