Longitudinal lung function declines among California flavoring manufacturing workers

Background The California Department of Public Health received serial spirometry data for flavoring manufacturing workers at 20 companies at risk of bronchiolitis obliterans. Methods We graded spirometry quality; identified individual workers with excessive decline in forced expiratory volume in 1 s (FEV1) using relative longitudinal limits of decline based on 4% average within-person variability; and analyzed declines by occupational risk factors. Results The quality of 1,696 spirometry tests from 724 workers varied by 17 providers, with poorer quality from commercial providers. Of 416 workers with at least two tests, 40 (9.6%) had abnormal FEV1 decline. Of 289 workers with high quality spirometry, 21 (7.3%) had abnormal decline. Only one of the 21 had airways obstruction. Abnormal FEV1 decline rates (per person-month) were greater among workers at companies using ≥800 lbs/year diacetyl than at companies using lesser amounts. Abnormal FEV1 decline rates were greater at companies previously having four-person clusters of spirometric obstruction than at companies with no or only one worker with obstruction. Conclusions Spirometric surveillance of flavoring workers can identify individual workers with an abnormal FEV1 decline for preventive intervention, even when the FEV1 itself remains within the normal range. Good quality spirometry and classification of abnormal with relative longitudinal limit of decline minimize misclassification of possible work-related health effects. Am. J. Ind. Med. 55:657–668, 2012. © 2011 Wiley Periodicals, Inc.