Heavy metal poisoning, or more properly metal toxicity is the toxic effect of certain metals in certain forms and doses on life. Some metals are toxic when they form poisonous soluble compounds. Certain metals have no biological role, i.e. are not essential minerals, or are toxic when in a certain form. In the case of lead, any measurable amount may have negative health effects. Often heavy metals are thought as synonymous, but lighter metals may also be toxic in certain circumstances, such as beryllium, and not all heavy metals are particularly toxic, and some are essential, such as iron. The definition may also include trace elements when considered in abnormally high, toxic doses.
Toxic metals sometimes imitate the action of an essential element in the body, interfering with the metabolic process to cause illness. Many metals, particularly heavy metals are toxic, but some heavy metals are essential, and some, such as bismuth, have a low toxicity. Most often the definition of “heavy metals” includes cadmium, lead, mercury and the radioactive metals. Metalloids (such as arsenic, polonium) may be included in the definition. Radioactive metals have both radiological toxicity and chemical toxicity. Metals in an oxidation state abnormal to the body may also become toxic: chromium(III) is an essential trace element, but chromium(VI) is a carcinogen.
Toxicity is a function of solubility. Insoluble compounds as well as the metallic forms often exhibit negligible toxicity. The toxicity of any metal depends on the molecules it is bound to. In some cases, organometallic forms, such as methylmercury and tetraethyl lead, can be extremely toxic. In other cases, organometallic derivatives are less toxic such as the cobaltocenium cation.
Decontamination for toxic metals is different from organic toxins. Because toxic metals are elements, they cannot be destroyed. Toxic metals may be made insoluble or collected, possibly by the aid of [[chelation|chelating agents. The standard practice to deal with large amounts of metal contaminated material is to keep it in one place, such as a tailings pond or hardzardous waste landfill and hope the engineered barriers do not allow the contaminants to dilute into the environment. Small increases in fat soluble contaminants lead to much larger increases in animals including humans.
Toxic metals can bioaccumulate in the body and in the food chain, Therefore, a common characteristic of toxic metals is the chronic nature of their toxicity. This is particularly notable with radioactive heavy metals such as radium, which imitates calcium to the point of being incorporated into human bone, although similar health implications are found in lead poisoning| or mercury poisoning. The exceptions to this are barium and aluminium, which can be removed efficiently by the kidneys.
Heavy metal toxicity is, in most cases, a zebra diagnosis – the condition itself is rare and the variety of symptoms mimic many other diseases. As a result, metal toxicity has a very high mortality rate even when victims seek timely medical treatment. In many other cases, the diagnosis is delayed long enough for permanent damage to occur. However, it is often found in clusters as from an epidemiological standpoint, the two most likely reasons for heavy metal toxicity are environmental contamination and occupational exposure. However, iron and lead exposure are fairly common and are usually diagnosed in a timely manner. However, the link between metal and mortality is ancient in origin, having been first described by Hippocrates who saw consistent symptoms in men who ran smelting operations. There is also a strong link between metal exposure and certain types of cancer
In some cases, metal toxicity has been traced to food or nutritional supplements which were either tainted or were in and of themselves toxic. For example, Maria Palko poisoned her husband with a folk medicine that contained gold salts, and Arlene Cuddy used a folk remedy that contained a lead salt. Many athletes have deliberately injected themselves with mercury in the mistaken belief that it builds muscle mass. In one infamous case, cardiomyopathy among beer drinkers was traced to cobalt used to stabilize the head of foam. Toxic metals have also been found in illegal drugs.
- Radioactive metals:
Aluminum has no known biological role and its classification into toxic metals is controversial. Significant toxic effects and accumulation to tissues have been observed in renally impaired patients. However, individuals with healthy kidneys can be exposed to large amounts of aluminium with no ill effects. Thus, aluminium is not considered dangerous to persons with normal elimination capacity.
Vanadium poisoning is notable as it is an anti-corrosive component of automotive steel, fragments of which can be left in passengers during an automobile accident.
Trace elements with toxicityEdit
- Chromium as hexavalent Cr(VI)
- Nickel – nickel salts are carcinogenic
- Copper – copper toxicity
- Zinc – zinc toxicity
- Iron – iron toxicity
Some heavy nonmetals may be erroneously called "metals", because they have some metallic properties.
Heavy metal poisoning is usually diagnosed by doing gas chromatography of a blood, hair or tissue sample. Heavy metals all have a distinct spectrum that is easy to distinguish from the normal chemicals found in human tissue. In addition, they are usually found in people who work in particular industries or with particular products, so an environmental scan of the patient's home and workplace can provide valuable clues.
Heavy metal poisoning is usually treated with chelation, the use of chemicals that bind to the heavy metal which are then processed through the kidney and allow the metals to be lost in urine or feces. However, chelation will only stop further damage to tissue – it cannot repair existing damage.
Types of Heavy Metal Poisoning Edit
Also see – Iron toxicity
As seen in:
- Emancipation – Culo developed the condition from being given too many iron supplements by his brother.
- The Jerk – Nate's iron levels were high due to his hemochromatosis and his recent switch to a diet containing meat.
Iron is the most commonly diagnosed form of metal toxicity. Although it is a vital nutrient, critical to the formation of hemoglobin for red blood cells, it is also ubiquitous in the environment. Iron toxicity can be the result of ingestion of a diet too rich in iron (including the use of iron supplements, which were once a common sight on pharmacy shelves to fight "tired blood"), occupational exposure, and genetic conditions. Although it is clear the body can process iron from the diet and dispose of excess iron in body waste, the mechanism by which this occurs to keep iron levels at an appropriate level is still poorly understood.
Lead and lead compounds are toxic to many of the body's tissues, including the heart, blood, reproductive system, digestive tract, kidneys, and nerves. Because these tissues develop more quickly in children, lead poisoning is particularly severe in young patients. Even non-lethal doses can have severe morbidity, leading to permanent problems with intellectual development. Lead poisoning can present with abdominal pain, headache, anemia, peripheral neuropathy and irritability. In severe cases, it can cause seizure, coma and death.
Lead is very common in the environment. It is found in many compounds used in industry, such as solder, and is one of the primary elements used in automobile batteries. Prior to 1970, lead was commonly used in the pigments of house paint, and homes built before that most likely have lead paint. Lead is easy to ingest when it is in the environment and is often found in drinking water. It is one of the most common employment related diseases.
Diagnosis of lead poisoning is fairly easy as it shows up clearly in blood tests.
Also see Lead
Cadmium does not occur naturally in the human body and even very low doses are toxic. In addition, the element tends to accumulate in the human body as it is not excreted in sweat, feces or urine. It is generally found in individuals who work in industry as it is used in certain types of solder and in plating operations. It can also be found in the air and soil around industrial facilities. Batteries, coatings and plastics often use cadmium (it is, for example, one of the main ingredients in certain types of rechargeable batteries). Cadmium causes symptoms that look like influenza, but more severe exposures can cause inflammation of the trachea and bronchial tubes, inflammation of the lungs, and pulmonary edema. After the respiratory problems, the element damages the kidneys and liver. It then starts to affect bone density leading to soft bones and osteoporosis. It can lead to both gout and loss of the sense of smell.
Mercury is a metallic element that is liquid at room temperature and vaporizes at a fairly low temperature. It also forms compounds with other elements rapidly. Although liquid mercury and solid mercury alloys (like dental amalgam) are not toxic and are readily passed through the digestive tract without harming human tissue, mercury vapors and mercury compounds are almost universally toxic to all life. All types of mercury poisoning can affect cognitive functions such as vision, hearing and speech, and can affect coordination. It's initial symptoms are peripheral neuropathy which manifests as burning, itching and edema. As mercury is not excreted from the body once it enters the bloodstream, it accumulates in animal tissue. Animals at the top of large food chains in mercury laden environments can have large amounts of mercury in their symptoms. This is particularly true of large carnivorous fish (e.g. swordfish), which are the main source of mercury in the human diet. Humans can also be exposed to mercury in many industries, such as mining and smelting. In the 19th century, mercury was often used to treat the felt in hats. Hat makers often suffered from mercury exposure which caused brain damage. The phrase "As mad as a hatter" and The Mad Hatter in Alice in Wonderland are two examples of this industrial illness having an effect on language well into the 21st century.
See also Mercury
Thallium is a metallic element and its compounds and vapors are also toxic. Because thallium compounds dissolve easily in water, they can be absorbed easily through the skin. Thallium is particularly dangerous because it binds to the same chemical processes as the essential trace element potassium and therefore interferes with its processing in the body. It used to be used widely in rat and ant poisons, but because of the danger in using it, it is no longer used in those applications. Most exposure is due to its use in electronics and glass manufacturing, but it is also used in pharmaceutical manufacturing. Its key symptoms are loss of hair and damage to the peripheral nerves. Due to the fact that most of its compounds are tasteless and it can be easily administered, it has been used as a means of deliberate poisoning.
Thallium poisoning can be treated with Prussian Blue, a pigment commonly used in artist's oil paints, which binds to thallium and allows it to be excreted.
As seen in Need to Know – "John" developed selenium poisoning by eating large numbers of nuts which had been grown in selenium rich soil. Unlike many heavy metals, the body does use selenium in trace amounts. However, excess selenium causes a condition known as selenosis, It is characterized by a garlic-like odor on the breath, gastro-instestinal problems, loss of hair and fingernails, fatigue, irritability and nerve damage. Food grown in selenium rich soil can often lead to selenosis.
Cobalt is also required by the body in small quantities. However, in larger quantities, it causes symptoms similar to intoxication. It is usually caused by exposure during the production of tungsten carbide, but can also be found in rechargeable batteries, industrial catalysts, glass coloring and paint pigments.
In its metallic form, gold is not toxic and is often added to specialty foods and drinks. None of the body's natural processes can break gold down into its atomic form, and gold easily resists corrosion even by stomach acid. However, most gold compounds, such as gold salts, are toxic as they break down in the body, releasing a gold ion. These can damage the liver and kidneys. One of the most common forms of gold poisoning is potassium gold cyanide, which is used in gold plating. Both the gold and the cyanide are toxic and both must be treated separately.
On the showEdit
Different types of heavy metal poisoning are one of the most common diagnoses on the show, having been the final diagnosis five times. Only cancer has more appearances, and only porphyria has as many. In addition, it shows up commonly in the differential diagnosis and is a common excuse for doing an environmental scan.
- In Sports Medicine, House realizes that Lola Wiggen has lost her sense of smell, which leads him to realize that both her and her much sicker husband Hank have been exposed to cadmium
- In Clueless, House determined that Bob Palko was being poisoned by gold at the hands of his wife Maria
- In Three Stories, House realizes that the usual lecturer Dr. Riley has lead poisoning when he looks at the doctor's home-made lead glazed mug.
- In All In, Foreman suggests Ian Alston has heavy metal poisoning, but House rules it out because Ian's hematocrit level was normal.
- In Son of Coma Guy, House believes that Kyle Wozniak may have mercury poisoning after learning from Gabriel Wozniak that he may have been exposed to mercury based paint.
- In Words and Deeds, Foreman thinks that thallium poisoning may explain why Derek Hoyt sees everything as the color blue.
- In Airborne, the team runs routine tests for heavy metals on Fran, which all come back negative.
- In Need to Know, Travis Brennan deliberatly poisons Casey Alfonso with thallium to mimic polio so he can "cure" her with massive doses of Vitamin C.
- Also in Need to Know, House finally diagnoses "John" with selenium poisoning after realizing he was eating Brazil nuts, not chestnuts.
- In Games, House suspected that Jimmy Quidd had been exposed to metals through contaminated drugs.
- In Living the Dream, House orders tests for heavy metal poisoning on Evan Greer and uses his suspicions to go to the soap opera studio to do an environmental scan.
- In Wilson's Heart, Taub suggests Amber Volakis might have lead poisoning.
- In The Itch, House finally traced Stewart Nozick's illness to lead from a previous gunshot wound.
- House orders chelation for Emmy in Let Them Eat Cake on the suspicion that she has heavy metal poisoning.
- In Big Baby, Kutner suggests Sarah's uncontrollable need to urinate is the result of heavy metal poisoning.
- In Epic Fail, Vince Pearson demands to be tested for mercury poisoning. Foreman gives in, but the levels are only slightly elevated. Pearson insists on receiving chelation to see if it works.
- In Locked In after finding out that Lee had been secretly working as a janitor in a battery factory, House suspected cadmium poisoning.
- In Knight Fall, House suspects Sir William may have been poisoned by the lead based miniatures he keeps in his apartment.
- In Open and Shut, Thirteen suggests mercury poisoning during the final differential of Julia, only to have House realize what is really wrong with her.
- In The Choice, Taub notes that Ted Taylor's old apartment has lead based paint.
- In Unwritten after finding out that Alice Tanner eats a lot of tuna, House suspects she might have mercury poisoning.
- In Massage Therapy, Taub suggests Margaret McPherson has lead poisoning and House agrees to test for it.
- In Small Sacrifices, Chase suggests Ramon Silva has heavy metal poisoning and House agrees to an environmental scan.
- In Family Practice, Arlene Cuddy is originally treated for lead poisoning when the team find a lead compound she has been using as medicine. However, the metal that is really killing her, and has been for years, was the cobalt in her hip joint replacement.
- In You Must Remember This, the team finds laxatives during an environmental scan and thinks that Nadia has magnesium poisoning.
- In Carrot or Stick, when both Driscoll and Landon Parks develop the same symptoms, Martha M. Masters thinks it may have been from lead batteries that she had seen.
- In Bombshells, Taub thinks that Ryan was exposed to lead through tainted marijuana.
- In Last Temptation, they think Kendall Pearson might have mercury poisoning from a high-fish diet, but they immediately rule it out because her red blood cells are normal.
- In Changes, the team thinks that Cyrus Harry may have heavy metal poisoning from subsisting on canned food. However, instead of chelation, which would also treat the other possible diagnosis of solvent inhalation, he orders forced urination. Thirteen tries to work around it by doing chelation behind House's back, but they are stymied when Cuddy cuts off House's hospital privileges. By the time House's privileges are restored, Cyrus develops more symptoms which rule out both conditions.
- When Chi Park discovers that one of Stevie Weathers' blood donors had been exposed to lead paint, they suspect lead poisoning.
- In Dead & Buried House thinks that Drew Lemayne had heavy metal poisoning, but rules it out after testing examples from an environmental scan.
Even clinic patients are not immune
- Sheldon and George suffered from antimony poisoning from the sizing used on their cheap polyester uniforms.
- Metal toxicity at Wikipedia – This article incorporates text from this Wikipedia article
- Dartmouth Toxic Metal Research Facility.
- OSHA. Safety and Health Topics: Toxic Metals.
- Heavy metal toxicity at Emedicine
- Heavy metal poisoning at The Free Dictionary
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