Mercury
Your Health and the Environment

Exposure

This section covers the various potentially hazardous sources of exposure to mercury such as exposure through the consumption of fish, the use of certain consumer products, dental amalgam and thimerosal vaccines. Exposure to mercury can occur as part of everyday activities through contact with water and soil, exposure to products containing mercury and even in the air we breathe.

Q7. What are the main sources of mercury exposure?
Because mercury occurs naturally in the environment at low levels, everyone is exposed to some level of mercury in air, water and food.

• In the general population, the major sources of exposure to mercury occur through the consumption of larger species of fish (see Q.12 - Q.17) and from dental amalgam (see Q.28 - Q.29).
• Exposure can also occur when mercury-containing products are broken and mercury is released or spilled at home or in the workplace. (See Q.22 - Q.25)
• Another potential source of exposure is the use of mercury in various cultural practices and hobbies, including some types of jewellery, such as glass pendant necklaces and some artist's paints (see Q.20).
• Minor methyl mercury exposure can occasionally occur from handling contaminated soil or drinking contaminated water (see Q.55).

Q8. Are Canadians at risk from methyl mercury exposure?
The Canadian population, in general, is not being subjected to an increase in methyl mercury exposure, but some people may have higher exposure than others.

• People who eat a lot of fish and marine mammals as part of their daily diet tend to have higher methyl mercury exposures, because the potentially high levels of methyl mercury found in some of these species can be passed on to humans.
• Scientific research suggests that it is the developing fetus and the breast-fed children of women who consume greater amounts of the larger species of fish during pregnancy and lactation who are the most susceptible to health problems (see Q.43 - Q.46).

Q9. What uses of metallic (elemental) mercury in the home increase mercury exposure?
Any use of metallic (elemental) mercury in the home can be dangerous. A number of unsafe household uses have been identified. These include:

• Sprinkling or spreading mercury in the house or car;
• Mixing mercury with water or other liquids and using this mixture as a washing solution;
• Burning mercury in candles for good luck (white magic);
• Hobbies: heating mercury on a stove to purify gold or silver;
• Using metallic mercury, often sold under the name "azogue", including placing it in a pouch worn around the neck, sprinkling it in the home, mixing it with bath water or perfume or placing it in devotional candles;
• Folk remedies: ingesting mercury (azogue) to treat constipation, colic or stomach ache (empacho), or;
• Playing with mercury as a novelty or carrying it as a charm.

Q10. What types of workplace environments potentially increase mercury exposure?
Workplaces and occupations that have a greater potential for elemental mercury exposure include:

• Manufacturers of electric equipment (mercury switches, dry cell batteries, mercury lamps, etc.), medical devices (thermometers, manometers, etc.) or automotive parts that contain mercury;
• Chemical processing plants that use mercury (production of chlorine, caustic soda, pesticides, biocides, slimicides and fungicides, latex and antifouling paints);
• Metal processing;
• Manufacturing plants producing explosive detonators;
• Waste incineration plants (municipal, medical and hazardous wastes), incinerators, landfills and crematoriums/cemeteries;
• Construction sites where building parts contain mercury (e.g. electrical switches, thermostats, thermometers, latex paints containing organomercurial fungicides, ship repair facilities);
• Medical facilities where equipment may contain elemental mercury (e.g. some blood pressure gauges, dental amalgams, thermometers, etc.); and
• Canada uses the Threshold Limit Values (TLVs) for Chemical Substances, as determined by the American Conference of Governmental Industrial Hygienists for national occupational health standards (Canada Labour Code and its Regulations). Federal regulations use the TLV's as amended from year to year, whereas most provinces use the TLV's as adopted for a specific year. For information on occupational exposure guideline limits, please refer to Q.58.

Q11. Is there any method of testing that will determine individual exposure to mercury?
Yes. Hair, blood or urine samples are typically tested to detect elevated mercury levels in the body, if there is a suspected exposure. These samples can be easily taken in a doctor's office. Analytical methods can detect inorganic mercury and/or total mercury (the difference being considered organic mercury). The test for elemental mercury is the same test as for inorganic mercury, interpretation of the result being dependent on the type of exposure. While these tests are useful in determining the concentration of mercury, they cannot determine the type of mercury exposure beyond inorganic (includes elemental) or organic mercury exposure.

If your doctor suspects metallic (elemental) mercury poisoning, he/she will obtain a complete occupational and environmental history and may test your blood and/or urine for elemental mercury.

• For acute effects resulting from exposure to high levels of elemental or inorganic mercury, physicians often test whole blood. Whole blood is an indicator of recent mercury exposure. For occupational exposure, whole blood is collected at the end of the last work shift of the work week.
• If exposure to low levels of elemental or inorganic mercury vapour occurs over a period of time, a urine sample is preferred. Urine is collected pre-shift.
• Hair samples provide a good method for the determination of the variation of mercury intake over a long period of time, if the hair is analysed by segments.
• The concentration of mercury detectable in blood and urine in the non-occupationally exposed population is dependent on the analytical procedure used to measure the mercury and the living environment of the subject.
• Blood levels in the occupationally unexposed population vary between 0.1 and 10 micrograms of mercury per litre of blood. A whole blood concentration of 15 micrograms per litre is considered to be the biological exposure index (BEI) for occupational exposure. Blood concentrations above 15 micrograms per litre should be followed up by a physician. Symptoms should not be present at the BEI concentration. The BEI concentration of 15 micrograms per litre is equivalent to 0.008 micromoles/decilitre.
• Urine samples, for the non-occupationally exposed population, typically have a concentration of elemental or inorganic mercury of less than 3 micrograms per litre. For the occupationally exposed population or for populations with exposure to unusually high environmental concentrations, the elemental or inorganic BEI concentration limit is set at 35 micrograms mercury per gram of creatinine. The BEI concentration of 35 micrograms per gram of creatinine is equivalent to 20 micromoles of mercury per mole of creatinine.