What constitutes a heavy metal?
The definition of the term ‘heavy metal’ is somewhat vague. Some definitions rely on atomic weight, others on specific gravity, some definitions include actinides, – and others do not. In recent times the phrase ‘heavy metal has become associated with those metals thought to be toxic to humans and/or the environment.
Heavy metal toxicity is an unusual diagnosis and not always recognised or even suspected by medical professionals – the exceptions to this would include iron toxicity resulting from accidental or deliberate ingestion or exposure to lead.
However, left untreated, heavy metal exposure can lead to serious, life threatening complications. It is essential that suspected heavy metal toxicity is recognised and treated appropriately in order to avoid these complications.
Useful or useless to humans?
Many chemical elements recognised as heavy metals are of no benefit to the human body – these include lead, mercury and cadmium – all considered to be toxic to humans. Other metals are, however, essential to health as they are involved in the various processes and reactions of the body – these beneficial elements include the following –
- Zinc – essential to a number of enzyme reactions
- Vitamin B-12 contains cobalt
- Iron provides haemoglobin
- The trace elements copper, manganese, selenium, chromium, and molybdenum are all important components of a healthy diet
- In medicine metals such as aluminium, bismuth, gold, silver, lithium and gallium are all used to therapeutic effect but, when used incorrectly, may be detrimental to health.
The effects of heavy metals on any individual is dependent on several factors and the signs and symptoms of poisoning may also vary –
- Total amount of the heavy metal absorbed and/or ingested
- Exposure levels
- Age of the individual
- Route of exposure
- Form of the toxin
Age of the individual
Young children are much more vulnerable to the effects of exposure to lead due to the immaturity of their brains – any brief exposure to toxic heavy metals may influence the development of young children and infants.
Route of exposure
The route of exposure to any heavy metal may have varying effects – elemental mercury causes little effect when ingested or absorbed through skin that is unbroken, but when inhaled or injected the results may well be catastrophic.
Chemical forms affect the toxic profile of some heavy metal elements. Barium salts are known to be rapidly absorbed and potentially life threatening whilst barium sulphate is non-toxic. Radioactive elements, such as polonium, are known for emitting toxic particles rather than their ability to bind cell proteins.
When heavy metal toxicity is suspected
Because exposure to heavy metals may have occurred for a variety of reasons – from diet, environment, medication or during activities related to work or play – it is essential that a full history be obtained from the patient. Examining the patient’s diet and lifestyle may well lead to identification of the heavy metal source and its removal – this is often the only treatment required.
There are a number of possible hidden sources of exposure to heavy metals – these include
- Contamination of dietary supplements
- Leeching into food or drinks particularly when stored in metal containers
- Ingesting of colloidal metals for their supposed health benefits
- Dental Amalgams
During the 1970’s cobalt was added to some beers in order to stabilise the product – this was found to cause cardiomyopathy in alcoholics.
Manganese toxicity was recently identified as the cause of a Parkinson’s like syndrome amongst intravenous drug users in Latvia – due to their use of methcathinone.
There are a number of cases where environmental contamination has occurred with devastating consequences for the local communities –
- Minimata Bay – during the 1950’s industrial waste was dumped into Minimata Bay, Japan, this lead to an accumulation of mercury in the bay resulting in high concentrations of mercury in local sea life. A number of adults developed signs and symptoms associated with (http://webctor.com/diseases/mercury_poisoning,3655,1.html) mercury poisoning, however the greatest effect was seen in subsequent generations with many individuals affected by neurologic defects from birth.
- Bangladesh – millions of Bangladeshis are affected by arsenic in their water supply, this leads to high incidence of cancer and dysfunction of the vital organs. This arsenic poisoning is the result of deep water wells used to bypass contaminated ground water – the resulting water, used for crop irrigation as well as human consumption has a high concentration of arsenic from the bedrock deep in the water table.
- North America – lead poisoning in children has been linked to old paint
Heavy metals, war, and crime
Heavy metals are regularly used as a murder weapon – for example, arsenic is very often regarded as a poison although it should be classified as a metalloid.
The use of chemical weapons during warfare has been documented since the First World War when arsenic was used during trench warfare in the form of a spray known as Lewisite. By the outbreak of the Second World War, the Germans had developed an antidote to Lewisite, which today provides the basis for chelation therapy.
The majority of incidence of exposure to heavy metals occurs because of occupational exposure – the effects of arsenic and mercury on metalworkers is recorded as long ago as 370 BC.
Metalworkers frequently exhibit classic signs of heavy metal toxicity including fever, headache, fatigue, cough, and a metallic taste in the mouth. This effect is referred to as metal fume fever (MFF) and is frequently seen in workers exposed to metal oxide fumes – it may also be referred to as ‘brass founder’s ague’, ‘zinc shakes’ or ‘Monday morning fever’.
Continual, long-term exposure to heavy metal dusts has been implicated in the development of various cancers, pneumoconiosis, neuropathies, and degeneration of the liver and/or kidneys.
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Guest Post by: My name is Joanna Stryjak. I am one of the specialists on http://webctor.com. The portal is a health center which is responsible for bringing free and accurate medical information to the Internet. You can follow the portal on twitter https://twitter.com/#!/webctor_com.