Mercury, a naturally occurring element, is an environmental pollutant released into the environment through both natural processes and human activities. Understanding its forms and exposure pathways is crucial for recognizing its potential dangers to human health.
Understanding Mercury’s Forms
Mercury exists in several forms, each with distinct properties and potential for harm. Elemental mercury, also known as metallic mercury, is a shiny, silver-white liquid at room temperature and is historically used in thermometers and some electrical switches. Exposure primarily occurs through inhaling its invisible, odorless vapor, which is readily absorbed by the lungs.
Inorganic mercury compounds form when elemental mercury combines with other elements like chlorine or sulfur. These compounds are often found in certain consumer products and can be absorbed through ingestion, affecting the gastrointestinal tract and kidneys. Unlike elemental mercury, inorganic forms are not lipid-soluble and generally do not cross the blood-brain barrier easily.
Organic mercury, predominantly methylmercury, forms in aquatic environments from inorganic mercury. This highly toxic form accumulates in the food chain, particularly in fish and shellfish. Consumption of contaminated seafood is the most common pathway for human exposure.
Common Exposure Pathways
Mercury enters the environment through various natural and human-caused pathways. Natural sources include volcanic eruptions, forest fires, and the erosion of mercury-containing rocks, which release elemental mercury into the atmosphere.
Anthropogenic, or human-caused, sources significantly increase mercury levels in the environment. Industrial activities such as coal-fired power plants are the largest atmospheric source, accounting for about 42% of man-made mercury emissions. Other industrial contributors include artisanal gold mining, chlor-alkali plants, and cement production.
Mercury is also present in numerous consumer products, including older thermometers, fluorescent light bulbs (CFLs), some batteries, and dental amalgam fillings. Improper disposal of these products can release mercury into the air, soil, and water.
How Mercury Harms the Body
Mercury is a toxic substance that can disrupt various bodily functions by binding to proteins, interfering with cellular processes, enzyme activity, and neurotransmission. Its toxicity varies depending on the specific form of mercury, the dose, and the duration of exposure. The central nervous system and kidneys are primary target organs for both elemental and inorganic mercury.
Methylmercury is particularly damaging to the nervous system and can readily cross both the blood-brain barrier and the placenta. This makes developing fetuses and young children especially vulnerable to its neurotoxic effects. Exposure during development can lead to cognitive impairment, motor skill deficits, memory problems, and difficulties with attention, language, and vision. In adults, high levels of methylmercury can cause tremors, memory loss, coordination problems, and vision or hearing impairment.
Inhalation of elemental mercury vapor can also lead to neurological issues such as irritability, tremors, and memory problems. Inorganic mercury compounds are known to cause kidney damage, potentially leading to kidney dysfunction or acute renal failure in severe cases. Mercury exposure has also been linked to immune system effects, including immunosuppression or autoimmune responses, and an increased risk of cardiovascular diseases like hypertension, coronary heart disease, and atherosclerosis.
Reducing Your Risk
Minimizing mercury exposure involves informed choices and proper handling of mercury-containing items. A primary way to reduce risk is through careful dietary choices, particularly regarding fish consumption. Select fish low in mercury, such as salmon, sardines, anchovies, shrimp, and cod, while limiting intake of high-mercury fish like shark, swordfish, king mackerel, and tilefish. Consulting local fish advisories can provide specific guidance.
Proper disposal of mercury-containing products prevents environmental contamination. Items such as compact fluorescent light bulbs (CFLs) and old thermometers should never be placed in regular trash or poured down drains. Instead, they should be taken to designated household hazardous waste collection programs or recycling centers. If a mercury-containing product breaks, ensuring adequate ventilation in the area during cleanup is important.
Awareness of mercury in dental amalgam fillings is also important; while existing fillings are generally considered safe, modern alternatives are available. Supporting policies that aim to reduce industrial mercury emissions can also contribute to a healthier environment and reduced overall exposure. These collective efforts help protect both individual health and broader ecosystems from mercury’s harmful impacts.