Hemopoietic, Hemostatic and Mutagenic Effects of Lead and Possible Prevention by Zinc and Vitamin C
Lead is used extensively in industrial and community settings and hence exposure to it is inevitable. The exposure occurs through respiratory or gastro-intestinal route or through skin due to contaminated air, food and water. Acute toxicity of lead is well known for its haematological, neurological and renal effects but of serious concern is chronic exposure to low-level lead exposure associated with cognitive dysfunction, neurobehavioral disorders, hypertension, cardiovascular abnormalities, chromosomal aberrations, somatic and germ cell mutations and genotoxicity. Chelation is the conventional recommendation in the case of blood lead levels associated with acute toxicity. Chronic toxicity can be prevented and even treated with alternate non-pharmacological methods such as dietary or herbal agents. In this article hemopoietic, hematotoxic, hemostatic and genotoxic effects of lead will be highlighted. In addition, possible preventive role of dietary components such as zinc and vitamin C will be discussed Lead, the 5 th most abundant metal in the earth's crust, is known to man since the beginning of the civilization. Due to its versatile properties like ductility, high resistance to erosion and corrosion, lead has been used by man since centuries for making tools, pots, statues, water pipes and other hardware. In the modern civilization lead has found a variety of industrial applications by humankind. As a consequence, today it has become one of the most widely distributed pollutant in environment. Lead is not biodegradable and therefore persists in the soil, in the air, in drinking water, and in homes. It continues to accumulate where it is deposited and get biomagnified to toxic levels in animals and human beings. The main sources of human exposure to lead include leaded gasoline, industrial processes such as lead smelting and coal combustion, lead-based paints, lead-containing pipes or lead-based solder in water supply systems, battery recycling, making grids and bearings etc., Vehicular traffic was the single largest source of environmental lead pollution in the world including India until its use in gasoline was stopped. Introduction of unleaded petrol in the year 2000 has resulted in substantial lowering of mean blood lead levels in Indian population. Exposure to lead occurs mainly through the respiratory and gastrointestinal routes. Approximately 30-40 percent of inhaled lead is absorbed into the bloodstream (1). Gastrointestinal absorption varies depending on nutritional status and age. Infants can absorb up to 50 percent of lead ingested from food, water, contaminated dust, or soil, while adults absorb only 10-15 percent (2). Inorganic lead (food, water, paint, toys, vinyl products) is minimally absorbed through the skin, but tetraethyl or alkyl-lead (leaded gasoline), which is still legally allowed in aircraft, watercraft, and farm machinery is absorbed through the skin (3). Once absorbed, 99 percent of circulating lead is bound to erythrocytes for approximately 30-35 days