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Vol. 8 No. 1 - January 2002

Health Hazards of Heavy Metals

By: U.N. Rai and Amit Pal

For the first time in his entire cultural history, man is facing one of the most horrible ecological crisis- the problem of pollution of environment especially with toxic metals, which sometime in the past was pure, virgin, undisturbed, uncontaminated and basically quite hospitable for him. Today, the cry of "Pollution" is heard from all the nooks and corners of the globe and it has become a major threat to the very existence of mankind on the planet earth. Heavy metal pollution affects flora, fauna and other abiotic components of the ecosystem. Metal leads to various metabolic alterations and undesirable changes, which in many cases may cause severe injury and health hazards. There are several factors like human population explosion, unplanned urbanization, deforestation, profit oriented society and technological advancement etc., whose cumulative effect is responsible for the origin of pollution crisis on the earth. The ecological crisis of environmental pollution has been blamed on different things and one of the major things is the pollution due to metals in the environment.

Toxic metal pollution can be a much more serious and insidious problem, as these are intrinsic components of the environment. At high concentrations, all the metals are toxic to animals and plants both. Metals are omnipresent in the environment occurring in varying concentrations in parent rock, soil, water, air and all biological matter. Moreover, metals are also released into environment from a wide spectrum of anthropogenic sources such as smelting of metallic ores, industrial fabrication and commercial application of metals, agro-chemicals pesticides as well as burning of fossil fuels. These metals are redistributed in the biosphere and dispersed in the air, soil, water and consequently in human beings through food chain bio-magnification causing chronic ailments.

Metals are significant to human because some of them are most important trace elements as a co-factor in various metabolic enzymes and constituents of cells. Zinc, copper and iron form important component of cell and co-factor in several metalloenzymes, while organically chelated chromium (Cr3+) compound act as a co-factor in insulin hormone response controlling carbohydrate metabolism in human. Some non-essential metals are present in all tissue and organs of man like under normal conditions more than 90% of lead (Pb) is retained in the skeleton. Human can tolerate 100-200 times its total body content of Cr without harmful effects. However, increased concentration of these metals can affect mineral and enzyme status of human beings. The metals irreversibly bind to active sites of enzymes, thereby destroying normal metabolism producing high-level toxicity. Human can be affected directly by air, water and soil metal pollutants as well as indirectly through contaminated food supplies. In recent past, a large number of silent epidemics have been reported due to metal contamination, which is escalating day by day.

In 1947 an unusual and painful disease of rheumatic nature was recorded in the case of 44 patients from a village on the banks of jintsu River, Toyama prefecture, Japan. During subsequent years it became known as 'itai-itai' disease (meaning 'ouch-ouch') in accordance with the patients shrieks resulting from painful skeletal deformities. The incubation period for chronic cadmium intoxication varies considerably usually between 5-10 years but in some cases upto 30 years. During the first phase of poisoning, a yellow discolouration of teeth, "cadmium ring" is formed, the sense of smell is lost, and mouth becomes dry, subsequently the number of red blood cells is diminished which results in impairment of bone marrow. The most characteristic feature of diseases is lumbar pains and leg myalgia. These conditions continuing for several years until the patient becomes bed ridden and clinical conditions progress rapidly. Urinary excretion of albuminous substances result from the severe kidney damage. Cadmium induced disturbances in calcium metabolism accompanied by softening of bones; fractures and skeletal deformations take place with a marked decrease in body height up to 30 cm.

The importance of arsenic as a health hazard, which is also known as 'slow killer' is now well recognised. The most obvious signs are the blisters on the palms of the hands and soles of the feet, which can eventually turn gangrenous and cancerous. Meanwhile, the poison also attacks internal organs, notably the lungs and kidneys, which can result in a battery of illnesses including cancers. Arsenic (As) poisoning has been reported from several places. A major outbreak of arsenic poisoning occurred in young children in the summer of 1955 in Japan. The intoxication stemmed from the consumption of dry milk powder to which arsenic contaminated sodium phosphate had been added as a stabilizer. The sodium phosphate was a waste product generated during production of aluminum from bauxite. Altogether 12000 cases were reported and 130 of them more fatal. The poisoning has been due to persistent changes in central nervous system including mental disturbances and changes in electroencephalograms. Epidemiological studies on children, living in the vicinity of a coal power plant in Czechoslovakia where coal that was used contained about 1000-1500 g arsenic per tonne, showed respiratory symptoms and hearing loss. Long term ingestion of arsenic contaminated drinking water produced gastrointestinal, skin, liver and nerve tissue injuries. In Taiwan, wide spread occurrence of black foot disease resulted from high levels of As in ground water. The maximum arsenic value amounted to 2.5 ppm. Chronic As poisoning appears to be regional but certainly not limited to Taiwan. For example in Mexican village, Toreon, 60% of the inhabitants showed varying degrees of chronic intoxication from drinking water which contained 4-6 ppm As. Similar cases of As poisoning have been reported from West Bengal (India) and Bangladesh in recent years. In the 1970s, international agencies headed by the UNICEF began pumping millions of dollars of aid money into Bangladesh for tube-wells to provide "clean" drinking water. According to the World Health Organization, the direct result has been the biggest outbreak of mass poisoning in the history. Upto half the country's tube-wells, now estimated to number 10 million, are poisoned. Tens, perhaps hundreds of thousands will die. Indeed the WHO released a report in September estimating that between 35 and 77 million Bangladeshis may be drinking water containing more than the safety limit of 10 parts per billion of arsenic. According to the report's author, Allan Smith of the University of California, Berkeley, the scale of the disaster is "beyond Bhopal; beyond Chernobyl."

So far as we know there is no medicine available for chronic arsenic toxicity. The only treatment is safe water, nutritious food and time. This can clear up the skin blotches on people in the early stages of poisoning. But once gangrene and cancer have taken hold they may be beyond hope.

Mercury (Hg) is considered to be highly toxic metal for living organisms. Even at very low concentration, Hg and its compounds present potential hazards due to enrichment in food chain. Poisoning by methyl mercury compounds presents a bizarre neurological picture as observed in large-scale outbreaks in Japan, China, Iraq and various parts of the world. The profound capacity of soft acid (acceptor) CH3Hg+ to bind soft ligands explains the high toxicity of methyl mercury compounds than Hg. The outbreaks of a hitherto unknown and mysterious, non-injections neurologic illness amongst inhabitants especially fishermen and their families who mainly subsist on seafood - living around Minamata bay in South Western Kyushu, Japan. The patients who had consumed fish and shellfish from that region progressively suffered from a weakening of muscles, loss of vision, impairment of cerebral functions and eventual paralysis, which in numerous cases resulted in coma and death. This disease was known as Minamata disease and after extensive investigations it was revealed in 1959 that the deaths were caused by the consumption of the fish and other foodstuffs contaminated with methyl mercury.

In 1960 fatal incidents of lung cancer were reported from the Kiryama factory of Nippon-Denki concern on the Islands of Hokkaido; Medical warnings were issued that inhalation of dust containing Cr in high oxidation states (IV) and (VI) was associated with malignant growth in the respiratory tract and painless perforation in nasal septum among trivalent and hexavalent states being the most stable and common in terrestrial environments. Hexavalent chromium is the form considered to be the greatest threat because of its high solubility, its ability to penetrate cell membranes and its strong oxidizing ability. Hence, Cr (+6) is more toxic than Cr (+3) because of its high rate of absorption on living surface. Cr (+6) exists only as oxy-species such as Cr03, Cr04, and Cr207 and is strong oxidizing agent. An incidence of catastrophic heavy metal poisoning was reported from highly toxic Cr(VI) contained in untreated slimes and factory wastes. The largest chromium consumer in Japan, the Nippon chemical industries has deposited approximately 530,000 tonnes of uninduced slimes and wastes containing hexavalent chromium around Tokyo and in the neighbouring Chiba prefacture. Due to its hardening properties the material has found extensive use for construction purposes. Complete housing blocks have been erected in Tokyo, on spoil heaps containing highly toxic Cr(VI) compounds. However, authorities paid no heed to this problem and it is a 'tragic irony' that the factory workers themselves regarded perforated nose as a status symbol, displaying 'sincerity' and loyalty towards a particular employment. Few official figures of this catastrophe: 30 dead, over 200 incurables which only appear to herald the beginning of a corporeal, scandalous disaster.

Lead is the number one environmental poison amongst the toxic heavy metals all over the world, causing serious health hazards to humans, especially to young children. In a developing country like India, lead poisoning remains a serious problem. The full impact of lead poisoning on the health of children and adults is becoming clearer to most countries, and many governments have begun to take action. Significant health and economic benefits have been realized by those countries which have developed lead prevention programs.

The ancients regarded lead as the father of all metals, but the deity they associated with the substance was Saturn, the ghoulish titan who devoured his own young. The very word "saturnine," in its most specific meaning, applies to an individual whose temperament has become uniformly gloomy, cynical, and taciturn as the results of lead intoxication.

Lead was a key component in face powders, rouges, and mascaras; the pigment in many paints ("crazy as a painter" was an ancient catch phrase rooted in the demented behavior of lead-poisoned painters); a nifty spermicide for informal birth control; the ideal "cold" metal for use in the manufacture of chastity belts; a sweet and sour condiment popular for seasoning and adulterating food; a wine preservative perfect for stopping fermentation or disguising inferior vintages; the malleable and inexpensive ingredient in pewter cups, plates, pitchers, pots and pans, and other household artifacts; the basic component of lead coins; and a partial ingredient in debased bronze or brass coins as well as counterfeit silver and gold coins.

The Romans were aware that lead could cause serious health problems, even madness and death. However, they were so fond of its diverse uses that they minimized the hazards it posed. Romans of yesteryear, like Americans of today, equated limited exposure to lead with limited risk. What they did not realize was that their everyday low-level exposure to the metal rendered them vulnerable to chronic lead poisoning, even while it spared them the full horrors of acute lead poisoning.

Although human body contains sufficiently large amounts of lead, moderately increased Pb concentrations become toxic from health point of view. The large affinity of Pb+2 for thiol (-SH) and phosphate containing legands inhibits the biosynthesis of heme and thereby affects the membrane permeability of kidney, liver and brain cells. These result in either reduced functioning or a complete breakdown of these tissues since Pb is a cumulative poison. A British military unit stationed in Hong Kong, was overtaken by acute lead poisoning and suffered from severe vomiting intestinal cramps and circulatory disorder. The source was traced to lead chromate, which had been used to improve the colouration in curry powder. Analysis revealed a lead content of 1.08%. Since this spice is effective in many countries it should be subject to government control.

Ecosystems supporting clusters of sporadic Transmissible Spongiform Encephalopathy (TSE) are characterized by common properties of high-manganese (Mn)/low-copper (Cu), zinc, selenium mineral status, and high altitude/snow-covered/pre-Cambrian mountain terrain where above-average intensities of ultra violet/ozone oxidants are prevalent. For instance, TSE outbreaks have erupted for the first time in Germany, Spain and Italy, while continuing to increase in European countries already affected such as France, Ireland and Portugal despite bans on meat and bone meal inclusions into their cattle feed rations being implemented back in 1990. TSE outbreaks are currently escalating across many regions of N. Europe, presenting a potentially serious pubic health crisis. Could the UK's increased loading of a cocktail of environmental oxidants that penetrated the central nervous system of the UK bovine (ultra violet microwaves/ozone/ systemic Cu-chelating insecticides) account for a more virulent Mn4+ mediated acceleration of the TSE degenerative process in Mn-contaminated/genetically predisposed individuals, manifesting as the widespread emergence of new-variant bovine BSE, variant Creutzfeldt-Jacob disease in younger mammals? Preventive measures and pharmacological therapies for controlling TSEs can only be effectively implemented once the original cause of this insidious disease has been thoroughly comprehended.

The extent of the growing crisis in contamination of the environment and food chain by endocrine disrupting chemicals is reflected by the growing list of health advisories regarding eating fish and wildlife which would serve as a warning that similar bioaccumulation and effects are occurring in people as in fish and wildlife. For 1999 the US EPA list of warnings that are in effect regarding toxic levels in fish or wildlife included over 52,000 U.S. lakes, 20% of total significant lakes, all Great Lakes, and approx. 7% of all U.S. river miles. The number of health warnings rose again for mercury. In addition to the health advisories regarding the danger in eating fish and wildlife, there are widespread findings of hormonal and reproductive disorders/failures in wildlife caused by the toxic exposures, and this is also true in most urban and industrial coastal waters. There were approx. 50,000 warnings regarding mercury in water bodies in at least 42 states. Large quantities of endocrine system disrupting chemicals that have adverse effects on the hormonal and reproductive systems of animals and humans have been released into the environment since second world war and are accumulating in the food chain, animals, and humans. These chemicals have been found to act as estrogens, anti-estrogens, androgens, anti-androgens, or to interfere with thyroid hormone, cortisol, insulin, or growth regulators. Evidence that they are having widespread catastrophic effects on wildlife and domestic animals, and serious widespread effects on humans are now also being seen. A recent report by the National Research Council found that 50% of all pregnancies in the U.S. are now resulting in prenatal or postnatal mortality, significant birth defects, neurological conditions, or chronically unhealthy babies. Approximately, 250,000 U.S. children are born each year with birth defects diagnosed at or shortly after birth.

The toxic metals mercury, lead, and cadmium have also been found to have reproductive and endocrine system disrupting effects. Aluminum has been found to cause Alzheimer's disease in human beings reported from several parts of the world. Exposure to relatively low levels of these chemicals have been documented to have had catastrophic effects on populations of Beluga whales, alligators, turtles, mink, otters, bald eagles, osprey, cormorants, terns, herring gulls, migratory birds, chickens, lake trout, chinook and coho salmon, etc. throughout the U.S. and Canada. Animals and human foetal development is dependent on hormonal levels at various phases of development and the endocrine, reproductive, neurological, and immune systems are all being affected, often seriously or catastrophically. These chemicals are being found to have estrogenic effects and/or antiandrogenic effects on the hormonal/endocrine system.

Dr. U. N. Rai is a Scientist and Dr. Amit Pal is a Research Associate at National Botanical Research Institute, Lucknow-226001, India.

This article has been reproduced from the archives of EnviroNews - Newsletter of ISEB India.

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