Mercury's Air Pollution: Understanding The Toxic Impact

Mercury is a naturally occurring element found in the Earth's crust and is present in the air, water, and soil. While it occurs naturally, human activities such as mining, fossil fuel combustion, and industrial pollution have led to widespread global mercury pollution. Mercury emitted into the air can travel thousands of miles before being deposited back onto the Earth, causing air pollution and contributing to adverse health effects and environmental degradation. The burning of coal, oil, and wood releases mercury into the atmosphere, and it can remain airborne for extended periods, posing risks to human health and the environment.

Mercury in fossil fuels

Mercury is a naturally occurring chemical element found in the Earth's crust. It exists in several forms, including elemental or metallic mercury, a shiny, silver-white metal liquid at room temperature, historically referred to as quicksilver. When dropped, it breaks into smaller droplets, and when heated, it becomes a colorless, odorless gas.

Mercury occurs naturally in fossil fuels, with coal being the most significant contributor to mercury emissions among fossil fuels. The burning of coal, oil, and wood as fuel can cause mercury to become airborne and go into the atmosphere. Inorganic mercury can also enter the water or soil from the weathering of rocks that contain inorganic mercury salts or from factories or water treatment facilities that release contaminated water.

The energy industry is currently the second-largest anthropogenic source of mercury pollution worldwide, with coal washing, oil production, and coal-fired power plants being significant contributors. In the United States, power plants that burn coal to create electricity are the largest source of mercury emissions, accounting for about 44% of all man-made mercury emissions.

Mercury emissions are a global problem that knows no national or continental boundaries. Mercury emitted into the air can travel thousands of miles before being deposited back to Earth in rainfall or dry gaseous form. This airborne mercury can fall to the ground in raindrops, dust, or simply due to gravity (known as "air deposition"). Once deposited, certain microorganisms can convert it into methylmercury, a highly toxic form that builds up in fish, shellfish, and animals that eat fish. Most human exposure to mercury is through the consumption of contaminated fish and shellfish, both in the United States and worldwide.

Health risks of mercury pollution

Mercury is considered by the WHO as one of the top ten chemicals of major public health concern. It is a neurotoxin and exposure to it, even in small amounts, may cause serious health problems. Mercury occurs naturally in the earth's crust but human activities, such as mining and fossil fuel combustion, have led to widespread global mercury pollution.

The main way that people are exposed to mercury is by eating fish and shellfish that contain high levels of methylmercury, a highly toxic organic compound. 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, which builds up in fish, shellfish, and animals that eat fish. Most human exposure to mercury is from consuming fish and shellfish contaminated with methylmercury, both in the United States and worldwide. Children of women who consumed large amounts of contaminated fish during pregnancy are at the highest risk of mercury-related developmental problems. The developing brains and nervous systems of children are very sensitive to mercury and may be irreversibly damaged by it.

A less common way people are exposed to mercury is by breathing mercury vapors, which can happen when mercury is released from a container, or from a product or device that breaks. If the mercury is not immediately contained or cleaned up, it can evaporate, becoming an invisible, odorless, toxic vapor. Mercury vapors can pass easily from the lungs to the bloodstream and can harm the nervous system, lungs, and kidneys.

Mercury is also released into the environment from other human activities, such as burning coal, oil, and natural gas, burning household trash, and mining ore deposits. Mercury occurs naturally in coal and other fossil fuels, so when people burn these fuels for energy, the mercury becomes airborne and goes into the atmosphere. In the United States, power plants that burn coal to create electricity are the largest source of mercury emissions. Globally, artisanal and small-scale gold mining is the largest source of anthropogenic mercury emissions, followed by stationary coal combustion.

Sources of mercury emissions

Mercury emissions are a global issue that transcend national and continental boundaries. Once emitted into the air, mercury can travel thousands of miles before eventually settling back on Earth through rainfall or dry gaseous deposits.

There are two types of mercury emissions: natural and anthropogenic (human-caused). Volcanic eruptions and emissions from the ocean are natural sources of mercury. On the other hand, human activities such as mining and fossil fuel combustion have significantly contributed to the global mercury pollution we see today.

Natural Sources

Mercury occurs naturally in the Earth's crust and can be released into the atmosphere through volcanic eruptions and oceanic emissions.

Anthropogenic Sources

The largest source of anthropogenic mercury emissions is artisanal and small-scale gold mining (ASGM), which accounts for 37.7% of global emissions. This is followed by the stationary combustion of coal, contributing 21% of emissions. Other significant sources include non-ferrous metals production (15%) and cement production (11%).

The burning of coal, oil, and wood as fuel can release mercury into the atmosphere. Similarly, the combustion of wastes containing mercury can also contribute to airborne mercury levels. Power plants that burn coal to generate electricity are the largest source of mercury emissions in the United States, accounting for about 44% of all anthropogenic emissions.

Inorganic mercury, which is abundant in the environment, can become airborne through mining deposits of ores containing mercury. Coal-fired power plants, the burning of municipal and medical waste, and factories that utilise mercury can all emit inorganic mercury into the atmosphere.

Additionally, mercury can enter water or soil from the weathering of rocks containing inorganic mercury salts or from contaminated water released by factories and water treatment facilities.

Mercury in the global cycle

Mercury is a naturally occurring element in the Earth's crust and in various forms on the Earth's surface. It can be elemental, inorganic, or organic. Human activities, such as mining and fossil fuel combustion, have led to widespread global mercury pollution. Mercury emitted into the air can travel thousands of miles before being deposited back onto the earth in rainfall or in dry gaseous form. This process is known as the mercury cycle, a biogeochemical cycle influenced by natural and anthropogenic processes that transform mercury through multiple chemical forms and environments.

The mercury cycle involves the movement of mercury between the atmosphere, land, and water. In its inorganic form, mercury can be found as the minerals cinnabar and metacinnabar and as impurities in other minerals. It can combine with chlorine, sulfur, and other elements to form inorganic salts, which can be transported in water and occur in soil. These salts can enter the air through mining deposits of ores containing mercury or the burning of coal, oil, and wood as fuel.

Once emitted into the atmosphere, mercury can remain in the air for prolonged periods, travelling across continents in the "global cycle". It eventually settles onto land or water, where it can be converted by microorganisms into methylmercury, a highly toxic form of mercury that builds up in fish, shellfish, and other marine species. This is the main way that people are exposed to mercury, as consuming contaminated fish and shellfish can lead to toxic effects, especially in developing fetuses and young children.

Human activities have significantly impacted the global cycle of mercury. The largest sources of man-made mercury emissions are small-scale gold mining and burning coal for electrical generation. According to scientists, changes in human behaviour and rising global temperatures will continue to affect the environmental distribution of mercury worldwide. Efforts to reduce mercury emissions, such as the legally binding treaty on reductions in human uses and releases of mercury, are crucial to mitigating the health and environmental risks posed by mercury pollution.

Reducing mercury emissions

Mercury emitted into the air can travel thousands of miles before being deposited back on earth, threatening human health and wildlife. While mercury does occur naturally, human activities such as mining and fossil fuel combustion have led to widespread global mercury pollution.

To reduce mercury emissions, the US Environmental Protection Agency (EPA) has implemented various measures and partnered with international organizations. Here are some key strategies for reducing mercury emissions:

Regulations and Standards

The EPA has issued regulations and standards to limit mercury emissions from specific industries. For example, the Mercury and Air Toxics Standards (MATS) regulation targets coal- and oil-fired power plants, with an estimated positive impact on public health, preventing premature deaths, heart attacks, and asthma attacks. The EPA has also set standards for mercury emissions from chlor-alkali production, municipal waste combustors, and public incinerators that burn sewage.

International Collaboration

The EPA actively collaborates with international organizations to address mercury pollution globally. The United States joined the Minamata Convention on Mercury, a multilateral environmental agreement, to address human activities contributing to mercury pollution. The EPA also engages with partners through the United Nations Global Mercury Partnership to tackle key mercury issues.

Technology and Innovation

The EPA has partnered with the Argonne National Laboratory to develop the Gold Shop Mercury Capture System (MCS), a low-cost technology to reduce mercury emissions from small-scale gold buying and refining facilities worldwide. Additionally, they have collaborated on projects to demonstrate the effectiveness of injecting activated carbon sorbents to control mercury air emissions at coal-fired power plants.

Mercury Waste Management

Proper management and disposal of mercury-containing items are crucial. The EPA provides guidelines for managing and disposing of mercury-containing products, including automotive parts, consumer goods, and medical devices. Recycling mercury-containing products and collecting them for recycling can also help limit the need for new mercury mining.

Substitution of Mercury-Containing Products

Substituting products and processes that contain or use mercury with mercury-free alternatives can significantly reduce mercury releases. This includes switching from fossil-fueled power plants to non-fossil energy sources, such as natural gas, nuclear power, wind, or solar energy. Consumers can also play a role by choosing to buy and use mercury-free products, reducing mercury in households and the environment.

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