Bronte Wells
Mercury is a naturally occurring element that becomes a pollutant when released into the environment through human activities such as mining and fossil fuel combustion. While mercury emissions can occur naturally, such as through volcanic eruptions, human activities have led to widespread global mercury pollution. The largest source of anthropogenic mercury emissions is artisanal and small-scale gold mining (ASGM), contributing to 37.7% of global emissions. However, coal-fired power plants have also been identified as a significant source of mercury pollution, with vegetables, grains, and soils in surrounding areas showing high levels of contamination. The combustion of coal releases mercury into the atmosphere, where it can stay airborne for extended periods before settling into water or onto land. As a neurotoxin, mercury poses serious health risks to humans, especially developing fetuses and young children, as well as wildlife and ecosystems.
| Characteristics | Values |
|---|---|
| Largest source of mercury pollution | Coal-fired power plants |
| Second-largest source of mercury pollution | Stationary combustion of coal |
| Other large sources of mercury pollution | Artisanal and small-scale gold mining, non-ferrous metals production, and cement production |
| Health risks | Mercury is a neurotoxin that can cause irreversible toxic effects, especially in developing fetuses and young children |
| Environmental impact | Mercury pollution harms wildlife and ecosystems, including fish and shellfish |
| Global presence | Mercury can travel long distances and has been found in remote ecosystems, such as the Arctic Circle |
| Regulatory actions | Mercury and Air Toxics Standards (MATS), Clean Air Act, Biden administration's 2024 regulations |
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What You'll Learn
Coal-fired power plants
Mercury is a potent neurotoxin that poses a significant threat to human health and the environment. While mercury occurs naturally in the Earth's crust, human activities, such as fossil fuel combustion and mining, have led to widespread global mercury pollution. Coal-fired power plants are a major contributor to this issue, releasing large quantities of mercury into the atmosphere.
In the United States, coal-fired power plants have been identified as the biggest source of mercury pollution. According to the Environmental Defense Fund (EDF), the Martin Lake coal plant in East Texas was the highest emitter of mercury pollution by pound, releasing an estimated 338 pounds of mercury in 2020. Other top emitters include the Coal Creek plant in North Dakota and the Oak Grove plant in East Texas. These power plants endanger the health of nearby communities and contribute to the widespread presence of mercury in the environment.
To address this issue, the U.S. Environmental Protection Agency (EPA) finalized the Mercury and Air Toxics Standards (MATS) in 2012. These standards set limits on mercury emissions from coal-burning power plants, leading to a significant reduction in mercury pollution. However, despite the success of MATS, some power plants continue to emit high levels of mercury due to exemptions and the need for stronger safeguards.
The Biden administration took action in 2024 by tightening limits on mercury emissions from coal-burning power plants, particularly lignite coal-fired plants, which have higher mercury emissions. These stronger rules aim to protect the health of all individuals, especially those living near power plants and vulnerable groups such as children. Additionally, relatively inexpensive technologies, such as activated carbon injection, can help reduce mercury emissions from lignite coal.
While efforts to reduce mercury pollution from coal-fired power plants have shown progress, there is still a need for stronger standards and enforcement to protect public health and the environment from the toxic effects of mercury contamination.
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Artisanal and small-scale gold mining
Mercury-based artisanal and small-scale gold mining (ASGM) is the largest source of mercury pollution on Earth, contributing to 37.7% of global anthropogenic mercury emissions. ASGM refers to gold mining conducted by individuals or small businesses with limited capital investment and production capacity. In ASGM, mercury is used to extract gold from ore as an amalgam. The amalgam is typically isolated by hand and then heated to distill the mercury and isolate the gold. This process releases mercury vapour into the atmosphere, contributing to air pollution. The leftover mercury contaminates water and soil, leading to the accumulation of mercury in food staples such as fish, which poses significant health risks to humans and wildlife.
The health effects of mercury exposure on miners are severe, including neurological damage, kidney damage, and other health issues such as severe headaches, dizziness, and vision and motor disorders. The contamination of water and soil also affects nearby communities, with mercury-contaminated water being consumed by women of childbearing age and leading to developmental issues in children. The impact of mercury emissions from ASGM extends beyond the immediate vicinity, as the emissions can be transported and deposited in destinations far from the source.
ASGM activities often take place in the "informal" economy, where participants operate unlicensed or without legal authorization, making effective regulation of mercury emissions challenging. Despite this, ASGM contributes significantly to the local and global economy, generating approximately 15-25% of the world's gold. The techniques used in ASGM have not changed significantly since the California Gold Rush in the mid-1800s, and the environmental and health impacts of mercury pollution from this era are still evident today.
To address the mercury pollution caused by ASGM, the Minamata Convention on Mercury, signed by 128 countries in 2013, regulates the use of mercury in artisanal gold mining. Additionally, the U.S. Environmental Protection Agency (EPA) has developed the Mercury Capture System (MCS), which aims to capture mercury emissions at the source and prevent their release into the environment. The MCS is designed to be inexpensive, easy to construct using locally available materials, and highly effective in capturing mercury.
While the complete elimination of mercury from the ASGM process is ideal, significant emissions reductions can be achieved in the near term by capturing mercury during amalgam burns in gold shops, which are key components of the ASGM gold supply chain. By limiting the path of mercury release, the captured mercury can be redirected for reuse, storage, or proper disposal.
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Burning fossil fuels
The combustion of coal has led to widespread mercury pollution globally. Once emitted into the air, mercury can travel long distances before settling into water bodies or onto land surfaces. It can then be washed into waterways, where it poses a significant threat to aquatic ecosystems and wildlife. Mercury can undergo chemical transformations in the environment, converting into highly toxic forms such as methylmercury, which accumulates in fish, shellfish, and animals that consume fish. This contamination has led to fish consumption advisories being issued in every state in the nation, as consuming contaminated seafood is the primary source of human exposure to mercury.
To address the issue of mercury pollution from coal-fired power plants, regulations and standards have been implemented to reduce mercury emissions. The Biden administration, for instance, tightened limits on mercury emissions from lignite coal-burning power plants, resulting in a 70% reduction. Additionally, pollution-control technologies, such as activated carbon injection, have been employed to lower mercury emissions from these plants. These efforts have led to significant decreases in mercury pollution from coal-fired power plants, with a 90% reduction reported over time.
However, despite these efforts, challenges remain. The Trump administration, for example, allowed nearly 70 coal-fired power plants to exempt themselves from air pollution limits, resulting in increased mercury emissions. Additionally, certain clusters of lignite-burning power plants in states like North Dakota and Texas have annual mercury emissions exceeding 100 kilograms, impacting nearby communities, including Indigenous reservations.
To further mitigate mercury pollution from burning fossil fuels, various strategies can be employed. These include the use of high-rank coals, selective mining of coal to avoid high-mercury content areas, coal washing to reduce mercury content, switching to cleaner fuel sources like natural gas, and implementing post-combustion removal technologies for mercury in power plant stack emissions. By combining regulatory measures and technological advancements, we can effectively reduce mercury emissions from burning fossil fuels and protect human health and the environment.
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Mercury in food
Mercury is a naturally occurring element that can be found in the Earth's crust. While it is present in the environment, human activities have significantly increased its presence, causing widespread global mercury pollution. Mercury emitted into the air eventually settles into water or onto land, where it can be washed into bodies of water. Certain microorganisms can then convert it into methylmercury, a highly toxic organic compound.
Methylmercury is the most common and harmful form of mercury found in seafood. It accumulates in fish, shellfish, and animals that consume fish. Nearly all fish and shellfish contain trace amounts of methylmercury. The consumption of seafood is the most common way people worldwide are exposed to mercury.
The health risks associated with methylmercury exposure vary depending on the amount consumed, the age of the consumer, and the duration and frequency of exposure. Developing fetuses and young children are most at risk of adverse health effects. In adults, consuming average amounts of seafood typically does not lead to harmful levels of methylmercury exposure. However, in cases of suspected methylmercury poisoning, a physician should be consulted for diagnosis through blood or urine tests.
To mitigate the risks associated with mercury in food, regulatory bodies such as the FDA and the European Commission have established maximum levels for mercury in certain foods. The FDA also provides recommendations for high-risk groups, such as pregnant or breastfeeding individuals, to ensure they make healthy food choices while limiting exposure to contaminants like mercury. Similarly, the European Commission advises limiting the consumption of fish and seafood species with high methylmercury content to a few servings per week.
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Mercury in soil
Mercury is a potent neurotoxin that poses a serious risk to human health and wildlife. It is released into the environment through natural sources and human activities, such as volcanic eruptions, rock weathering, and mining. While mercury occurs naturally in the earth's crust, human activities have led to widespread global mercury pollution.
Soil represents the largest store of mercury in terrestrial ecosystems. It is primarily introduced into the soil through deposition from the atmosphere. Mercury emitted into the air eventually settles onto land, where it can be washed into water. This deposition mainly occurs in the oxidized form (Hg2+), and its transformations are associated with the oxidation-reduction potential of the environment and the biological and chemical processes of methylation.
The presence of mercury in soil can have significant health risks. Exposure to mercury can occur through direct contact with contaminated soil particles or by consuming contaminated produce. High levels of inorganic mercury, which is commonly found in soils, can damage the kidneys, stomach, and intestines. It can also affect the nervous system, causing mood swings, memory loss, and behavioural changes. Skin exposure can result in rashes and dermatitis. Children and pregnant women are particularly vulnerable to the toxic effects of mercury exposure.
To address mercury contamination in soil, various remediation techniques have been developed. These include the use of nanomaterials such as carbon nanotubes, nanosheets, and magnetic nanocomposites. Organic matter from contaminant-free sources, such as compost, can also help dilute mercury concentrations in soil. Additionally, covering bare soil with mulch and maintaining moisture can reduce mercury particles in the air from dust.
While soil is a significant reservoir of mercury, it is important to recognize that mercury pollution extends beyond soil and can also impact water and air. The complex nature of mercury and its compounds presents a challenge in understanding its global cycle and predicting the effectiveness of regulatory efforts to reduce emissions and their impact on the environment and human health.
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Frequently asked questions
Globally, artisanal and small-scale gold mining (ASGM) is the largest source of anthropogenic mercury emissions (37.7%), followed by stationary combustion of coal (21%). Coal-fired power plants are the largest source of mercury emissions in many regions of the world.
Other large sources of emissions include non-ferrous metals production (15%) and cement production (11%). Mercury is also released from fuels or raw materials, or from uses in products or industrial processes.
Mercury is a potent neurotoxin that poses health risks to humans and wildlife. It can accumulate in fish to levels that are harmful to human health and the health of fish-eating wildlife. Most human exposure to mercury is from eating fish and shellfish contaminated with methylmercury.
