Mercury-Containing Devices (MCD)

Mercury-containing devices are electrical products or other devices, excluding batteries and lamps, that contain mercury as a necessary component for their operation. Some examples include mercury thermostats, thermometers, electric switches and relays, marine float switches and manometers. Due to the large quantities of this toxic heavy metal found in these products, mercury-containing devices are the largest source of mercury in municipal solid waste.

Mercury is among a group of pollutants called persistent bio-accumulative toxins, or PBTs. These pollutants "persist" in the environment, meaning that they do not break down or go away. Mercury cannot be destroyed, it cannot be combusted and it does not degrade. When mercury is deposited in waterways, bacteria convert it to methylmercury, which builds up in the tissue of fish. Contaminated fish can then be eaten by other wildlife or by people.

Mercury-containing devices present special disposal considerations due to the quantity of mercury they contain and since they are usually considered to be hazardous wastes when disposed of. The amount of mercury in a device is relatively large. For example, a thermostat can contain as much mercury as 75-100 fluorescent or other mercury-containing lamps. Mercury is a toxic metal that in its various forms can accumulate in living tissue and cause adverse health effects. When a device is broken and is disposed of in a solid waste landfill or incinerator, the mercury can contaminate the air, surface water, and ground water.

These types of devices, including those from households, have been banned from disposal at solid waste facilities, including landfills and incinerators, since January 1, 1996, in any quantity.