Revised October 1989

Mercury

TABLE OF CONTENTS

• HOW TO FIND OUT IF YOU ARE WORKING WITH MERCURY
• HOW MERCURY ENTERS AND AFFECTS YOUR BODY
• TESTS FOR EXPOSURE AND MEDICAL TESTS
• LEGAL EXPOSURE LIMITS
• REDUCING YOUR EXPOSURE
• RESOURCES

Health Hazard Summary: Overexposure to elemental (metallic) mercury most commonly affects the nervous system, causing weakness, fatigue, and loss of appetite. It can also damage the kidneys. In limited studies, mercury has been found to affect pregnancy or fertility in male and female laboratory animals. A major source of chronic exposure to mercury is from inadequate cleanup of spills.

HOW TO FIND OUT IF YOU ARE
WORKING WITH MERCURY

Odor and Appearance: Elemental mercury is an unusual metal because it is a liquid rather than a solid, and it slowly evaporates at room temperature. Mercury has no odor. Another name for elemental or metallic mercury is "quicksilver." This is the kind of mercury used in thermometers. Mercury can combine with other chemicals to form organic (carbon-containing) or inorganic mercury compounds. These other mercury compounds, such as might be found in contaminated fish, are not discussed here. This Fact Sheet deals only with elemental, or metallic, mercury in its liquid and vapor (gas) forms.

Jobs Where Mercury Is Used: Mercury is commonly used in dentistry, for the preparation of fillings; in laboratories and hospitals, as a reagent and fixative; and in medical instruments, electrical equipment, thermometers, barometers, pharmaceuticals, and some fluorescent light bulbs. It is also used in the chloralkali industry, the manufacture of glassware and jewelry, and the recovery of gold and silver.

Your Right to Know: Under the state and federal Hazard Communication Standards (California GISO 5194 and U.S. 29 CFR 1910.1200), your employer must tell you if you are working with any hazardous substances, including mercury, and must train you to use them safely.

If you think you may be exposed to hazardous chemicals at work, ask to see the Material Safety Data Sheets (MSDSs) for the products in your work area. An MSDS lists the hazardous chemical contents of a product, describes its health and safety hazards, and gives methods for its safe use, storage, and disposal. The MSDS should also include information on fire and explosion hazards, reactivity, first aid, and procedures for handling leaks and spills. Your employer must have an MSDS for any workplace product that contains a hazardous substance, and must make it available to employees on request.

This Fact Sheet is an aid for worker training programs. It does not take the place of a Material Safety Data Sheet.

HOW MERCURY ENTERS AND
AFFECTS YOUR BODY

Liquid mercury easily changes into a vapor. You are most likely to be exposed by breathing in mercury vapors, which are easily absorbed through your lungs into your body. Liquid mercury is not well absorbed through the skin. However, harmful absorption can occur through broken or damaged skin, or if there is lengthy skin contact.

Most effects of mercury exposure develop slowly over time. Symptoms usually occur only after repeated overexposure. These effects include insomnia, loss of appetite, nausea, weakness, and muscle tremors. Brief exposures to very high levels of mercury vapors can affect the lungs.

Nervous System: Long-term overexposure to mercury vapors can cause a number of symptoms. The first symptoms may be loss of appetite, fatigue, insomnia, and changes in behavior or personality (nervousness, excitability, and shyness). Later, more serious symptoms may include nausea, abdominal cramps, diarrhea, weight loss, weakness, and muscle tremors. Some of these symptoms have been reported after years of exposure to mercury at air levels slightly above the legal limits (see "Legal Exposure Limits"). When overexposure stops, these symptoms will usually go away.

Severe mercury poisoning can permanently damage the nervous system. Such damage may be accompanied by hallucinations, whole-body tremors, a tingling "pins and needles" sensation, pain, tenderness, numbness, and weakness. An interesting note is the past use of mercury in felt production. Felt hat manufacturers suffered from many symptoms of high-level mercury exposure, as witnessed in the Mad Hatter character in Alice in Wonderland, and the popular phrase "mad as a hatter."

Kidney: Long-term overexposure to mercury can injure the kidneys. In most cases, this damage is reversible and kidney function will gradually recover once exposure is stopped. No obvious symptoms are associated with kidney damage, unless the injury is severe. Special urine tests are used to detect this kidney damage (see "Tests for Exposure and Medical Effects"). Generally you will not have kidney damage if you do not have other symptoms of chronic mercury overexposure.

Lungs: Inhalation of very high levels of mercury vapors can affect the lungs, causing coughing, chest tightness and pain, difficulty in breathing, and pulmonary edema (fluid in the lungs). Fever, chills, nausea, and vomiting may also occur. If you develop these symptoms after an exposure to mercury, see your physician immediately.

Eyes, Nose, and Throat: Long-term mercury overexposure can cause increased salivation and inflammation of the mouth and gums. Repeated exposure to mercury vapors may also discolor the lenses of your eyes. This discoloration (usually brown) is a sign of mercury overexposure. It can occur with or without other symptoms of overexposure.

Skin: Prolonged skin contact with liquid mercury can irritate the skin and cause a rash that allows increased absorption through the skin.

Cancer: There is little reason to think that mercury could cause cancer, although that possibility has not been studied.

Reproductive System: The effects of metallic mercury on pregnancy and reproduction have not been studied thoroughly. When metallic mercury vapor is absorbed into your body, some of it is changed into another form, inorganic mercury. In limited studies, exposure of pregnant animals to moderate levels of either metallic or inorganic mercury caused growth retardation, birth defects, and death of the fetus or of the offspring shortly after birth. In another study, exposure of male animals to inorganic mercury reduced their fertility.

It is not known whether mercury causes similar effects in humans, but, based on the animal studies, you should handle it as a potential human reproductive toxin and minimize your exposure (see "Reducing Your Exposure"). Nursing women should also avoid exposure to mercury, since inhaled mercury can enter a woman's breast milk.

TESTS FOR EXPOSURE AND MEDICAL EFFECTS

The amount of mercury in your body can be estimated by measuring mercury in urine or blood. Urine analyses are best for assessing long-term exposures. Blood tests are useful for assessing recent high-level exposures, if the test is done immediately after exposure. Tests for mercury exposure should be selected and evaluated on a case-by-case basis by medical personnel who are familiar with these tests. Other medical tests may be needed, as determined by a physician. For example, follow-up of neurological and kidney function may be appropriate for employees with long-term exposures. More details on these tests are available through HESIS.

LEGAL EXPOSURE LIMITS

California's Division of Occupational Safety and Health (DOSH, or "Cal-OSHA") makes and enforces regulations for chemical exposure in the workplace. Cal/OSHA has adopted two kinds of legal limits for the amount of mercury in your breathing zone. The first is a Permissible Exposure Limit (PEL) of 0.05 milligrams of mercury per cubic meter of air (0.05 mg/m³), as an average level over eight hours. This means that you may be exposed to a level greater than 0.05 mg/m³ during part of the work day, as long as you are exposed to less than 0.05 mg/m³ at other times, so that your average exposure during any eight-hour work shift is no more than 0.05 mg/m³.  Cal/OSHA's second limit is a 0.1 mg/m³ "ceiling limit" which must never be exceeded for any period of time.

If you think that you may be overexposed, talk to your supervisor and/or your union. If any state, county, or local government employee might be exposed to a substance at more than the legal limit, the employer must measure the amount of the chemical present in the air in the work area (Cal/OSHA regulation GISO 5155). You have the right to see the results relevant to your work area (GISO 3204).

You also have the right to see and copy your own medical records and records of your exposure to toxic substances. These records are important in determining whether your health has been affected by your work. Employers who have such records must keep them and make them available to you for at least 30 years after the end of your employment.

REDUCING YOUR EXPOSURE

Your employer is required to protect you from being exposed to mercury at levels above the legal limits. For information about how Cal/OSHA and Cal/OSHA Consultation Service can help you and your employer, see the "Resources" section on page 4.

Spills: An emergency response procedure should be created for areas where spills of liquid mercury can occur. Spilled mercury should be collected promptly. It is much easier to clean up spills on floors that do not have cracks or seams. Rugs should not be used in areas where mercury can be spilled, because rugs can absorb substantial amounts of spilled mercury, which will slowly evaporate to contaminate the workplace air.

If a spill occurs:

People not involved in the cleanup should leave the immediate area.

• Windows should be opened to help ventilate the area.
• Do not use a regular vacuum cleaner to clean up a spill; regular vacuum cleaners will spread mercury around the room and increase airborne contamination.
• Small spills may be picked up with adhesive tape or a hypodermic syringe.
• Large spills can be suctioned into a wash bottle trap partially filled with water, or you can use a mercury spill cleanup kit commercially available from a safety equipment supplier. A wash bottle trap or a cleanup kit should always be on hand, and you should be trained to use them.
• After all visible mercury has been collected,
  the area should be washed with a calcium polysulfide solution (about 2-4 tablespoons of lime sulfur per gallon of water), then washed with a detergent solution, and rinsed.

Following cleanup, the area should be monitored using a mercury sniffer. The employer can contact the Cal/OSHA Consultation Service (a non-enforcement agency) to request a worksite visit to assess whether cleanup has been adequate (see "Resources" on page 4).

Safe Work Practices: Safe work practices can greatly reduce your exposure to mercury. Store mercury in unbreakable containers in a cool, dry, well ventilated area away from heat. Keep containers of liquid mercury tightly sealed, and place suitable metal or plastic pans under mercury equipment to reduce hazards from spills. Sealed waste containers (rather than open ones) can minimize vapors escaping into the room.

Do not heat mercury. When heated, liquid mercury evaporates more rapidly. Dangerous levels of mercury in the air may result. Good personal hygiene will help prevent exposure of yourself and others. Always wash your hands before eating, drinking, or smoking. Mercury on your hands or under your fingernails is a dangerous source of exposure. If liquid mercury is spilled on you, change out of contaminated clothing to avoid spreading the contamination to your home.

Engineering Controls: When possible, employers must use engineering and administrative controls rather than personal protective equipment to prevent overexposure. Engineering control methods include installing ventilation and changing the work process. Certain work processes can be isolated, enclosed, or automated to reduce exposures.

Local exhaust ventilation systems ("hoods") are the most effective type of ventilation control. These systems capture contaminated air at its source before it spreads into the air in your breathing zone.

Personal Protective Equipment: When engineering controls cannot sufficiently reduce exposures, a respirator must be worn and a respiratory protection program must be developed by the employer, as outlined in Cal/OSHA regulations (GISO 5144). The only respirators approved for protection against mercury vapor are supplied-air devices, in which compressed breathing-quality air is delivered to a facepiece or hood. An industrial hygienist or other knowledgeable person should be consulted to ensure that the equipment is appropriate and is used correctly.

If skin or eye contact with liquid mercury is possible, other protective equipment such as gloves or faceshields should be worn. Protective clothing should be made of a material resistant to mercury, such as rubber. Gloves should be replaced frequently (especially after finishing with a mercury handling procedure), because residues on your gloves can contaminate the work area. Gold jewelry should not be worn when working with mercury, because the vapors may discolor the metal.

Disposal: Mercury can often be recycled. Mercury waste must be disposed of as hazardous waste according to state and local regulations. Mercury must not be poured down the sink. (See "Resources" for disposal information).

Substitution: The most effective way to reduce hazardous chemical exposures is to use a safer chemical, if one is available. The health and safety hazards of the substitute must also be carefully considered, to ensure that it is actually safer. However, for most uses of mercury there are few effective substitutes.