Longitudinal decline in pulmonary diffusing capacity among nitrate fertilizer workers

This study is part of a 3-year follow-up of lung function among nitrate fertilizer production workers.

To study the possible adverse effects of occupational exposure to aerosols and gases on pulmonary diffusing capacity.

A longitudinal study of a cohort of fertilizer workers who performed single-breath carbon monoxide diffusing capacity (DLco) tests and spirometry in 2007 and 2010. The workers completed a questionnaire on respiratory symptoms and smoking habits. Exposure to mineral dust, acid aerosols and inorganic gases was measured. The overall median inhalable and thoracic aerosol mass concentrations were 1.1mg/m(3) (min-max: <0.93-45) and 0.21mg/m(3) (min-max: <0.085-11), respectively.

There were 308 participants in 2007 with 168 returning subjects in 2010. Overall, we found a statistically significant decline in the DLco of 0.068 mmol/min/kPa/year, adjusted for gender, age, height, weight, smoking status and doctor-diagnosed asthma during the 3-year follow-up (P < 0.01). The change in DLco did not vary significantly between the various job groups. Subjects with respiratory symptoms did not show a larger decline in DLco than those without symptoms.

This study indicates a larger than expected decline in the DLco of fertilizer workers during a 3-year follow-up. However, the decline was not related to specific exposures at work, or to possible covariates of exposure.