Heavy metal poisoning
Heavy metal poisoning is the toxic accumulation of heavy metals in the soft tissues of the body.
Heavy metals are chemical elements that have a specific gravity (a measure of density) at least five times that of water. The heavy metals most often implicated in human poisoning are lead, mercury, arsenic, and cadmium. Some heavy metals, such as zinc, copper, chromium, iron, and manganese, are required by the body in small amounts, but can be toxic in larger quantities. Heavy metals may enter the body through food, water, or air, or by absorption through the skin. Once in the body, they compete with and displace essential minerals such as zinc, copper, magnesium, and calcium, and interfere with organ system function. People may come in contact with heavy metals in industrial work, pharmaceutical manufacturing, and agriculture. Children may be poisoned as a result of playing in contaminated soil.
Sources of exposure for some heavy metals
- lead: old paint, leaded gasoline, old pipes
- mercury: contaminated fish, industrial and agricultural wastes
- cadmium: industrial waste, insecticides, old galvanized pipes
- arsenic: insecticides and industrial processes, some drinking water
Causes & symptoms
Symptoms will vary, depending on the nature and quantity of the heavy metal, and whether it was ingested or inhaled. Patients who ingest a heavy metal may complain of cramps, nausea, vomiting, diarrhea, stomach pain, headache, sweating, and a metallic taste in the mouth. Mercury can cause skin burns if it has touched the skin, and inhaled mercury vapor can cause severe inflammation of the lungs. If lead is inhaled in the form of lead dust, insomnia, headache, mania, and convulsions may occur. In severe cases of heavy metal poisoning, patients exhibit obvious impairment of cognitive, motor, and language skills. The expression "mad as a hatter" comes from the mercury poisoning prevalent in seventeenth-century France among hatmakers who soaked animal hides in a solution of mercuric nitrate to soften the hair.
Heavy metal poisoning may be detected using blood, urine, and stool tests, hair and tissue analysis, or x rays. In children, blood lead levels above 80 mcg/dl generally indicate lead poisoning; however, significantly lower levels (>.30 mcg/dL) can cause mental retardation and other cognitive and behavioral problems in chronically exposed children. The Centers for Disease Control and Prevention considers a blood lead level of 10 mcg/dl or higher in children a cause for concern. In adults, symptoms of lead poisoning are usually seen when blood lead levels exceed 80 mcg/dl for a number of weeks. Blood levels of mercury should not exceed 3.6 mcg/dl, while urine levels should not exceed 15 mcg/dl. Symptoms of mercury poisoning may appear when mercury levels exceed 20 mcg/dl in blood and 60 mcg/dl in urine. Mercury levels in hair may be used to gauge the severity of chronic mercury exposure, but a 2002 report says that these tests have questionable validity.
Since arsenic is rapidly cleared from the blood, blood arsenic levels may not be very useful in diagnosis. Arsenic in the urine (measured in a 24-hour collection following 48 hours without eating seafood) may exceed 50 mcg/dl in people with arsenic poisoning. If acute arsenic poisoning is suspected, an x ray may reveal ingested arsenic in the abdomen (since arsenic is opaque to x rays). Arsenic may also be detected in the hair and nails for months following exposure. Cadmium toxicity is generally indicated when urine levels exceed 10 mcg/dl of creatinine and blood levels exceed 5 mcg/dl.
Emergency treatment of acute poisoning, especially in children, can be handled by calling a poison control line (800-222-1222) or by dialing 911. Alternative practitioners often rely on the same chelating agents used by standard doctors to treat heavy metal poisoning, but also use natural supplements and additional techniques to assist the body's own detoxification processes. One highly contested issue between alternative medicine and mainstream dentistry surrounds mercury poisoning. Alternative practitioners believe that there is a large body of evidence suggesting that silver amalgam tooth fillings, which contain mercury, are a major factor in mercury poisoning. For those with high mercury levels in their bodies, they recommend that all mercury-containing tooth fillings be removed by a holistic dentist. The National Institutes of Health hope to put some of the debate over amalgam fillings to rest with two clinical trials on fillings currently underway. However, the results are not expected until 2005.
Dietary changes are used to support the treatment of heavy metal poisoning. Detoxification diets are predominantly vegetarian, and reduce or avoid foods that may stress the immune system, such as processed foods, fried foods, sugar, fat, alcohol, caffeine, meat, and dairy products. Organic foods are recommended to avoid exposure to pesticides and chemicals. Detoxification diets include plenty of high-fiber foods, including oat bran and psyllium seeds, to help cleanse the digestive tract. Apples, pears, and legumes are high in pectins, which are believed to have chelating effects on heavy metals. Foods high in antioxidants are recommended, such as fruits, vegetables, and fresh juices. Sulfur-containing foods such as garlic, onions, and eggs (organically produced) are utilized, as are dark-green leafy vegetables that contain high amounts of chlorophyll. Foods that may contain heavy metals are avoided, including many fish and shellfish. Factory-farmed chicken and eggs are avoided as well, because chickens are often fed fish meal. A 2002 study reported that eating tofu may reduce lead levels in the blood. Tofu is rich in calcium, which may help reduce the blood's ability to absorb and retain lead.
Nutritional supplements include antioxidant vitamins A, C, and E, and multimineral supplements that contain calcium, iron, magnesium, copper, chromium, selenium, and zinc. Cysteine, methionine, L-gluthione, and DMSA (dimethyl succinate) are other supplements. Herbal support includes herbs that have detoxification effects, such as milk thistle, burdock, and numerous others. Spirulina and chlorella sea algae are used as well, and acidophilus helps rebuild the digestive tract.
Homeopathic remedies, which prompt the body's detoxification mechanisms, have shown success with heavy metal poisoning. Detoxification therapies are also highly recommended, including fasting, sweating, colonics, and therapeutic vomiting. Ayurvedic medicine has an intensive detoxification and healing program called panchakarma.
In an emergency, patients should call 911 or a poison control hotline (800) 222-1222. The treatment for most heavy metal poisoning is chelation therapy. A chelating agent specific to the metal involved is given orally, intramuscularly, or intravenously. The three most common chelating agents are edetate calcium disodium, dimercaprol (BAL), and penicillamine. Succimer (DMSA) is used for children suffering from lead poisoning. The chelating agent encircles and binds the metal in the body's tissues, forming a complex that is then released from the tissue and travels in the bloodstream. The complex is filtered out of the blood by the kidneys and excreted in the urine. This process may be lengthy and painful, and typically requires hospitalization. Chelation therapy is effective in treating lead, mercury, and arsenic poisoning, but is not useful in treating cadmium poisoning. To date, no treatment has been proven effective for cadmium poisoning. In cases of acute mercury or arsenic ingestion, vomiting may be induced. Washing out the stomach (gastric lavage) may also be useful. The patient may also require treatment such as intravenous fluids for complications of poisoning such as shock, anemia, and kidney failure.
The chelation process can only halt further effects of the poisoning; it cannot reverse neurological damage already sustained.
Because exposure to heavy metals is often an occupational hazard, protective clothing and respirators should be provided and worn on the job. Protective clothing should then be left at the work site and not worn home, where it could carry toxic dust to family members. Industries are urged to reduce or replace the heavy metals in their processes wherever possible. Exposure to environmental sources of lead, including lead-based paints, plumbing fixtures, vehicle exhaust, and contaminated soil, should be reduced or eliminated.
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