Arsenic Pollution: Understanding The Causes And Sources

Arsenic pollution is a pressing issue that poses serious risks to human health and ecosystems. Arsenic is a naturally occurring metalloid chemical element in the Earth's crust, present in over 200 minerals, and is introduced into drinking water through natural geological processes or human activities like mining and burning fossil fuels. While arsenic in the environment is usually not immediately dangerous, its presence in groundwater, soil, and food can lead to arsenic poisoning, causing severe health issues such as cancer, liver disease, and even death. The contamination of groundwater, a crucial source of drinking water for millions, is a significant concern, especially in regions like Bangladesh, India, and China.

Arsenic in drinking water

Arsenic is a naturally occurring element in the Earth's crust and is found in more than 200 minerals, the most common of which is arsenopyrite. It is also produced commercially from arsenic trioxide, a byproduct of metal smelting operations. Arsenic is released into the atmosphere primarily as arsenic trioxide through high-temperature processes such as coal-fired power plants, burning vegetation, and volcanic activity.

Arsenic can contaminate drinking water through its natural geological presence in local bedrock and arsenic-containing bedrock formations are known in Bangladesh, West Bengal (India), and regions of China. Arsenic-rich geothermal fluids can contaminate surface waters and soil when they come into contact. Arsenic can also be released into groundwater as a result of human activities, such as mining and the use of arsenic in industry, animal feed, wood preservatives, and pesticides. The burning of fossil fuels and coal, as well as the use of arsenic-containing pesticides, have also led to arsenic contamination of water sources.

In drinking water supplies, arsenic poses a significant risk to human health as it is toxic even at low levels and is a known carcinogen. Long-term exposure to arsenic in drinking water has been linked to various adverse health effects, including skin lesions, pigmentation changes, hard patches on the palms and soles (hyperkeratosis), and an increased risk of cancer, particularly skin, bladder, and lung cancer. Other health effects associated with long-term ingestion of arsenic-contaminated water include developmental effects, diabetes, pulmonary disease, and cardiovascular disease.

The World Health Organization (WHO) has set a provisional guideline value of 10 μg/L for arsenic in drinking water, and the Environmental Protection Agency (EPA) in the United States has established the same standard. However, drinking water with arsenic levels below this standard over extended periods can still increase the risk of cancer. Therefore, the EPA has set a goal of 0 μg/L for arsenic in drinking water. It is recommended that individuals with private wells test their water for arsenic regularly and use an alternate source or install a treatment system if arsenic levels are above the acceptable limit.

The presence of arsenic in drinking water is a significant concern, and efforts are being made to address this issue. The USGS, for example, studies local and national sources of arsenic to help health officials manage water resources effectively. Providing safe water supplies to affected communities is crucial to prevent further exposure to arsenic and mitigate its harmful health effects.

Arsenic in food

Arsenic is a naturally occurring element that is widely dispersed in the Earth's crust. It exists at an average concentration of approximately 5 mg/kg and occurs as a constituent in more than 200 minerals. Arsenic is also introduced into the environment through human activities, such as mining, metal smelting, and the burning of fossil fuels.

The consumption of contaminated foodstuffs is a major source of arsenic exposure. Arsenic can enter the food supply through plants and animals that ingest it from the environment. It is more common in certain foods and those grown in geographical areas with higher levels of arsenic. Arsenic can also enter food during processing, such as when contaminated water is added to a food product or when processing aids for filtering juices contain arsenic.

The FDA monitors and regulates arsenic levels in foods, including dietary supplements and cosmetics, to protect public health. They work with manufacturers to minimize or prevent chemical hazards and take regulatory action if a food product is found to be unsafe due to arsenic levels. The FDA has issued guidance to manufacturers to not exceed certain levels of inorganic arsenic in specific foods, such as infant rice cereals and apple juice. However, these are recommendations and not legally enforceable limits.

It is important to note that arsenic compounds usually have no smell or taste, so it can be challenging to detect their presence in food or water. The World Health Organization and the Centers for Disease Control and Prevention have identified contaminated drinking water as the most common source of high levels of inorganic arsenic exposure. Therefore, it is recommended to test drinking water sources, especially for those who rely on private wells, to ensure they meet the recommended guidelines for arsenic levels.

Arsenic in the air

Arsenic is a naturally occurring metalloid that is widely distributed in the Earth's crust. It is found in water, air, food, and soil. Arsenic is a significant risk factor for cancer after exposure to contaminated drinking water, cigarettes, foods, industry, occupational environment, and air. Arsenic is a confirmed carcinogen and is the most significant chemical contaminant in drinking water globally.

Inorganic arsenic compounds (such as those found in water) are highly toxic, while organic arsenic compounds (such as those found in seafood) are less harmful to health. Inorganic arsenic is more likely to be found in groundwater, whereas organic arsenic is mainly found in sea-living organisms. Inorganic arsenic poses more problems than organic arsenic. Arsenic is tasteless, colourless, and odourless, so testing is required for detection.

The major industrial processes that contribute to arsenic contamination of the air are mining, metal smelting, and burning fossil fuels. The use of arsenic-containing pesticides in the past has left large areas of agricultural land contaminated. Arsenic is also used in the preservation of timber, and this has led to environmental contamination. Arsenic can attach to very small particles in the air, stay airborne for many days, and travel long distances.

Air is an important source of arsenic exposure in areas with industrial activity. The presence of arsenic in airborne particulate matter is considered a risk for certain diseases. Natural, low-temperature biological reactions involving microbes also release arsenic into the atmosphere. Microbes acting on arsenic in soils and sediments generate arsine gas or other volatile arsenic compounds. Arsine reacts with oxygen in the air and is converted back to non-volatile forms of arsenic, which settle back to the ground.

Arsenic in soil

Arsenic is a naturally occurring element in the Earth's crust, present in over 200 minerals, the most common of which is arsenopyrite. It is also produced commercially from arsenic trioxide, a by-product of metal smelting operations.

Arsenic is introduced into the environment through natural and anthropogenic sources. Natural sources include volcanic activity, coal-fired power plants, burning vegetation, and the presence of arsenic in bedrock and groundwater. Anthropogenic sources include mining, metal smelting, burning fossil fuels, and the use of arsenic-containing pesticides and timber treatment.

When arsenic-rich geothermal fluids come into contact with surface waters, significant natural contamination of soil and water can occur. This has been observed in regions with arsenic-containing bedrock formations, such as Bangladesh, West Bengal (India), and regions of China.

Human activities, particularly mining and related operations, have been implicated in causing or exacerbating arsenic pollution. The use of arsenic in the past as a preservative for timber and in agriculture as a growth additive in poultry feed and pesticides has left large areas of agricultural land contaminated.

Gardeners and children are particularly vulnerable to arsenic exposure by ingesting or handling contaminated soil, touching treated wood, or breathing in contaminated soil particles. Rice is known to take up higher amounts of arsenic from the soil, posing a potential risk to consumers. While garden-related arsenic exposure is likely a small portion of a person's overall arsenic exposure, reducing exposure is advisable, especially for vulnerable individuals.

Industrial processes

Arsenic is a naturally occurring element in the Earth's crust and is present in more than 200 minerals. It is the 20th most abundant component of the Earth's crust. It is commercially produced from arsenic trioxide, which is a by-product of metal smelting operations.

Mining, metal smelting, and burning fossil fuels are the major industrial processes that contribute to arsenic contamination of air, water, and soil. Arsenic is used industrially as an alloying agent and in the processing of glass, pigments, textiles, paper, metal adhesives, wood preservatives, and ammunition. It is also used in the hide tanning process and, to a limited extent, in pesticides, feed additives, and pharmaceuticals.

The burning of fossil fuels, such as coal, releases arsenic into the atmosphere. Coal-fired power plants are a significant source of arsenic emissions. When coal is burned, ash is produced, which contains most of the naturally occurring arsenic. This ash is often collected and sent to disposal sites or recycled into commercial products. However, in countries like China, India, and South Africa, domestic coal use can result in higher arsenic exposure for the local population.

Metal smelting, particularly copper smelting, is another major contributor to arsenic pollution. Atmospheric arsenic emissions from copper smelting represent the largest contribution of arsenic from the mining and metals industry. Arsenic can be captured and removed from wastewater and smelting stacks before it is released into the environment, and technologies such as scrubbers, electrostatic precipitators, and baghouses can effectively control air pollution from smelters.

The use of arsenic-containing pesticides and wood preservatives in the past has also led to the contamination of agricultural land and the environment. Industrial tailing leakage accidents have caused arsenic contamination in freshwater ecosystems, resulting in catastrophic changes to the health and stability of these ecosystems.

Frequently asked questions