Lead poisoning

Sources

Environmental

• Water
• Air
• Soil
• Food
• Gasoline(greatest environmental source)

Household

• Crayons and toys
• Paint flakes
• Furniture
• Lead-glazed dishes, cups

Industrial – 

• Storage battery workers – Miners – Spray painters
• Most common mode of absorption in case of occupational lead poisoning is inhalation of flumes and dust of lead and its compounds. 

Mechanism of toxicity

• The pathogenesis hypochromic anaemia in lead poisoning is due to  Inhibition of enzymes involved in heme biosynthesis
• Binding to sulfhydryl groups of protein molecules
• Structural and functional changes in mitochondria
• Inhibition of heme formation
• Interferes with heme synthesis by preventing conversion of delta-aminolevulinic acid to porphobilinogen and incorporation of iron into protoporphyrin IX

PHARMACOKINETICS

• Initially distributed to soft tissues
• Then redistributed and incorporates into bone ,hair ,and teeth as a tertiary lead phosphate.
• Diet low in phosphate favors release of lead into blood
• High phosphate intake promotes storage
• Vitamin D promotes storage

INTRODUCTION:

• International lead poisoning prevention week is celebrated in October  

CLINICAL FINDINGS: 

• The clinical findings of lead poisoning are different in the inorganic and organic lead exposures. 

Inorganic lead poisoning:

• Aabdominal colic
• Constipation
• Loss of appetite
• Blue line on the gums
• Stippling of red cells
• Anemia
• Wrist drop and foot drop.

Organic lead poisoning: 

• Toxic effects of organic lead poisoning are mostly on the CNS causing insomnia, headache, mental confusion, delirium, etc.

Characteristic features of chronic lead poisoning includes:

• Facial pallor: Particularly of the mouth is the earliest and most consistent sign.
• Anemia: Anemia associated with polychromasia, punctate basophilia, reticulocytosis, poikilocytosis, anisocytosis and sideroblastosis. Basophilic stippling refers to the presence of dark blue pinhead sized spots in the cytoplasm of red blood cells. 
• Saturnism = Saturnine poisoning– ALA in urine, Coproporphyrin in urine, facial pallor, Basophilic stippling/Punctate basophilia (dark blue, pin-head spots in cytoplasm of RBCs), Burtonian line (blue line gums’ margin, PbS, 50-70% cases, near carious/dirty teeth, Lead palsy, Pb encephalopathy, wrist drop, foot drop, Colic, Constipation, Menstrual irregularity, Sterility, Nephropathy, X-ray- radio-opaque bands at metaphyses of long bones, Pb >0.03mg% in blood is diagnosticLead line or Burtonian line: seen on gums in 70% cases.
• Colic and constipation seen in 85% of cases.
• Lead palsy: Radial nerve is most commonly involved resulting in wrist drop. 
• Encephalopathy: It is seen in every case of plumbism. Lead encephalopathy is irreversible and 85% have permanent brain damage.

INVESTIGATIONS:

• Epiphyseal plate ‘lead lines’ on long bone X-rays.
• Normocytic, normochromic anaemia
• Coproporphyrin in urine (CPU)
• The aminolevulinic acid in urine (ALAU)
• Lead in blood and urine
• Protoporphyrin levels >100 μg/dl