ABSTRACT
INTRODUCTION Inclusion of a risk assessment chapter in an edited work on nasal toxicology is appropriate for a variety of reasons. First, whether we speak of human or experimental animal data, the upper respiratory tract is often the direct target of toxic action. Second, biological effects observed in the upper airway may serve as a surrogate for potential airway or parenchymal injury in the more distal respiratory tract. The latter is particularly relevant for inhalation toxicity studies involving rodents, since the anatomy of their upper airways provides a more efficient barrier to lung exposure than is the case in humans. Whether the task at hand is interpreting experimental data from laboratory animals or humans, or the interpretation of epidemiologic data, the role of risk assessment is to extrapolate across dose rates, durations, and often species to arrive at a quantitative estimate of the risk of exposure-related harm to humans. This chapter concentrates on risk assessment for noncancer endpoints in the upper airway, beginning with a review of generic risk assessment tools. The reader who is interested in assessing cancer risk related to inhalational exposure is referred to Ref. 1.
