Epidemiological measurement of bronchial responsiveness in polyurethane workers

A shortened protocol was developed for the epidemiological measurement of bronchial responsiveness to methacholine without compromising sensitivity, power, precision or safety, and without distorting the numerical value of the PD20.FEV1 (the cumulative dose from a doubling incremental sequence which provokes a 20% decrement in FEV1). It was used in a survey of 254 polyurethane workers (83% of the eligible workforce) exposed occupationally to toluene diisocyanate. The mean duration of each test proved to be 38 min, it was well tolerated and 64 workers (25%) proved to be reactors. PD20.FEV1 appeared to be distributed unimodally. It was significantly correlated with questionnaire records of shortness of breath, chest tightness, and wheeze; and with pre-shift FEV1 and FEF25-75. Even the reactors requiring the highest dose of 640 cumulative inhalation units (1 unit = one 8.9 microliters inhalation of methacholine 1 mg.ml-1) to generate a PD20 measurement reported significantly more wheeze than the non-reactors. This indicates that the test had clinical meaning throughout its dose range of 0.3-640 units. No correlation was found between PD20 and individual changes in ventilatory function across the working shift, but mean shift changes were negligible and not statistically significant. PD20 was also found to be unrelated to age, sex, race, smoking, cough and atopy.