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Last updated: 10/24/2024
Years published: 1989, 1991, 1998, 2006, 2024
NORD gratefully acknowledges Gioconda Alyea, MD (FMG), MS, National Organization for Rare Disorders, for assistance in the preparation of this report.
Heavy metal poisoning is the accumulation of heavy metals, in toxic amounts, in the soft tissues of the body. Symptoms and physical findings associated with heavy metal poisoning vary according to the metal accumulated. Many of the heavy metals, such as zinc, copper, chromium, iron and manganese, are essential to body function in very small amounts. But, if these metals accumulate in the body in concentrations sufficient to cause poisoning, then serious damage may occur. Children are more susceptible to being poisoned than adults.
The common list of non-essential heavy metals that cause toxicity includes arsenic, cadmium, lead, mercury and those that are essential to humans in trace quantities for many cellular activities, such as cobalt, copper, chromium, iron, manganese, nickel, selenium and zinc.
The heavy metals most commonly associated with poisoning of humans are lead, mercury, arsenic and cadmium. Heavy metal poisoning may occur as a result of industrial exposure, air or water pollution, foods, medicines, improperly coated food containers, or the ingestion of lead-based paints.
Treatment includes stopping exposure and removing the toxic metal from the body. Chelating agents are special drugs that bind to the metals and help the body excrete them.
The symptoms of heavy metal poisoning vary according to which type of metal overexposure is involved.
The Centers for Disease Control and Prevention (CDC) offers information in many heavy metals that you can see by using the Substances A-Z index. Some specific examples are:
ARSENIC POISONING
Arsenic is used in the manufacture of pesticides. The gas from arsenic also has some industrial uses. Overexposure may cause headaches, drowsiness, confusion, seizures and life-threatening complications. Neurological symptoms include brain damage (encephalopathy), nerve disease of extremities (peripheral neuropathy), pericapillary hemorrhages within the white matter and loss or deficiency of the fatty coverings (myelin) around these nerve fibers (demyelination). Skin problems include transverse white bands on the fingernails (meesโ lines) and excessive accumulation of fluid in the soft layers of tissue below the skin (edema). Gastrointestinal symptoms include a flu-like illness (gastroenteritis) that is characterized by vomiting; abdominal pain; fever; and diarrhea, which, in some cases, may be bloody. Other symptoms include breakdown of the hemoglobin of red blood cells (hemolysis), a low level of iron in the red blood cells (anemia) and low blood pressure (hypotension). Some individuals may experience a garlic-like odor that may be detectable in the breath.
In cases of chronic poisoning, weakness, muscle aches, chills and fever may develop. The onset of symptoms in chronic arsenic poisoning is about two to eight weeks after exposure. Skin and nail symptoms include hardened patches of skin (hyperkeratosis) with unusually deep creases on the palms of the hands and the soles of the feet, unusual darkening of certain areas of the skin (hyperpigmentation), transverse white bands on the fingernails (meesโ lines) and a scale like inflammation of the skin (exfoliative dermatitis). Other symptoms include inflammation of sensory and motor nerves (polyneuritis) and the mucus membrane lining the throat.
Inorganic arsenic accumulates in the liver, spleen, kidneys, lungs and gastrointestinal tract. It then passes through these sites but leaves a residue in tissues such as skin, hair and nails. Symptoms of acute inorganic arsenic poisoning include severe burning of the mouth and throat, abdominal pain, nausea, vomiting, diarrhea, low blood pressure (hypotension, and muscle spasms. Individuals with severe inorganic arsenic poisoning may experience heart problems (cardiomyopathy); accumulation of acid in the tubes of the kidneys (renal tubular acidosis); breakdown of the hemoglobin of red blood cells (hemolysis); irregular heart rhythms (ventricular arrhythmias); coma; seizures; bleeding within the intestines (intestinal hemorrhage) and yellowing of the skin, mucous membranes and whites of the eyes (jaundice).
CADMIUM POISONING
Cadmium is used for many items, including electroplating, storage batteries, vapor lamps and in some solders. The onset of symptoms may be delayed for two to four hours after exposure. Overexposure may cause fatigue, headaches, nausea, vomiting, abdominal cramps, diarrhea and fever. In addition, progressive loss of lung function (emphysema), abnormal buildup of fluid within the lungs (pulmonary edema) and breathlessness (dyspnea) may also be present. Some affected individuals may have increased salivation; yellowing of the teeth; an unusually rapid heartbeat (tachycardia); low levels of iron within the red blood cells (anemia); bluish discoloration (cyanosis) of the skin and mucous membranes due to insufficient oxygen supply to these tissues and/or an impaired sense of smell (anosmia). Individuals with cadmium poisoning may also experience improper functioning of the canals with the kidney (renal tubular dysfunction) characterized by excretion of abnormally high levels of protein in the urine (proteinuria), minor changes in liver function and/or softening of certain bones (osteomalacia).
CHROMIUM POISONING
Chromium is used in the manufacture of cars, glass, pottery and linoleum. Exposure to too much chromium may cause lung and respiratory tract cancer as well as kidney diseases. In addition, overexposure to chromium may also cause gastrointestinal symptoms such as diarrhea and vomiting, often with blood. Symptoms may lead to severe water-electrolyte disorders, increased mild acidity of blood and body tissues (acidosis) and/or inadequate blood flow to its tissues resulting in shock. Lesions on the kidneys, liver, and muscular layer of the heart (myocardium) may also develop.
COBALT POISONING
Cobalt, used in making jet engines, may cause nausea, vomiting, lack of appetite (anorexia), ear ringing (tinnitus), nerve damage, respiratory diseases, an unusually large thyroid gland (goiter) and/or heart and/or kidney damage.
LEAD POISONING
Lead production workers, battery plant workers, welders and solders may be overexposed to lead if proper precautions are not taken. Lead is stored in the bone but may affect any organ system. The effects of lead poisoning vary depending on the age of the individual and the amount of exposure.
In children, symptoms vary depending upon the degree of exposure to lead. Some affected individuals may not have any noticeable symptoms. Symptoms usually develop over a three-to-six-week period. Lead overexposure may cause children to be less playful, clumsier, irritable and sluggish (lethargic). In some people, symptoms include headaches, vomiting, abdominal pain, lack of appetite (anorexia), constipation, slurred speech (dysarthria), changes in kidney function, unusually high amounts of protein in the blood (hyperproteinemia) and unusually pale skin (pallor) resulting from a low level of iron in the red blood cells (anemia). Neurological symptoms associated with lead overexposure include an impaired ability to coordinate voluntary movements (ataxia), brain damage (encephalopathy), seizures, convulsions, swelling of the optic nerve (papilledema) and/or impaired consciousness. Some affected children experience learning or behavioral problems such as intellectual disability and selective deficits in language, cognitive function, balance, behavior and school performance. In some people symptoms may be life-threatening.
In adults, overexposure to lead may cause high blood pressure and damage to the reproductive organs. Additional symptoms may include fever, headaches, fatigue, sluggishness (lethargy), vomiting, loss of appetite (anorexia), abdominal pain, constipation, joint pain, loss of recently acquired skills, incoordination, listlessness, difficulty sleeping (insomnia), irritability, altered consciousness, hallucinations and/or seizures. In addition, affected individuals may experience low levels of iron in the red blood cells (anemia), peripheral neuropathy and, in some people, brain damage (encephalopathy). Some affected individuals experience decreased muscle strength and endurance; kidney disease; wrist drop and behavioral changes such as hostility, depression and/or anxiety. In some people symptoms may be life-threatening.
Lead is excreted in urine and feces. However, it may also appear in hair, nails, sweat, saliva and breast milk.
MANGANESE POISONING
Manganese is used as a purifying agent in the production of several metals. Symptoms associated with overexposure to manganese may include damage to the central nervous system and pneumonia. Additional symptoms and physical findings include weakness, fatigue, confusion, hallucinations, odd or awkward manner of walking (gait), muscle spasms (dystonia), rigidity of the trunk, stiffness, awkwardness of the limbs, tremors of the hands and psychiatric abnormalities.
MERCURY POISONING
Mercury is used by dental assistants and hygienists and chemical workers. Mercury can affect the lungs, kidneys, brain and/or skin. Symptoms of mercury poisoning include fatigue, depression, sluggishness (lethargy), irritability and headaches.
Respiratory symptoms associated with inhalation to mercury vapors include coughing, breathlessness (dyspnea), tightness or burning pain in the chest and/or respiratory distress. Some affected individuals may experience abnormal buildup of fluid in the lungs (pulmonary edema); pneumonia and/or abnormal formation of fibrous tissue (fibrosis).
There may be behavioral and neurological changes associated with overexposure to mercury poisoning, such as excitability and quick-tempered behavior, lack of concentration and loss of memory. Shock and permanent brain damage may also result from mercury poisoning. Some affected individuals experience mental confusion. A progressive cerebellar syndrome with impaired ability to coordinate voluntary movements (ataxia) of the arms may also be present. Abnormal involuntary movements of the body such as uncontrolled jerky movements combined with slow, writhing movements (choreoathetosis) are common. Additional symptoms include non-inflammatory degenerative disease of the nerves (polyneuropathy); impaired ability to coordinate voluntary movements (cerebellar ataxia); tremors of the legs and arms and in some people, of the tongue and lips; seizures and/or slurred speech (dysarthria). Changes in mood, behavior and consciousness may also occur.
In some cases of chronic exposure to inorganic mercury a personality disorder known as erethism, or mad hatter syndrome may occur. Symptoms associated with mad hatter syndrome include memory loss, excessive shyness, abnormal excitability and/or insomnia. This syndrome was described in workers with occupational exposure to mercury in the felt-hat industry.
Many affected individuals experience sensory impairments such as visual problems (e.g. constriction of visual fields, tunnel vision and blindness) as well as hearing loss.
Some individuals may experience skin changes such as painful swelling and pink coloration of the fingers and toes (acrodynia); persistent redness or inflammation of the skin (erythema); extreme sensitivity (hyperesthesia) of the affected areas and tingling and sensory disturbances.
Some affected individuals may experience stomach and intestinal disturbances; kidney damage; dehydration; acute renal failure; inflammation of the gums (gingivitis); severe local irritation of the mouth and pharynx, accompanied by vomiting and/or abdominal cramps with bloody diarrhea.
Mercury is mainly excreted through the urine and feces.
PHOSPHORUS POISONING
Symptoms associated with phosphorus poisoning include weakness, headaches, vomiting, sweating, abdominal cramps, salivation, wheezing secondary to bronchial spasm, drooping of the upper eyelids (ptosis), contraction of the pupil (miosis) and/or muscular weakness and twitching. In addition, non-inflammatory degenerative disease of the sensorimotor nerves (sensorimotor polyneuropathy) may advance to progressive deterioration (atrophy). In some people respiratory paralysis may also occur.
THALLIUM POISONING
Symptoms associated with thallium poisoning include extreme drowsiness (somnolence), nausea, vomiting, abdominal pain and bloody vomiting (hematemesis). Some affected individuals may experience the loss of most or all of their scalp hair (alopecia); rapidly progressive and painful sensory polyneuropathy; motor neuropathy; cranial nerve palsies; seizures; impaired ability to coordinate voluntary movements (cerebellar ataxia) and/or intellectual disability. Some individuals may experience eye symptoms including wasting away (atrophy) of the optic nerve (optic atrophy), inflammation of the optic nerve (retrobulbar neuritis) and impaired functioning of the muscles of the eyes (ophthalmoplegia). In some people, thallium poisoning may progress to include renal and cardiac failure, confusion, psychosis, organic brain syndrome and/or coma.
ADDITIONAL METAL POISONINGS
Additional metals that may cause poisoning include antimony, aluminum, barium, bismuth, copper, gold, iron, lithium, platinum, silver, tin and zinc. Common symptoms of poisoning from these metals may include gastrointestinal, renal and neurological symptoms, such as headaches, irritability, psychosis, stupor, coma and convulsions.
Heavy metal poisoning is a result of the toxic accumulation of certain metals. Such metals compete with and replace certain essential minerals during which any of several of the bodyโs organ systems may be affected.
Arsenic poisoning may be caused by medications including Fowlerโs solution (potassium arsenite) and some topical creams used in the treatment of some skin conditions. Ingestion of herbicides, insecticides, pesticides, fungicides, or rodenticides containing arsenic may cause arsenic poisoning. Occupational exposure to arsenic in the manufacture of paints, enamels, glass and metals may cause arsenic poisoning. Other forms of occupational exposure include galvanizing, soldering, etching, lead plating, smelting and wood preserving. Arsenic is also found in contaminated water, seafood and algae.
Cadmium poisoning may be caused by ingestion of food (e.g. grains, cereals and leafy vegetables) and cigarette smoke. Occupational exposure to cadmium in metal plating, battery and plastics industries may also occur.
Lead poisoning may be caused by exposure (e.g. chewing or ingestion) to deteriorating lead paint in older houses. Occupational exposure to lead in painting, smelting, firearms instruction, automotive repair, brass or cooper foundries, printing, battery manufacturing, mining, brass foundry, gasoline, glass and bridge, tunnel and elevated highway construction may also occur. Another cause of lead poisoning is through the contamination of water from lead pipes. Additional causes of lead poisoning include calcium products, progressive hair dyes, kajal, surma, kohl and foreign digestive remedies.
Manganese poisoning may be caused by chronic inhalation and ingestion of manganese particles. Occupational exposure to manganese in mining and separating manganese ore may also occur.
Mercury poisoning may be caused by exposure to large amounts of mercury in the manufacturing of thermometers, mirrors, incandescent lights, x-ray machines and vacuum pumps. Another cause of mercury poisoning is contaminated water and fish. Children often are exposed to mercury through paint, calomel, teething powder and mercuric fungicide used in washing diapers. An additional cause of mercury poisoning is exposure to mercury in thermometers, dental amalgams and some batteries.
Phosphorus poisoning may be caused by insecticides such as tetraethylpyrophosphate.
Thallium poisoning may be caused by ingestion of rodenticides containing thallium. Thallium in pesticides, insecticides, metal alloys and fireworks can be absorbed through skin as well as through ingestion and inhalation.
In 2021, the National Poisoning Data System (NPDS) of the American Association of Poison Control Centers (AAPCC) reported 8884 single exposures to heavy metals. Of those exposures, 2787 were in children younger than 6 years and 4014 were in patients older than 19 years.
Lead is the most common toxic metal in the U.S., with exposure often coming from lead-based paint in older homes. About 4 million households in the U.S. have children exposed to lead. In children, even low blood lead levels (below 10 ฮผg/dL) can negatively affect brain development. In 2021, 2,079 cases of lead exposure were reported with 957 in children under 6 and 683 in adults over 19. Lead exposure in adults is mostly related to work in mining, construction, or manufacturing where lead is used.
Arsenic exposure can happen through industrial work, contaminated water, or even arsenic-based pesticides. Criminal use of arsenic for poisoning has also occurred. In 2021, there were 610 cases of arsenic exposure (excluding pesticides) with 22 additional cases involving arsenic-based pesticides.
Iron poisoning is mainly caused by swallowing iron supplements, which is especially dangerous for children. Iron-containing multivitamins are a common cause of accidental poisoning in children. In 2021, there were 5,311 cases of iron exposure with 2,154 in children under 6 and 1,528 in adults. There were also 7,635 exposures to iron-containing multivitamins with 5,973 involving children under 6.
Mercury poisoning can come from inhaling fumes (from broken thermometers or industrial sources) or from ingesting contaminated fish. In 2021, there were 612 exposures to elemental mercury with 49 cases in children under 5 and 360 cases in adults. There were 1,048 exposures to mercury thermometers, mostly in children under 6 and adults over 20.
Children are more susceptible to heavy metal poisoning because they absorb metals more easily than adults. For example, children can absorb up to 50% of ingested lead, compared to 10% in adults. In the U.S., African American children living in lower-income areas are at higher risk for lead exposure due to delays in removing lead from the environment.
Heavy metal poisoning remains a significant public health concern, especially for vulnerable populations like children and workers in high-risk occupations. Globally, lead poisoning is a major issue in countries with leaded gasoline, paint, or older plumbing, especially in lower-income regions.
Heavy metal toxicity is often underdiagnosed, requiring a high level of suspicion to detect. Various factors, such as occupational exposure, living in older homes with lead pipes or paint, or residing near industrial areas increase the risk. Even alternative medicine practices like Ayurveda, homeopathy and traditional Chinese medicine can contribute to heavy metal (HM) buildup due to their use of certain metals.
Children are especially vulnerable to heavy metal exposure. Signs of toxicity in children may include:
Lead exposure is a particular concern in children living in homes with lead-based paint or water pipes. In adults, occupational exposure in industries such as mining or manufacturing is a common source of lead poisoning. Chronic exposure, which is harder to detect than acute cases, can cause symptoms that vary depending on which organ system is affected.
Diagnosing heavy metal toxicity relies on a combination of clinical suspicion, history of exposure and specialized testing. Ongoing advancements in testing methods are improving the ability to detect and manage these exposures effectively. The main symptoms that doctors need to consider when making a heavy metal poisoning diagnosis may include:
The diagnosis of heavy metal toxicity often involves a combination of blood, urine, hair, or nail tests. Special precautions are needed to ensure accurate results, such as avoiding seafood for 48 hours before testing due to the natural presence of metals like mercury in fish. For workers in industrial settings, itโs recommended to test at the end of the workweek, when exposure levels are highest.
In certain cases, ancillary tests like liver and kidney function tests can provide further clues, especially if symptoms like anemia or kidney damage are present. Advanced imaging techniques like chest X-rays or CT scans can detect lung damage due to inhalation of toxic metals. For some metals, specific tests like the beryllium lymphocyte proliferation test (BeLPT) and the Chronic Arsenic Intoxication Diagnostic Score (CAsIDS) help diagnose and assess risk.
Recent technologies, such as real-time biosensors are revolutionizing the detection of HM pollution in water, providing faster and more accurate assessments. Toxicogenomics is another emerging field, offering insights into how heavy metals may contribute to cancer development.
The primary goal in treating heavy metal poisoning is to stop exposure and remove the toxic metal from the body. Treatment options include chelating agentsโspecial drugs that bind to the metals and help the body excrete them.
General treatment for heavy metal poisoning
The first step in treating heavy metal poisoning is stopping exposure. This may involve:
In severe cases, additional procedures like hemodialysis (a treatment that filters waste and excess fluid from the blood) or plasma exchange (a procedure that removes and replaces the personโs blood- plasma) may be required to help the body eliminate the toxins. Chelation therapy, using drugs that bind to metals, is a key method of removing these toxic substances from the body.
Chelation therapy
Chelating agents work by binding to heavy metals which are then excreted through the urine. Some commonly used chelating agents include:
However, chelation therapy isnโt recommended for all metals, as it can sometimes cause more harm than good. Decisions on treatment should always involve a medical toxicologist.
Lead poisoning
Lead poisoning has affected humans for thousands of years, and today, itโs most common in children exposed to lead-based paint or contaminated soil, water, toys and even old homes under renovation. There is no safe level of lead exposure, especially for children, as it can cause developmental delays, learning difficulties and behavior problems. In adults, lead poisoning can lead to high blood pressure and kidney damage.
Mercury poisoning
Mercury exists in various forms, such as metallic mercury, inorganic mercury (found in some industrial products) and organic mercury (found in contaminated fish). Exposure to mercury can lead to lungs, kidney, and nervous system damage. Symptoms vary depending on the type of mercury but can include tremors, blindness, and nerve damage.
Arsenic poisoning
Arsenic exposure can occur through contaminated water or food, particularly in regions with naturally high arsenic levels in groundwater. Acute poisoning causes severe gastrointestinal symptoms like vomiting and diarrhea, while long-term exposure can lead to skin changes, numbness and even cancer.
Iron poisoning
Iron poisoning, once a common cause of death in children, occurs when large amounts of iron are ingested, often from adult iron supplements. Symptoms include vomiting blood, diarrhea and shock. Over time, iron can damage the liver and gastrointestinal tract.
Bismuth poisoning
Cadmium poisoning
Chromium poisoning
Cobalt poisoning
Copper poisoning
Manganese poisoning
Nickel poisoning
Selenium poisoning
Silver poisoning
Thallium poisoning
Zinc poisoning
For metals with no clear chelation therapy, it is essential to consult a medical toxicologist always for proper guidance.
Preventing heavy metal exposure
Preventive measures are critical for avoiding heavy metal poisoning:
In conclusion, heavy metal poisoning is a serious health issue that requires prompt identification and treatment. Removing the source of exposure and using chelation therapy under medical supervision are critical steps in managing the condition.
Clinical guidelines on treatment of iron exposure is available from the American Association of Poison Control Centers. The Agency for Toxic Substances and Disease Registry has information about the medical management guidelines for mercury exposure.
Information on current clinical trials is posted on the Internet at www.clinicaltrials.gov. All studies receiving U.S. government funding, and some supported by private industry, are posted on this government web site.
For information about clinical trials being conducted at the NIH Clinical Center in Bethesda, MD, contact the NIH Patient Recruitment Office:
Tollfree: (800) 411-1222
TTY: (866) 411-1010
Email: [email protected]
Some current clinical trials also are posted on the following page on the NORD website:
https://rarediseases.org/living-with-a-rare-disease/find-clinical-trials/
For information about clinical trials sponsored by private sources, contact: www.centerwatch.com
For information about clinical trials conducted in Europe, contact: https://www.clinicaltrialsregister.eu/
INTERNET
Adal A. Heavy Metal Toxicity. Medscape Reference. Mar 10, 2023. https://emedicine.medscape.com/article/814960-overview#a6 Accessed Oct 16, 2024.
Poison Control. Chelation: Therapy or โTherapyโ? National Capital Poison Center. https://www.poison.org/about-poison-control Accessed Oct 16, 2024.
Rajkumar V, Lee VR, Gupta V. Heavy Metal Toxicity. [Updated 2023 Mar 23]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK560920/ Accessed Oct 16, 2024.
REVIEW ARTICLES
Chaney RL, Angle JS, McIntosh MS, et al. Using hyperaccumulator plants to phytoextract soild Ni and Cd. Z Naturforsch [C]. 2005;60:190-98.
Bhan A, Sarkar NN. Mercury in the environment: effect on health and reproduction. Rev Environ Health. 2005;20:39-56.
Peter AL, Viraraghavan T. Thallium: a review of public health and environmental concerns. Environ Int. 2005;31:493-501.
Eicher T, Avery E. Toxic encephalopathies. Neurol Clin. 2005;31:353-76.
Kazantzis G. Cadmium, osteoporosis and calcium metabolism. Biometals. 2004;17:493-98.
Crossgrove J, Zheng W. Manganese toxicity upon overexposure. NMR Biomed. 2004;17:544-53.
Nuttall KL. Interpreting mercury on blood and urine of individual patients. Ann Clin Lab Sci. 2004;34:235-50.
Kwong WT, Friello P, Semba RD. Interactions between iron deficiency and lead poisoning: Idemiology and pathogenesis. Sci Total Environ. 2004;330:21-37.
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