Blinded by Science blog 12: Mercury danger from home CFLs.

We’ve made it to the latter half of April and the weather seems to be finally turning.

Probably turning into this.

With the advent of spring and soon summer, the days are continuing to get longer so you’re probably not turning on lights as often as you did during the fall and winter.  So with my wonderful and obviously appropriate timing, today I will answer a question about compact fluorescent light bulbs (CFLs).

Steve P. asks, “I recently broke a CFL lightbulb in my house.  I know that CFLs contain mercury (although I am not sure what part contains the mercury).  How much mercury was I exposed to from the broken lightbulb?  How does this mercury exposure compare to mercury from eating fish?  Am I going to die?”

To answer this question, it’s probably a good idea to first explain what mercury is and why it is dangerous.  Mercury is a metal, though unlike other metals, it is found as a liquid at room temperature.  This property has caused mercury to be known by another name, quicksilver.

 

Nope. Wrong one.

There we go.

There are a lot of dangers associated with mercury and certain mercury compounds.*  Metallic mercury (elemental mercury), which is the type that is liquid at room temperature, does not tend to pass through intact skin and if swallowed, does not get absorbed readily by the gastrointestinal tract.  However, metallic mercury tends to vaporize quickly and it passes through the lungs into the bloodstream if you breathe this mercury vapor in.  On the other hand, organic mercury compounds like methylmercury are readily absorbed into the body through the gastrointestinal tract.  In general, they are not easily absorbed through intact skin, though there is a form, dimethylmercury, which can rapidly enter the body through the skin.

The nervous system is particularly susceptible to mercury, so health concerns related to mercury exposure include: loss of peripheral vision (methylmercury); impairment of speech, hearing or walking (methylmercury); insomnia (elemental mercury); headaches (elemental mercury); skin rashes (inorganic mercury); or memory loss (inorganic mercury) (1, 2).  Damage to the gastrointestinal tract or to the kidneys can also be the result of mercury exposure.

With regards to sources of mercury exposure, due to the nature of food chains and the way mercury is absorbed by fish, mercury can become concentrated in certain types of fish.  The higher on the food chain the fish is found, the more mercury found in the fish.  In fact, here is a handy table that shows the amount of mercury in various species of fish.  It is important to note that the type of mercury found in fish tends to be methylmercury, which is a highly toxic compound of mercury.  Eating small amounts of fish is unlikely to cause problems for the majority of people (though it is important to limit the amount of fish consumed that are relatively high in the food chain).  However, pregnant women are advised to stay away from certain types of fish during pregnancy because the mercury can cause problems for the developing nervous system.

Due to the physical requirements of creating CFLs, mercury vapor is necessary for the CFL to function.  There is only a small amount of mercury in each light bulb, about 4 milligrams on average.  And when these bulbs are broken, only a tiny fraction of the total mercury is released, though the longer you let the broken bulb stay there without cleaning it up, the more mercury is released.  In other words, as long as you clean up the broken bulb quickly (and according to the appropriate procedures!!), the amount of mercury released will not pose a health hazard.

Also, from what I can find, the type of mercury in CFLs is elemental mercury which is not quite as dangerous or toxic as an organic mercury compound such as the methylmercury found in fish.

So in conclusion, mercury is a dangerous compound, though the extent of the danger and the damage caused is based on the type of mercury compound and the route of exposure.  Methylmercury can be found in the tissues of some fish while small amounts of elemental mercury are found in compact fluorescent light bulbs.  A small percentage of what is found in these light bulbs can be released if the light bulb breaks, though it is not enough to cause worry (though be certain to clean up the broken pieces of the bulb properly and dispose of these pieces properly as well).

Overall, you have less to worry about from the mercury exposure from a broken CFL than you do from the mercury exposure from eating fish, and even that exposure should not cause you much worry as long as you don’t eat too much fish.

*Not every compound containing mercury is equally dangerous.  Ethylmercury, which can be found in thiomersal (thimerosal), has different properties from its more dangerous methylmercury cousin.  I would not be surprised if I get a question that requires me to go more in depth on this in the future, but for now, please understand that different chemical compounds have different physical properties (including toxicity), even if they contain some of the same atoms.