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Heavy Metal Poisoning

Heavy Metal Toxicity

Heavy metal poisoning is the toxic manifestation of accumulated undesired levels of heavy metals in the body tissues, including blood.


Presentation

Indications of heavy metal poisoning depend upon the extent of exposure. The early signs in mild cases of poisoning are vague and may be presented by exhaustion, headache, and inability to concentrate or think. In case of severe toxicity, affected person may experience indigestion, constipation, muscle pain, anemia, dizziness, tremors, and lack of coordination.

In cases of acute lead toxicity, commonly observed symptoms cover gastrointestinal problems, such as loss of appetite, cramps, nausea, vomiting, constipation. These symptoms may affect sleep, mood, fatigue, and sexual desire. Prolonged lead exposure causes more severe condition such as involvement of nervous system, blood-forming problems, and even death.

In the long-term, the effects of arsenic poisoning are debilitating and fatal. Symptoms found include gross pigmentation and hyperkeratinization of skin, dermatitis, wart formation, vasospasticity, bronchitis, rhinitis, conjunctivitis, reduced velocity of nerve conduction, encephalopathies, peripheral neuropathies and even death.

Effects of short-term mercury toxicity are nausea, vomiting, skin rashes, eye irritation, tachycardia and hypertension. In chronic exposure, damage to nervous system and kidneys may develop leading to symptoms of tremors, loss of vision, hearing problems and memory loss.

Fatigue
  • This model gives greater insight into how the body responds throughout the stages of adrenal fatigue.[drlam.com]
  • I had fatigue that was like a cloud in my brain.[wholenewmom.com]
  • This form of poisoning can result in a number of serious health conditions developing; from joint pain to chronic fatigue to hypothyroidism and many more.[lifeworkswellnesscenter.com]
  • Symptoms of heavy metal toxicity include mental confusion, pain in muscles and joints, headaches, short-term memory loss, gastrointestinal upsets, food intolerances/allergies, vision problems, chronic fatigue, and others.[diagnose-me.com]
  • Symptoms of heavy metal toxicity include mental confusion, pain in muscles and joints, headaches, short-term memory loss, gastrointestinal upsets, food intolerances/allergies, vision problems, chronic fatigue , and others.[diagnose-me.com]
Gastric Lavage
  • Induced emesis or gastric lavage is indicated within 4 to 6 hours of acute ingestion; Prussian blue prevents absorption and is given orally at 250 mg/kg in divided doses.[drdooley.com]
  • With ingestion, gastric decontamination by emesis or gastric lavage soon after exposure.[authorstream.com]
  • Washing out the stomach (gastric lavage) may also be useful. The affected person may also require treatment such as intravenous fluids for complications of poisoning such as shock, anemia, and kidney failure.[healthofchildren.com]
  • Washing out the stomach (gastric lavage) may also be useful. The patient may also require treatment such as intravenous fluids for such complications of poisoning as shock, anemia, and kidney failure.[medical-dictionary.thefreedictionary.com]
  • . • Gastric lavage is recommended for organic ingestion, especially if the compound is observed on an abdominal radiograph series. • Activated charcoal is indicated for GI decontamination because it binds inorganic and organic mercury compounds to some[slideshare.net]
Sudden Infant Death Syndrome
  • Cot mattresses and sudden infant death syndrome . BMJ 1995 ; 310: 1216 – 7. Google Scholar Crossref Medline 170.[doi.org]
Vomiting
  • THALLIUM POISONING Symptoms associated with thallium poisoning include extreme drowsiness (somnolence), nausea, vomiting, abdominal pain, and bloody vomiting (hematemesis).[rarediseases.org]
  • "Gastric crises," sudden stabbing pains followed by vomiting and diarrhea, was originally included by Duchenne, but later, syphilologists disputed its relevance to syphilis.[ncbi.nlm.nih.gov]
  • Nausea, vomiting and diarrhoea. Impaired sensation. Difficulty breathing, cough, chest pain. Complications include pneumonitis and pulmonary oedema.[patient.info]
Diarrhea
  • "Gastric crises," sudden stabbing pains followed by vomiting and diarrhea, was originally included by Duchenne, but later, syphilologists disputed its relevance to syphilis.[ncbi.nlm.nih.gov]
  • Overexposure may cause fatigue, headaches, nausea, vomiting, abdominal cramps, diarrhea, and fever.[rarediseases.org]
  • The man first went to the emergency room in December 2014 because of stomach pain, nausea and diarrhea, Liu said.[livescience.com]
Abdominal Pain
  • 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.[rarediseases.org]
  • Arsenic Symptoms include nausea or vomiting, abdominal pain, diarrhea, garlic odor on breath, excessive salivation, headache, vertigo, fatigue, paresthesia, paralysis, kidney failure, progressive blindness, and mental impairment.[diagnose-me.com]
  • Arsenic Symptoms include nausea or vomiting, abdominal pain , diarrhea , garlic odor on breath, excessive salivation, headache, vertigo , fatigue , paresthesia , paralysis , kidney failure , progressive blindness, and mental impairment.[diagnose-me.com]
  • Gastrointestinal upset (abdominal pain, gingivitis and stomatitis, nausea, vomiting). Renal problems include acute renal failure, nephrotic syndrome and acute tubular necrosis.[patient.info]
Abdominal Cramps
  • Overexposure may cause fatigue, headaches, nausea, vomiting, abdominal cramps, diarrhea, and fever.[rarediseases.org]
  • Symptoms include headaches, drowsiness, confusion, seizures, nausea, vomiting, abdominal cramps, tinnitus, goiter, anorexia and diarrhea. Treatment includes chelation therapy.[prnewswire.com]
  • Gastrointestinal: Food sensitivities, bacterial or fungal overgrowth, recurrent parasitic infections, abdominal cramps, irritable bowl symptoms. Systemic : Premature aging, fatigue, fibromyalgia.[tinnitustalk.com]
Food Poisoning
  • Eating shellfish caught in waters near industrialized areas often causes food poisoning and allergic reactions.[drmanik.net]
  • poisoning (ingestion) Bronchitis (inhalation) Interstitial pneumonitis (inhalation) Pulmonary edema (inhalation) A condition that mimics metal fume fever Children who eat dirt (pica behavior) are at risk Signs & Symptoms - Chronic: Signs & Symptoms -[authorstream.com]
Hypotension
  • 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).[rarediseases.org]
  • […] nickel carbonyl: myocarditis, ALI, encephalopathy Occupational (inhaled): pulmonary fibrosis, reduced sperm count, nasopharyngeal tumors Excessive exposure: 8 µg/L (blood) Severe poisoning: 500 µg/L (8-h urine) * Selenium Caustic burns, pneumonitis, hypotension[emedicine.medscape.com]
  • . • In most sever cases, tachycardia, hypotension acute encephalopathy, acute renal failure, congestive heart failure, stupor, convulsions, paralysis, coma and even death can occur. 67.[slideshare.net]
Tinnitus
  • Other Industrial Illnesses include: Noise-induced Hearing Loss /Deafness and Tinnitus Silicosis Tennis elbow Rarer, but still valid, industrial disease claims are those caused by exposure to lesser known dangerous substances in the workplace, such as[simpsonmillar.co.uk]
  • Immune Suppression Poor Balance Cataracts Impaired Learning Poor Concentration Colic Insomnia Poor Coordination Confusion Joint Pain Prostate Cancer Constipation Kidney Failure Speech Impairment Convulsion Liver Disease Testicular Atrophy Deafness Low IQ Tinnitus[vitalityandwellness.com.au]
  • Symptoms include headaches, drowsiness, confusion, seizures, nausea, vomiting, abdominal cramps, tinnitus, goiter, anorexia and diarrhea. Treatment includes chelation therapy.[prnewswire.com]
  • • Suicidal tendencies • Difficulty in making decisions B) Central nerve system • Dizziness • Loss of muscle control in the hand sometimes in the feet • Loss of muscle co-ordination • Muscle paralysis • Vision gets more and more limited or troubled • Tinnitus[newhealthvitamins.com]
Hematuria
  • Arsenic Useful lab tests include Urinalysis ( Oliguria, Hematuria, Hemoglobinuria); Complete Blood Count and Peripheral Smear (Macrocytic Anemia ); Tissue Exam (reveals arsenic deposits – urine, nails, hair) and Serum Arsenic levels.[diagnose-me.com]
  • Arsenic Useful lab tests include Urinalysis ( Oliguria , Hematuria , Hemoglobinuria); Complete Blood Count and Peripheral Smear (Macrocytic Anemia ); Tissue Exam (reveals arsenic deposits – urine, nails, hair) and Serum Arsenic levels.[diagnose-me.com]
  • […] or metallic taste Burning mucosa Nausea and vomiting Diarrhea Abdominal pain Hematemesis Hematochezia, melena Rice-water stools Immediate Immediate Minutes Minutes to hours Minutes to hours Minutes to hours Hours Hours Hematopoietic system Hemolysis Hematuria[authorstream.com]
  • Several weeks Pulmonary (primarily in inhalational exposures) Cough Dyspnea Chest Pain Pulmonary edema Immediate Minutes to hours Minutes to hours Minutes to hours Liver Jaundice Fatty degeneration Central necrosis Days Days Days Kidneys Proteinuria Hematuria[slideshare.net]
Oliguria
  • Arsenic Useful lab tests include Urinalysis ( Oliguria, Hematuria, Hemoglobinuria); Complete Blood Count and Peripheral Smear (Macrocytic Anemia ); Tissue Exam (reveals arsenic deposits – urine, nails, hair) and Serum Arsenic levels.[diagnose-me.com]
  • Arsenic Useful lab tests include Urinalysis ( Oliguria , Hematuria , Hemoglobinuria); Complete Blood Count and Peripheral Smear (Macrocytic Anemia ); Tissue Exam (reveals arsenic deposits – urine, nails, hair) and Serum Arsenic levels.[diagnose-me.com]
Tremor
  • A person with severe toxicity may also experience muscle pains, indigestion, tremors, constipation, anemia, pallor, dizziness, and poor coordination.[sharecare.com]
  • In cases of severe toxicity, common symptoms are indigestion, constipation, anemia, dizziness, tremor, and muscle pain.[symptoma.com]
  • Overexposure to tin may damage the nervous system and cause psychomotor disturbances including tremor, convulsions, hallucinations, and psychotic behavior.[rarediseases.org]
  • Early: insomnia, forgetfulness, anorexia, mild tremor Late: progressive tremor and erethism (red palms, emotional lability, and memory impairment) Salivation, excessive sweating, renal toxicity (proteinuria, or nephrotic syndrome) Dental amalgams do not[authorstream.com]
Peripheral Neuropathy
  • Subsequent peripheral neuropathy, hepatic dysfunction or renal failure may develop. Chronic poisoning Irritability. Personality changes. Headache. Peripheral neuropathy. Memory problems. Ataxia. Coma. Respiratory problems (pneumonitis and ARDS).[patient.info]
  • Lead Signs and Symptoms include combinations of gastrointestinal complaints, hypertension, fatigue, hemolytic anemia, abdominal pain, nausea, constipation, weight loss, peripheral neuropathy, cognitive dysfunction, arthralgias, headache, weakness, convulsions[diagnose-me.com]
  • Lead Signs and Symptoms include combinations of gastrointestinal complaints, hypertension , fatigue, hemolytic anemia , abdominal pain, nausea, constipation , weight loss, peripheral neuropathy , cognitive dysfunction, arthralgias, headache, weakness,[diagnose-me.com]
  • In addition, affected individuals may experience low levels of iron in the red blood cells (anemia), peripheral neuropathy, and, in some cases, brain damage (encephalopathy).[rarediseases.org]
Hand Tremor
  • Hand tremor induced by industrial exposure to inorganic mercury. Arch Environ Health. 1973 ; 26 : 249 – 252 Albers JW, Kallenbach LR, Fine LJ, et al. Neurological abnormalities associated with remote occupational elemental mercury exposure.[pediatrics.aappublications.org]

Workup

Following tests are required to determine the level of exposure and extent of damage done:

  • Specific laboratory testing for metals (lead, mercury, arsenic or iron) is required when toxicity symptoms are significant.
  • Complete blood cell count (CBC) of peripheral smear reveals basophilic stippling of RBCs in arsenic poisoning; it is not specific in case of lead and the anemia caused by lead is of normocytic or microcytic type.
  • Liver function tests
  • Renal function tests to find out the damage to kidneys
  • Urine analysis to investigate proteinuria
Iron Increased
  • Low iron increases toxicity of cadmium and lead, causing impaired cognitive function. Cd also replaces zinc in metallothionine (the mechanism by which zinc is absorbed from the gut).[drmyhill.co.uk]

Treatment

Children are the most vulnerable group to metal toxicity, in particular lead. It is critical that the source of exposure should be immediately removed. When radiographic evidence points to retained metal parts such as toys, coins and paint chips in the elementary tract, whole-bowel irrigation with polyethylene glycol electrolyte solution may be carried out.

Lead exposure through inhalation or ingestion is followed by its incorporation in the skeletal system which acts as a toxic reserve and is difficult to remove. Certain chelating agents are used to reduce or control toxicity of metals; the chelating agents bind with the metals and are then eliminated from the body. However, removal does not restore any neurocognitive damage that already developed [14]. Chelating agents are administered orally, intravenously, intradermally or through suppositories [15].

Suitable supportive care is necessary depending upon the severity and symptoms of the case. Care is required to correct dysrhythmias, maintain electrolyte balance due to fluid loss, ensure proper rehydration and provide mechanical ventilation if necessary.

Treatment is directed to reduce damage to central nervous system, liver and kidneys and induce recovery.

Prognosis

Cases of heavy metal toxicity are rare in clinical practice and therefore their prognosis is difficult to follow. This poses a problem because untreated metal toxicity cases can lead to serious consequences such as multi-organ failure, cancer and even death.

Heavy metals have an increased affinity to bind with organs like brain, nerves and kidneys and thus affect their functions resulting in neurological and other serious problems. There is also an association between high blood pressure and higher lead contents and other heavy metals contents in the body. In cases of poisoning by some metals, neurological damage may lead to permanent disability. Studies have demonstrated relationship between the deposit of heavy metals (lead, mercury, cadmium and aluminium) in the body of children and the presence of learning disabilities and lower IQ.

In cases of long-term exposure to arsenic contents in water, the common risks are skin lesions such as hyperkeratosis, pigmentation and skin cancers. Exposure under the occupational or industrial situations leading to inhalation of arsenic contents can cause lung cancer. High dosage of arsenic exposure poses greater health risks.

Etiology

The most common cases of heavy metal poisoning are due to exposure to lead. Following the ban on usage of lead content in paint, food cans and petrol in advanced countries, exposure to this metal has been reduced drastically [4]. Occupational lead exposure however continues during processes such as mining, smelting, welding of lead-based painted materials, glass manufacturing and in operations involving battery manufacture. In areas near these operations, air, water and soil may be contaminated by lead, which may ultimately find its way into the human food chain causing risks to human health.

Arsenic poisoning can result from criminal as well as suicidal intent to its usage. Some medicinal preparations used in traditional systems of medicine can contain arsenic risking serious effects to health. For the general population, arsenic becomes a risk when food and water are contaminated. In places, where ground water is contaminated with high inorganic arsenic contents, drinking of such water leads to serious health problems.

Iron toxicity is largely caused due to excessive use of iron pills alone or in combination with multivitamin formulations. In children, iron toxicity is caused by accidental ingestion of iron pills [5].

Mercury poisoning may be caused by ingestion, inhalation and skin absorption [6]. The most common source of mercury poisoning is consumption of contaminated food, such as fish. Several uses of mercury pose risk to pollution of the environment. Medical wastes, mining operations and emissions from plants using coal as energy source are some possible sources. Metallic mercury is used in devices such as thermometers, blood pressure measuring instruments, barometers, and electrochemical process of chlorine manufacturing that uses mercury as an electrode [3]. Contamination of animals involved in human food chain ultimately leads to mercury poisoning in humans. Use of mercuric compounds in dental surgeries also poses a risk to human health.

Cadmium toxicity can result from exposure due to ingestion, contamination of environment and smoking. In nature cadmium is found in combination with zinc. Wastes generated from household and industries contain cadmium, which contaminate soil and water resources. In last several decades human exposure to cadmium has increased substantially [6] [7]. Cigarette smoking also causes 4 to 5 times higher blood cadmium levels compared to non-smokers [8]. Presence of cadmium in most food stuffs leads to its varying levels in different individuals, due to individual differences in food habits.

Epidemiology

Epidemiology of heavy metal poisoning varies among countries, depending on the socioeconomic status of the given population and the age group. In countries like UK, even industries considered high risk have rare instances of heavy metal poisoning [9]. In China and South East Asia, heavy metal toxicity has assumed the status of a serious occupational hazard associated with the informal electronic recycling industry. In this industry, protective measures are not adequately regulated.

Health risks due to lead poisoning following the use of paints, cosmetics, leaded gasoline and piped water supply in lower income countries continue as major health problem. Cases of lead poisoning have been reported in over 2000 children living near smelting plants [10] [11].

Humans are exposed to arsenic from the air, water and food. Contamination of drinking water by arsenic is caused by arsenical pesticides, mineral deposits containing arsenic and improperly disposed arsenical compounds. Water contaminated with arsenic is the major cause of arsenic poisoning in over 30 countries in the world [12]. Chronic arsenic toxicity has assumed endemicity in some areas of Bangladesh and India due to the natural occurrence of arsenic in their native bed-rock.

In both acute and chronic cases of heavy metal toxicity, encephalopathy is the most common cause of mortality. In the United States, lead toxicity is reported among African Americans due to inadequate removal of lead bearing sources from the environment.

Children are the most affected class among the vulnerable populations to suffer from heavy metal toxicity, largely due to accidental exposure. Lead poisoning in children can cause cognitive and behavioral changes [13].

By the end of 20th century, production of heavy metals has declined in developed countries leading to a lowering of emissions. In the UK, for example, heavy metal emissions between 1990 and 2000 were reduced by 50%. However, in developing world, the contamination of environment by heavy metal remains problematic due to their continued usage. Mercury is still used in gold mining in parts of Latin America. Arsenic is used in wood preservatives and tetraethyl lead is used as an additive in petrol.

Sex distribution
Age distribution

Pathophysiology

Pathophysiological effects of high concentration of different heavy metal in the body, often referred to as toxidromes, are relatively similar. Following their entry into the body by ingestion, inhalation or absorption through the skin and mucus membranes, heavy metals compete with other ions and bind to sulfhydryl groups of proteins such as enzymes and alter their functions.

The transport of most heavy metals throughout the body is carried out by the formation of ligands with protein, but some metals compete with ionized calcium and zinc and move through membrane channels in ionic form. Impaired enzymes lead to damage of organs and systems throughout the body and this damage manifests as toxic effects. The most commonly involved systems are central nervous system, gastrointestinal system, renal system, cardiovascular system, musculoskeletal system and reproductive system.

Binding to sulfhydryl groups also plays a critical role in the homeostasis of heavy metals and serves a protective role. An increase in the synthesis of metal binding proteins, reported after exposure to heavy metals, is primarily a part of the body's defense against metal poisoning.

The overall severity of pathophysiological changes in various systems, however, depends upon the metal involved, the extent of exposure and the age of person exposed.

Prevention

Clinicians need to play a role in early detection of lead in patients subject to occupational exposure and advise necessary measures to prevent further exposure. Whenever cases of serious exposure are found, measures are required to reduce further risks and damage done by poisoning.

In case of children exposed to lead it should be considered as a public health emergency because a long-term approach is necessary for removal of contamination and its source. Protection of children against lead exposure continues to be the only most reliable measure because cognitive and behavioral changes following lead exposure are not reversible.

In the Unites States, healthcare providers are required to ensure that blood levels of lead in pregnant women and newborn are screened and documented in medical records.

To avoid exposure to heavy metals, their possible sources should be abandoned or handled with protective measures. Certain items should be abandoned such as lead-based paints, lead containing glazed food containers, and collapsible metallic tubes for toothpastes which may cause lead contamination.

Summary

There is a difference of opinion as to which elements fall within the category of 'heavy metals'. Some opinion favors a definition based on atomic weight while the other suggests specific gravity as the basis for consideration. According to the most commonly accepted view, heavy metals are elements that have an atomic weight and density five times greater than water. Heavy metals also include metalloids, like arsenic, which are toxic at low concentrations [1]. In recent years multiple uses of heavy metals for industrial, agricultural, medical and domestic purposes have led to their widespread distribution in environment, raising serious health concerns [2].

There are 23 heavy elements in all: arsenic, antimony, bismuth, cadmium, cerium, chromium, cobalt, copper, callium, gold, iron, lead, manganese, mercury, nickel, platinum, silver, tellurium, thallium, tin, uranium, vanadium, zinc [3]. While some of these elements such as zinc, copper, chromium, iron and manganese are essential for human physiological processes, many of these elements have no known benefits to bodily functions.

Heavy metal poisoning develops when a person is exposed to heavy elements over time leading to their accumulation at toxic levels in the tissues of the body. The common sources of heavy metal poisoning are contamination of food or water or during accidents in industrial settings. The nature of toxicity of heavy metals depends upon their chemical nature, route of administration and dose. Other factors that determine the effects of overall poisoning are age, gender, genetics and nutritional status of affected individuals.

From the public health point of view, heavy metals responsible for causing serious poisoning to humans are arsenic, cadmium, chromium, lead, and mercury. These metallic elements cause systemic toxic effects leading to multiple organ damage, even at low levels of exposure.

Patient Information

Heavy metal poisoning is the consequence of toxicity due to accidental or industrial exposure, for short-term or long-term, to heavy or semi-metals. The most commonly occurring cases of heavy metal poisoning are reported with mercury, lead, arsenic and cadmium. Arsenic poisoning is common in some parts of the world due to contaminated ground water. Poisoning with heavy metals is reported in children and adults following accidental exposure or in adults working in industries using heavy metals. Though use of heavy metals is regulated in advanced countries, cases of poisoning are still increasing in some parts of the world.

Heavy metal poisoning occurs by all possible routes, ingestion, inhalation, and skin absorption. Once absorbed in the body, heavy metals compete with ions in the body and get bound to proteins and accumulate in body tissues. As their toxic levels are built in tissues, body tissues are damaged leading to symptoms of toxicity or poisoning. Exposure over time can lead to chronic exposure causing nonspecific symptoms. If the symptoms are not recognized and condition is not diagnosed, it may lead to permanent damage to nervous tissue leading to neurological deficit, other organs' damage or even cancer. The symptoms of mild cases of poisoning are nonspecific such as fatigue, headache and inability to concentrate. In cases of severe toxicity, common symptoms are indigestion, constipation, anemia, dizziness, tremor, and muscle pain. Based on the patient's history, specific laboratory tests are carried out to determine the level of exposure and severity of poisoning.

Prevention against further exposure is the best approach to safeguard against serious conditions such as neurological damage. If radiological evidence suggests the presence of paint chips, coins or toys in the alimentary tract, treatment includes whole-bowel irrigation by using polyethylene glycol electrolyte. Chelation therapy is carried out for general toxicity caused by metal poisoning.

References

Article

  1. Duffus JH. Heavy metals-a meaningless term? Pure Appl Chem. 2002; 74 (5):793-807
  2. Saunders JE, Jastrzembski BG, Buckey JC, et al. Hearing loss and heavy metal toxicity in a nicaraguan mining community: audiological results and case reports. Audiol Neurootol. 2013;18(2):101-113.
  3. Tchounwou PB, Yedjou CG, Patlolla AK, et al. Heavy Metals Toxicity and the Environment. EXS. 2012;101:133-164. doi:10.1007/978-3-7643-8340-4_6.
  4. Pirkle JL, Brody DJ, Gunter EW, et al; The decline in blood lead levels in the United States. The National Health and Nutrition Examination Surveys (NHANES). JAMA. 1994; 272 (4):284-291.
  5. Chang TP, Rangan C. Iron poisoning: a literature-based review of epidemiology, diagnosis, and management. Pediatr Emerg Care. 2011; 27(10):978-985.
  6. Nriagu JO, Pacyna JM. Quantitative assessment of worldwide contamination of air, water and soils by trace metals. Nature. 1988; 333 (6169):134-139.
  7. Elinder CG, Järup L. Cadmium exposure and health risks: Recent findings. Ambio. 1996; 25:370-373.
  8. Jarup L, Berglund M, Elinder CG, et al. Health effects of cadmium exposure—a review of the literature and a risk estimate. Scand J Work Environ Health. 1998; 24 (Suppl 1): 1-51.
  9. Baldwin DR, Marshall WJ; Heavy metal poisoning and its laboratory investigation. Ann Clin Biochem. 1999;36(Pt 3):267-300.
  10. Parry J. Metal smelting plants poison hundreds of Chinese children. BMJ. 2009; 339: b3433.
  11. Watts J. Lead poisoning cases spark riots in China. Lancet. 2009; 374 (9693):868.
  12. Chakraborti D, Rahman MM, Paul K, et al. Arsenic calamity in India and Bangladesh sub-continent-whom to blame? Talanta. 2002; 58 : 3-22.
  13. Hornung RW, Lanphear BP, Dietrich KN. Age of greatest susceptibility to childhood lead exposure: a new statistical approach. Environ Health Perspect. 2009; 117(8):1309-1312.
  14. Chisolm JJ Jr. The use of chelating agents in the treatment of acute and chronic lead intoxication in childhood. J Pediatr. 1968;73 (1):1-38.
  15. Rogan WJ, Dietrich KN, Ware JH, et al. The effect of chelation therapy with succimer on neuropsychological development in children exposed to lead. N Engl J Med. 2001; 344:1421.

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Last updated: 2019-07-11 21:01