Mercury Toxicity


Article Author:
Shawn Posin


Article Editor:
Sandeep Sharma


Editors In Chief:
Joshua Gibson
Jim Powers
Kermit Huebner


Managing Editors:
Avais Raja
Orawan Chaigasame
Carrie Smith
Abdul Waheed
Khalid Alsayouri
Trevor Nezwek
Radia Jamil
Patrick Le
Anoosh Zafar Gondal
Saad Nazir
William Gossman
Hassam Zulfiqar
Steve Bhimji
John Shell
Matthew Varacallo
Heba Mahdy
Ahmad Malik
Sarosh Vaqar
Mark Pellegrini
James Hughes
Beata Beatty
Nazia Sadiq
Hajira Basit
Phillip Hynes
Tehmina Warsi


Updated:
3/3/2019 8:49:57 AM

Introduction

Mercury has been used for centuries in multiple capacities including medicinal and widespread industrial use. Because of this, it is a common chemical exposure and environmental pollutant. There are several forms of mercury which lead to different mercury intoxication syndromes.[1]

Etiology

Mercury exists in organic and inorganic forms. The inorganic form could be further subdivided into elemental mercury (also known as "quicksilver") and mercury salts. Elemental exposures are typically from mercury-containing devices such as thermometers. Mercury salt exposures can be seen with disc battery ingestion or laxative abuse. Organic mercury can also be subdivided into short-chain and long-chain compounds. Organic mercury exposure usually occurs from ingestion of contaminated seafood, paints containing mercury, or ingestion/injections of thimerasol.[2]

Epidemiology

In the United States, a 2013 report documented 1300 single mercury exposures, and only 24 had moderate to major effects. However, internationally, there are much higher rates of exposure including mercury mining in China, small-scale gold mining, and food contaminated with mercury. Two major toxic incidents occurred in Minamata Bay, Japan and in Iraq. Mercury was dumped into Minamata Bay, and members in the community developed toxicity from eating the fish containing methylmercury. In Iraq, over 6000 people developed toxicity from eating bread baked with grain that was treated with methylmercury based fungicide.

Children and fetuses have a higher susceptibility to mercury toxicity, and therefore, more severe clinical manifestations. The primary source of dietary ingestion is consumption of contaminated fish. Since the fetal brain is more susceptible to toxicity, the FDA recommends pregnant or breastfeeding women, as well as children, avoid fish with high mercury content. These fish include shark, king mackerel, tilefish, swordfish, and tuna. Freshwater fish including pike, walleye, muskellunge, and bass should be eaten in moderation.[3]

Pathophysiology

Elemental mercury is primarily absorbed by inhalation. There is minimal absorption through ingestion, and it does cross the blood-brain barrier where it can deposit. Elemental mercury is more volatile as it is heated and is readily absorbed when it is aerosolized by vacuuming. Pulmonary, central nervous system (CNS), and renal toxicity are common with elemental mercury. The gastrointestinal tract primarily absorbs inorganic mercury salts, and secondarily they are absorbed through intact skin. The salts mainly cause renal and gastrointestinal (GI) toxicity. Organic mercury is also primarily absorbed by the GI tract and secondarily through intact skin.  Organic mercury toxicity typically leads to neurologic symptoms which are characteristically delayed.[4]

Histopathology

Mercury primarily binds to sulfhydryl groups and secondarily to an amide, carboxyl, and phosphoryl groups which interrupt cellular enzymes and protein systems throughout the body. Therefore, mercury can cause significant dysfunction of enzymes, membranes, transport mechanisms, and structural proteins. Inhibition of enzymes such as choline acetyltransferase and catechol O-methyltransferase can lead to acetylcholine deficiency, hypertension, and tachycardia. Mercury salts cause damage to the gastrointestinal tract mucosa and proximal renal tubules early after exposure. This damage is from direct oxidative effects of mercuric ions. Inorganic salts have low lipid solubility, so they have a poor penetration of the blood-brain barrier, but due to slow elimination, there is some accumulation. [5]Organic mercury such as methylmercury is lipophilic and distributes across all tissues including the central nervous system. The organic mercury deposits in the CNS are thought to be converted to inorganic mercury causing toxicity. Neurologic findings on MRI of atrophy of the cerebellar hemisphere, postcentral gyri, and calcarine area correlates with ataxia, sensory neuropathy, and visual field constriction.[6]

Toxicokinetics

Excretion of mercury is dependant on its original form. Elemental and inorganic salts are primarily excreted through the kidney and minimally through the GI tract with a total half-life of 30 to 60 days. Excretion of organic mercury compounds is primarily fecal with enterohepatic recirculation leading to a longer half-life of approximately 70 days.[7]

History and Physical

Primary absorption of elemental mercury is through inhalation which causes shortness of breath, cough, fever, nausea, vomiting, diarrhea, headache, metallic taste, salivation, and visual disturbance. Severe exposure may lead to respiratory distress and failure. Ingested elemental mercury can be metabolized to inorganic mercury salts and can also develop those symptoms. Acute ingestion of organic salts typically will cause a metallic taste and a graying of the oral mucosa. Most common findings of significant ingestion include abdominal pain, hemorrhagic gastroenteritis, acute tubular necrosis, and shock. [8]Subacute mercury salt ingestion can lead to a wide array of GI, neurologic, and renal symptoms including loose teeth, salivation, burning sensation in the mouth, tremors, erethism, nephrotic syndrome, proteinuria, neurasthenia, and acrodynia. Organic mercury toxicity is primarily neurologic and is usually permanent. The related toxic symptoms typically occur weeks to months after exposure. Early findings of orofacial paresthesias, headaches, tremors, and fatigue can occur. More severe cases can progress to ataxia, blindness, movement disorders, and dementia. In addition to the severe neurologic findings, patients also develop mild renal, GI, and respiratory distress.[9]

Evaluation

In the Emergency Department, the most critical facet of the evaluation is a thorough history including possible exposures and identifying the symptoms consistent with any of the mercury toxicity syndromes.  Initial testing would include a chest radiograph, urinalysis,  and basic bloodwork such as a complete blood count and a metabolic panel.  A 24-hour urine collection for mercury levels should be obtained as well as whole-blood mercury levels in the case of organic mercury exposure as there is very little urinary excretion of these compounds.  Positive levels confirm exposure, but the levels do not directly correlate with toxicity.

Treatment / Management

Initial treatment in the emergency department consists of removal from the exposure and decontamination of the patient. After the patient and department are safe from the exposure supportive measures should begin including oxygen and intravenous (IV) fluids. Monitor and manage any complications of the toxicity such as respiratory distress, gastrointestinal bleeding, renal failure, and bowel perforation. GI decontamination should be attempted if possible although there are risks of perforation. Charcoal which is not highly effective binding metals should still be attempted, in addition to whole bowel irrigation even if only minimally effective. Chelation should be initiated early in mercury exposure cases as it may decrease the toxic effects. Inorganic mercury and elemental mercury can be treated with an initial course of intramuscular dimercaprol and then followed by oral succimer. The dosing regimen for dimercaprol starts at 5 mg/kg per dose every 4 hours for 48 hours, followed by 2.5 mg/kg per dose every 6 hours for 48 hours, and then 2.5 mg/kg per dose every 12 hours for 7 days. Oral succimer follows this treatment at a dose of 10 mg/kg per dose orally 3 times a day for 5 days then twice daily for 14 days. Organic exposures should not be treated with dimercaprol as there is evidence it can exacerbate neurologic toxicity.  In these cases, the only succimer should be administered. It is controversial whether peritoneal dialysis or hemodialysis is beneficial due to the high degree of protein binding and distribution; although dialysis may be necessary due to renal damage. In addition, exchange transfusions should be attempted, but there is no supporting evidence of improved outcomes.[10]

Differential Diagnosis

Mercury toxicity can be very difficult to diagnose due to nonspecific signs and symptoms and the variability of onset of the symptoms.  These can easily mimic several other disease processes affecting multiple systems including renal, gastrointestinal, nervous, and pulmonary.  Which is why it is imperative to obtain a complete, thorough history.  A differential diagnosis includes the following list.

Alzheimer disease, senile dementia, Parkinson disease, CVA, cerebellar tumor, metabolic encephalopathy, gastrointestinal bleed, acid or alkali ingestion, iron toxicity, arsenic toxicity, phosphorus toxicity, cerebral palsy, vertigo, amyotrophic lateral sclerosis, intrauterine hypoxia, brainstem gliomas, carbon monoxide poisoning, and alcohol or drug withdrawal.  

Prognosis

The prognosis for mercury exposure is highly variable but is dependant on the level of exposure. Significant exposures can lead to coma and death. Minor symptoms may resolve over time. Neurologic symptoms which can be delayed in the presentation may persist for decades. Fetus and children are highly susceptible and can lead to death, permanent neurologic deficits, or mental retardation.

Pearls and Other Issues

Mercury toxicity can be very difficult to identify with multisystem involvement. It is imperative to have a high index of suspicion and obtain a thorough history while always keeping in mind the complex of symptoms found in the toxidromes. Symptoms of mercury exposure and toxicity can easily be misdiagnosed as normal medical problems such as gastritis, GI bleeding, and respiratory distress. A keen awareness leading to early identification and treatment is critical due to the severe and potentially irreversible damage.


Interested in Participating?

We are looking for contributors to author, edit, and peer review our vast library of review articles and multiple choice questions. In as little as 2-3 hours you can make a significant contribution to your specialty. In return for a small amount of your time, you will receive free access to all content and you will be published as an author or editor in eBooks, apps, online CME/CE activities, and an online Learning Management System for students, teachers, and program directors that allows access to review materials in over 500 specialties.

Improve Content - Become an Author or Editor

This is an academic project designed to provide inexpensive peer-reviewed Apps, eBooks, and very soon an online CME/CE system to help students identify weaknesses and improve knowledge. We would like you to consider being an author or editor. Please click here to learn more. Thank you for you for your interest, the StatPearls Publishing Editorial Team.

Mercury Toxicity - Questions

Take a quiz of the questions on this article.

Take Quiz
Which part of the kidney is most affected by mercury poisoning?



Click Your Answer Below


Would you like to access teaching points and more information on this topic?

Improve Content - Become an Author or Editor and get free access to the entire database, free eBooks, as well as free CME/CE as it becomes available. If interested, please click on "Sign Up" to register.

Purchase- Want immediate access to questions, answers, and teaching points? They can be purchased above at Apps and eBooks.


Sign Up
A metal worker presents to the emergency room with mild acute mercury poisoning. What is the preferred treatment?



Click Your Answer Below


Would you like to access teaching points and more information on this topic?

Improve Content - Become an Author or Editor and get free access to the entire database, free eBooks, as well as free CME/CE as it becomes available. If interested, please click on "Sign Up" to register.

Purchase- Want immediate access to questions, answers, and teaching points? They can be purchased above at Apps and eBooks.


Sign Up
A frantic mother brings her child into your emergency department. She relates to you that approximately 5 hours ago her 3 year-old son ingested the mercury from a meat thermometer. The child has no significant past medical or surgical history. He is asymptomatic and the physical exam is within normal limits. The child is interacting appropriately and has stable, age-appropriate vital signs. Which of the following is the most appropriate next step in management?



Click Your Answer Below


Would you like to access teaching points and more information on this topic?

Improve Content - Become an Author or Editor and get free access to the entire database, free eBooks, as well as free CME/CE as it becomes available. If interested, please click on "Sign Up" to register.

Purchase- Want immediate access to questions, answers, and teaching points? They can be purchased above at Apps and eBooks.


Sign Up
Which of the following forms of mercury is most likely to be responsible for acute toxicity?



Click Your Answer Below


Would you like to access teaching points and more information on this topic?

Improve Content - Become an Author or Editor and get free access to the entire database, free eBooks, as well as free CME/CE as it becomes available. If interested, please click on "Sign Up" to register.

Purchase- Want immediate access to questions, answers, and teaching points? They can be purchased above at Apps and eBooks.


Sign Up
A patient presents to the emergency department after a methylmercury exposure, and supportive care is initiated. Chelation is being considered. What therapy is contraindicated in this type of exposure?



Click Your Answer Below


Would you like to access teaching points and more information on this topic?

Improve Content - Become an Author or Editor and get free access to the entire database, free eBooks, as well as free CME/CE as it becomes available. If interested, please click on "Sign Up" to register.

Purchase- Want immediate access to questions, answers, and teaching points? They can be purchased above at Apps and eBooks.


Sign Up
While working in an emergency department (ED), you get numerous ambulance reports with patients coming from a local school. Several students were working in a chemistry lab and are all experiencing respiratory distress. The chemistry teacher was not present but found a vacuum on the floor and a container of mercury open. The first student to arrive at the ED has a heart rate of 124 beats/min, respiratory rate 28/minute, blood pressure 105/62 mmHg, and a pulse oximeter reading of 84% on 2 liters of oxygen by nasal cannula. A chest radiograph shows interstitial pneumonitis. What is the best initial management?



Click Your Answer Below


Would you like to access teaching points and more information on this topic?

Improve Content - Become an Author or Editor and get free access to the entire database, free eBooks, as well as free CME/CE as it becomes available. If interested, please click on "Sign Up" to register.

Purchase- Want immediate access to questions, answers, and teaching points? They can be purchased above at Apps and eBooks.


Sign Up
A 39-year-old woman presents with a history of traveling to China for 3 months of the summer. She does not recall any exposures but was around the shore and ate seafood almost every day. Since she got home, she has been doing well over the past month. For the past week, she has had with orofacial numbness and has developed a headache and weakness. She has noticed some muscle rigidity and is having problems hearing. She is worried she is having a stroke and presents for evaluation. What is the most likely etiology of her symptoms?



Click Your Answer Below


Would you like to access teaching points and more information on this topic?

Improve Content - Become an Author or Editor and get free access to the entire database, free eBooks, as well as free CME/CE as it becomes available. If interested, please click on "Sign Up" to register.

Purchase- Want immediate access to questions, answers, and teaching points? They can be purchased above at Apps and eBooks.


Sign Up
A patient is rushed to the medical facility in Surinam from a local small-scale gold mine. He was working on separating the gold from amalgam when he suddenly started coughing and became short of breath. Upon arrival, he is in respiratory distress. His vitals are heart rate 144 bpm, respiratory rate 26/minute, blood pressure 146/92 mmHg, and pulse oximetry 82%. He is intubated. His chest x-ray is concerning for acute respiratory distress syndrome. Resuscitation is started but what other therapy would be indicated?



Click Your Answer Below


Would you like to access teaching points and more information on this topic?

Improve Content - Become an Author or Editor and get free access to the entire database, free eBooks, as well as free CME/CE as it becomes available. If interested, please click on "Sign Up" to register.

Purchase- Want immediate access to questions, answers, and teaching points? They can be purchased above at Apps and eBooks.


Sign Up

Mercury Toxicity - References

References

Disk Battery Ingestion, Dijkstra B,Gossman WG,,, 2017 Jun     [PubMed]
Metal chelators and neurotoxicity: lead, mercury, and arsenic., Bjørklund G,Mutter J,Aaseth J,, Archives of toxicology, 2017 Dec     [PubMed]
The toxicology of mercury: Current research and emerging trends., Bjørklund G,Dadar M,Mutter J,Aaseth J,, Environmental research, 2017 Nov     [PubMed]
The 9th Conference on Metal Toxicity and Carcinogenesis: The conference overview., Wise JTF,Wang L,Zhang Z,Shi X,, Toxicology and applied pharmacology, 2017 Sep 15     [PubMed]
Heavy metal poisoning: management of intoxication and antidotes., Rusyniak DE,Arroyo A,Acciani J,Froberg B,Kao L,Furbee B,, EXS, 2010     [PubMed]
Acute mercury chloride intoxication. Effects of hemodialysis and plasma exchange on mercury kinetic., Sauder P,Livardjani F,Jaeger A,Kopferschmitt J,Heimburger R,Waller C,Mantz JM,Leroy M,, Journal of toxicology. Clinical toxicology, 1988     [PubMed]
Wise J, Higher levels of mercury in brain are not linked to increased risk of Alzheimer's, study finds. BMJ (Clinical research ed.). 2016 Feb 3;     [PubMed]
Sakamoto M,Nakamura M,Murata K, [Mercury as a Global Pollutant and Mercury Exposure Assessment and Health Effects]. Nihon eiseigaku zasshi. Japanese journal of hygiene. 2018;     [PubMed]
Asaduzzaman A,Riccardi D,Afaneh AT,Cooper SJ,Smith JC,Wang F,Parks JM,Schreckenbach G, Environmental Mercury Chemistry - In Silico. Accounts of chemical research. 2019 Feb 19;     [PubMed]
Ahmad S,Mahmood R, Mercury chloride toxicity in human erythrocytes: enhanced generation of ROS and RNS, hemoglobin oxidation, impaired antioxidant power, and inhibition of plasma membrane redox system. Environmental science and pollution research international. 2019 Jan 5;     [PubMed]

Disclaimer

The intent of StatPearls is to provide practice questions and explanations to assist you in identifying and resolving knowledge deficits. These questions and explanations are not intended to be a source of the knowledge base of all of medicine, nor is it intended to be a board or certification review of Environmental and Wilderness. The authors or editors do not warrant the information is complete or accurate. The reader is encouraged to verify each answer and explanation in several references. All drug indications and dosages should be verified before administration.

StatPearls offers the most comprehensive database of free multiple-choice questions with explanations and short review chapters ever developed. This system helps physicians, medical students, dentists, nurses, pharmacists, and allied health professionals identify education deficits and learn new concepts. StatPearls is not a board or certification review system for Environmental and Wilderness, it is a learning system that you can use to help improve your knowledge base of medicine for life-long learning. StatPearls will help you identify your weaknesses so that when you are ready to study for a board or certification exam in Environmental and Wilderness, you will already be prepared.

Our content is updated continuously through a multi-step peer review process that will help you be prepared and review for a thorough knowledge of Environmental and Wilderness. When it is time for the Environmental and Wilderness board and certification exam, you will already be ready. Besides online study quizzes, we also publish our peer-reviewed content in eBooks and mobile Apps. We also offer inexpensive CME/CE, so our content can be used to attain education credits while you study Environmental and Wilderness.