Lead poisoning, also known as plumbism, is a medical condition caused by elevated levels of lead in the body. Lead is a toxic metal that interferes with a variety of body systems, particularly the nervous, hematopoietic, renal, and cardiovascular systems. Chronic exposure, even at low levels, can cause significant harm, especially in children and pregnant women.
Lead is found in paints, batteries, water pipes, contaminated soil, and certain types of cosmetics and traditional medicines. Both occupational and environmental exposure contribute to lead poisoning.
Pathophysiology: Lead exerts its toxicity by mimicking and competing with essential divalent cations, such as calcium, iron, and zinc, disrupting various enzymatic and cellular functions:
- Hematological Effects: Lead inhibits two enzymes in the heme synthesis pathway: delta-aminolevulinic acid dehydratase (ALAD) and ferrochelatase. This results in decreased heme production and the accumulation of precursors like protoporphyrin, leading to microcytic, hypochromic anemia and basophilic stippling of red blood cells.
- Neurological Effects: Lead disrupts synaptic transmission by altering calcium homeostasis, affecting neurotransmitter release and neuronal growth. This causes cognitive deficits, developmental delays, and behavioral problems, especially in children.
- Renal and Cardiovascular Effects: Chronic lead exposure causes nephropathy and increases blood pressure by disrupting renal sodium metabolism and causing arterial vasoconstriction.
Sources of Lead Exposure:
- Environmental:
- Lead-based paints (especially in homes built before 1978).
- Contaminated water (due to lead pipes or solder).
- Contaminated soil (near highways or industrial plants).
- Leaded gasoline (now largely phased out but still present in soil).
- Occupational:
- Battery manufacturing.
- Construction and demolition (lead-based paints).
- Mining and smelting.
- Cultural/Traditional:
- Folk remedies (e.g., Ayurvedic or traditional Chinese medicine).
- Ceramics, cosmetics (e.g., Kohl, Sindoor).
- Lead-glazed pottery.
Clinical Features:
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Acute Lead Poisoning:
- Gastrointestinal Symptoms:
- Abdominal pain (“lead colic”), nausea, vomiting, diarrhea, or constipation.
- Neurological Symptoms:
- Headache, irritability, encephalopathy (in severe cases).
- Convulsions or coma in severe pediatric cases.
- Gastrointestinal Symptoms:
-
Chronic Lead Poisoning:
- Neurological Effects:
- Cognitive deficits, memory loss, poor concentration, and learning disabilities.
- Peripheral neuropathy: Wrist drop, foot drop (especially in adults exposed occupationally).
- Behavioral changes: Hyperactivity, aggressiveness, or lethargy.
- Hematological Effects:
- Microcytic, hypochromic anemia with basophilic stippling of RBCs.
- Fatigue, pallor, and weakness.
- Renal Effects:
- Chronic lead nephropathy (interstitial fibrosis, hypertension).
- Musculoskeletal Effects:
- “Lead lines” in long bones (seen on X-rays, particularly in children).
- Bone pain or arthralgia due to interference with calcium deposition.
- Reproductive Effects:
- Increased risk of miscarriage, preterm birth, or low birth weight.
- Decreased sperm count and motility in men.
- Neurological Effects:
Diagnosis:
- History of exposure is key to identifying potential sources.
- Blood Lead Level (BLL): The gold standard for diagnosis.
- Normal BLL: < 5 μg/dL in children (CDC threshold), but any detectable lead is considered harmful.
- BLL > 5 μg/dL indicates lead exposure requiring intervention.
- BLL > 45 μg/dL is considered severe and mandates chelation therapy.
- Peripheral Blood Smear: Microcytic anemia with basophilic stippling.
- X-Rays (in children): May show “lead lines” at the metaphyses of long bones.
- Urinary delta-aminolevulinic acid (ALA): Elevated in lead poisoning.
Management:
-
Removal from Source:
- Immediate removal from the lead-contaminated environment.
- Public health measures: Abatement of lead in paint, soil, water, and dust.
-
Chelation Therapy:
- Indications:
- BLL > 45 μg/dL in children.
- Symptomatic patients with high BLL.
- Agents:
- Dimercaprol (BAL): Used in combination with calcium disodium EDTA for severe poisoning.
- EDTA (calcium disodium edetate): Given intravenously, particularly for moderate to severe poisoning.
- Succimer (DMSA): Oral chelation agent, used for mild-to-moderate poisoning, especially in children.
- Penicillamine: Less commonly used due to side effects.
- Indications:
-
Supportive Care:
- Hydration and electrolyte balance, particularly in patients with renal impairment.
- Iron supplementation: In cases of concurrent iron deficiency anemia.
- Monitoring: Regular blood lead levels to track response to therapy.
Prevention:
- Public Health Interventions:
- Elimination of lead-based paints, pipes, and gasoline.
- Screening programs for children living in high-risk areas.
- Education on safe handling of materials containing lead.
- Routine blood lead level screening in children aged 1-2 years in high-risk areas.
- Personal Protective Measures:
- Workers in lead-related industries should use protective equipment and undergo regular lead level testing.
Prognosis:
- Acute lead poisoning can be life-threatening but may be reversible with early diagnosis and chelation therapy.
- Chronic exposure often leads to long-term cognitive, renal, and neurological damage, especially in children. Prompt removal from the source of exposure and treatment can improve outcomes, but the damage, particularly to the CNS, may be irreversible in severe cases.