Compact Fluorescent Lighting (CFL) and Mercury

Concern over mercury contained in Compact Fluorescent Lighting (CFL) might lead you to decide against adopting this energy-saving light source. This article explores the issue to help you make an informed choice.

Mercury and Health Risks

The most common way mercury affects our health is in the form of methylmercury. Microorganisms convert inorganic mercury in the environment to methylmercury, an organic form that is readily absorbed in animals. The most common link to humans is by eating fish and shellfish, where mercury has ‘bioaccumulated’ at the end of the aquatic food chain. Once ingested, it ends up mimicking amino acids and is freely transported throughout the body where it can harm the brain, heart, kidneys, lungs, and the immune system (to name a few) . The US Environmental Protection Agency (EPA) and Food and Drug Administration (FDA) have released a joint advisory on reducing mercury exposure from seafood consumption. How we release mercury into the environment has a major impact on this common form of mercury in our food chain.

A less common path to exposure is inhaling mercury vapor from sources like broken CFL bulbs or old-style thermometers. While mercury vapor is not as readily absorbed as methylmercury, it can pose a health danger as well. Several US government agencies have recommended exposure limits. For example, the National Institute for Occupational Safety and Health (NIOSH) recommends limiting exposure to mercury vapor densities to less than 50ug/m3 for up to a 10-hour workday.

Sources of Mercury

Mercury is a naturally occurring element, usually locked up in minerals. Natural phenomenon like volcanic activity can release mercury into the atmosphere where it eventually finds its way into aquatic environments. About 1/3 of atmospheric mercury is from these natural sources. The remaining 2/3 enters through human activity (anthropogenic causes).

While waste disposal, cement production, non-ferrous metal and gold production can liberate mercury into the environment, the majority of anthropogenic atmospheric mercury comes from burning coal to produce electricity. Almost half the electricity generated in the US relies on coal.

The EPA estimated in 1999 that the total annual coal deliveries to US power plants contain 75 tons of mercury. Approximately 50 tons of this was released into the air. Burning coal to generate electric power releases, on average, 0.012 mg/kWh of mercury into the atmosphere. This translates to releasing over 1kg of mercury to power 1 million 60W incandescent bulbs for 4 hours every day for 1 year (also releasing over 58,000 tons of carbon dioxide ‘greenhouse’ gas using the EIA US national average of 1.34lbs/kWh).

Mercury in CFL bulbs

All fluorescent lights use phosphor-coated glass tubes with electrodes at each end. The tube contains mercury vapor which emits ultraviolet light when the electrodes are energized. The light we see comes from the ultraviolet light stimulating the phosphor to emit visible light. This is fundamentally different from incandescent bulbs which use heat to generate light (which is less energy efficient). CFL bulbs contain a small amount of mercury, typically less than 5mg, sealed in the spiral-coiled glass tube. This is equivalent to a 0.89mm diameter drop at room temperature; about the size of a small sand grain or tip of a ballpoint pen. In comparison, a standard four foot T-12 fluorescent tube contains about 12mg of mercury. In all cases, the mercury is necessary to generate light.

The Net Impact of CFL Bulbs on Environmental Mercury

The most relevant local, short-term impact occurs when a CFL bulb breaks and releases mercury vapor into a room (this has always been true for traditional fluorescent tubes too). The EPA has released recommendations for clean-up of broken fluorescent lamps which focus on minimizing the amount of mercury that gets into the air in the room. Several studies have shown that the release rate for mercury is highest when the bulb is first broken, due to the ready availability of mercury vapor, and then tapers off. A study by the Maine DEP concluded that air-born mercury from broken CFL’s can be reduced by:

  1. Opening windows for 15 minutes to vent the room.
  2. Avoid using a vacuum cleaner, which tend to accelerate dispersion of mercury into the air.
  3. Storing the broken pieces in a good air-tight container like a glass jar with a metal lid and gum seal prior to recycling.

The more global, long-term impact of CFL bulbs is their influence on how mercury makes its way into the food chain. Since coal-powered electricity generation accounts for most anthropogenic mercury release, the greater energy efficiency over incandescent bulbs reduces the need to build additional plants that would release even more mercury. The disposal of used fluorescent bulbs also impacts environmental mercury. The EPA estimates that a typical CFL replacement for a 60W incandescent would result in 1.8mg of net released mercury, versus 5.8mg net release mercury for the incandescent- a more than 3X savings. When the CFL is recycled, this becomes a 4.6X savings. If the electricity was not generated by burning coal, then the CFL introduces 0.6mg of mercury if not recycled compared to nothing from the incandescent. The EPA estimates that 14% of the mercury content from a used bulb ends up released when broken in a landfill; most of the mercury ends up bound to the phosphor coating on the glass.


If your electricity generation is coal-powered, you will help reduce environmental mercury by switching to CFL bulbs. To get the full benefit, make sure you recycle all used CFL bulbs- this has become much easier now that Home Depot is now offering in-store recycling. As electricity generation creates cleaner coal-powered sources and better alternatives, it will become even more important to properly recycle used CFL bulbs.

Knowing what to do when CFL bulbs break and minimizing this occurrence by using precautions like:

· Using drop clothes during changes

· Handling bulbs only by their base

· Avoid using CFL bulbs in fixtures that might tip over and break

Hopefully this article has helped you understand the issues with mercury in fluorescent tubes and CFL bulbs so you can decide on their use in your home.

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