Mercury is a naturally-occurring metallic chemical element found in the rock of the Earth’s crust (i.e., it is found in coal deposits). But, it is also found in the air, water, and soil.
We learned in chemistry class that mercury is recognized by the symbol “Hg” on the periodic table with the atomic number 80. However, this metallic chemical is also one of the most toxic elements in the world.
Exposure to mercury, even in very small amounts, can cause some pretty serious health issues. While the average person doesn’t spend much time (if any) thinking about mercury exposure, there are some signs you should look out for when it comes to mercury poisoning.
Heavy Metals in the Environment
Due to its relatively high density as a metallic chemical element and its toxicity at low concentrations, mercury is considered a heavy metal.
Heavy metals are considered “heavy” because they have a high density compared to water. These metals are found naturally in various concentrations in the environment.
Generally, there are five heavy metals that pose the greatest concern to human health. These toxic heavy metals include lead, chromium, cadmium, arsenic, and mercury.
Environmental phenomena and ecological factors (e.g., land erosion) redistribute these heavy metals within the environment. Industrialization is another factor that contributes to heavy metal redistribution.
Also, urban and landfill runoff are common culprits when it comes to heavy metal redistribution. As environmental impacts from things like industrialization continue, the threats of heavy metal exposure to human health also increase.
Mercury and Its Different Forms
Not only is mercury one of the most dangerous toxins, it can also be found in several forms. These three forms are the most common: Elemental mercury, inorganic mercury, and methylmercury.
Elemental or metallic mercury is known for being liquid at room temperature. This shiny, silver-like metal was commonly used in thermometers, electrical light switches, and fluorescent lightbulbs. Once exposed at room temperature, metallic mercury can evaporate as an odorless toxic vapor.
Exposure to Elemental Mercury
The most common way that people are exposed to metallic mercury is when the mercury is released from its container in consumer products (e.g., a thermometer breaking). If it is not cleaned up promptly and carefully, it is possible to inhale toxic vapor as it evaporates.
Other potential exposures with metallic mercury include:
- Novelty jewelry – Some imported jewelry, like glass pendants, contain mercury. If broken, these can expose mercury into the environment.
- Fever thermometers – Thermometers that are used to detect fevers also contain mercury. It is not uncommon for these fever thermometers to break in the mouth (especially among children), allowing some to be swallowed.
Mercury is found in its inorganic form within the environment. Oftentimes, it forms with other compounds, such as chlorine and sulfur, to form inorganic mercury salts. These can be found in water and soil and can be emitted from various industrial plants like the ones mentioned above.
Exposure to Inorganic Mercury
Mercury salts are also used in consumer products, such as medical products. However, inorganic mercury compounds are still commonly found in skin lightening creams and soaps. Also, a mercury compound known as mercuric chloride is commonly used in topical antiseptics, disinfectants, and more.
In terms of exposure to inorganic mercury and its salts, those that work in occupations such as mining, chemical, and metal processing are at a much higher risk than the general public.
Out of all the forms of mercury, methylmercury is the form that people are exposed to the most. This highly toxic organic compound is formed when inorganic mercury salts and compounds attach to airborne particles and get deposited on land through precipitation.
Over time, this cycle through the land, water, and atmosphere causes chemical and physical transformation to mercury (e.g., combining with carbon). This triggers a change from inorganic mercury compounds to an organic form — methylmercury.
Exposure to Methylmercury Through Air Emissions
Mercury emissions in the air are very common. This can naturally occur through ecological factors and natural phenomenons like volcanos and forest fires. But, various industries also contribute to mercury emissions — e.g., coal-burning plants.
Other causes of mercury emissions in the air include:
- Burning wood/oil/coal that contains mercury.
- Burning waste products that contain mercury.
- Steel refineries that burn iron ore, coke, and limestone.
The industries above offer examples of how heavy metals enter the atmosphere and end up in bodies of water, water supply systems, and food (e.g., mercury in fish). In fact, most exposures to methylmercury in the United States occur through fish and shellfish consumption.
Signs of Mercury Exposure and Poisoning
Mercury exposure poses some severe health risks, having potentially toxic effects on the nervous, immune, and digestive systems. The effects of mercury poisoning and exposure can vary from subtle to severe, and the extent of the effects depend on several factors, such as:
- The form of mercury that you’ve been exposed to
- Amount of mercury you’ve been exposed to and the length of the exposure
- Manner in which you are exposed, e.g., skin contact, breathing, ingestion
- Age and overall health
Mercury poisoning simply refers to the toxicity that occurs from mercury consumption. The neurological effects that are associated with mercury poisoning are the most well-known, but symptoms present differently for everyone.
According to the Food and Drug Administration, the most common sign and symptoms of mercury poisoning include:
- Physical tremors
- Issues with memory
- Changes in hearing and/or vision
- Irritability or nervousness
- Numbness and tingling in feet, hands, and around the mouth
Typically, mercury toxicity builds up over time, so it may be hard to recognize these symptoms or even associate them with mercury poisoning. However, the sudden onset of these symptoms might point to acute mercury toxicity and poisoning.
Adults may experience symptoms that include, but are not limited to:
- Muscle fatigue and weakness
- General fatigue
- Lack of coordination
- Nerve loss in face and hands
- Metallic taste in the mouth
- Nausea and vomiting
- Sudden changes in vision, hearing, and speech
- Difficulty breathing
Mercury poisoning in children and infants
Children and infants are often more susceptible to mercury poisoning than adults. In fact, mercury poisoning can severely affect and disrupt fetal and early childhood development.
For example, children and infants that have been exposed to high levels of mercury might experience developmental delays in the following areas:
- Speech and language development
- Visual/spatial awareness
- Fine motor skills
- Delays in cognition
Although therapies like EDTA chelation therapy do provide some relief from heavy metal exposures, long-term exposure to high amounts of mercury can cause permanent neurological damage as well as organ damage.
The Bottom Line
Mercury is a naturally-occurring metallic element that can be found in the rock of the
Earth’s crust. As a heavy metal, mercury is also one of the most metallic toxins found in the environment.
Ecological and manmade factors are responsible for redistributing mercury from its natural environment, bringing it into closer contact with humans through food and water systems.
Neurological issues are the most pronounced mercury poisoning symptoms, and children are typically more susceptible than adults.