[Indoor pollution: a report of 2 clinical cases of occult carbon monoxide poisoning].

A large part of the general population is potentially exposed to excessive concentrations of carbon monoxide (CO), both in the domestic and work environment. Beside acute, often fatal poisoning, the possibility of occult intoxication should be considered; this condition can affect people who are often unaware of the existence of a toxic exposure in their homes or work places. We describe two non-smoking patients, husband and wife, 53 and 57 years old, respectively, who suffered cephalea, nausea and neurobehavioural disturbances during a period of approximately one year; these symptoms were reported to improve or disappear on several occasions during the patients' absence from home. Careful anamnesis suggested a protracted exposure to nonlethal concentrations of CO contaminating the patients' bed-chamber from the misfunctioning flue of the heating system. It was not possible to measure carboxyhaemoglobinemia until approximately 24 hours since the last presumptive exposure. The levels found were therefore relatively low (4-5%), yet higher than the reference values for normal non-smoking subjects. Carboxyhaemoglobin concentrations almost returned into the normal range during the period of hospitalization. These two cases exemplify how low level CO exposure may cause aspecific pathological manifestations that are often misdiagnosed or overlooked.