Mercury Pollution: How Far Does The Poison Spread?

Mercury is a toxic pollutant that poses a serious threat to human health and the environment. It is a heavy metal that cycles through the atmosphere, water, and soil, and can travel thousands of miles before being deposited back to Earth. This means that irrespective of the region where mercury is released, it can affect areas far beyond, making mercury pollution a global concern. Mercury is emitted through both natural processes, such as volcanic activities, and human activities, such as industrial pollution and electricity production. Once released, mercury can undergo chemical transformations and be converted into methylmercury, a highly toxic form that accumulates in fish and affects humans and animals that consume them. As a result, mercury pollution can potentially impact a wide area, including regions with high fish consumption, and have detrimental effects on human health, wildlife, and ecosystems.

Mercury's global reach

Mercury is a heavy metal that cycles through the atmosphere, water, and soil, irrespective of which part of the world releases it. It is emitted in a combination of different chemical forms, each of which behaves differently once emitted. Elemental mercury, for example, comprises 95%-99% of mercury in the atmosphere and can circulate in the air for up to a year before being deposited on land or in water. It is, therefore, a "global pollutant" and can travel thousands of miles before settling back on earth.

Mercury emitted into the air eventually settles into water or onto land, where it can be washed into water. Once deposited, certain microorganisms can change it into methylmercury, a highly toxic form that builds up in fish, shellfish, and animals that eat fish. Most human exposure to mercury is from eating fish and shellfish contaminated with methylmercury. Mercury can enter the ocean through atmospheric deposition, air-water exchange, and via rivers, estuaries, and sediments.

Mercury can also enter water or soil from the weathering of rocks that contain inorganic mercury salts and from factories or water treatment facilities that release contaminated water. Mercury emissions from power plants are a major source, with coal-fired power plants being the highest emitters, accounting for about 34% of the total in the US. In addition, power plants produce 33 tons of mercury as coal waste. Mercury emissions from the utility industry are not regulated at the federal level or in New York State.

Mercury has severe impacts on aquatic ecosystems, especially those with large wetland areas. Two properties of methylmercury, its ability to bioaccumulate and bioconcentrate, contribute to its toxicity. Bioaccumulation refers to the build-up of a pollutant within an organism's body over time, while bioconcentration (or biomagnification) refers to how mercury concentrations increase going up the food chain, becoming concentrated in higher-level predators such as fish, birds, minks, and otters. Even relatively low concentrations of mercury in water can contaminate an entire food chain and make fish unsafe for human consumption.

Human activities causing pollution

Mercury is a toxic heavy metal that cycles through the atmosphere, water, and soil, and can travel thousands of miles before being deposited back to Earth. Human activities have significantly increased the amount of mercury in the environment, and it is now a global concern. Two-thirds of the mercury in the world is released into the environment by human activities, and it can affect a large area, irrespective of its origin point.

Industrial Pollution

Industrial processes and commercial products are a major source of mercury pollution. Mercury is used in and released from a range of industries, including:

• Fossil fuel combustion, especially coal-fired power plants
• Metal mining and smelting
• Waste incineration
• Chlor-alkali industry
• Cement production
• Consumer product waste
• Crematoria

Mining

Mining, particularly artisanal and small-scale gold mining, is the largest source of anthropogenic mercury emissions. Mercury is released from the fuels and raw materials used in mining, as well as from the mining processes themselves.

Power Generation

Coal-fired power plants are the highest emitters of mercury, with approximately 34% of total emissions. In addition to direct emissions into the air, power plants also produce mercury as coal waste.

Products and Waste

Mercury is found in a variety of products, including button batteries, fluorescent tube lights, fever thermometers, thermostats, switches, relays, barometers, and dental fillings. Improper disposal of these products can cause mercury to leach from landfills or be emitted from burning waste, adding to environmental mercury levels.

Natural Sources

It is important to note that natural sources of mercury, such as volcanic eruptions, undersea vents, and forest fires, also contribute to mercury pollution. However, human activities have boosted the levels of mercury in the atmosphere.

Natural processes polluting the environment

Mercury is a heavy metal that cycles through the atmosphere, water, and soil in various forms to different parts of the world. Due to this natural mercury cycle, irrespective of which part of the world releases mercury, it could affect an entirely different part of the world, making mercury pollution a global concern. Mercury emitted into the air can travel thousands of miles in the atmosphere before it is eventually deposited back onto the earth in rainfall or in a dry gaseous form.

• Volcanic activities: Volcanoes release mercury from underground reservoirs upon eruption.
• Land emissions through the soil: This occurs in regions closer to plate-tectonic boundaries where soils are enriched with minerals such as cinnabar (insoluble mercury sulfide, HgS). This mercury is released, usually as a salt, either by natural weathering of the rocks or by geothermal reactions.
• Emissions from the ocean: Oceans can act as a "storage closet" for mercury.

These natural processes, along with anthropogenic (human-caused) emissions, contribute to the global concern of mercury pollution, which poses risks to both human health and the environment.

Health risks of mercury exposure

Mercury is a heavy metal that cycles through the atmosphere, water, and soil. It is released into the environment through both natural and anthropogenic processes. Natural sources of mercury include volcanic eruptions, emissions from the ocean, and weathering of rocks. Human activities, such as mining, fossil fuel combustion, and industrial processes, have significantly increased mercury concentrations in the environment. Mercury emitted into the air eventually settles into water or land and can be washed into water bodies.

The health risks of mercury exposure depend on several factors, including the form of mercury, the amount of exposure, the duration of exposure, the age of the person exposed, and the route of exposure (inhalation, ingestion, or skin contact). Mercury exposure can cause serious health problems, even in small amounts. Here are the health risks associated with mercury exposure:

Neurological and Behavioural Effects

Mercury is a neurotoxin, which means it can be poisonous to nerve tissue. Exposure to mercury, especially methylmercury, can cause adverse effects on the nervous system, including loss of peripheral vision, impaired coordination and movement, speech and hearing impairment, and cognitive dysfunction. In infants and children, mercury exposure can negatively impact cognitive thinking, memory, attention, language skills, and fine motor skills. High levels of mercury exposure have also been linked to emotional changes, such as mood swings, irritability, and nervousness.

Kidney Damage

Mercury exposure, particularly inorganic mercury, can result in kidney damage. High exposures to inorganic mercury can lead to kidney toxicity, and in severe cases, kidney failure.

Gastrointestinal Issues

Inorganic mercury exposure can cause damage to the gastrointestinal tract. Symptoms may include skin rashes, dermatitis, and mental disturbances.

Respiratory Problems

Inhaling mercury vapour can lead to acute mercury poisoning, causing respiratory difficulties and, in severe cases, respiratory failure.

Cardiovascular Issues

High levels of mercury exposure have been associated with cardiovascular problems, including increased blood pressure and heart rate.

Developmental Impacts

Mercury exposure poses a particular threat to the development of unborn children and infants. In utero exposure to methylmercury can adversely affect the growing brain and nervous system of the unborn child, leading to cognitive and developmental issues. Mercury exposure during early childhood can also impact children's cognitive, motor, and behavioural development.

Other Health Effects

Mercury exposure has been linked to various other health issues, including skin problems, eye irritation, headaches, insomnia, and immune system dysfunction. High doses of mercury in animal studies have caused increases in several types of tumours, but the link between mercury exposure and cancer in humans is still uncertain.

How mercury affects the ecosystem

Mercury is a naturally occurring metal that is not particularly toxic in its pure form. However, when it enters the environment, it poses a significant threat to wildlife and ecosystems. Mercury emitted into the atmosphere can travel thousands of miles before being deposited back onto the earth through rainfall or dry gaseous form. This means that irrespective of the source, mercury pollution can affect different parts of the world, making it a global concern.

Mercury enters freshwater lakes and rivers through chemical reactions and precipitation. It accumulates in the sediments at the bottom, where bacteria convert it into highly toxic methylmercury. This compound is then taken up by small organisms, entering aquatic food chains and accumulating in the fat of animals. Through bioaccumulation, methylmercury reaches high concentrations in top-level predators such as large fish and fish-eating birds, a process known as biomagnification.

The impact of mercury on wildlife was evident in the Minamata tragedy in Japan during the 1950s. Birds struggled to fly and exhibited abnormal behaviour, cats suffered convulsions and died, and fish became easy prey for children. The source was a chemical factory discharging waste containing large amounts of methylmercury into Minamata Bay. This event brought to light the severe consequences of mercury poisoning for both animals and humans.

Methylmercury is a neurotoxin that poses a particular risk to developing fetuses, causing severe neurological effects, reproductive issues, and damage to the developing nervous system. It can cross the placental barrier, and even low concentrations in bird eggs can lead to adverse reproductive effects. Mercury exposure in humans primarily occurs through the consumption of contaminated fish and shellfish, with almost everyone having trace amounts of methylmercury in their tissues. Certain communities, such as those with higher fish consumption, are at an increased risk of mercury contamination.

In addition to the health risks, mercury also affects ecosystems by reducing microbiological activity in soils, which is vital to the terrestrial food chain. This impact has been observed in large parts of Europe and may be occurring in other regions with similar soil characteristics. Mercury pollution in the ocean is also a significant concern, with the ocean acting as a "storage closet" for mercury. The total anthropogenic mercury released into the ocean is estimated to be around 80,000 to 45,000 metric tons, with two-thirds found in waters shallower than 1000 meters where consumable fish live.

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