Overview of Hazards

Elemental or metallic mercury vapor is highly toxic when inhaled. Although the vapor pressure is not very high at room temperature (0.0012 mmHg), the vapors emitted from open metallic mercury pose a serious inhalation hazard. Heating mercury dramatically increases its evaporation and the potential for exposure. Prolonged or repeated exposure can cause severe neurological damage and death. Early symptoms of mercury poisoning include fine tremors in the fingers, eyelids, and lips. Other symptoms include neurological manifestations such as sensory impairment (vision, hearing, and speech), disturbed sensation, and a lack of coordination. Such symptoms may not be felt for many months or years. Acute mercury poisoning can result in fever, fatigue, and respiratory distress. 

Note: Organic mercury compounds are even more toxic than metallic mercury. They are readily absorbed through the skin and are also toxic when inhaled. Dimethylmercury is one of the most toxic mercury compounds. It rapidly penetrates most glove materials; a few drops on the skin can be fatal. The guidelines in this document are NOT sufficient for safely handling organic mercury compounds. A standard operating procedure should be developed for the use of organic mercury compounds in the laboratory.

Eliminating the Hazard

Replace devices that contain mercury with safer alternatives whenever possible. 

Replace mercury

• thermometers with alcohol or digital thermometers,
• gas-bubblers with oil bubblers (a check valve can be installed to prevent accidental air contamination of inert manifolds when using an oil bubbler),
• pressure gauges with electronic gauges.

Safe Handling

Wear standard laboratory attire, i.e., a lab coat, clothing that covers the legs, close-toed shoes, safety glasses and gloves (nitrile or nitrile rubber) when handling mercury.

Mercury should be used only in closed systems to prevent exposure to vapors. Use secondary containment for vessels containing mercury to capture spills. Handle and place vessels containing mercury only on a smooth solid surface that can be cleaned easily should a spill occur. Porous and soft materials (concrete, carpeting) often cannot be decontaminated and should be disposed of after contact with mercury. 

Do NOT use mercury thermometers in ovens. If the thermometer breaks, the heat will lead to dangerous concentrations of mercury in the air. Use additional caution when placing or storing mercury thermometers to reduce the risk of breakage. 

Emergency Procedures

Accidental Exposure

A short, one-time exposure to metallic mercury usually does not cause any health effects. If symptoms of acute or chronic exposure occur after exposure (even months later) seek medical attention, and inform the doctor of the mercury exposure.

Skin contact

Wash the affected area thoroughly with soap and water. Brush underneath fingernails if hands were affected.

Eye Contact

Use the eyewash to thoroughly rinse the eye.

Inhalation

If large amounts of mercury vapor were inhaled, seek medical attention immediately.

Spill Procedure

A spill kit for mercury must be available if metallic mercury is present in the lab. The directions provided in the kit should be followed.

Spilled metallic mercury forms little spheres that roll into corners and cracks in the floor. If not completely cleaned up, mercury vapor will continue to be released into the air. 

Mercury vapor released from mercury drops spilled onto a carpet was visualized by using a short-wave ultraviolet light source and a fluorescent background. Screenshot from a video by Bowling Green State University.

Use mercury-absorbing powder from a commercial spill kit to cover the spill area. The powder forms an amalgam that does not emit mercury vapor. Make sure not to miss mercury droplets that have rolled further away. Sweep up the amalgam and collect it in a heavy-duty plastic bag. Close and label the bag as “waste–mercury debris”. Most spill kits also contain a mercury indicator to check if the spill site is clean. 

Do NOT use a regular vacuum cleaner or Shop-Vac® to clean up mercury spills. Doing so will emit toxic mercury vapor in the immediate area and contaminate the vacuum cleaner.

Storage

Store metallic mercury in tightly closed, sturdy containers that do not break easily. Keep it away from incompatible material such as strong oxidizing agents, ammonia, azides, and copper. 

Disposal

Dispose of all waste containing mercury and broken mercury thermometers through DRS. Place broken thermometers into a sealable container such as a wide mouth polyethylene jar with a screw cap. If the thermometer is too big to fit into a container, place heavy tape over the broken ends and put it into a heavy-duty plastic bag. Label as “Waste–broken mercury thermometer”.

Place metallic mercury into a polyethylene container in good condition (no cracks or holes.) The maximum weight per container is 20 pounds (approximately 670 ml). Do not mix with amalgams or mercury compounds.

Links and References

Centers for Disease Control and Prevention:
http://emergency.cdc.gov/agent/mercury/mercelementalcasedef.asp

Current Trends Acute and Chronic Poisoning from Residential Exposures to Elemental Mercury --- Michigan, 1989 – 1990:
http://www.cdc.gov/mmwr/preview/mmwrhtml/00014464.htm

OSHA Safety Hazard Information Bulletin on Dimethylmercury
https://www.osha.gov/dts/hib/hib_data/hib19980309.html

Video from Bowling Green State University making mercury vapor visible:
http://www.youtube.com/user/MBB1961