American Journal of Industrial Medicine 24525-532 (1993) Nonspecific Nasal Responsiveness in Workers Occupationally Exposed to Respiratory Irritants Davor Plavec, MD, MSC, Emese Somogyi-Zalud, MD, MSC, and Jasminka Godnic-Cvar, MD, PhD The aim of the study was to establish the level of the nonspecific nasal responsiveness in a group of workers (N = 84) occupationally exposed to rcspiratory irritants, and to compare it with its level in healthy subjects (N = 60). Another goal was to study the effect of occupational exposure to irritants, smoking, and atopy on nonspecific nasal responsiveness. The modified method of nonspecific nasal provocation with histamine developed by van Wijk and Dieges (Clin Allerg 17563-570, 1987) was used. The method was performed by spraying doubling concentrations of histamine (0.03-32 mg/mL), starting with saline, in a cumulative manner into each nostril. The reaction was measured by total nasal resistance (“opening” interruption technique). The result of the test was expressed as provocation concentration of histamine that caused 275% rise of total nasal resistance compared to its value measured after saline. We found a significantly higher percentage of nasal hyperreactors and a significantly greater nonspecific nasal responsiveness among 65 exposed workers (x2 = 78.6; p < 0.001, t = -5.48; p < 0.001, respectively) than in the group of healthy subjects. A significantly (t = 4.25; p < 0.001) increased nonspecific nasal responsiveness was observed during exposure when compared to nonspecific nasal responsiveness assessed after 2 weeks out of exposure, when tested in 19 patients. Higher smoking rate as measured by smoking category (number of cigarettes multiplied with years of smoking) was associated with the lower levels of nonspecific nasal responsiveness. Also, we failed to confirm a relation between atopy and nonspecific nasal responsiveness in a group of workers exposed to irritants. o 1993 Wiley-Liss, Inc. Key words: human, occupational exposure, respiratory irritants, smoking, atopy, nasal challenge, histamine, hyperresponsiveness, nasal resistance INTRODUCTION We have observed that 80% of patients with symptoms of irritant-induced bronchial hyperresponsiveness (IBHR) suffer from some rhinitic complaint [Plavec, 199 11. Due to the conditions of exposure to respiratory irritants and to anatomical and physiological similarities between the upper and lower levels of the airways it was reasonable to expect that occupational exposure to respiratory irritants (OERI) could cause similar disorders in the nose and in the bronchi. Moreover, nasal-specific Institute for Medical Research and Occupational Health, University of Zagreb, Zagreb, Croatia. Address reprint requests to Jasminka Godnic-Cvar, MD, PhD, Institute for Medical Research and Oc- cupational Health, 41000 Zagreb, Ksaverska cesta 2, Croatia. Accepted for publication December 17, 1992. 0 1993 Wiley-Liss, Inc.