Introduction:
Occupational exposure to grain dust causes respiratory symptoms and pathologies. To decrease these effects, major changes have occurred in the grain processing industry in the last twenty years. However, there are no data on the effects of these changes on workers’ respiratory health.

Objectives:
The aim of this study was to evaluate the respiratory health of grain workers and farmers involved in different steps of the processing industry of wheat, the most frequently used cereal in Europe, fifteen years after major improvements in collective protective equipment due to mechanisation.

Material and Methods:
Information on estimated personal exposure to wheat dust was collected from 87 workers exposed to wheat dust and from 62 controls. Lung function (FEV₁, FVC, and PEF), exhaled nitrogen monoxide (F_ENO) and respiratory symptoms were assessed after the period of highest exposure to wheat during the year. Linear regression models were used to explore the associations between exposure indices and respiratory effects.

Results:
Acute symptoms – cough, sneezing, runny nose, scratchy throat – were significantly more frequent in exposed workers than in controls. Increased mean exposure level, increased cumulative exposure and chronic exposure to more than 6 mg.m^-3 of inhaled wheat dust were significantly associated with decreased spirometric parameters, including FEV₁ and PEF (40 ml and 123 ml.s ^-1), FEV₁ and FVC (0.4 ml and 0.5 ml per 100 h.mg.m^-3), FEV₁ and FVC (20 ml and 20 ml per 100 h at >6 mg.m^-3). However, no increase in F_ENO was associated with increased exposure indices.

Conclusions:
The lung functions of wheat-related workers are still affected by their cumulative exposure to wheat dust, despite improvements in the use of collective protective equipment.