2.2.2.1 Acids

Chemicals capable of causing corrosive injury to tissues constitute a very large group of poisons. Most cause injury by acid-base reactions but damage can also result from hydrocarbon dissolution, re-dox reactions, denaturation, and alkylation reactions.

Small volumes of acids and bases with extremes of pH (<2 or >12) and large amounts of weak acids and bases can produce significant damage to tissues.

Systemic toxicity following corrosive injury is usually secondary to inflammation, acidosis, infection, and necrosis. Chemicals such as phenol, hydrazine, arsenic and other heavy metals, cyanide, acetic acid, formic acid, fluoride, hydrazine, hydrochloric acid, nitrates, sulfuric acid, phosphoric acid and chromic acid can be absorbed after dermal exposure or ingestion and cause systemic toxicity directly.

Organs particularly at risk from corrosive injury include the gastrointestinal tract, the eyes and lungs.

Management of corrosive injury is primarily directed to prompt and thorough decontamination. Evaluation of burns to the gastrointestinal tract may require upper gastro-intestinal endoscopy. Following a significant corrosive exposure local and systemic complications need to be considered.

Hydrofluoric acid (HF) is a relatively weak acid with minimal corrosive effects at low concentrations. Tissue damage is primarily related to dissociation of the acid in tissues and combination of free fluoride ions with intracellular divalent cations (calcium and magnesium) resulting in cell death.

It is commonly used in various forms of industry for glass etching, computer silicone chip production, metallurgy and as a cleaning fluid additive. In low concentrations (<10%), it may be bought at hardware stores for domestic use as a tile or car wheel cleaner.

Most exposures to HF are topical. Patients will commonly present following two distinct types of exposures. First, those who have been exposed to low concentrations of HF found in domestic products. Second, patients who have been exposed to higher concentrations of HF following workplace exposures. Uncommonly, patients may present following the ingestion of HF for the purposes of deliberate self-harm.