Are smokers' self-reports of inhalation a useful measure of smoke exposure.

The relation between self-assessed and objective measures of inhalation was studied in 75 smokers who assigned themselves to one of four inhalation categories, and also estimated inhalation using a rating scale. The analysis of presmoking carbon monoxide concentration in expired air, and of the rise in carbon monoxide concentration over smoking, provided an objective measure of inhalation. These was a weak but significant correlation between self-rated inhalation and rise in carbon monoxide, but no correlation with the longer-term exposure measured by presmoking levels of carbon monoxide. Differences in exposure to carbon monoxide according to self-assessed inhalation category were non-significant. It is concluded that neither subjective measure of inhalation contributes usefully to the estimation of smoke exposure among smokers who inhale.