The different Sources of Lead are as follows:
1. Mining and refining
2. Automobile emission (tetraethyl lead used as anti-knocking agent)
3. Electrical storage battery industry
4. Ceramic industry
5. Agricultural industry (preparation of insecticides, e.g., lead arsenate.)
6. Paints, pigments, varnishes
7. Hair dyes, eye paints, canned foods, sea food, painted toys, etc.
Pb exerts its activity through sulphydryl inhibition. Pb has affinity for sulphur and it also reacts with carbonyl and phosphoryl groups. The main biochemical effect of lead is due to its interference with hemesynthesis, leading to hematological damage.
It prohibits utilization of 02 and glucose for the life sustaining energy production, i.e., interferes with normal metabolic function. When the blood lead level reaches 0.8 ppm, symptoms of anemia occur with high degree kidney infection and brain damage.
One of the most harmful effects of Pb is that it can replace Ca in the bones, accumulate there and subsequently remobilize to soft tissue along with phosphates from the bones and cause severe toxic effects while transporting. Chronic exposure leads to weight loss, loss of teeth, etc.
Organic lead, like tetraethyl lead has been proved more poisonous than inorganic lead. Organic lead can penetrate the skin; can get absorbed in the body tissue faster as compared to the inorganic lead.
Organic lead compounds being lipophilic, are selectively localized in central nervous system causing high degree of toxicity. Organic lead might cause genetic modification also. The tolerance limit of lead is 7 mg / kg body weight of an adult.
Effects of Lead:
1. Lever and kidney damage
2. Mental retardation
3. Genetic modification
It is now believed that the fall of Roman Empire (30 BC to AD 220), was due to lead poisoning. Lead was an expensive metal during the era of Roman Empire.
Roman aristocracy used lead containers for storing wine and for cooking. The leaching of lead ultimately caused chronic lead poisoning and caused mental imbalance, degenerated behaviour and collapse of Empire.