Bronte Wells
Mercury is a toxic pollutant that poses serious health and environmental risks. It is a global pollutant that does not recognise national or continental boundaries, and it can remain in the atmosphere for up to a year before being deposited back to Earth. Mercury is released into the environment through both natural processes and human activities, with two-thirds of global mercury emissions being attributed to industrial pollution. As a criteria air pollutant, mercury's presence in the environment is of significant concern.
| Characteristics | Values |
|---|---|
| Type of Pollutant | Global, regional, and local pollutant |
| Sources | Natural sources (e.g., volcanic eruptions, undersea vents, rock weathering) and anthropogenic (human-caused) sources (e.g., electricity production, waste incineration, industrial pollution, mining, fossil fuel combustion) |
| Impact | Toxic effects on human health, wildlife, and ecosystems; bioaccumulation and bioconcentration in fish and other top predators |
| Mitigation | Policies and regulations to limit Hg releases from human activities and control its transport; strategies geared towards specific locations |
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What You'll Learn
Mercury is a global pollutant
Once emitted, mercury can remain in the atmosphere for up to a year before being deposited back to the earth in rainfall or dry gaseous form. It can travel thousands of miles in the atmosphere, knowing no national or continental boundaries. This means that even regions far away from emission sources can be affected by mercury pollution.
When mercury is deposited on land, it can contaminate soil and plants, with areas near Hg mines showing significantly higher Hg content. Mercury deposition on the ground with low vegetation is 3-5 times lower than in forests, and areas of land devoid of vegetation emit more Hg than those with plants. Mercury emitted into the environment does not degrade and can be emitted back into the atmosphere through various processes.
Mercury deposited on water bodies enters streams, lakes, estuaries, and coastal waters, affecting aquatic ecosystems, especially those with large wetland areas. Mercury accumulates in fish and other organisms, leading to bioaccumulation and bioconcentration. As a result, humans and animals that consume contaminated fish are at risk of exposure to methylmercury, which has various toxic effects. Developing fetuses and young children are particularly vulnerable to the harmful effects of mercury exposure, and it is estimated that more than 75,000 newborns in the United States each year may have an increased risk of learning disabilities associated with in-utero exposure to methylmercury.
To address the issue of mercury pollution, policies and regulations have been implemented to limit Hg releases from human activities and control its transport within and among the atmosphere, freshwaters, the lithosphere, and the ocean at local, regional, and global scales. However, mercury continues to be a pervasive global pollutant, and further research is needed to improve our understanding of Hg dynamics and the effectiveness of control measures.
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Human activities cause mercury pollution
Mercury is a global pollutant that affects human and ecosystem health. While mercury does occur naturally in the earth's crust, human activities have led to widespread global mercury pollution. Two-thirds of the mercury in the world is released into the environment by human activities, such as electricity production and waste incineration.
The largest source of anthropogenic mercury emissions is artisanal and small-scale gold mining (ASGM), which accounts for 37.7% of emissions. Mercury is used in the gold extraction process and often released through the burning of coal. Coal-fired power plants are the highest emitters, at approximately 34% of the total. In addition to direct emissions into the air, power plants also produce 33 tons of mercury as coal waste.
Another major source of mercury emissions is the stationary combustion of coal for power and heat, accounting for 21% of emissions. Coal contains mercury and other hazardous air pollutants that are released when burned in industrial boilers and household stoves. Residential coal burning for heating and cooking is also a significant contributor to mercury emissions.
Industrial processes and waste incinerators are other human activities that release mercury into the environment. Mercury is emitted into the air and eventually settles into water or onto land, where it can be washed into water bodies such as streams, lakes, and estuaries. Once deposited, certain microorganisms can convert it into methylmercury, a highly toxic form that builds up in fish, shellfish, and animals that consume them.
The continued release of mercury into the environment from these human activities has led to the adoption of the Minamata Convention on Mercury in 2013. The convention aims to address mercury emissions and phase out certain mercury-containing products.
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Mercury's impact on human health
Mercury is a global pollutant that affects human health. It is released into the environment through human activities such as mining and fossil fuel combustion. Once emitted into the air, mercury can travel thousands of miles before settling into water bodies or onto land, where it can be washed into water. Certain microorganisms can then transform it into methylmercury, a highly toxic substance that accumulates in fish, shellfish, and animals that consume these aquatic organisms. As a result, most human exposure to mercury occurs through the consumption of contaminated fish and shellfish.
The health effects of mercury exposure can vary from severe to subtle, or there may be no observable effects at all. The inorganic salts of mercury are particularly harmful when ingested, causing corrosion to the skin, eyes, and gastrointestinal tract, and leading to kidney toxicity. Exposure to elemental mercury in the air at levels of 20 μg/m3 or higher over several years can result in mild, subclinical signs of central nervous system toxicity. Neurological and behavioural disorders may also arise from inhaling, ingesting, or coming into contact with various mercury compounds. Symptoms include tremors, insomnia, memory loss, neuromuscular issues, headaches, and cognitive and motor dysfunction.
Developing fetuses are particularly vulnerable to the harmful effects of mercury. Exposure to methylmercury during pregnancy can pose risks to the unborn child. It is estimated that over 75,000 newborns in the United States each year may have an increased risk of learning disabilities associated with in-utero exposure to methylmercury. Additionally, high doses of certain mercury forms have been linked to increased tumour growth in rats and mice, although there is currently no direct evidence of a link between mercury exposure and cancer in humans.
To address the health risks associated with mercury exposure, interventions such as the Minamata Convention on Mercury have been established. This convention obliges participating governments to take action, such as reducing mercury emissions and phasing out specific mercury-containing products. The World Health Organization (WHO) also plays a crucial role in raising awareness, providing guidance on identifying at-risk populations, and developing tools to reduce mercury exposure, especially among vulnerable groups like pregnant women and infants.
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Natural sources of mercury
Mercury is a naturally occurring element that is found in the Earth's crust. Natural sources of mercury emissions include volcanic eruptions, evaporation from soil and water surfaces, degradation of minerals, forest fires, geothermal springs, and the ocean. While mercury does occur naturally, human activities such as mining, fossil fuel combustion, coal combustion, waste incineration, industrial uses, and non-ferrous metals production have significantly increased its presence in the environment, leading to widespread global mercury pollution.
Volcanic eruptions are a significant natural source of mercury emissions. When volcanoes erupt, they release mercury into the atmosphere, which can then be transported over long distances. Volcanic activity contributes to the overall global mercury burden, with the emitted mercury eventually settling back to the Earth in rainfall or dry gaseous form.
Soil and water surfaces are also natural sources of mercury emissions. Mercury can evaporate from soil and water, leading to the release of mercury vapour into the atmosphere. This process contributes to the environmental mercury levels and the overall global mercury cycle.
Additionally, the degradation of minerals and forest fires can release mercury into the atmosphere. Forest fires, in particular, can result in the rapid and uncontrolled release of mercury, contributing to local and regional mercury concentrations.
Geothermal springs are another natural source of mercury. The heated waters of geothermal springs can contain elevated levels of mercury, which can be released into the surrounding environment.
Lastly, the ocean is a natural source of mercury emissions. The ocean is a complex reservoir of mercury, with exchanges occurring between the ocean surface and the atmosphere. While the ocean can act as a sink for mercury, absorbing and sequestering it, it can also release mercury back into the atmosphere through emissions.
While natural sources of mercury emissions exist, it is important to note that human activities have significantly contributed to the overall levels of mercury in the environment. The available information indicates that natural sources account for less than 50% of total mercury releases, with anthropogenic sources being the major contributors to mercury emissions in the atmosphere, water, and soil.
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Mercury's effect on wildlife and ecosystems
Mercury is a highly hazardous substance that poses significant risks to wildlife and ecosystems. It is a global pollutant that does not respect national or continental boundaries. Once emitted into the air, mercury can travel thousands of miles before settling back onto the earth in rainfall or dry gaseous form. This means that even remote ecosystems are at risk of mercury contamination.
Mercury affects both biotic (living organisms) and abiotic (non-living) components of ecosystems. In aquatic ecosystems, mercury accumulates in fish and other marine life through a process called bioaccumulation. This process results in higher concentrations of mercury in organisms higher up the food chain, such as top predators like eagles and seals. Birds and mammals that consume contaminated prey can experience neurological damage, reproductive issues, and even death. This, in turn, can lead to population declines and disruptions in ecosystem dynamics.
Mercury contamination also extends beyond aquatic environments, impacting terrestrial mammals such as otters and dolphins. These animals can suffer similar neurological and reproductive issues, leading to behavioral changes and population declines. Mercury's toxicity can also affect plant health, disrupting natural habitats and further impacting wildlife.
The impact of mercury pollution on fish populations has socio-economic consequences, particularly for fisheries and local communities. Fish species that accumulate high levels of methylmercury, such as tuna, swordfish, and freshwater bass, are commonly consumed by humans, leading to potential health risks. Evidence suggests that mercury pollution leads to reduced stock sizes of commercial fish species, which can affect the profitability of fisheries and the livelihoods of those who depend on them.
The complex nature of mercury in the environment makes it challenging to determine the precise ecological and human health risks associated with exposure. However, the development of frameworks such as the System for Environmental Economic Accounting (SEEA) can help systematically map the natural and monetary effects of mercury pollution. Global efforts to reduce mercury emissions and protect ecosystems and human health are ongoing.
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Frequently asked questions
Yes, mercury is a local, regional, and global pollutant. It is a criteria air pollutant that can harm human health, wildlife, and the environment.
Mercury is released into the environment through human activities and natural sources and processes. Human activities, such as electricity production, waste incineration, mining, and fossil fuel combustion, contribute to about two-thirds of mercury emissions globally. Natural sources include volcanic eruptions, undersea vents, and emissions from the ocean.
Mercury is a toxic pollutant that accumulates in fish and other aquatic organisms, affecting humans and animals that consume them. It can also contaminate soil and plants, entering the food chain. Exposure to mercury can have irreversible toxic effects, especially for developing fetuses and young children. It poses risks to human health, with warnings issued against consuming certain types of fish from specific water bodies.
