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by Dr. D.P. Atukorale

Lead is a naturally occurring element that has been used by man since the beginning of civilisation. Many industrial activities produce lead so that all humans have lead in their bodies and this is more in the urban areas than rural areas. Lead poisoning is a preventable disease.

Lead poisoning occurs in the manufacture of storage batteries and ceramics. Children with pica (geophagy) who chew on lead painted railings and ceramics or who eat contaminated soil, develop lead poisoning. People who consume drinks from lead glazed mugs too get lead poisoning. Ingestion of lead based powders in paint and some baby tonics also cause lead poisoning. use of lead containing cosmetics applied to the face especially in asian countries has resulted in lead intoxication.

Tetraethyl lead which was used as an anti-knock agent in leaded petrol was one of the commonest causes of lead poisoning in Sri lanka up to recent times. As leaded petrol is prohibited, lead poisoning from petrol fumes is a thing of the past, thanks to the Petroleum Corporation's policy of banning the use of leaded petrol. Lead can pass from mother to foetus through the placenta thus reducing the viability of the foetus, reduced birth weight and premature death.

According to Centres for Disease Control in Atlanta, concentration of lead at which intervention is indicated is from 250 ug/L of lead down to 100ug/L of blood lead. Children get symptoms of lead poisoning at lower concentrations. In USA four million children are at risk of lead poisoning and one million workers are exposed to lead.

Once lead is absorbed into the body either via ingestion or inhalation, it is mainly deposited in bones and teeth. As in man, in animals too lead is deposited in bones. It is advisable for meat eaters especially children to avoid consumption of food prepared using bones.

Symptoms of lead poisoning

Mild intoxication may lead to lethargy, colicky abdominal pain, vomiting constipation and encephalitis develops especially in children incase of severe intoxication.

Lead colic was first described by Hippocrates and there are occasions surgeons have operated the abdomen when patients present with acute abdomen due to lead poisoning.

Lead poisoning can result in foot drop, kidney dysfunction resulting in excretion of glucose aminoacids and phosphates in urine.

Sometimes renal insufficiency can lead to hypertension. Blue gum margin in lead poisoning is rare and occurs in patients with poor oral hygiene.

Lead poisoning in children leads to development of low I.Q. lead poisoning causes anaemia both in children and adults.

Treatment of lead poisoning

Public health attention should be given to elimination of lead hazards for children and exposed workers especially those involved in battery manufacture and ceramic industry.

Best treatment for lead poisoning is EDTA chelation therapy and ideal amount of EDTA should be calculated after measuring lead concentration in blood.

EDTA is more efficient than DMSA in increasing lead excretion and must be given intravenously and the patient has to be admitted to hospital.

In severe cases of lead poisoning calcium edtake (75 mg per kg body weight per day for 5 days) provides rapid relief of symptoms and a second course can be given after one week. Alternately Penicillamine can be given in mild cases. EDTA chelation is the treatment of choice in acute cases.

References

1. CDC (1991) Preventing lead poisoning in young children, US Department of health and Human Services, Washington.

2. Tsuchia, K (1986) Handbook on the toxicity of metals.

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