Arrest in ciliated cell expansion on the bronchial lining of adult rats caused by chronic exposure to industrial noise.

Workers chronically exposed to high-intensity/low-frequency noise at textile plants show increased frequency of respiratory infections. This phenomenon prompted the herein investigation on the cytology of the bronchial epithelium of Wistar rats submitted to textile noise. Workplace noise from a cotton-mill room of a textile factory was recorded and reproduced in a sound-insulated animal room. The Wistar rats were submitted to a weekly schedule of noise treatment that was similar to that of the textile workers (8h/day, 5 days/week). Scanning electron microscopy (SEM) was used to compare the fine morphology of the inner surface of the bronchi in noise-exposed and control rats. SEM quantitative cytology revealed that exposure to noise for 5-7 months caused inhibition in the natural expansion of the area occupied by ciliated cells on the bronchial epithelium as adult rats grow older. This difference between noise-exposed and age-matched control rats was statistically significant (P<0.05) and documents that the cytology of the rat bronchial epithelium is mildly altered by noise exposure. The decrease in the area of bronchial cilia may impair the mucociliar clearance of the respiratory airways and, thus, increase vulnerability to respiratory infection.

Reduction of rat pleural microvilli caused by noise pollution.

Scanning electron microscopy (SEM) was used to investigate whether chronic exposure to noise modifies pleural morphology. Rats were submitted to 8-h/day schedule of noise that is similar to the working hours at cotton-mill rooms. Morphometry of the area occupied by microvilli on the pleural surface showed a decrease in microvilli after 3 months of rat exposure to noise. The reduction of microvilli was 10% after 3 months of noise exposure (reaching 20% after 7 months of noise treatment) and is consistent with pleural effusions found in some of the patients working in noise-polluted environments.

Chronic exposure of rats to cotton-mill-room noise changes the cell composition of the tracheal epithelium.

The work environment of cotton mill rooms of modern textile plants is characterized by noise pollution. We have taped and reproduced this noisy environment to study its effects on experimentally exposed rats. Because we have previously documented that chronic noise causes alterations in the respiratory epithelium, we have focused our investigation on the morphology of the tracheal lining. Wistar rats were exposed to the textile-type noise from 1 up to 7 months, with an average 40 hours weekly exposure of the animals. The rats were sacrificed monthly and the tracheas were studied by scanning electron microscopy (SEM) to quantify the areas of the airway lining that were covered by ciliated, serous or other cells of the epithelium. We found that noise exposure of the rats caused a significant loss of tracheal ciliated cells; an increased density of serous cells on the epithelium balanced this change. This modification of the rat trachea was already established after 1 month of noise treatment of the animals; it did not change significantly throughout the 7-month course of the herein investigation. Loss of ciliated cells was more intense in areas of the tracheal epithelium located between the regions of cartilage rings. We conclude that the ciliated cell is an elective target for damage caused on the respiratory epithelium by the workplace noise occurring in cotton mill rooms. This modification of the respiratory epithelium is likely to impair clearance of the airways since this function depends on the activity of ciliated cells.