Carbon monoxide absorption through the oral and nasal mucosae of cynomolgus monkeys.

Previous studies have shown that blood levels of carbon monoxide increase during cigarette smoking. It has generally been assumed that increases in blood levels of carbon monoxide could be interpreted as evidence that deep lung penetration of cigarette smoke had occurred. This study was designed to examine whether increased blood levels of carbon monoxide could result from absorption in the nasal and oral cavities. The nasal and oral cavities of cynomolgus monkeys were exposed, independently of the lungs, to cigarette smoke under rigorous smoking conditions. Pre- and post-exposure blood levels of carbon monoxide were measured. As a positive control, similar volumes of cigarette smoke were passed directly into the lungs, thus bypassing the oral and nasal cavities, and blood levels of carbon monoxide were again measured. The results indicate that absorption of carbon monoxide in the oral and nasal cavities is negligible under the heavy smoking regimen employed here, and hence, would be negligible under normal smoking conditions.