Formic acid: a rare but deadly source of carbon monoxide poisoning.

BACKGROUND

Formic acid decomposes upon contact with strong acids producing carbon monoxide. Carbon monoxide poisoning from such a source, however, is extremely rare.

METHODS

A 26-year-old man committed suicide by mixing 2.5 L of formic acid and 2.5 L of sulfuric acid in three beakers and staying in a closed room. The 53-year-old father performed cardiopulmonary resuscitation on his son but soon lost consciousness. In hospital, he initially manifested coma, hypoxemia, metabolic acidosis, and a carboxyhemoglobin level of 45.8%. He was treated with hyperbaric oxygen but developed acute respiratory distress syndrome on day four despite an early improvement. He was successfully weaned from the ventilator on day 8. The 53-year-old mother felt dizziness, headache and had a carboxyhemoglobin level of 23.0%. Her symptoms improved after oxygen therapy.

CONCLUSIONS

Formic acid is a highly fatal source of carbon monoxide poisoning when mixed with sulfuric acid. In addition to the toxicities of carbon monoxide, concomitant inhalation of formic acid fumes can cause severe lung injury, which may complicate the management of carbon monoxide poisoning.