This lecture presents the longitudinal nature of research on safe levels of exposure in the workplace and the value of quantitative structure–activity relationship (QSAR) approaches. A wide variety of airborne chemicals can stimulate trigeminal nerve endings (TNE) in the cornea and upper respiratory tract (URT). Sensory irritation (SI) of the eye and URT serves as a basis used by the American Conference of Governmental Industrial Hygienists (ACGIH) to establish guidelines, known as Threshold Limit Values (TLVs) for safe levels of exposure.

A bioassay was published in 1966 relying upon the respiratory reflex reactions due to stimulation of TNE during exposure to airborne chemicals, making it possible to measure the potency (abbreviated as RD₅₀) of any airborne chemical as a sensory irritant. An excellent correlation between RD₅₀ values and TLV values was demonstrated as the number of chemicals evaluated with this bioassay increased. In 2015, a QSAR was published using a database of RD₅₀s for 145 chemicals, with excellent results. These updates should permit obtaining reliable estimates of TLVs for new chemicals prior to introducing them in the workplace, as well as for storing and transporting them.

Yves Alarie Biography

Yves Alarie, PhD, DABT, ATS, is Professor Emeritus of the Environmental and Occupational Health Department, Graduate School of Public Health, University of Pittsburgh. In 1963 he received the PhD in Physiology from the Département de Physiologie, Faculté de Médecine, Université de Montréal. At the Hazleton Laboratories in Falls Church, Virginia, he developed the “mouse bioassay” or the “RD₅₀method” used to screen and evaluate the potency of airborne chemicals as sensory irritants. The method was widely used and tabulations of RD₅₀ values are the largest published databases in inhalation toxicology. After joining the University of Pittsburgh in 1970 his research continued on the effects of inhaled chemicals at the surface of the respiratory tract, from the tip of the nose to the alveolar level. He published extensively on the use of animal models to estimate safe levels of exposure for airborne chemicals of industrial importance as well as investigating toxicity of smoke produced in fires and on the cause(s) of death in fire victims. He joined SOT in 1968 and received the SOT Achievement Award (1971), the Frank Blood Award (1974, 1981), the Enhancement of Animal Welfare Award (2000), and the Career Award from the Inhalation Section of SOT (2004).