To screen for, detect, and monitor excessive exposure to specific heavy metals
Periodically when you work with heavy metals, or when your doctor suspects that you may have been exposed. If you have a metal-on-metal hip prosthesis, depending upon the size and type of implant, you may need annual blood monitoring of metal ions (e.g. chromium and cobalt). Consult your doctor for further advice.
A heavy metals panel is a group of tests that measures the quantity of specific, potentially toxic metals in the blood, urine, or more rarely in the hair or other body tissue or fluid. A laboratory may offer several different groupings of heavy metals panels as well as tests for individual metals. The most common combination includes lead, mercury, and arsenic. Other panels may include one or more additional metals, such as cadmium, copper, or zinc. For hip replacement monitoring, the panel includes chromium and cobalt. A doctor will select which metals to test for based upon what a person may have been exposed to in addition to clinical symptoms.
The term "heavy metals" is loosely defined. It is related to the periodic table of elements and refers to a variety of elements with high density or metallic properties. These elements are found naturally throughout the environment and are also used by industries to manufacture a wide range of common products. Some of them, such as iron, copper, selenium, molybdenum, and zinc, are required in trace amounts by the body for normal function but can be toxic at higher levels. Significant concentrations of any of the heavy metals can be irritating or damaging to the body and can contaminate soil, air, food, and water, persisting indefinitely in the environment. Because they are a source of potential injury, the term "heavy metals" is frequently used interchangeably with the term "toxic metals."
The signs and symptoms that a person may experience depend upon the type of metal, its form, the quantity, the length of exposure, the type of exposure, the age of the person, and the person's general state of health. Some metals are much more toxic than others, and one form of a metal may be more harmful than other forms. How a person is exposed can influence the amount of metal absorbed and the part(s) of the body that are affected. For example, a metal that does little when it is held in someone's hand, or is only moderately harmful and poorly absorbed when swallowed, may be much more toxic and cause severe lung damage when its vapours are inhaled.
Severe acute exposure can cause damage and, in some cases, can be life-threatening, but moderate exposures over time should also be monitored. The body is able to process small amounts of heavy metals, but moderate to large quantities can accumulate in the kidneys, liver, bones and brain. Some metals are considered carcinogenic – they increase the risk of developing cancer – and some can affect the body's ability to produce red and white blood cells. Unborn and young children are at the highest risk because exposures to low or moderate concentrations can affect physical and mental development and can permanently damage the organs and brain. Many of the metals can be passed from the mother to the foetus, and some can be passed to the infant in breast milk.
How is the sample collected for testing?
Heavy metal testing is usually performed on a blood sample obtained by inserting a needle into a vein in the arm or on a 24-hour urine collection. Special metal-free blood or acid-washed urine containers are used to minimise the potential for sample contamination by any outside sources of metal. For chromium and cobalt testing a plastic-lined needle should be used to take the sample. Alternatively, if this is not possible a metal needle can be used but it is recommended that the first 10mL of blood collected is discarded or used for other (non-metal) laboratory tests.
Urine and blood can both be used for heavy metal testing, but they do not necessarily test for the same forms of a metal. For instance, methylmercury – an organic highly toxic form of mercury found in fish – can be detected in the blood but not in urine. Urine is the preferred sample for measuring inorganic forms of mercury and for measuring arsenic.
Hair and fingernail analysis can give an indication of exposure that has occurred over time or in the past but does not show recent exposures. Blood and urine will reflect exposures that are chronic or that have happened in the last few days.
Is any test preparation needed to ensure the quality of the sample?
No test preparation is needed.
How is it used?
Heavy metal testing is used to screen for or to diagnose heavy metal poisoning in those who may have been acutely or chronically exposed to one or more heavy metals and to monitor excessive metal concentrations in those who work with various heavy metals. Testing is also conducted to monitor the efficacy of chelation therapy, a treatment to rid the body of high amounts of a heavy metal (e.g. iron).
Panels are set up in groups of tests that mirror potential metal exposures. A laboratory may offer several different groupings that are specific for either blood or urine. A doctor will request the most appropriate tests that correspond to the person's occupation, hobby, suspected exposure, and/or clinical symptoms. Some of the metals that are more commonly tested include:
If the doctor suspects that someone has been exposed to a specific metal, such as lead, the doctor may request that specific test instead of, or in addition to, a group of tests. Lead is usually requested by itself when screening for exposure, especially in children because of how susceptible they are to its effects. Some metals can also be measured in fluid, hair, fingernails, and body tissues. Usually these are requested individually.
When is it requested?
Tests for heavy metals may be requested if a doctor suspects that someone has been acutely or chronically exposed to one or more heavy metals. Signs and symptoms of heavy metal exposure will vary in nature and intensity depending on the type and quantity of metal involved; early symptoms of poisoning can be missed because they are often non-specific. Excessive exposure and damage to several different organs can occur even if a person has no, few, or nonspecific symptoms. Some signs and symptoms of metal poisoning may include:
- Abdominal pain, nausea, vomiting and diarrhoea
- Nervous system symptoms such as numbness, tingling of hands and feet, weakness
- Kidney damage
- Liver damage
- In the lungs – irritation, oedema
- Brain dysfunction, memory loss
- Mees lines (horizontal lines on nails)
- Changes in behaviour
- Malformed bones in children, weakened bones
- In pregnant women – miscarriage, premature labour
People who may be exposed to metals in the workplace are usually monitored periodically. Safety measures minimise risk to employees and help address problems when they are identified. In the UK, the Health & Safety Executive provides advice, guidance and legislation as an independent regulator of work-related health and safety issues. If excessive concentrations are detected, affected persons are monitored and steps are taken to reduce their exposure.
What does the test result mean?
Care must be taken in the interpretation of heavy metals test results. A low level of a heavy metal in the blood does not necessarily mean that excessive exposure has not occurred. Heavy metals do not stay in the blood and will not be present in the urine for extended periods of time. Lead, for instance, migrates from the blood into the body's organs and over time is incorporated into the bones. If someone was chronically exposed to lead, then this may result in lead being present in the blood, urine, organs, and bones.
Very low levels of heavy metals may be present in the blood and urine of apparently healthy people because these metals are present within our environment. Recommendations for safe levels of heavy metals depend on the age of the person and may change over time as more information about their safety emerges.
To learn more about minimal risk levels and/or health effects of a particular metal, visit the Health & Safety Executive website. For advice about blood metal ion levels in hip replacements visit the MHRA or NHS choices websites.
Is there anything else I should know?
Exposures to the same amounts and types of heavy metals will not necessarily lead to the same effects in different people because people absorb and eliminate metals at different rates. Those who have underlying health conditions may be more vulnerable than others to the same exposures.
Methylmercury, a 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. NHS choices recommend that pregnant women avoid or limit intake of certain types of fish during their pregnancy because of pollutants or mercury's potential harm to the foetus.
Lead was once routinely used in paint, plumbing pipes, and as an additive in petrol. In the UK, these environmental sources of lead have decreased, but it can be present in the existing paint and plumbing of older homes. 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.
All of the sources of heavy metal exposure in the air, water and in the environment are controlled, regulated, and monitored by European and UK legislation. The Food Standards Agency may assess the level of heavy metals in certain foodstuffs and publish guidance in response to any concerns. The European Food Safety Authority and the European Commission are also involved in the investigation of any incidents and for issuing guidance to food manufacturers and industry.. The Environmental Agency (http://www.environment-agency.gov.uk/) is a leading public body for applying environmental standards. Regional water authorities are responsible for adhering to standards stated by the Water Supply Regulations/Drinking Water Inspectorate and can supply water quality information (including heavy metal levels) in local drinking water.
How long will it take to get the results of my test?
How is someone exposed to toxic 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.
How can I test my soil, water, or the paint on my house for heavy metals?
In addition to lead, mercury, arsenic, cadmium and chromium, what are some other metals that may be tested?