How Lead Poisons Our Environment
Scope Environmental Management Research and information centre (SEMRIC) Karachi, has compiled a report on lead and its adverse impact on Environment. The report prepared by Research Coordinator Sadaf Hafeez at SEMRIC by compiling available data and information from various national and international sources concludes that excessive quantum of lead is existing in the environment. Human health is being affected by lead -poisoning which gets access in the human body through blood, body tissues, and bone marrow.
Food
The ingestion of food is a major source of most individuals total lead uptake. Although the relative contribution is a function of size, body weight, age and type of diets. Yet the occurrence of lead in the diet may result from,
Natural Source of Lead
Deposition of airborne lead particle onto crops, forage, feed, soils and water.
Harvesting, processing, transport packaging, preparation and storage of food. The concentration of lead in foods are typically less than 100 ug/kg.
Canned foods often have mush higher concentration of lead than foods packed in the manners, The USA EPA estimated that about 42% of lead in foods comes from lead soldered cans or other metal sources. Canned food may absorb substantial quantities of lead from solder used to seal the can, especially if the food is at a low pH.
Food packed in lead soldered cans may have lead levels as high as 100 to 400 ug/kg or 5 to 30 times the lead content of frozen or fresh foods. Atmospheric deposition is also another important source of lead in food.
Health Hazards
Lead is accumulative poison small but constant intakes result in accumulation in the body snd eventually may reach s point where the symptoms of associated diseases may occur.
Elevated blood lead levels have been linked to wide range of health hazards with particular concern focusing on young children. The hazards range from relative change in biochemical measurements at low doses (e.g. 10ug/dl) to serve retardation end even death at very high levels (e.g. 100ug/dl) lead can interfere with blood forming process. Vitamin D metabolism, kidney functioning and neurological process.
The negative impact of lead on intelligence performance (as indicated by IQ Test) in schools, and other means is generally accepted as moderate to high blood lead level.
Reproduction
Female: data are mixed with respect to the risk of spontaneous abortion and reduced weight associated with maternal PbB (lead blood) level below 1.44 u mole/litre (30 u g/dl). Recent epidemiological studies have shown exposure related perturbations in length of gestation, significantly greater risks being associated with pbB levels of 0.72 u mole/L (15 u g/dl) or more.
Male: Blood lead concentration above 1.92 u mole/L have been shown to affect sperm morphology and function. At present the reproduction consequence of these changes is not known.
Carcinogenicity
Renal tumour occurs in rats and mice administered high dose of lead. However the evidence for the carcinogenicity of inorganic lead compounds in humans is inadequate.
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