title: Molecular restrictions for human eye irritation by chemical vapors.
abstract: Previous research showed a cut-off along homologous volatile organic compounds (VOCs) in their ability to produce acute human mucosal irritation. The present study sought to specify the particular cut-off homolog for sensory eye irritation in an acetate and n-alcohol series. A 1900-ml glass vessel system and a three-alternative forced-choice procedure served to test nonyl, decyl, and dodecyl acetate, and 1-nonanol, 1-decanol, and 1-undecanol. Flowrate to the eye ranged from 2 to 8 L/min and time of exposure from 3 to 24 s. Decyl acetate and 1-undecanol were the shortest homologs that failed to produce eye irritation under all conditions, producing a cut-off effect. Increasing the vapor concentration of decyl acetate and 1-undecanol by 3 and 8 times, respectively, via heating them to 37 degrees C made either or both VOCs detectable to only half of the 12 subjects tested, even though the higher vapor concentration was well above a predicted eye irritation threshold. When eye irritation thresholds for homologous acetates and n-alcohols were plotted as a function of the longest unfolded length of the molecule, the values for decyl acetate and 1-undecanol fell within a restricted range of 18 to 19 A. The outcome suggests that the basis for the cut-off is biological, that is, the molecule lacks a key size or structure to trigger transduction, rather than physical, that is, the vapor concentration is too low to precipitate detection.
authors.affiliation: Chemosensory Perception Laboratory, Department of Surgery (Otolaryngology), 9500 Gilman Dr.-Mail Code 0957, University of California, San Diego, La Jolla, CA 92093-0957, USA. ecometto@ucsd.edu
authors.forename: J Enrique
authors.initials: JE
authors.lastname: Cometto-Muñiz
authors.forename: William S
authors.initials: WS
authors.lastname: Cain
authors.forename: Michael H
authors.initials: MH
authors.lastname: Abraham
mesh_terms: D000085:Acetates / Q000633:toxicity; D000328:Adult; D000438:Alcohols / Q000633:toxicity; D000465:Algorithms; D004952:Esters / Q000633:toxicity; D005128:Eye Diseases / Q000139:chemically induced*; D005260:Female; D006801:Humans; D007509:Irritants / Q000633:toxicity*; D008297:Male; D008452:Maximum Allowable Concentration; D008875:Middle Aged; D013329:Structure-Activity Relationship; D013696:Temperature; D018675:Toxicity Tests / Q000379:methods*
chemical_list: D000085:Acetates; D000438:Alcohols; D004952:Esters; D007509:Irritants