Environment and Mercury Exposure
Ways We Can Become Exposed to Mercury
There are several ways we can be exposed to mercury such as through improperly disposed of products containing mercury, workplace exposure and consuming fish.
Mercury is a naturally occurring element found in the earth’s crust. There are three different forms of mercury, which are elemental, inorganic and organic:
- Elemental, or metallic mercury - this is the shiny silvery liquid we are all familiar with, used in thermometers.
- Inorganic compounds are formed when elemental mercury is combined with sulphur, chlorine or oxygen and are known as mercury salts.
- Organic mercury occurs when elemental mercury is combined with carbon and hydrogen.
Natural Released Mercury
- Mercury is released into the environment through volcanoes, mercury rich geologic zones and hot springs. It can then travel through natural occurrences such as fires and floods.
Human Released Mercury
- Humans release mercury into the environment by burning fossil fuels, mining, through cement productions and production of chlorine and sodium hydroxide.
- The improper disposal of products that contain mercury can also release more into the environment from such things as thermometers, mercury vapor lamps, dental amalgam waste and florescent light bulbs.
Workplaces that increase mercury exposure
- Manufacturers of electrical equipment such as electric switches, dry cell batteries and mercury lamps.
- Chemical processing plants that use mercury in the production of chlorine, caustic soda, pesticides and antifouling paints.
- Metal processing.
- Manufacturing plants that produce explosives.
- Waste and incineration plants.
- Construction sites.
- Medical facilities.
What are ways you can manage toxic mercury exposure in your home?
Buy rechargeable batteries or ones that are specifically labeled “mercury free”.
Use digital or spirit (red) thermometers instead of those using mercury.
Mercury in Fish
- The main way most humans ingest mercury is through consuming fish. Mercury is first deposited into land and water. Microorganisms then convert it into methyl mercury, which is a highly toxic form of mercury that builds up in living tissues. Small organisms and plants take the mercury in and then the larger animals consume them. This accumulates into higher concentrated levels of mercury in the larger animals and is called biomagnification.
- People who ingest a lot of fish are more likely to experience higher methyl mercury exposure. Older predatory fish tend to have higher levels of mercury. Children and women who are pregnant and/or lactating are more vulnerable to health problems from eating fish that contain mercury. Exposure to mercury can affect children's brain development, which can interfere with both their motor and cognitive skills.
Health Canada advises consumers to limit their consumption of shark, swordfish and fresh or frozen tuna to a maximum of no more than one meal per week. For children and pregnant women this is extended to once per month. Canned tuna actually contains lower levels of mercury, which is because different and smaller species are used for canning. The lowest levels for tuna are found in light canned tuna such as yellowfin and skipjack.
The reason it is so important that pregnant and lactating women are especially careful is because the mercury can be transferred through the placenta or breast milk. It can then accumulate in children's blood to a higher concentration than the mothers.
For more information on mercury see Canada-Wide Standards for Mercury(pdf)or Environment Canada.
Source: (Mercury Your Health and the Environment: Health Canada Mercury Issues Task Group, October 1, 2004)
Related: Farmed Salmon and PCBs
