Sister chromatid exchange analysis in workers exposed to noise and vibration

Background: There has been a growing interest in the combined effects of no ise and vibration. In a population of aeronautical workers diagnosed with v ibroacoustic disease (VAD), a large incidence of malignancy was detected. T hese workers were exposed to large pressure amplitude (LPA) (greater than o r equal to 90 dB SPL) noise, with energy content concentrated within the lo w frequency (LF) bands (less than or equal to 500 Hz) and whole-body vibrat ion (WBV). To bur knowledge, there are no studies conducted in humans or an imals that address the issue of the potential genotoxic effects of vibratio n combined with noise. In the present study, the levels of sister chromatid exchanges (SCE) and of cells With high frequencies of SCE (HFC) were analy zed in peripheral blood lymphocytes of workers employed in various occupati ons within the aeronautical industry. Methods: SCE and HFC were analyzed in lymphocytes of 50 workers occupationally exposed to noise and vibration an d of 34 office-worker controls (G0). The exposed group included: 10 hand-vi brating tool operators (G1), 15 engine test cell technicians (G2), 12 aircr aft run-up technicians (G3) and 13 Portuguese Air Force helicopter pilots ( G4). Groups 2-4 were exposed to WBV and LPALF noise; group 1 was exposed to LPA high frequency noise and local vibration. Statistical analysis of the mean SCE count per cell was carried out by multiple regression analysis com paring various predictor variables: type of exposure, duration of exposure, age, and cigarette consumption. Results: Only cigarette consumption and ty pe of exposure were found to be significantly correlated with the mean SCE frequency. After allowing for the effects of smoking, the analysis indicate s that: 1) there was no significant difference between G1 and CO (p > 0.05) ; 2) the differences between G2 and GO, G3 and CO, G4 and CO were all highl y significant (p < 0.001); 3) there was no significant difference between G 2 and G3 (p > 0.05), nor between G2 and G3 combined and G4 (p > 0.05); and 4) G2 and G4 combined had a significantly elevated mean SCE frequency compa red GO (p < 0.001). Statistical analysis of the proportion of HFC was consi stent with these results. Conclusion: Our data suggest that occupational ex posure to LPALF noise and WBV may lead to increased levels of SCE in men. T hese results also suggest a reason for the high incidence of malignancy in VAD patients. The observed effects may not reflect a direct action of these physical agents on DNA. Alternative explanations may lie in the noise-, vi bration-, and/or stress-induced pathophysiological changes.