Aim: Determination of usefulness of spirometric results gained in routine occupational medical examinations for early recognition of exposure-related changes in the airways with regard to the 50 ml criterion stipulated in the G-examination guideline G 1.4 for the annual reduction in spirometric parameters. Method: Selection of cases with at least 3 spirometric medical examinations and a minimum period between first and last examination of 6 years from 806 192 data sets for 410 875 persons examined between 1978 and 2003 by the occupational health service of the Berufsgenossenschaft der Bauwirtschaft, region Hanover. Eligible were 31 857 persons with a mean age of 44.2 ± 10.53 years. Conventional evaluation of spirometry (comparison with reference values) was compared with the evaluation of annual decline in lung function values computed by linear regression analysis to look for job-related effects. Results: The different methods of data evaluation revealed similar trends for functional impairment with only minor differences between exposure categories. Comparison with an internal control group without dust exposure revealed significantly elevated odds ratios for the following jobs: cleaning jobs, insulators/fitters, road workers, concrete construction workers, roofers and chimneysweeps. Prevalence values identified by the 50 ml criterion were about twice the prevalence values determined on the basis of conventional evaluation. Conclusions: Epidemiological evaluation of spirometric data yields relevant information on residual exposure risks requiring intervention also when the data was obtained in routine occupational health surveillance. The 50 ml criterion is much more sensitive than the conventional comparison of results using reference values. It is proposed that persons in jobs involving risks and persons with appropriate disposition are subjected more frequently to spirometric examination than is currently recommended in the G-examination guidelines to ensure reliable and timely diagnosis.