Objectives: Long-term effects of occupational diving on lung function are uncertain. No previous study has been conducted on New Zealand occupational divers. The aim of this study was to investigate changes in divers' lung function over a five year period.
Methods: The lung function data of all occupational divers with two spirometric determinations separated by a five year interval (N = 336 out of 1,475 currently registered divers) were entered into a database and analysed for changes (5.6 years mean). The trends were correlated against gender, smoking status and years of diving experience (as more accurate diving exposure data were not available). Spirometric indices were compared with predicted reference values derived from New Zealand (WRS), Australian (Gore), and American (NHANES III and Knudson) populations.
Results: Small, but signifi cant, decreases were found in FEV1 (0.27% against predicted per annum, P = 0.02) and PEF (0.47% per annum, P = 0.04) using the NHANES III equations. No other changes in lung function parameters reached statistical significance (P < 0.05) using any of the four sets of prediction equations. No changes correlated significantly with reported years diving.
Conclusion: Observed changes to occupational divers' lung function tests over 5.6 years were small and unrelated to years of diving, which might be due to a 'healthy worker effect'. Clinical relevance is unlikely, but this requires further evaluation. There was significant disparity in normative values derived from the four sets of prediction equations and there is some consequential concern about the ongoing utility of such surveillance of New Zealand professional divers.