Earlier studies of Wistar rat respiratory epithelia exposed to low frequency noise (LFN) (< or =500 Hz, including infrasound) showed that LFN effects trauma on the respiratory tract. In rats gestated and born in LFN environments, trauma was still treated in accordance with 86/609/EC. Respiratory epithelial fragments were prepared for light and scanning/transmission electron microscopy. Group A brush cell (BC) microvilli tended to group together; in Group B they were clearly clustered together, and in Groups C-F they became fused. Rosetta structures (rings of secretory cells centered on a BC) were visible in Groups A-D and difficult to identify in Groups E,F. The amount of sheared cilia increased with exposure time, as did the images of cellular de-differentiation. LFN exposure induces severe trauma on the respiratory epithelial cells in these rats.