Persistence of Toluene Diisocyanate-Induced Asthma Despite Negligible Workplace Exposures: MATERIALS AND METHODS part 2
Measurement of Bronchial Responsiveness to Methacholine
Using a modification of the French-Rosenthal dosimeter method, nebulized methacholine dilutions were administered. The FEV, was measured using a Pulmonaire bellows spirometer (Jones Medical Instruments Co., Oak Brook, IL). Following baseline FEV, measurements, the maximal FEV, was determined from three expiratory maneuvers, five minutes after each incremental dose of methacholine. The initial methacholine dose was 0.3 cumulative methacholine inhalation units (five breaths of 0.6 mg/ml solution), with doubling concentrations to a maximum of 640 cumulative methacholine inhalation units or until a 20 percent decline in the FEV, compared with baseline occurred. The PD20 FEV, was used to describe the degree of bronchial responsiveness to methacholine.
Personal TDI Measurements
The TDI exposures were measured using the model MCM continuous paper tape monitor (MDA Scientific, Lincolnshire, IL). In order to improve response and resolution of the monitor, it was altered to collect sequential samples. As modified, the MCM monitor collected samples of 12-minute duration every 36 minutes. Exposures were measured from the start to approximately 30 minutes prior to the end of the work shift. Monitors were worn at the workers waist and inspected occasionally to be certain the instrument was positioned appropriately and functioned properly. At the completion of sampling, the tape was removed and examined for contamination by interfering materials. Stains thought to represent contamination were not used in calculating TDI exposure. The TDI samples were quantitated by passing the paper tape through a Model 4100 Reflectance meter (MDA Scientific, Lincolnshire, IL). For 1982, the average lower limit of detection was 1.0 ppb for the 12-minute sampling period. In subsequent years, this meter was modified and the average lower limit of detection decreased to 0.5 ppb. For calculation of the TWA concentration, 12-minute samples without detectable TDI were assigned values one half the lower limit of detection.
Apcalis Oral Jelly
We compared TDI exposures of the six asthmatic subjects with two other groups of workers. The first group was the foam line workers (n = 49), employees involved in foam production and likely to have the highest exposures. The second group was the finishing workers (n = 132), employees who work away from foam production with exposures typically arising from general background levels of TDI. Mean and standard deviation TWA concentrations for these three groups were compared using Tukeys multiple comparison test. A p value of 0.05 or less was considered statistically significant.