2016 Eminent Toxicologist Lecture Series: QSARs to Commemorate the Fiftieth Anniversary of the RD50

Speaker: Yves Alarie

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.