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.
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.
Comments
Post a Comment