heavy metal poisoning

What is heavy metal poisoning

Heavy metal poisoning refers to when excessive exposure to a heavy metal affects the normal function of the body. Some debate exists as to exactly what constitutes a “heavy metal” and which elements should properly be classified as such 1. Some authors have based the definition on atomic weight; others, on a specific gravity of greater than 4.0, or greater than 5.0. The actinides (the chemical elements with atomic numbers from 89 to 103, actinium through lawrencium; e.g., uranium) may or may not be included. Most recently, the term “heavy metal” has been used as a general term for those metals and semimetals with potential human or environmental toxicity 2. Examples of heavy metals that can cause toxicity include lead, mercury, arsenic, cadmium, and chromium. Exposure may occur through the diet, from medications, from the environment, or in the course of work or play 1. Heavy metals can enter the body through the skin, or by inhalation or ingestion. Toxicity can result from sudden, severe exposure, or from chronic exposure over time. Symptoms can vary depending on the metal involved, the amount absorbed, and the age of the person exposed. For example, young children are more susceptible to the effects of lead exposure because they absorb more compared with adults and their brains are still developing. Nausea, vomiting, diarrhea, and abdominal pain are common symptoms of acute metal ingestion. Chronic exposure may cause various symptoms resulting from damage to body organs, and may increase the risk of cancer. Treatment depends on the circumstances of the exposure.

Exposures to the same amounts and types of heavy metals will not necessarily lead to the same effects in different people because they absorb and eliminate metals at different rates. Those who have underlying health conditions may be more vulnerable than others to the same exposures.

Trace concentrations of heavy metals are monitored and minimized but are almost impossible to avoid altogether. For instance, naturally-occurring arsenic is a contaminant that can be found in some sources of drinking water throughout the world. Small amounts of mercury are found in fluorescent light bulbs and some thermometers. If these break, the mercury can be released. Methylmercury, an organic form of mercury that is produced by bacteria in water, can build up in fish over time. Concentrations vary regionally and with the size of the fish. The highest levels are typically found in bigger and older fish. In most cases, the benefits of eating fish outweigh the small risk of ingesting excess mercury. However, women who are pregnant may want to take extra precautions. The March of Dimes recommends that pregnant women avoid certain types of large fish during their pregnancy because of mercury’s potential harm to the fetus.

Lead was once routinely used in paint, plumbing pipes, and as an additive in gasoline. In the U.S., these environmental sources of lead have decreased, but it can be present in the existing paint and plumbing of older homes. In Flint, Michigan, in 2015, for example, no corrosion control was used to prevent lead from entering the water when the town switched its water source from Detroit’s water to the Flint River’s water (on top of the fact that the river contained eight times as much chloride as Detroit’s water). When water from the river flowed through those pipes, it ate away at the pipes, which caused lead to enter the water supply and was deemed unsafe to drink.

When lead house paint deteriorates, it creates lead chips and dust that can be stirred up with the movement of air and can find their way into the soil around the house. While anyone may be harmed by lead exposure, children are at the highest risk. They may eat paint chips, mouth painted surfaces, breath in lead dust, and play in contaminated soil.

In addition to lead, other heavy metals such as arsenic and cadmium have been found to contaminate some toys and jewelry.

All of the sources of heavy metal exposure in the air, water, food supply, and in the environment are controlled, regulated, and monitored by three governmental agencies and the medical community. The Environmental Protection Agency (EPA) evaluates the effects of exposures, regulates industrial emissions, and establishes maximum contaminant levels for heavy metals such as arsenic in drinking water. The Food and Drug Association (FDA) establishes limits for metals in food, and the Centers for Disease Control and Prevention (CDC) recommends testing young children for lead, especially for those who live in or routinely visit a house built before 1978.

How is someone exposed to heavy metals?

Heavy metals can enter the body through the skin or by inhalation or ingestion. Toxicity occurs when the metals displace the essential elements in the body and begin to affect the normal function of various organs. Most people will never be sufficiently exposed to be harmed or require testing.

The majority of acute and chronic exposures occur in the workplace, especially in industries that use metals to manufacture products; such as the cadmium, lead, and mercury used in batteries and the arsenic used in some pesticides. Exposures can also occur in agricultural workers, in people whose job it is to clean up contaminated environmental sites, in those who work with certain products such as auto mechanics working with car batteries, and in those with hobbies that involve the use of metals such as the lead used by stained glass artisans.

Most exposures to excessive concentrations in the general population are primarily due to increased levels of metals in food or water, products that they use, or soil contamination in or near the areas that they work and live.

In addition to lead, mercury, arsenic, cadmium and chromium, what are some other metals that may be tested?

Some metals that are tested less frequently in suspected toxicity include:

  • Aluminum
  • Beryllium
  • Cobalt
  • Copper
  • Iron
  • Manganese
  • Nickel
  • Platinum
  • Selenium
  • Silicon
  • Silver
  • Thallium

Lead

Lead is a naturally occurring soft bluish-gray metal found in small amounts in the earth’s crust. Lead can be found in all parts of your environment. Much of it comes from human activities including burning fossil fuels, mining, and manufacturing. Lead has many different uses. It is used in the production of batteries, ammunition, metal products (solder and pipes), and devices to shield X-rays. When lead is inhaled or ingested, lead can cause damage to the brain, organs, and nervous system. Because of health concerns, lead from gasoline, paints and ceramic products, caulking, and pipe solder has been dramatically reduced in recent years.

Affected organ systems: Neurological (Nervous System) and Renal (Urinary System or Kidneys)

Even at low levels, lead can cause irreversible damage without causing physical symptoms. In an infant, lead can cause permanent cognitive impairment, behavioral disorders, and developmental delays. Lead exposure can cause weakness, anemia, nausea, weight loss, fatigue, headaches, stomach pain, and kidney, nervous system, and reproductive dysfunction. Lead can be passed from mothers to their unborn children and can cause miscarriages and premature births.

In the past, lead was used in paints, gasoline, water pipes, and other household products, such as the solder used in canned food. Although these uses have been limited in the U.S., lead is still used in many products and industrial processes both in the U.S. and around the world. Housing built prior to 1978 may contain lead-based paint and lead-contaminated household dust. Soil surrounding these houses may also be contaminated with lead.

Children under 6 years of age are the most likely to be exposed to lead because they often put their hands in their mouths, accidentally ingesting lead dust or paint chips. They can also inhale lead dust and mouth or chew lead-contaminated items. Adult lead exposure is usually related to occupational or recreational (hobby) exposure. Children of those who work with lead may also become exposed when lead contamination is brought home on the work clothes of their parents.

Cancer Classification:

  • The US Environmental Protection Agency (EPA): Probable human carcinogen.
  • International Agency for Research on Cancer (IARC): Inorganic lead – probably carcinogenic to humans.
  • The US National Toxicology Program (NTP): Reasonably anticipated to be a human carcinogen

Summary

The Centers for Disease Control and Prevention (CDC) has updated its recommendations on children’s blood lead levels. Experts now use an upper reference level value of 97.5% of the population distribution for children’s blood lead. In 2012-2015 that value is 5 micrograms per deciliter (µg/dL) to identify children with blood lead levels that are much higher than most children’s levels 3. Today at least 4 million households have children living in them that are being exposed to high levels of lead. There are approximately half a million U.S. children ages 1-5 with blood lead levels above 5 micrograms per deciliter (µg/dL), the reference level at which CDC recommends public health actions be initiated.

Mercury

Mercury is a naturally occurring metal. Mercury is the only metal on earth which is liquid at room temperatures. Metallic mercury is the pure form of mercury. It is a shiny, silver-white, odorless liquid, much heavier than water. Metallic mercury is used in oral thermometers, barometers, sphygmomanometers (devices used to test blood pressure), wall thermostats for heating and cooling, fluorescent light bulbs/tubes, some batteries, electric light switches, some indoor gas meter regulators (in houses built before the 1960’s), and for a variety of other purposes. It is also used in some ethnic religious and cultural practices, and is the form of mercury that is commonly used in middle and high school chemistry labs. Metallic mercury is the form of mercury that many adults remember rubbing on coins as children to make them shine; and it is because of this practice that many people do not realize the true danger of being exposed to metallic mercury.

Mercury combines with other elements, such as chlorine, sulfur, or oxygen, to form inorganic mercury compounds or “salts”, which are usually white powders or crystals. Mercury also combines with carbon to make organic mercury compounds. The most common one, methylmercury, is produced mainly by microscopic organisms in the water and soil. More mercury in the environment can increase the amounts of methylmercury that these small organisms make.

Metallic Mercury is a dense liquid that vaporizes easily at room temperature. Metallic mercury is not easily absorbed into unbroken skin. However, it vaporizes, even at room temperature. The higher the temperature, the more vapors are released. Mercury vapors are colorless and odorless, though they can be seen with the aid of an ultraviolet light.

Metallic mercury is used to produce chlorine gas and caustic soda, and is also used in thermometers, dental fillings, and batteries. Mercury salts are sometimes used in skin lightening creams and as antiseptic creams and ointments.

People can be exposed to metallic mercury when glass thermometers or other devices containing mercury are broken, or when mercury is brought into the home (most often by children) from schools, abandoned industrial sites, or other sites where it may be stored. If not promptly and properly cleaned up and disposed of, it can be spread by walking (tracking), sweeping, or vacuuming, thereby presenting a potential health threat. Tracking throughout the house or into automobiles or school buses has spread mercury contamination in many instances in the past.

While the health risk is not great at the time of a spill, it will increase over time if the mercury is not properly removed. At air temperatures found in homes, mercury evaporates slowly. Mercury vapors are heavier than air and tend to remain near the floor or mercury source, but can get into the ventilation system and be spread throughout the home. Outdoors, mercury vapors tend to go away quickly, but indoors (particularly with windows closed), mercury vapors will accumulate in the air. People can absorb metallic mercury into their bodies when they breathe the vapors. Because of the amount of time spent at home, this means of exposure to mercury can be a concern, especially for young children and pregnant women.

Metallic mercury is absorbed into the body primarily by breathing the airborne vapors. Metallic mercury cannot go through intact skin very well, so touching the beads is less of a problem than breathing the vapors. If you swallow the metal mercury (which is certainly not recommended), it passes through your body almost completely without being absorbed. Therefore, in almost all circumstances, breathing the mercury vapors in the air is the only real source of entry of metallic mercury into the human body.

Affected Organ Systems: Developmental (effects during periods when organs are developing) , Neurological (Nervous System), Renal (Urinary System or Kidneys)

The nervous system is sensitive to metallic mercury. Exposure to very high levels of metallic mercury vapor can cause brain, kidney, and lung damage and may seriously harm a developing fetus. Exposure to mercury vapor concentrations high enough to produce such serious effects might also cause coughing, chest pains, nausea, vomiting, diarrhea, increases in blood pressure or heart rate, skin rashes, and eye irritation. Exposure to lower levels of airborne mercury for prolonged periods of time would produce more subtle effects, such as irritability, sleep disturbances, excessive shyness, tremors, coordination problems, changes in vision or hearing, and memory problems. Most of the effects of mercury resulting from prolonged lowerlevel exposure are reversible, once exposure is terminated and the mercury has left your body.

Very young children are more sensitive than adults to the effects of mercury. Children 5 years of age and younger are considered to be particularly sensitive to the effects of mercury on the nervous system, since their central nervous system is still developing.

Some children exposed to high mercury vapor levels develop a reversible condition called acrodynia, in which the palms of the hands and soles of the feet often become reddened and tender, before beginning to peel. Children with acrodynia may also have mood swings, increased irritability, difficulty sleeping, and muscle or joint pains. Exposure levels high enough to cause acrodynia might also cause coughing or pain in the chest area. Acrodynia is usually, but not always, associated with urine mercury concentrations of 100 micrograms (or more) of mercury per liter of urine.

When pregnant women are exposed to mercury, the mercury can pass from the mother’s body to the developing fetus; it can also be passed to a nursing infant through breast milk. However, since breast feeding itself has significant health benefits, a physician should be consulted before stopping breast feeding because the mother may have been exposed to mercury.

Cancer Classification:

  • EPA: Possibly carcinogenic to humans.
  • IARC: Probably carcinogenic to humans.
  • NTP: Not evaluated

Arsenic

Arsenic is a natural element that can be found in rocks and soil, water, air, and in plants and animals. It can also be released into the environment from some agricultural and industrial sources. In the environment, arsenic is combined with oxygen, chlorine, and sulfur to form inorganic arsenic compounds. Arsenic in animals and plants combines with carbon and hydrogen to form organic arsenic compounds.

Although it is sometimes found in its pure form as a steel grey metal, arsenic is usually part of chemical compounds. These compounds are divided into 2 groups:

  • Inorganic compounds (arsenic combined with elements other than carbon): These compounds are found in industry, in building products (such as some “pressure-treated” woods), and in arsenic-contaminated water. Inorganic arsenic compounds are mainly used to preserve wood. This is the form of arsenic that tends to be more toxic and has been linked to cancer. Copper chromated arsenic (CCA) is used to make “pressure-treated” lumber. Copper chromated arsenic (CCA) is no longer used in the U.S. for residential uses; it is still used in industrial applications. Organic arsenic compounds are used as pesticides, primarily on cotton plants.
  • Organic compounds (arsenic combined with carbon and other elements): These compounds are much less toxic than the inorganic arsenic compounds and are not thought to be linked to cancer. These compounds are found in some foods, such as fish and shellfish.

Arsenic compounds have been used in many ways, including:

  • As a preservative in pressure-treated lumber
  • In pesticides
  • As a preservative in animal hides
  • As an additive to lead (such as in lead-acid batteries) and copper
  • In some glass manufacturing
  • As arsine gas to enhance electrical junctions in semiconductors

Arsenic can get into air, water, and the ground from wind-blown dust. It may also get into water from runoff.

You may be exposed to arsenic by:

  • Taking in small amounts in food, drinking water, or air
  • Breathing sawdust or burning smoke from arsenic-treated wood
  • Living in an area with high levels of arsenic in rock
  • Working in a job where arsenic is made or used

In food

For most people, food is the largest source of arsenic, although much of this is likely to be in the less dangerous, organic form. The highest levels of arsenic (in all forms) in foods can be found in seafood, rice, rice cereal (and other rice products), mushrooms, and poultry, although many other foods can contain low levels of arsenic.

Rice is of particular concern because it is a major part of the diet in many parts of the world. It is also a major component of many of the cereals eaten by infants and young children. (Nearly all rice products have been found to contain at least some arsenic, although the levels can vary widely.)

In drinking water

Drinking water is an important and potentially controllable source of arsenic exposure. In fact, drinking water is a major source of arsenic exposure in some parts of the world. In parts of Taiwan, Japan, Bangladesh, and western South America, high levels of arsenic occur naturally in drinking water.

Water in some areas of the United States, especially in the West, also naturally contains arsenic. Most US areas with higher levels of arsenic in drinking water are rural communities. Albuquerque, New Mexico, is the only urban area in the US with substantial natural arsenic levels in drinking water.

Arsenic levels tend to be higher in drinking water that comes from ground sources, such as wells, as opposed to water from surface sources, such as lakes or reservoirs.

Arsenic levels in public drinking water are regulated in the United States by the Environmental Protection Agency (EPA). Since January 2006, the maximum level of arsenic allowed in US drinking water is 10 μg/L (micrograms per liter), or 10 ppb (parts per billion).

At work

Arsenic has not been produced in the United States since 1985, although it is imported from other countries. In the past, workers in smelters and in plants that manufactured, packaged, or distributed products that contained arsenic had high exposures from breathing in arsenic fumes and dust.

Arsenic was a common ingredient in many pesticides and herbicides in the past. People who made, transported, applied, or worked around these products may have been exposed to higher levels of arsenic. Inorganic arsenic compounds have not been used in pesticides in the US since 1993, and organic compounds have been phased out of pesticides (with one exception used on cotton plants) as of 2013.

Today workplace exposure to arsenic can still occur in some occupations that use arsenic, such as copper or lead smelting, and wood treating. Regulations in place can help limit this workplace exposure.

In the community

Communities near previous or current agricultural or industrial sources may be exposed to arsenic. Industrial buildings such as wood preservative and glass factories can contaminate nearby air, soil, and water. Communities near smelters, or near farm fields or orchards where arsenic pesticides were used, may also have contaminated soil. Burning fossil fuels (such as coal) and tobacco can also release small amounts of arsenic into the air.

Affected Organ Systems: Dermal (Skin), Gastrointestinal (Digestive), Hepatic (Liver), Neurological (Nervous System), Respiratory (From the Nose to the Lungs)

Exposure to arsenic can cause many health problems. Being exposed to low levels for a long time can change the color of your skin. It can cause corns and small warts. Exposure to high levels of arsenic can cause death.

Short-term arsenic exposure

Breathing in high levels of arsenic may cause a sore throat and irritated lungs.

Swallowing high levels of arsenic can cause things like:

  • Stomachache
  • Nausea and vomiting
  • Diarrhea
  • Muscle weakness and cramping
  • “Pins and needles” sensations in hands and feet
  • Skin changes or rashes
  • Bruising (caused by blood vessel damage)

Exposure to high enough amounts of arsenic can be fatal.

Contact with the skin can cause redness and swelling, although it’s not known if it can cause other health problems.

Long-term arsenic exposure

Exposure to lower levels of arsenic over longer periods of time can cause many of the same health problems listed above. It can also result in:

  • Irregular heartbeat
  • Liver and kidney damage
  • A shortage of red and white blood cells, which can lead to fatigue and an increased risk of infections

Skin changes are a common sign of chronic arsenic exposure. The changes can include darkened patches of skin and the appearance of areas of thickened skin, usually on the palms and soles.

Cancer Classification:

  • EPA: Confirmed human carcinogen.
  • IARC: Carcinogenic to humans.
  • NTP: Known to be a human carcinogen.

Cadmium

Cadmium is a natural element in the earth’s crust. Cadmium is usually found as a mineral combined with other elements such as oxygen (cadmium oxide), chlorine (cadmium chloride), or sulfur (cadmium sulfate, cadmium sulfide).

All soils and rocks, including coal and mineral fertilizers, contain some cadmium. Most cadmium used in the United States is extracted during the production of other metals like zinc, lead, and copper. Cadmium does not corrode easily and has many uses, including batteries, pigments, metal coatings, and plastics.

Cadmium’s primary industrial uses are for the manufacturing of batteries, pigments, plastic stabilizers, metal coatings, alloys and electronics. Recently, cadmium has been used in manufacturing nanoparticles (quantum dots) for use in solar cells and color displays.

Cadmium is used for the following:

  • batteries (83%)
  • pigments (8%)
  • coatings and platings (7%)
  • stabilizers for plastics (1.2%)
  • nonferrous alloys, photovoltaic devices, and other uses (0.8%)

In the United States, for nonsmokers the primary source of cadmium exposure is from the food supply. In general, leafy vegetables such as lettuce and spinach, potatoes and grains, peanuts, soybeans, and sunflower seeds contain high levels of cadmium, approximately 0.05- 0.12 mg cadmium/kg.

Tobacco leaves accumulate high levels of cadmium from the soil.

The national geometric mean blood cadmium level for adults is 0.38 µg/L. A geometric mean blood cadmium level of 1.58 µg/L for New York City smokers has been reported. The amount of cadmium absorbed from smoking one pack of cigarettes per day is about 1- 3 µg/day. Direct measurement of cadmium levels in body tissues confirms that smoking roughly doubles cadmium body burden in comparison to not smoking.

  • About 5-50% of the cadmium you breathe will enter your body through your lungs.
  • A small amount of the cadmium in food and water (about 1-10%) will enter your body through the digestive tract. If you do not have enough iron or other nutrients in your diet, you are likely to take up more cadmium from your food than usual.

Affected Organ Systems: Cardiovascular (Heart and Blood Vessels), Developmental (effects during periods when organs are developing) , Gastrointestinal (Digestive), Neurological (Nervous System), Renal (Urinary System or Kidneys), Reproductive (Producing Children), Respiratory (From the Nose to the Lungs)

Breathing air with very high levels of cadmium can severely damage the lungs and may cause death.

Breathing air with lower levels of cadmium over long periods of time (for years) results in a build-up of cadmium in the kidney, and if sufficiently high, may result in kidney disease.

Eating food or drinking water with very high cadmium levels severely irritates the stomach, leading to vomiting and diarrhea, and sometimes death.

Eating lower levels of cadmium over a long period of time can lead to a build-up of cadmium in the kidneys. If the build-up of cadmium is high enough, it will damage the kidneys.

Exposure to lower levels of cadmium for a long time can also cause bones to become fragile and break easily.

Cancer Classification:

  • NTP: Known to be a human carcinogen.
  • EPA: Probable human carcinogen.
  • IARC: Carcinogenic to humans

Chromium

Chromium is a naturally occurring element found in rocks, animals, plants, soil, and in volcanic dust and gases. Chromium is present in the environment in several different forms. The most common forms are chromium (0), chromium (III), and chromium (VI). No taste or odor is associated with chromium compounds. Chromium(III) occurs naturally in the environment and is an essential nutrient. Chromium(VI) and chromium(0) are generally produced by industrial processes. The metal chromium, which is the chromium(0) form, is used for making steel. Chromium(VI) and chromium(III) are used for chrome plating, dyes and pigments, leather tanning, and wood preserving.

Chromium can be found in many consumer products such as:

  • wood treated with copper dichromate,
  • leather tanned with chromic sulfate, and
  • stainless steel cookware.
  • metal-on-metal hip replacements

The general population is most likely to be exposed to trace levels of chromium in the food that is eaten. Low levels of chromium(III) occur naturally in a variety of foods, such as fruits, vegetables, nuts, beverages, and meats.

Chromium is occasionally detected in groundwater, drinking water, or soil samples. Some ways to be exposed to chromium include:

  • drinking water containing chromium
  • bathing in water containing chromium

You can be exposed to trace levels of chromium by breathing air containing it. Releases of chromium into the air can occur from:

industries using or manufacturing chromium
living near a hazardous waste facility that contains chromium
cigarette smoke

Rural or suburban air generally contains lower concentrations of chromium than urban air.

  • <10 ng/m³ in rural areas
  • 0-30 ng/m³ in urban areas
  • as a result of smoking, indoor air contaminated with chromium can be 10-400 times greater than outdoor air concentrations

Affected Organ Systems: Immunological (Immune System), Renal (Urinary System or Kidneys), Respiratory (From the Nose to the Lungs)

The most common health problem in workers exposed to chromium involves the respiratory tract. These health effects include irritation of the lining of the nose, runny nose, and breathing problems (asthma, cough, shortness of breath, wheezing). Workers have also developed allergies to chromium compounds, which can cause breathing difficulties and skin rashes.

The concentrations of chromium in air that can cause these effects may be different for different types of chromium compounds, with effects occurring at much lower concentrations for chromium(VI) compared to chromium(III). However, the concentrations causing respiratory problems in workers are at least 60 times higher than levels normally found in the environment.

Respiratory tract problems similar to those observed in workers have been seen in animals exposed to chromium in air.

The main health problems seen in animals following ingestion of chromium(VI) compounds are to the stomach and small intestine (irritation and ulcer) and the blood (anemia). Chromium(III) compounds are much less toxic and do not appear to cause these problems.

Sperm damage and damage to the male reproductive system have also been seen in laboratory animals exposed to chromium(VI).

Cancer Classification:

  • EPA: Hexavalent chromium – inhalation – confirmed human carcinogen; oral – Not classifiable as to its carcinogenicity. There is inadequate or no human and animal evidence of carcinog.
  • IARC: Hexavalent chromium – carcinogenic to humans.
  • NTP: Known to be a human carcinogen

What are the signs and symptoms of heavy metal poisoning

Signs and symptoms of heavy metal poisoning vary depending on the type and amount of metal involved. Fetuses and young children are at the highest risk for severe and long term health consequences from heavy metal exposure. Early symptoms may be missed because they are often nonspecific. Excessive exposure and damage to several organs can occur even if a person has no symptoms. Some signs and symptoms of metal poisoning may include:

  • Abdominal pain, nausea, vomiting, and diarrhea (the hallmark symptoms with most cases of acute metal ingestion)
  • Dehydration
  • Heart abnormalities such as cardiomyopathy or abnormal heart beat (dysrhythmia)
  • Nervous system symptoms (e.g. numbness, tingling of hands and feet, and weakness)
  • Anemia (a classic symptom of chronic metal exposure)
  • Kidney damage
  • Liver damage
  • Lung irritation, or fluid accumulation (edema)
  • Brain dysfunction such as memory loss
  • Horizontal lines on the nails
  • Changes in behavior
  • Malformed bones in children, or weakened bones
  • Miscarriage or premature labor in pregnant women

People who may be exposed to metals in the workplace are usually monitored periodically. Safety measures minimize risk to employees and help address problems when they are identified. The U.S. Occupational Safety and Health Administration (OSHA) regulates the use and monitoring of several toxic metals that may be found on the job. If excessive concentrations are detected, affected persons are monitored and steps are taken to reduce their exposure.

Heavy metal poisoning diagnosis

Diagnosing heavy metal poisoning can be difficult, as it relies on having a known exposure and positive results on approved tests. Heavy metal poisoning is often first suspected based on a patient’s history and/or symptoms consistent with excessive exposure.

Heavy metal poisoning test

The following tests may help make the diagnosis of heavy metal toxicity, or help determine how severe the exposure is:

  • Complete blood count (CBC) with peripheral smear
  • Renal (kidney) function tests
  • Urine analysis (looking for protein in the urine)
  • Liver function studies
  • Imaging studies such as abdominal radiographs
  • Electrocardiogram

Testing is available in panels (where multiple exposures are tested) or by individual metal. The testing performed depends on the person’s symptoms and suspected exposure. Metals more commonly tested for include lead, mercury, arsenic, cadmium, and chromium. Metals less commonly tested for include aluminum, beryllium, cobalt, copper, iron, manganese, nickel, platinum, selenium, silicon, silver, and thallium.

Heavy metal poisoning treatment

Decontamination

Removal of the patient from the source of exposure is critical to limiting dose.

Treatment may include whole-bowel irrigation with polyethylene glycol electrolyte solution if radiographic studies show evidence of retained metal (toys, coins, paint chips) in the gastrointestinal tract.

Resuscitation

Good supportive care is critical. Ensure airway patency and protection, provide mechanical ventilation where necessary, correct dysrhythmias, replace fluid and electrolytes (significant fluid losses generally occur and require aggressive rehydration), and monitor and treat the sequelae of organ dysfunction.

Chelation

Chelation is rarely indicated in the emergent setting. A possible exception is lead encephalopathy. Consideration of chelation therapy for patients with suspected or confirmed metal exposures should be made in conjunction with a medical toxicologist or the local poison control center.

Table 1. Typical presentation of the most commonly encountered metals and their treatment

Metal Acute Chronic Toxic Concentration Treatment
ArsenicNausea, vomiting,

“rice-water” diarrhea,

encephalopathy,

multi-organ dysfunction syndrome, long QT syndrome,

painful neuropathy

Diabetes,

hypopigmentation/ hyperkeratosis,

cancer: lung, bladder, skin, encephalopathy

24-h urine:

≥50 µg/L urine, or

100 µg/g creatinine

BAL (acute, symptomatic)

Succimer

DMPS (Europe)

BismuthRenal failure; acute tubular necrosisDiffuse myoclonic encephalopathyNo clear reference standard*
CadmiumPneumonitis (oxide fumes)Proteinuria, lung cancer, osteomalaciaProteinuria and/or ≥15 µg/ g creatinine*
ChromiumGastrointestinal hemorrhage, hemolysis, acute renal failure (Cr6+ ingestion)Pulmonary fibrosis, lung cancer (inhalation)No clear reference standardNAC (experimental)
CobaltBeer drinker’s (dilated) cardiomyopathyPneumoconiosis (inhaled); goiterNormal excretion:

0.1-1.2 µg/L (serum)

0.1-2.2 µg/L (urine)

NAC

CaNa2 EDTA

CopperBlue vomitus, gastrointestinal irritation/ hemorrhage, hemolysis, multi-organ dysfunction syndrome (ingested); metal fume fever (inhaled)vineyard sprayer’s lung (inhaled); Wilson disease (hepatic and basal ganglia degeneration)Normal excretion:

25 µg/24 h (urine)

BAL

D-Penicillamine

Succimer

IronVomiting, gastrointestinal hemorrhage, cardiac depression, metabolic acidosisHepatic cirrhosisNontoxic: < 300 µg/dL

Severe: >500 µg/dL

Deferoxamine
LeadNausea, vomiting, encephalopathy (headache, seizures, ataxia, obtundation)Encephalopathy, anemia, abdominal pain, nephropathy, foot-drop/ wrist-dropPediatric: symptoms or [Pb] ≥45 µ/dL (blood); Adult: symptoms or [Pb] ≥70 µ/dLBAL

CaNa2 EDTA

Succimer

ManganeseMetal fume fever (inhaled)Parkinson-like syndrome,

respiratory, neuropsychiatric

No clear reference standard*
MercuryElemental (inhaled): fever, vomiting, diarrhea, acute lung injury;

Inorganic salts (ingestion): caustic gastroenteritis

Nausea, metallic taste, gingivo-stomatitis, tremor, neurasthenia, nephrotic syndrome; hypersensitivity (Pink disease)Background exposure “normal” limits:

10 µg/L (whole blood); 20 µg/L (24-h urine)

BAL

Succimer

DMPS (Europe)

NickelDermatitis; nickel carbonyl: myocarditis, acute lung injury, encephalopathyOccupational (inhaled): pulmonary fibrosis, reduced sperm count, nasopharyngeal tumorsExcessive exposure:

≥8 µg/L (blood)

Severe poisoning:

≥500 µg/L (8-h urine)

*
SeleniumCaustic burns, pneumonitis, hypotensionBrittle hair and nails, red skin, paresthesia, hemiplegiaMild toxicity: [Se] >1 mg/L (serum); Serious: >2 mg/L*
SilverVery high doses: hemorrhage, bone marrow suppression, pulmonary edema, hepatorenal necrosisArgyria: blue-grey discoloration of skin, nails, mucosaeAsymptomatic workers have mean [Ag] of 11 µg/L (serum) and 2.6 µg/L (spot urine)Selenium, vitamin E (experimental)
ThalliumEarly: Vomiting, diarrhea, painful neuropathy, coma, autonomic instability, multi-organ dysfunction syndrome

Late: Alopecia, Mees lines, residual neurologic symptoms

Alopecia, neuropathyToxic: >3 µg/L (blood)MDAC

Prussian blue

ZincMetal fume fever (oxide fumes); vomiting, diarrhea, abdominal pain (ingestion)Copper deficiency: anemia, neurologic degeneration, osteoporosisNormal range:

0.6-1.1 mg/L (plasma)

10-14 mg/L (red cells)

*

Abbreviations: BAL = British Anti-Lewisite; DMPS = 2,3-dimercapto-1-propane-sulfonic acid; CaNa2 EDTA = edetate calcium disodium; MDAC = multi-dose activated charcoal; NAC = N-acetylcysteine.

[Source 1 ] References
  1. Heavy Metal Toxicity. https://emedicine.medscape.com/article/814960-overview
  2. Saunders JE, Jastrzembski BG, Buckey JC, Enriquez D, MacKenzie TA, Karagas MR. Hearing loss and heavy metal toxicity in a nicaraguan mining community: audiological results and case reports. Audiol Neurootol. 2013. 18(2):101-13.
  3. What Do Parents Need to Know to Protect Their Children? https://www.cdc.gov/nceh/lead/ACCLPP/blood_lead_levels.htm
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