Incidence of Airflow Limitation Among Employees in Norwegian Smelters

We have investigated the association between the incidence of airflow limitation and occupational exposure. The employees (n = 3,924) were investigated annually during five years (n = 16,570) using spirometry. Exposure was classified using job category and a job exposure matrix. Airflow limitation was expressed using two indices: (i) as forced expiratory volume in one second/force vital capacity (FEV1/FVC) <0.7 and (ii) lower limit of normal (LLN). The incidence of airflow limitation was 21.2/1000 years−1 and 15.1/1000 years−1 using the fixed limit (0.7) and the LLN criterion, respectively. We found a dose–response relationship between the incidence of airflow limitation and tobacco consumption and with job‐category in non‐smokers. The associations between airflow limitation and covariates were independent of how airflow limitation was defined. The incidence of airflow limitation defined as FEVl/FVC <0.7 yielded higher incidence rates of airflow limitation than LLN. We found a significant association between the incidence of airflow limitation and occupational exposure in non‐smokers.