Aluminium Sulphate (Alum) Poisoning

Chemical Identity

Toxicity Profile

• Solubility matters: Soluble Al salts (aluminium sulphate, aluminium chloride, aluminium nitrate) are rapidly absorbed from the lungs when inhaled, making them more acutely dangerous via inhalation than insoluble forms. - Tietz Textbook of Laboratory Medicine, 7th Edition

Sources and Routes of Exposure

Mechanism of Toxicity (Pathophysiology)

1. Oxidative stress: Catalyses reactive oxygen species (ROS) production, depletes antioxidant enzymes, causes lipid peroxidation and cell membrane damage.
2. Mitochondrial dysfunction: Inhibits the TCA cycle and electron transport chain (ETC), reduces ATP production, promotes anaerobic conditions and lipid accumulation.
3. Neuronal toxicity:
   • Inhibits protein phosphatase 2A, causing hyperphosphorylation of tau protein
   • Promotes accumulation of amyloid-beta plaques and neurofibrillary tangles
   • Disrupts neurotransmitter function, inhibits DNA/RNA synthesis and DNA repair
   • Alters NF-kB, p53, and JNK signalling pathways, promoting apoptosis
4. Bone toxicity: Aluminium accumulates at the mineralization front of bone, inhibits osteoblast function, reduces calcium/magnesium/phosphorus, and blocks bone mineralization.
5. Haematopoietic: Inhibits haem synthesis (microcytic anaemia), reduces EPO responsiveness.
6. Protein binding: Al avidly binds transferrin in plasma and distributes throughout the body - Tietz Textbook of Laboratory Medicine, 7th Edition.

Clinical Features

Acute Poisoning (Local)

• Ingestion: Nausea, vomiting, abdominal pain, diarrhoea. Mucosal irritation and burns (due to hydrolysis to H₂SO₄).
• Inhalation: Headache, nausea, cough, respiratory irritation, bronchoconstriction.
• Eye/skin contact: Irritation, redness, burns (corrosive to mucous membranes).
• Acute systemic (e.g., dialysate contamination): Encephalopathy with serum Al levels of 359-1189 µg/L in non-survivors vs 113-490 µg/L in survivors - Tietz Textbook of Laboratory Medicine.

Chronic/Systemic Toxicity

1. Neurological - "Dialysis Encephalopathy / Dialysis Dementia"

• Earliest: stuttering speech, dysphasia, dyspraxia
• Progressive: memory loss, personality changes, dementia, ataxia
• Late: myoclonic jerks, generalised convulsions, status epilepticus, mutism, coma
• Tremor, vertigo, lack of coordination, weakness

2. Musculoskeletal - Aluminium-Induced Bone Disease (Adynamic/Osteomalacic)

• Bone pain, non-healing fractures, osteomalacia, osteoporosis
• Reduced bone formation, pathological fractures
• Particularly in dialysis patients using Al-based phosphate binders

3. Haematological

• Microcytic anaemia (inhibition of haem synthesis)
• Reduced EPO responsiveness

4. Pulmonary (Occupational - "Aluminosis")

• Pneumoconiosis, pulmonary fibrosis from inhaled Al dust/fumes
• Chronic cough, dyspnoea

5. Other

• Hepatotoxicity (elevated liver enzymes)
• Renal impairment
• Chronic fatigue, sinus infections, chronic pain (occupational exposure)

Diagnosis

• Serum/blood aluminium level (using special Al-free collection tubes to avoid contamination):
  • Normal (non-occupational): <10 µg/L in serum; <30 µg/g creatinine in urine
  • Toxic: >60-100 µg/L (serum)
  • Critically toxic: >200 µg/L
• Urine aluminium: More sensitive for occupational exposure in those with normal kidneys
• Deferoxamine infusion test (DFO challenge): Rise in serum Al post-DFO confirms body burden; also therapeutic - Tietz Textbook of Laboratory Medicine.
• Bone biopsy: Gold standard for Al-related bone disease
• ICP-MS (Inductively Coupled Plasma Mass Spectrometry): Preferred analytical method; alternatively, atomic absorption spectrometry (electrothermal atomisation)
• Brain imaging, EEG for neurological involvement

Treatment

Acute Exposure

Systemic/Chronic Toxicity - Chelation Therapy

• Binds aluminium avidly, forming aluminoxamine complex for renal/dialysis excretion
• Given IV or subcutaneous infusion
• Often requires concurrent haemodialysis/haemodiafiltration to remove the Al-DFO complex (especially in renal failure patients)
• Caution: DFO can exacerbate or precipitate encephalopathy in patients with very high serum Al concentrations; may also cause visual/auditory toxicity with prolonged use - Bradley and Daroff's Neurology in Clinical Practice

• Succimer (DMSA): 900 mg twice daily x 19 days - reported useful in occupationally exposed workers (PMC8767391)
• Combination chelation therapy approaches are being studied

Supportive

• Dialysis (to remove aluminium and chelate complex)
• Stop Al-containing phosphate binders; switch to Ca-based or sevelamer
• Ensure Al-free dialysate (reverse osmosis water)
• Anticonvulsants for seizures
• Multidisciplinary: nephrology, neurology, toxicology, orthopaedics

Prevention

• Use of deionised/reverse osmosis water for dialysis (largely eliminated dialysis dementia since the 1990s)
• Avoidance of Al-containing phosphate binders in renal failure
• Occupational hygiene - engineering controls, PPE (nitrile/natural rubber gloves, full-face APR with HEPA filter >2 mg/m³, SCBA >19 mg/m³)
• Exposure limits: NIOSH 2 mg/m³ (10-hr TWA); ACGIH 1 mg/m³ (8-hr TWA) - as soluble Al salts

Prognosis

• Acute poisoning treated promptly with chelation: generally favourable
• Chronic toxicity (dialysis dementia, bone disease): depends on early recognition; neurological damage may be irreversible if advanced
• Severe/untreated cases: significant neurological impairment or death
• Kidney transplantation effectively treats dialysis-related Al encephalopathy - Comprehensive Clinical Nephrology, 7th Edition