Arsenic poisoning
Introduction
Arsenic is infamous for its toxicity and harmful effects on human health, responsible for the death of many well-known historical characters like Napoleon Bonaparte, Alexander the Great or Pope Clement II. Arsenic contamination in drinking water and food sources has raised significant public health concerns, as prolonged exposure to even low levels can lead to serious health issues, including cancer and organ damage.
Arsenic
Arsenic is a chemical element with the symbol As and the atomic number 33. It is a metalloid and one of the pnictogens. Arsenic is a notoriously toxic heavy metal. It occurs naturally in many minerals, usually in combination with sulfur and metals, but also as a pure elemental crystal. Accumulation of arsenic in living bodies can result in skin and stomach problems, and it can even be a carcinogen. It has been historically used in pesticides, wood preservatives, and as a poison for assassination.
Mechanism
Firstly, arsenic interferes with crucial enzymes that regulate energy production in cells, for example ATPases, and enzymes involved in glycolysis. The toxic ions of arsenic (As³⁺) chemically bind to sulfhydryl groups (-SH) on enzymes and proteins, which disrupt their normal function by changing their structures. This inhibition, thus, affects cellular respiration, leading to reduced ATP production and energy deficits. Secondly, this element can also interfere with the mitochondrial function, specifically inhibiting oxidative phosphorylation. It can uncouple the process of ATP formation, leading to the generation of reactive oxygen species (ROS). These species cause oxidative stress and damage cellular components, including lipids, proteins, and DNA. Arsenic has genotoxic properties, indicating that it can damage DNA and adversely affect cellular replication. It leads to mutations, chromosomal abnormalities, and eventually results in the development of cancerous cells. Arsenic disrupts the methylation of DNA and other molecules, as well. Methylation is a critical process in regulating gene expression, DNA repair, and maintaining genome stability, so inhibiting this process can lead to abnormal gene expression and the activation of oncogenes, further contributing to cancer development. Moreover, chronic arsenic exposure can weaken the immune system, making individuals more susceptible to infections and impairing the body’s ability to repair damaged tissues. Furthermore, Arsenic severely affects the function of white blood cells and disrupts immune signaling pathways. These overall deteriorate one’s healthy body functioning.
Symptoms
Ingestion of a large quantity of arsenic causes symptoms similar to that of food poisoning, with frequent abdominal pain, nausea, vomiting and diarrhea. Bloody diarrhea may result in severe fluid loss, which can lead to a hypovolemic shock. Arsenic consequences can also be adverse to the circulatory and nervous system, such as QT interval prolongation, heart failure, seizure, coma and in the worst cases, death. 2 to 24 hours after the inhalation of arsine, which is the most lethal form of arsenic, a multisystem disease will occur, with symptoms including gastrointestinal distress, headache, kidney and liver dysfunction, and the destruction of red blood cells. At low level arsenic exposure, visible changes in the skin can be seen, such as hyperpigmentation.
Sources of exposure
Being the 20th most common chemical element on Earth, Arsenic is quite ubiquitous. Its contamination of groundwater has been recorded in many countries like Brazil, Cambodia, Afghanistan, Australia, and Bangladesh. The arsenic leaches into wells and water sources, and prolonged exposure to arsenic-contaminated drinking water can lead to serious health issues. In flooded conditions, arsenic in soil, especially inorganic compounds, can be absorbed by rice plants. Seafood is also found to be high in organic arsenic, which is considered less detrimental than other forms. Near industrial sites where arsenic is produced in large quantities, arsenic dust or fumes are released into the atmosphere from burning, mining and smelting. Furthermore, arsenic was widely used for manufacturing pesticides and herbicides in the past, for example lead arsenate. Although its usage has been banned, residues can still remain in the environment, especially in soils where these chemicals were used.
Real-life cases
The Bangladesh and West Bengal Arsenic Contamination from 1990 until now is one of the most widespread cases of arsenic poisoning in history. Millions of people in these regions were exposed to arsenic-contaminated drinking water from tube wells. Eventually it became evident that arsenic naturally leached into the water from the soil, and prolonged exposure resulted in severe health issues. This exposure is linked to various diseases, including skin cancer, lung cancer, bladder cancer, and cardiovascular diseases in the locals.
Another well-known case is the death of Napoleon Bonaparte, which although still under the shadow of doubt, has been suggested to be caused by arsenic poisoning from his wallpaper in the bedroom.
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