Carbon monoxide (CO) is the leading cause of fatal toxic inhalation in the United States, but the medical literature contains few reports of mass exposures. Warehouse workers' headache (WWH) is an infrequently reported form of CO poisoning due to industrial exposure.

We describe 30 persons who developed WWH after inhaling exhaust from a propane-fueled forklift, their emergency medical management at a small community hospital, and their long-term courses.

Workers with more direct exposures to vented exhaust had significantly higher expired CO levels (21.1 ± 0.7% versus 8.4 ± 4.8%, P <0.0001) and higher acute symptom scores (9.0 ± 2.2 versus 4.7 ± 3.3, P = 0.01) than persons with less direct exposures. Work location, expired CO levels, and acute symptom scores did not correlate with symptom scores 2 years after exposure. Workers experiencing acute difficulty concentrating or confusion had higher expired CO levels than persons with neither of these symptoms (16.3 ± 6.7% versus 8.4 ± 5.2%, P = 0.005) and developed higher chronic symptom scores (3.9 ± 3.0 versus 1.1 ± 1.5, P = 0.04), suggesting that mis subgroup may require closer follow-up for long-term complications.

With earlier recognition of ongoing CO toxicity, this disaster would likely have been averted. Since CO exposures are more common than is often recognized, general internists must be familiar with the manifestations of CO toxicity, its timely evaluation, management, and prevention.