Arsenic and Mercury Poisoning Arsenic and Mercury Poisoning Joseph Campbell And Alicia Elgar

Arsenic Arsenic is found with other metals in natural mineral deposits. Forms of arsenic can be organic or inorganic. The inorganic form has the most toxicity. Many inorganic forms of arsenic come from industrial and agricultural waste. Our discussion will focus on the inorganic form of arsenic.

Absorption According to the Centers for Disease Control, an average person in the U.S. consumes 50 mg per day. Absorption of arsenic most commonly occurs through the GI tract, lungs, and skin. Most of the arsenic we ingest comes from our drinking water, but many forms of arsenic can also be found in food, and wine. The Environmental Protection Agency allows 10 parts per billion in drinking water. Arsenic is found in tobacco treated by older pesticides. It is absorbed through the skin by direct contact, industrial and agricultural workers are most susceptible to this form of absorption.

Distribution Most of our organs are susceptible, including barriers such as our skin. The cardiovascular system efficiently delivers the toxin to major organs. Concentrations in urine can cause bladder and kidney damage.

Action Kills by allosteric inhibition of essential metabolic enzymes. Targets a number of metabolic processes which affect nearly all organ systems. The toxin reacts with sulfhydrl groups. Pyruvate and Succinate oxidation pathways may be disrupted. Krebs cycle may be disrupted  depletes ATP stores. Prevents transformation of thiamine into acetyl-coenzyme A and succinyl  CoA  thiamine deficiency. Arsenic anions disrupt oxidative phosphorylation by replacing phosphoryl with less stable compounds  leads to arsenolysis (cell death). Reduction in glutathione and antioxidant enzymes  hepatic membrane damage. (Chattopadhyay 2002)

Metabolism Arsenic is changed into a less toxic form by methylation in the liver.

Excretion Arsenic is excreted in the urine but is highly nephrotoxic. Most arsenic is cleared from our systems within a few days if the dose is small.

Acute exposure Diffuse capillary leak (internal bleeding) and cardiomyopathy (heart inflammation)  shock. Renal failure. Elevates liver enzymes and kills liver cells. Noncarcinogenic effects of the skin may develop several years later after exposure!! Increases the frequency of spontaneous abortions in pregnant women and congenital defects in offspring. Patients are treated with chelating agents  arsenic forms a heterocyclic ring which is less toxic  excreted in the urine. Vitamins C and E have been shown to partially reverse arsenic toxicity. (Santra 2000) 1000 cases are reported each year, but fatalities are rare. Most people exposed to high concentrations suffer from secondary organ damage.

Chronic exposure Lung, skin, bladder, kidney, and liver cancer is often attributed to arsenic. Long-term ingestion through drinking water  more pronounced blood vessels outside the heart and brain. May destroy neurons  peripheral neuropathy. May develop bone marrow depression  inability to make blood cells. Pigment changes and thickening of the skin on the hands and feet.

Mercury Mercury is a metal that can be found in both organic and inorganic forms. Mercury is used in fluorescent light bulbs, some medications, thermometers, drinking water, and many other things. Young children are more susceptible to getting mercury poisoning than adults. The vapor form of mercury is the most toxic.

Absorption Most commonly by breathing contaminated air. Can also be absorbed by drinking water or eating contaminated food (usually fish, especially those that eat other fish). There about 2 ppm of mercury in one billion parts of drinking water.

Distribution Mercury is distributed to the bloodstream from the lungs, then the blood carries it to the central nervous system. This is especially harmful to young children, because their nervous systems are still developing.

Action There are no known mechanisms for mercury.

Metabolism Mercury is converted to HgCl2 where it remains in the body for years.

Excretion Mercury is excreted from the body through urine and feces. It can take the body several months to excrete it. Chelation therapy can also be used to help get rid of the toxin. This is where a substance that binds to the mercury is injected into the body, for easier removal.

Acute exposure Can lead to lung damage, vomiting, diarrhea, high blood pressure, eye and skin irritation. Mercury can cause damage to the body even before effects are noticed!! Some effects include: TremorsShynessIrritabilityInsomnia Changes in hearing or vision Difficulty with memory

Chronic exposure A few drops can raise the surrounding air to those of high contamination!! When mercury is inhaled it can lead to Acute necrotizing bronchitis Chemical pneumontis Death due to respiratory failure Damage to the kidneys, lungs, brain. Symptoms can be passed from child to fetus through the placenta, resulting in birth defects; Mental retardation BlindnessSeizures Problems with the nervous and digestive systems

References Chattopadhyay, SChattopadhyay, S ; Bhaumik, S ; Purkayastha, M ; Basu, S ; Chaudhuri, AN ; Das Gupta, S Apoptosis and necrosis in developing brain cells due to arsenic toxicity and protection with antioxidants. Toxicology Letters. v.136, no.1, p Bhaumik, SPurkayastha, MBasu, S Chaudhuri, ANDas Gupta, S Chattopadhyay, SBhaumik, SPurkayastha, MBasu, S Chaudhuri, ANDas Gupta, S Santra, A; Maiti, A; Das, S; Lahiri, S; Charkaborty, SK; Mazumder, DNG Hepatic damage caused by chronic arsenic toxicity in experimental animals. Journal of Toxicology. v.38, no.4, p MercPoison.htm MercPoison.htm