Millions of years ago, man had only little influence on the environment, the could only till the land to get what he eats, these foods he processed in a way which could be described as crude when compared to our contemporary food processing method and these foods were taken in a form which was as natural as possible. Little attempts were made towards complete processing of these foods while some of them were eaten raw.

Over the years, knowledge, science and technology has developed as fast as man himself, this is arguable anyway as many would argue that man has actually developed faster than science and technology, but technology has come to posses more ability than man who actually created it. This development can be seen in every aspect of human life and man have grown to have more influence on the ecosystem and their interaction with the organic and inorganic aspects of his environment has increased and he has since then gained more control over how things are run in the environment. This interaction has not only opened new ways but has exposed man to more life enhancing opportunities, man can now process his foods to an extent where the foods looks completely different from its natural form, the only sort of food taken in a relatively unprocessed form being the fruits which is even unworthy of this mention as many food processing technology researches and inventions have been geared towards fruits and vegetables processing.

This is only an instance of how science have developed all aspects of human life, man has not only come in close contact with foreign things in the ecosystem, he has also devised techniques to manipulate these foreign things to suit him. On the advantages, these developments have enriched life and have made human existence much more easier and valuable.
On the other hand however, this continued exposure to some aspect of the ecosystem have proven detrimental to human existence.

Metals have become a very essential part of our life, from the iron which most of our crude tools are made of, to the gold and silver which have formed a very vital constituents of our very expensive jewelries. Aluminum and tin are currently used in the packaging of processed and preserved foods; this amongst other applications have increased the frequency of our contact with these metals. When consumed in very little quantities, some of these metals are highly beneficial to the body, serving many vital purposes as minerals in the body, iron is an important part of Haemoglobin, the oxygen carrying pigment of the red blood cells and zinc enhances the immune system’s reactions and hastens healing and recovery from infections. Inadequacy of these micronutrients exposes the body to a form of malnutrition known as hidden hunger, even though these metals are required in little quantities, they perform a whole lot of task in the body, this gives an insight on their high reactivity, potency and efficacy.

Just like drugs however, a pharmacological substance with high efficacy and potency should be consumed in a small quantity relative to their efficacy and potency, this is to prevent their accumulation and the resultant toxicity.

Drugs and metals are foreign to the body and hence are metabolized via a common pathway hence their adverse effects in case of traumatic accumulation is felt by the same organs, which includes the kidney, live and gastrointestinal tract.

The ALMs

The periodic table consists of 118 elements out of which about 90 elements are metals, typical metals are elements which forms cations through electron loss and forms oxides with oxygen. Physically, they are high density elements with high thermal and electrical conductivity, many other elements which are sometimes regarded as non-metals also exhibits some of these properties of metals under certain conditions and manipulations and hence these elements are classified as both metals and non-metals with respect to the given conditions. These properties of metals have increased their application in different spheres of our civilized society, their strength and resilience has led to their frequent use in bridges and high rise buildings, home appliances and water distribution pipes.

Metals vary in certain chemical and physical properties such as in their atomic numbers, densities and atomic weight, this variation is the basis of their differentiation into heavy and light metals, while heavy metals are known to be metals of high density, atomic number and atomic weight, light metals have relatively smaller density and atomic weight and number.

Heavy metals are scarce on earth crust when compared to the light metals, this is probably due to inertness, hence little reactive abilities. These heavy metals are contemporarily more common due to modernization and enhanced scientific research, thus the increased exposure to these metals.

As already stated, the effect of these metals in the human body may be of importance in the case of zinc, cobalt, and iron, or harmless such as in silver and indium. But in high amount, these metals are toxic to the body, traumatic accumulation of heavy metals in the body is the sole cause of heavy metal poisoning. Humans are exposed to high amount of heavy metals through paints, industrial wastes, agricultural run off or due to their occupation as individuals working in these industries are also exposed to the greatest amount of these metals.

Arsenic, mercury and lead are the heavy metals of most medically reported cases of toxic accumulation in many countries, they make up the ALMs.

ARSENIC POISONING — THE SHRIMP TALES

ON JANUARY 3 2013, a lady who had died after consuming a large amount of shrimp had reportedly died due to arsenic poisoning, this is sequel to researches by scientists at the University of Chicago in the United States which revealed that foods such as soft shelled mollusks like shrimp contains much higher quantities of five potassium arsenic compounds. The deceased however suffered from this condition due to the reaction of the arsenic contained in shrimps with the vitamin which she routinely consumed.

Arsenic is a metalloid of atomic number 33 (thirty three) occurring as arsenic crystals and also in combination with other elements such as sulphur, arsenic is in alloys of lead and is the second most commonly used semiconductor, silicon being the most used; according to the United States Environmental Protection Agency, all forms of arsenic are a serious risk to human health and in 2001 was ranked as number 1 in the priority list of harzadous substances at Superfund sites and has been classified as group 1 carcinogen, several cases of arsenic contamination of ground water have also been reported and affects millions of people world wide, this may be due to natural deposition of Arsenic in the water and also from mining and agriculture.

Arsenic poisoning however, results only when these elements accumulates in high quantity as the element has been found to be essential in trace quantity in certain mammals such as hamsters. Acute arsenic poisoning may show symptoms such as bloody diarrhea, vomiting, abdominal pain and encephalopathy. Chronic arsenic poisoning may result in cancer, thickening of the skin which also appears to be darker, abdominal and heart diseases, numbness have also been reported in some cases.

LEAD POISONING

In early 2010, the northern Nigerian state of Zamfara had witnessed an alarming rate of disappearance of the much popular webbed feet bird — the Duck, however, this was of little concern as the bird is only of little importance, unfortunately, more attention grew as reported cases of sick children with similar symptoms grew, with conditions such as headache, vomiting, seizures and abdominal pain were commonly associated with this condition. A medical team sent to the affected communities of this state discovered high levels of lead in these communities with the disappearance of ducks being an earlier warning of this unhealthy state of the environment.

The state is known with its agricultural viability and high deposits of many natural metallic resources such as gold and lead, the lucrative nature of these metals had led the inhabitants of these communities to mine these gold and lead and store them inside their houses, this have also contaminated their water to a reasonable extent.

Lead is a soft malleable metal with a low melting point and an atomic number of 82,it is amphoteric and hence can react with acids and bases, it’s low melting point and ductility have seen lead being used in many industrial and construction processes such as in production of alloy, paints, radiation shields, solder and in plumbing.

Lead however is a neurotoxin that accumulates in the bones and soft tissues causing blood disorders and damages to the nervous system and may cause permanent brain damage. This is caused by much accumulation in the body. Lead poisoning may also lead to infertility and intellectual disabilities in children. Death have also been reported in severe cases due to anaemia, seizures and the already mentioned symptoms.

MECURY—THE LIQUID POISON

Probably you must have come across construction sites or at least building equipment, or maybe as a medical student, you must have come across a mercury-in glass thermometer or at least as a patient or on visits to the hospitals, mercury is a very unique metals being a liquid metal at standard temperature and pressure and a measure of relative humidity; it is a heavy silvery D-block element with atomic number of 80.

These chemical and physical properties of lead has enabled it’s in the production of mercury switches, barometer, florescent lamps, sphygmomanometer, thermometer and a civil-engineer’s plumb. It is also used in scientific research application and in amalgam for dental restoration.

Unfortunately, mercury is highly toxic humans and the physical environment, recent time human activities have increased the level of mercury in the environment, this has become a major worry for the World health institutions as exposure to this high level of mercury causes vision or hearing problems, infertility, heart, kidney and respiratory problems.

Increased level of mercury may be due to human activities such as mining, cement production, coal combustion, improper disposal of mercury containing products and improper waste management, there is a high level of these activities in Nigeria and hence the alarming increasing risk and cases of mercury poisoning in this region because this leads to inhalation of mercury vapor or ingestion of soluble forms of mercury.

WHY ARE THESE METALS POISONOUS

Throughout the course of this article, you must have understood that the accumulation of high levels of heavy metals is the sole cause of metal toxicity, but these metals do not just accumulate, they exhibit some action which disturbs the normal functioning of the body system.

The metals mimic the action of essential elements in the body and compete with these elements, such as calcium and zinc to move through membrane channels in free ionic form, hence these metals are distributed and deposited at these organs instead of the supposed elements, but these metals can not perform the actions done by the normal elements, hence they accumulate in these organs and the organ suffers not only due to the blocking action of the heavy metals but also due to the deficiency of the normal elements which should be supplied to them instead of the heavy metals. Heavy metals may also cause disruption of enzyme activity by binding to sulphydryl groups and also to oxygen and nitrogen.

FACTORS THAT CONTRIBUTES TO METAL POISONING

Before now, heavy metal poisoning isn’t a popular medical condition, but due to increased exposure, the frequency of reported medical cases of toxic accumulation of heavy metals have increased over time, one’s occupation may place him/her at high risk of heavy metal poisoning especially ones working in industries as these metals are used more in industries and hence are increased chances of life-threatening contact with them, lead is used in the production of paints, batteries and fire arms and also in road construction and in metallurgical industries, arsenic is used in the production of insecticides, pesticides and herbicides while mercury is an important constituents of thermometers, X-ray machines and vacuum pumps, hence workers in the companies where these products are being manufactured and used runs a high risk of ingesting or inhaling these metals in a traumatizing quantity.

Working in these industries also means that the individual is exposed to these metals for a longer time, continuous exposure to heavy metals over a long period of time also increases the risk of toxic accumulation.

The ability to absorb heavy metals decreases with age, hence younger people tend to absorb a higher percentage of heavy metal which they are exposed to, children between the age of 3-12 can absorb up to 50% of the heavy metals they are exposed to, this decreases as one gets older.

The chances of being poisoned by these heavy metals increases with the amount absorbed, this entails that people who absorb more heavy metals run more risks of metal poisoning, thus children who have more absorbing abilities are more likely to suffer from metal poisoning than the adults who are exposed to the same quantity of toxic metals. This is evidenced in the higher number of reported cases of children suffering from metal toxicity than adults.

WHICH WAY OUT?

Prevention is better than cure, but that looks easy to say, because sometimes preventive measures are not easy to adhere to. Prevention of heavy metals poisoning will include a more careful use of these metals and their products or products which contains these metals and also decreased use of heavy metals in industrial processes.

Lead pipes used in distribution of water to homes should be replaced with the much safer plastic pipes. These measure are already in place, but while we struggle to adhere to these measures, more routes of metal poisoning are only increasing as much amount of heavy metals have already been deposited and it will only take time before these deposited amount of heavy metals gets into the human system through some human activities which enhances their spread.

Chelation therapy have proven functional in the treatment of confirmed cases of metal poisoning, but this produces a better result in patients who have been exposed to these metals doe only a short period of time as chelation therapy for long time exposure have shown only a little effect.

Chelation therapy involves the use of chelating agents such as dimercaptosuccinic acid (DMSA), ethylene diamine tetra acetic acid (EDTA) or dimercarptopropane sulphonate(DMPS). These are molecules that have multiple electron donating groups which are able to form stable coordination complexes with metal ions, this complex prevents the metal ions from reacting with molecules in the body, hence enabling their dissolution and elimination in urine.

Chelation therapy should be performed with high professionalism and medic supervision as this process also exposes the patient to risk of cancer, neurodevelopmental toxicity and death in severe cases due to inappropriate administration. Chelation therapy can also affect other essential metallic elements in the body such as calcium in the same way it prevents the utilization of these heavy metals by the body tissues and organs.

REFERENCES

1Heavy metal poisoning ~NORD
2.Heavy metals~wikipedia
3.Heavy metal toxicity~medscape
4.metal toxicity~wikipedia
5.Beware of Arsenic poisoning in foods
6.lead poisoning investigation in Northern Nigeria

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