Meghan Hodges
Mercury is a global pollutant that affects human and ecosystem health. It is released into the environment through both primary and secondary sources. Primary pollutants are those that are emitted directly from a source, which can be of natural origin, such as volcanic eruptions, or anthropogenic origin, such as emissions from vehicles and industrial activities. Mercury released through anthropogenic sources far exceeds that of natural sources, leading to increased mercury reservoirs and subsequent secondary emissions that contribute to its global distribution. Secondary pollutants, on the other hand, are formed when primary pollutants interact and react in the atmosphere.
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What You'll Learn
Mercury is a global pollutant
Mercury (Hg) is a global pollutant that affects human and ecosystem health. Mercury is listed as a primary pollutant, which means it is directly emitted into the environment. Primary pollutants are emitted from many sources, including cars, coal-fired power plants, natural gas power plants, biomass burning, natural forest fires, and volcanoes.
Mercury is released into the environment through natural and anthropogenic processes. Natural geogenic sources of mercury include volcanic eruptions, while anthropogenic sources include industrial activities such as combustion facilities, cement or glass production, and waste incineration. Primary anthropogenic emissions of mercury greatly exceed natural sources, resulting in increases in mercury reservoirs and subsequent secondary mercury emissions that facilitate its global distribution.
Secondary pollutants, on the other hand, are formed through the interaction of primary pollutants in the atmosphere. While mercury is classified as a primary pollutant, it can also contribute to the formation of secondary pollutants. For example, mercury can react with other pollutants in the atmosphere to form tropospheric ozone, which is harmful to human health and can cause respiratory problems and eye irritation.
The elevated presence of mercury in the environment has significant implications for human and wildlife health. Human exposure to methylmercury, a neurotoxin, primarily occurs through the consumption of estuarine and marine fish. Developing fetuses are particularly vulnerable to the harmful effects of methylmercury. Additionally, the production of methylmercury in freshwater, terrestrial, and coastal environments poses risks to wildlife populations.
The global distribution of mercury and its impact on human and ecosystem health have prompted the implementation of policies and regulations to limit mercury releases from human activities. These efforts aim to control the transport and dispersion of mercury within and among the atmosphere, freshwaters, the lithosphere, and the ocean at local, regional, and global scales. Understanding the sources, pathways, and effects of mercury as a global pollutant is crucial for developing effective strategies to mitigate its harmful impacts.
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Mercury is a primary pollutant
Mercury is a heavy metal that does not degrade in nature, making it a significant concern for the environment and human health. Primary anthropogenic Hg emissions greatly exceed natural geogenic sources, resulting in increases in Hg reservoirs and subsequent secondary Hg emissions that facilitate its global distribution. The ultimate fate of emitted Hg is primarily recalcitrant soil pools and deep ocean waters and sediments.
Mercury can be transferred to the environment through atmospheric exchanges of wet and dry deposition and evasion from vegetation, soil organic matter, and ocean surfaces. The net production of methylmercury, which is toxic to humans and wildlife, is a key link between inorganic Hg inputs and exposure. Elevated human exposure to methylmercury primarily results from the consumption of estuarine and marine fish. Developing fetuses are most at risk from this neurotoxin, but health effects on highly exposed populations and wildlife are also a concern.
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. These efforts are crucial to mitigate the harmful effects of mercury pollution on human and ecosystem health.
In summary, mercury is a primary pollutant that is directly emitted into the environment through human activities. It poses significant risks to human and ecosystem health, and global efforts are underway to control and reduce mercury emissions.
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Mercury is a secondary pollutant
The burning of fossil fuels, such as coal, oil, and natural gas, releases mercury and other pollutants into the atmosphere. Industrial activities, such as cement or glass production, can also release mercury. Waste incineration is another source of mercury pollution, as mercury can be present in the waste stream. In addition, mercury can be released into the atmosphere from natural sources, such as volcanic eruptions.
Once emitted into the atmosphere, mercury can travel long distances and be deposited in water bodies, where it can be converted into methylmercury by microorganisms. Methylmercury is a highly toxic form of mercury that can accumulate in fish and other aquatic organisms, posing a risk to human health through the food chain.
Human activities have significantly contributed to the increase in mercury emissions. Primary anthropogenic Hg emissions greatly exceed natural geogenic sources, resulting in increases in Hg reservoirs and subsequent secondary Hg emissions that facilitate its global distribution. East Asia currently accounts for almost 40% of total primary global anthropogenic emissions of Hg.
International 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. These efforts are crucial in mitigating the impacts of mercury pollution on human health and the environment.
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Mercury emissions and human exposure
Mercury emissions are a global problem that does not respect national or continental boundaries. Mercury emitted into the air can travel thousands of miles before it is deposited back to Earth in rainfall or dry gaseous form. Human activity is the primary cause of mercury releases, with natural sources contributing a smaller amount. Primary anthropogenic sources of mercury emissions include industrial processes, coal-fired power plants, residential coal burning, waste incinerators, and the use of mercury in products. The largest source of anthropogenic mercury emissions is artisanal and small-scale gold mining (ASGM), contributing 37.7% of total emissions. This is followed by stationary coal combustion (21%), non-ferrous metals production (15%), and cement production (11%). Natural sources of mercury emissions include volcanic eruptions and ocean emissions.
Once mercury is emitted into the atmosphere, it can be deposited onto land or water, where it may be re-emitted into the atmosphere through exchanges of wet and dry deposition. Mercury can also be emitted from vegetation, soil organic matter, and ocean surfaces. The ultimate fate of emitted mercury is primarily recalcitrant soil pools and deep ocean waters and sediments. However, the transfer of mercury emissions to these reservoirs can take centuries.
Mercury is a significant health concern for humans, with even small amounts causing serious health problems. The developing fetus is most at risk from exposure to mercury, which can result in neurological and behavioural disorders, tremors, insomnia, memory loss, neuromuscular effects, headaches, and cognitive and motor dysfunction. Mercury can also have toxic effects on the nervous, digestive, and immune systems, as well as the lungs, kidneys, skin, and eyes. Most human exposure to mercury occurs through the consumption of contaminated fish and shellfish, with methylmercury being the primary compound of concern. Mercury builds up in fish, shellfish, and animals that eat fish, and it is this bioaccumulation that makes them dangerous to consume.
To address the issue of mercury emissions and human exposure, the Minamata Convention on Mercury was adopted in 2013. This convention obliges governments to take action on mercury emissions and phase out certain mercury-containing products. An amendment to the convention in 2023 prohibits the manufacture, import, or export of certain mercury-added products, including batteries, switches, relays, fluorescent lamps, non-electronic measuring devices, and cosmetics. Additionally, the World Health Assembly Resolution 67.11 (2014) focuses on the public health impacts of mercury exposure and the role of WHO and ministries of public health in implementing the Minamata Convention.
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Sources of mercury emissions
Mercury emissions are a global issue that does not respect national or continental boundaries. Mercury emitted into the atmosphere can travel thousands of miles before eventually settling on land or in bodies of water. Mercury contamination is a well-known environmental issue, with studies as early as the 1950s establishing the toxic effects of mercury on human health and wildlife.
There are two types of sources of mercury emissions: natural and anthropogenic (human-caused). Natural sources of mercury emissions include volcanic eruptions, emissions from the ocean, geothermal springs, and geologic deposits. These natural sources contribute 80 to 600 Mg yr–1 of mercury to the atmosphere.
However, human activities have significantly increased the amount of mercury in the environment, with primary anthropogenic sources releasing 1900-2900 Mg yr–1. Artisanal and small-scale gold mining (ASGM) is the largest source of anthropogenic mercury emissions (37.7%), followed by stationary combustion of coal (21%). Other significant sources include non-ferrous metal production (15%) and cement production (11%). Coal combustion, waste incineration, industrial processes, and mining are other human-related activities that release mercury into the environment.
The industrial sector and transportation are major contributors to primary pollutant emissions, with the burning of gasoline and diesel being particularly harmful. These activities release mercury and other pollutants into the atmosphere, leading to widespread contamination.
Mercury emitted from these various sources can have toxic effects on human health, with developing fetuses and young children being especially vulnerable. It is a potent neurotoxin that accumulates in fish, leading to health concerns for both humans and wildlife that consume these fish. The contamination of aquatic ecosystems by mercury has prompted policies and regulations to limit mercury releases from human activities and control its transport in the environment.
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Frequently asked questions
Primary pollutants are any type of pollutant emitted directly into the environment. They can be emitted from many sources, including cars, coal-fired power plants, natural gas power plants, biomass burning, natural forest fires, and volcanoes.
Yes, mercury is a primary pollutant. It is released into the environment through human activities such as combustion facilities, cement or glass production, and waste incineration facilities.
Secondary pollutants, on the other hand, are not emitted directly. They are formed when primary pollutants interact and react in the atmosphere. For example, tropospheric ozone, also known as "bad ozone", is a secondary pollutant that is formed through the interaction of various precursors, such as volatile organic compounds, carbon monoxide, and nitrogen oxides, in the presence of sunlight.
