Phosphoric acid in food: ingestion safety

Oral ingestion of phosphoric acid presents dose-dependent risk: food-grade H₃PO₄ in beverages and foods is safe; concentrated industrial-grade H₃PO₄ causes corrosive injury. Food and beverage exposure: FDA-approved food additive H₃PO₄ at concentrations used in soft drinks (pH ~2.5 in finished beverage) is safe for adult and pediatric consumption at normal dietary levels. Concentrated H₃PO₄ ingestion (industrial grade, 75–85%): causes immediate burning pain in mouth and throat, oropharyngeal burns, esophageal irritation, and potentially gastric injury — less severe than HCl or H₂SO₄ ingestion at equivalent concentrations due to weaker acid strength. Systemic phosphate toxicity: excessive phosphate intake (from extremely large ingestion of H₃PO₄ or phosphate salts) can cause hyperphosphatemia → hypocalcemia → neuromuscular effects (tetany, cardiac arrhythmia in extreme cases) — this is more relevant to phosphate laxative overdose than H₃PO₄ ingestion scenarios. Phosphate laxative solutions (sodium phosphate — different compound, but related hazard): FDA issued safety warnings about hyperphosphatemia and renal failure from phosphate-based laxatives (Fleet Phospho-Soda) — particularly in elderly and renally compromised patients. Dental etching gel ingestion: 35–37% H₃PO₄ dental etching gel accidentally swallowed during dental procedures causes transient GI discomfort but is generally not clinically significant given small volumes used. Management: water/milk dilution for concentrated ingestion; medical evaluation for children ingesting concentrated products.