ORIGINAL ARTICLE Pamela Dalton Odor, irritation and perception of health risk Received: 12 April 2001 /Accepted: 8 December 2001 / Published online: 19 March 2002 Ó Springer-Verlag 2002 Abstract Objectives: Understanding the potential for volatile chemicals to elicit chemosensory irritation in the upper respiratory tract is critical to setting occupational exposure limits that are protective of comfort and well- being for the majority of workers. However, the deter- mination of irritant potency for any volatile chemical has been limited by the lack of reliable and non-invasive assays for studying sensory irritation in humans and a failure to appreciate the many non-sensory factors that can influence the reactions to an odor or an irritant in the workplace. Methods: This paper reviews the issues involved in distinguishing and measuring sensations of odor and irritation from volatile chemicals, and de- scribes recent developments in psychophysical methods for evaluating chemical irritancy in humans, and dis- cusses some of the many non-sensory factors such as exposure history, attitudes and expectations and per- sonality variables that can significantly alter the per- ception of odor, irritation and health risk following exposure to a volatile chemical. Results: The availability of safe, non-invasive assays to measure directly odor and irritant responses in the species of interest, humans, can both simplify and improve accuracy in the process of developing appropriate occupational exposure guide- lines. Conclusions: Objective measures of irritation onset obtained in conjunction with subjective responses can lend valuable input to the decision process for deter- mining occupational exposure limits but should always account for other factors (e.g., cognitive or emotional) that may be modulating the subjective response. Keywords Sensory irritation ® Olfaction ® Occupational exposure ® Health symptoms ® Volatile chemicals Introduction Although most volatile chemicals are capable of eliciting upper respiratory tract irritation, their odors can often be detected at concentrations far below those that will objectively evoke sensory irritation. There is little ques- tion that the inherent variability in absolute sensitivity coupled with the subjectivity in response to odors and sensory irritants can produce significant problems for evaluating the potential for irritation, annoyance or health risk from workplace chemical exposures. Recent research suggests there are at least three im- portant issues to be considered when developing or in- terpreting data for occupational exposure limits based on chemosensory irritation from volatile chemicals. The first issue involves the extent to which evaluations of chemical irritancy are confounded by odor sensation and to what extent odor and irritation can be adequately distinguished and evaluated. Numerous studies have shown that the mere presence of odor, at concentrations well below those that are likely to elicit mucous mem- brane irritation, can nonetheless provoke adverse sen- sory responses and complaints. The second issue for consideration is the choice of method for measuring sensory irritation. Although data derived from sensory irritation assays performed in animals (i.e.,RD 50 ) (Alarie 1998) have been used to support occupational exposure limits for many chemicals, the need to extrapolate across species or to measure the responses of sensitive human sub-populations has limited their utility and widespread application. Fortunately, development and refinement of objective psychophysical and physiological assays now permit direct and more precise resolution of a chemical’s irritant potential in human observers. The third issue concerns the degree to which variables other than the properties of the chemical can influence reports of odor, irritation and perceived health risk during and Int Arch Occup Environ Health (2002) 75: 283–290 DOI 10.1007/s00420-002-0312-x This paper was presented at the International Workshop on Chemosensory Irritation, October 2000, sponsored by the Institute of Occupational and Social Medicine at the University of Heidel- berg, Germany. P. Dalton Monell Chemical Senses Center, 3500 Market Street, Philadelphia, PA 19104-3308, USA E-mail: pdalton@pobox.upenn.edu Tel.: +1-215-8985595 Fax: +1-215-8982084