Lead Poisoning

 

Lead

(i) Lead is a major constituent of the Lead-acid bat­­tery used extensively in car batteries

(ii) Lead was used as a white pigment in Lead paint

(iii) Lead is used as shielding from radia­tion

(iv)Tetra­ethyl lead has been used in leaded fuels to reduce engine knocking. However, this is no longer a com­mon practice in the Western World due to health concerns

(v) Lead is used as electro­des in the process of electrolysis.

Mechanism of action:

Most lead poisoning symptoms are thought to occur by interfering with an essential enzyme Delta-aminolaevulinic acid dehydrase. It combines with sulfhydryl groups and inhi­­­bits tissue enzyme systems. Lead also directly causes haemolysis of mature red cells.

Lead is absorbed into the system by: (i) Inhalation (ii) Gastrointestinal tract by ingestion (iii) From abraded skin. Plumbism is caused ten times more by inhalation as fine dust or fumes.

Salts of Lead

(i)  Lead acetate or sugar of lead; tastes sweet.

(ii) Lead sub-acetate

(iii)Lead carbonate or white lead; used in oil painting. Commonly responsible for lead poisoning in children who suck and bite toys

(iv) Lead nitrate; used in calico printing

(v) Lead sulphate; is supposed to be nontoxic

(vi) Lead tetroxide (Read lead or sindhur) is used as a pigment

 


Acute poisoning occurs due to lead acetate.

The symptoms start immediately:

(i) Metal­lic taste (ii) Burning sensation (iii) Dryness of throat and Intense thirst (iv) Tongue is coated (v) Vomiting within half hour; vomitus is mixed with blood (vi) Nausea and colicky pain coming at inter­vals but relieved by pressure (vii) Constipation is a constant feature (viii) Poor appetite and weight loss (ix) Urine is scanty (x) Foul offensive breath (xi) irritability, insom­nia and excess lethargy (xii) hyperactivity and head­ache (xiii) Neurological prob­lems, such as reduced IQ, drowsiness, insom­­­nia, headache, vertigo, muscle cramps, con­vul­sions and paralysis of lower limbs (xiv) In extreme cases, seizure and coma.

In humans, lead toxicity often causes the formation of bluish line along the gums, which is known as the Burtonian line.

 Acute lead encephalopathy:

The clinical features include: (i) anaemia (ii) mild colic (iii) vomiting (iv) apathy (v) drowsiness (vi) stupor (vii) ataxia and (viii) hyperactivity.

Fatal Dose: About 20 gm lead acetate and 40 gm of lead carbonate.

Fatal Period: 1-2 days

Autopsy Findings

 (i) Intestines are contracted and thickened

(ii) Stomach mucous membrane is thickened, softened, and eroded at places

(iii) A blue line may be visible on the gums

 (iv) The liver and kidneys are also contracted

(v)  Brain is pale and swollen

(vi) Heart is hypertrophied with athe­roma of aorta

 

Chronic Lead Poisoning (Plumbism or Saturnism)

Sources

(i) Drinking water stored in laden cisterns

(ii) Eating tinned food contaminated with lead

(iii) From use of ghee stored in brown or copper vessel lined inside with tin forms a poisonous salt (Oleate of lead)

(iv) Taking food cooked in lead vessels

(v) Absorption of lead through raw and intact skin: Hindu married females apply Vermillion on the parting of scalp hair. Vermillion contains red lead mixed with red synthetic dye that is absor­bed through the scalp.

Signs and Symptoms

Facial pallor:

It is one of the earliest and consis­tent signs and is independent of the degree of anaemia, seems to be due to vasospasm.

There is reticulo­cytosis, poikilocytosis, anisocytosis and nuclea­ted red cells are seen. The number of polymorphs and platelets is also decreased. Punctate baso­philia or basophilic stippling of red cells due to clustered ribosomes is pathognomic of plum­bism.


Lead line (Burtonian line): In 50-70% of the cases, the bluish line known as the lead line is seen on the gums due to sub epithelial deposits of granules at the junction with the teeth. It is deposited in the dirty or carious teeth within a week of exposure usually in the upper jaw. This line is due to the formation of lead sulphide by the action of H2S, which is for­med by the decomposed food in the mouth.

Colic and constipation: During colic, the abdominal wall is rigid and contracted and heavy pressure results in some relief. The attack of colic lasts for few minutes. Constipation is usually pre­sent, but diarrhoea and vomiting may also occur.

Lead palsy: It is more common in adults than children and in men than women. The muscle group that is more prone to fatigue is commonly affected.

Wrists drop-The extensor muscles of wrist are affected.

Foot drop- All the extensor mus­cles of foot except tibialis anterior are affected.

Lead encephalo­pathy: Encephalopathy is quite common in the children. It is present in every case in one form or the other. It depends on the: (a) intensity of the dis­ease (b) duration of exposure (c) age of the patient. The symptoms of lead encephalopathy are insomnia, headache, vomiting, restlessness, delirium, hallucinations, convulsions, and coma develops after the nervous symptoms and finally the death.

Cardiovascular and renal symp­toms: Lead causes vascular constriction those results in hypertension, arteriolar degeneration, chronic arteriosclerotic nephritis, interstitial nephri­tis.

Reproductive system: Menstrual derange­ments, sterility, abortion at 3-6 months and foetal abnormalities may occur.

Autopsy Findings

(i) Blue line on the gums at their junction with the teeth

(ii) Fatty degeneration of paralyzed limbs

(iii) Stomach and intestine show ulceration and haemorrhages and the walls are contracted

(iv) Liver and kidneys are contracted and show granular degeneration

(v) Heart is hypertrophied and shows atheromatous changes.

Medico legal aspects

(i) Metallic forms are not poisonous, but when acted upon by secretions of the intestine and may act as a poison after being absorbed into the sys­tem as a salt that are poisonous

(ii) Compounds of lead are poiso­nous provi­­ded they are in a condition fit for absorption. In the absence of air, pure water has no action on lead, but in the pre­sence of air, it is slightly soluble and lead hydroxide is formed

(iii) Chronic lead poisoning is regarded as one of the industrial diseases

(iv) Acute lead poisoning is rare, when it occurs, recovery usually occurs

(v) Accidental poisoning occurs in children by eating pica, old paint, plaster; feeding bottles made of glass contain lead, lead nipple shields, toys, and street dirt.

 

 #lead poisoning #Plumbism #lead

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