General Information

About Mercury

Mercury is a naturally occurring element that is found in air, water and soil. It exists in several forms—elemental (also known as metallic mercury), inorganic and organic. Pure elemental mercury, also called quicksilver, is a silvery liquid metal that easily evaporates, giving off invisible, odorless and toxic vapors.

Mercury cannot be created or destroyed, and exposure to mercury—even small amounts—can cause serious health problems.

Mercury occurs in deposits throughout the world mostly as cinnabar (mercuric sulfide), an inorganic mercury compound. Pure mercury is extracted by heating cinnabar, which turns the ore into a vapor, which in turn is captured and cooled to form elemental mercury.

The most toxic forms of mercury are its organic compounds, such as methylmercury. Organic mercury forms when mercury combines with carbon, the essential element in all organic compounds. Methylmercury forms naturally in water and soil and can build up to dangerous levels in fish.

Uses of Mercury

CFL bulbsHistorically, mercury has had many uses. It is found in energy-efficient fluorescent light bulbs; older-technology thermometers, thermostats and barometers; button cell batteries (used in watches, calculators and hearing aids); and various electrical relays and switches. It has also been widely used in dental fillings (silver-colored dental amalgams contain about 40-50 percent elemental mercury) and in the production of chlorine gas and caustic soda.

While the use of gaseous mercury in fluorescent lamps has been increasing with the growing use of the energy-saving bulbs, many other consumer applications and uses have been phased out due to health and safety concerns and regulations.

A miner collects elemental mercury from gas condensation (USGS).Mercury has also been widely used in extracting gold and silver from ore. Mercury readily combines with these metals, making compounds called amalgams that facilitate the recovery of the precious metals from their ores.

Historically, mercury’s use in large-scale mining operations following the Gold Rush has contributed significantly to mercury contamination in the Sacramento River watershed. Even today, mercury-contaminated leachate coming from gold mines abandoned more than a century ago continues to degrade downstream environments.

Why is mercury such a concern?

Because mercury can be a solid, liquid or a vapor, managing mercury can be a tricky task. Especially concerning is when mercury enters our waterways—that’s when bacterial processes convert it into more harmful methylmercury. Methylmercury “bioaccumulates” up the food chain, from small aquatic organisms and fish to larger fish, then to wildlife and humans that consume the fish. In other words, when smaller life forms are eaten by larger life forms, mercury contamination is passed up the food chain.

Exposure to high levels of metallic, inorganic or organic mercury can damage the nervous system and kidneys. When people regularly consume fish or other wildlife contaminated by mercury, they are at risk for serious health effects, including brain damage, behavioral and developmental problems. Studies have shown that people who ate fish and grain that contained large amounts of methylmercury had permanent damage to the nervous system and kidneys. Children and unborn babies are most at risk because their nervous systems are still developing. Loss of sensation in the hands, as well as hearing, speech and vision problems are examples of the effect mercury can have on adults. Much worse, mercury can accumulate in the body over time, and even result in death.

What are the sources of mercury pollution?

There are many ways that mercury can escape into the environment and contaminate our water, crops, fish and wildlife. When items containing mercury are broken or thrown away, that mercury eventually ends up in our air, soil and water. When mercury thermostats are thrown into the trash, for example, they are either sent to an incinerator or to a landfill. When incinerated, the liquid mercury in thermostats turns into a vapor that is released into the air. If mercury-containing devices are disposed in a landfill, they could be broken, allowing the liquid mercury to escape, vaporize and be vented into the atmosphere or enter the leachate. The airborne mercury is then deposited to our lakes and streams when it rains.

Mercury can also get into waterways through industrial, commercial, and domestic sewer discharges, stormwater runoff, leachate from municipal landfills and mining operations. Mercury pollution in the air emissions from coal-burning power plants has also been a substantial problem.

What kinds of animals are being affected by mercury pollution?
While there is awareness that fish are being affected by mercury pollution in our lakes, rivers and streams, mercury in the environment is also impacting other wildlife. Predominantly fish-eating birds (eagles and loons) and mammals (minks and otters) are showing effects (e.g., behavioral and reproductive changes) from mercury poisoning. Even insect-eating animals from forest ecosystems, such as songbirds and bats, are accumulating high levels of mercury, which is an indication that deposition of mercury in terrestrial environments is also a problem.

Why is mercury a problem for wastewater treatment?

Wastewater agencies, including Regional San, are now facing increased regulatory attention for levels of mercury in the wastewater they treat and ultimately discharge into receiving waters. As a result, treatment plants need the cooperation of citizens, business and industry to minimize the amount of mercury escaping down the drain, even small amounts. Every drop makes a difference. Once in the wastewater, mercury is difficult and costly to completely remove. Learn more about Regional San’s involvement in mercury issues here.