Table 1.
Health effects of most commonly encountering heavy metals and their industrial sources of generation
| Metal | Generation sources | Principal health hazards |
|---|---|---|
| Aluminium | Aluminium alloys’ production, packaging units, pharmaceutical industries | Aerial occupational exposure may produce lung fibrosis in humans In uremic patients, osteomalacia can occur due to aluminium in dialysis fluid May alter intestinal functions and metabolism of calcium in several organ systems |
| Cadmium | Alloys’ production, automotive and air craft industries, electroplating/galvanizing, metallurgical processing, mining, nickel–cadmium battery manufacturing industries, paint industries, plastic industries, textile printing | Affects the activity of alcohol dehydrogenase, arylsulfatase, delta-aminolevulinic acid dehydratase, delta-aminolevulinic acid synthetase, lipoamide dehydrogenase, pyruvate decarboxylase and pyruvate dehydrogenase Ingestion may result in disturbances in the gastrointestinal tract, vomiting, proteinuria, osteomalacia, liver dysfunction, kidney dysfunction/damage manifested by anemia and hypertension Long term low-level exposure leads to chronic obstructive pulmonary and renal tubular diseases and emphysema |
| Chromium | Cement manufacturing, chemical and refractory processing, chrome-plating, combustion of fossil fuels, ferrochrome production, metal-finishing industries, ore refineries, tanneries, textile plants | Low-level chronic exposure leads to kidney damage while occupational exposure may leads to asthma as well as cancer of the respiratory tract especially in the chrome production and chrome pigment industries May cause allergic dermatitis in humans |
| Cobalt | Cemented tungsten carbide industry, high temperature alloys’ manufacturing, paint industry | Exposure to low concentrations (0.002 to 0.01 mg/m3) causes respiratory irritation while to higher concentrations (0.1 mg/m3 or higher) can lead to “hard metal” pneumoconiosis Ingestion in excessive amounts can cause erythropiotic effects and cardiomyopathy Intravenous administration can cause deafness due to nerve damage, flushing of the face, giddiness, increased blood pressure, slowed respiration and tinnitus |
| Copper | Copper mining, metal fumes from smelting operations, welding | Excessive accumulation leads to Wilson’s disease Higher doses can cause anaemia, liver and kidney damage and irritation in stomach and intestine Ingestion of large amounts of copper sulfate may lead to hepatic necrosis and death |
| Iron | Hematite mining industries, metal industries, welding | Inhalation of iron oxide fumes or dust may leads to deposition of iron particles in lungs which produces an X-ray appearance like silicosis |
| Lead | Combustion of lead containing industrial emissions, glass polishing, hand loading of ammunition, jewelry making, lead-glazed pottery, painting, plastic industry, rubber industry, stained glass crafting | Deleterious effects include abdominal cramps, anorexia, insomnia, muscle aches, nausea, serious injuries to brain and kidneys, weakness of joints and weight loss It can pass the placental barriers and may reach the fetus resulting in miscarriages, abortions and still births In severe cases coma and death may occur |
| Manganese | Iron industry, welding | Chronic poisoning leads to a neuropsychiatric disorder characterized by difficulty in walking, irritability, speech disturbances and compulsive behaviour which may include fighting, running and singing |
| Mercury | Chlor-alkali industry, extraction of gold, in dentistry as amalgam tooth filling, paper industry, pulp manufacturing industry, smelting operations | Associated with kidney damage and its chronic poisoning may cause anemia, excessive irritation of tissues, gingivitis, loss of appetite, nutritional disturbances and salivation Inhalation of vapours at extremely high concentrations may lead to an acute, corrosive bronchitis and interstitial pneumonitis |
| Nickel | Combustion of fossil fuels, electroplating, fumes from alloys used in welding and brazing, metal plating industries, nickel mining, nickel-refining industries | Acts as a respiratory tract carcinogen |
| Zinc | Coal and waste combustion, mining, steel processing | Acute zinc toxicity leads to gastrointestinal distress and diarrhoea while inhalation of freshly formed fumes of zinc may cause metal fume fever |