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.     

Early Response of Lungs to Low Levels of Nitrogen Dioxide

Significant changes in the lungs of rats exposed to nitrogen dioxide occur during the first 72 hours in animals exposed to 17 ppm. These changes appear in focal areas at the level of the terminal bronchiole: loss of cilia; thickening of tissue; injury to the epithelium lining the adveoli adjacent to the terminal bronchioles, when whole type 1 cells slough away leaving the basement membrane exposed to the air; between 24 and 48 hours of continuous exposure, these areas are repaired with a low cuboidal cell type that tolerates NO₂ and thickens the air-blood barrier; and eventual formation of crystalloids and interruption of ciliogenesis. Changes at 2 ppm include loss of cilia, hypertrophy and focal hyperplasia in the epithelium of the terminal bronchiole, and “apparent” return to normal after 21 days of continuous exposure.     

Pulmonary Lesions Induced by Long-Term Exposure to Ozone

A tumor-resistant strain of 10-week-old Swiss-Webster mice was exposed to an ozone concentration of 2.5 ppm for two hours daily for 120 days. Groups of ten animals were killed periodically and the tracheobronchial tree was studied by light and electron microscopy. After the 45th day of exposure the trachea showed progressive metaplasia toward a squamoid epithelium containing many cytoplasmic secretory vesicles, with accompanying decrease in number of ciliated cells. Papillomatous proliferation of the bronchiolar epithelium occurred, together with abnormal cilia and micronodular hyperplasia of Clara-like cells.

The tracheal and bronchiolar changes appeared to be reversible 120 days after the last exposure. However, micronodular hyperplasia of Clara-like cells remained unchanged in frequency and morphologic appearance.     

Toxic effect of formaldehyde on the respiratory organs of rabbits: a light and electron microscopic study

In this study, the effect of direct exposure of formaldehyde in different concentration was observed in 14 rabbits aged 3-6 months and weighing 1100-1200 g. The animals were divided into two groups with six animals in each group, and two animals were kept as control. The animals of group I were exposed to 10% formalin for 12 weeks and those of group II to 40% formalin solution for 6 weeks. After completion of the experimental periods, the animals were killed and the tissue samples were collected from the nasal cavity, trachea and lungs in 10% neutral buffered formalin and Karnovsky's fixative to examine the histological and electron microscopic changes in the organs. The mucosal cells of nasal cavity showed loss of cilia and epithelial metaplasia was observed in places. There was vascular congestion and mild subepithelial odema. The tracheal epithelium was organized with hyperchromatic nuclei. There was subepithelial odema along with lymphomononuclear cellular infiltration. There was marked emphysema evident as bulla formation of air spaces due to rupture of interalveolar septum. An increased cellularity of alveolar wall was observed, resulting in its thickening. The epithelial lining of bronchioles showed loss of mucosal folds and hyperplasia of cells along with peribronchial lymphomononuclear cellular infiltration. Thickening of wall of blood vessels was evident. Congestion and haemorrhages were observed in places. It is concluded that the histopathological changes were more remarkable in the animals exposed to 40% formaldehyde for short duration than the animals exposed to 10% formaldehyde for longer duration with a more severe effect on the upper part of the respiratory tract than the lower one.     

Respiratory alterations due to urban air pollution: an experimental study in rats.

In order to assess the adverse effects of urban levels of air pollution, rats were used as biological indicators in a chronic exposure experiment. Animals were housed for 6 months in the center of S?o Paulo (the largest South American city) and were compared to controls kept for the same period in a clean area. Pollution levels were obtained from a State air pollution monitoring station, 200 m distant from the exposure place, which provided the levels of CO, SO2, particulates, and ozone. The animals were submitted to several tests focusing on the respiratory system, comprising pulmonary function tests, studies on mucociliary clearance and mucus rheology, histochemical evaluation of airways, bronchoalveolar lavage, and ultrastructural studies of the epithelium of the airways. Rats exposed to air pollution developed secretory cell hyperplasia in the airways, ultrastructural ciliary alterations, and a more rigid mucus, changes that caused mucociliary clearance impairment. In addition, nasal resistance and the number of inflammatory cells recovered by bronchoalveolar lavage were increased in air pollution exposed animals. The results obtained in the present investigation suggest that chronic exposure to urban levels of air pollution may cause respiratory lesions in rats.     

Response of human ciliated respiratory epithelium to brief in vivo ozone exposure: an ultrastructural study

Ciliated nasal epithelium obtained from human volunteers exposed under controlled conditions to 0.4 ppm of ozone for 4 hr was examined by transmission electron microscopy. These investigations were initiated to evaluate the utility of human ciliated nasal epithelium as a model for the characterization of possible ultrastructural level cytopathic effects induced by short-term, low-level in vivo exposure to ozone. Particular attention was given to both the qualitative and quantitative evaluation of ciliated cells in the nasal respiratory epithelium in response to ozone exposure. The results of these investigations indicated that cell structure is generally retained and no appreciable manifestation of injury is evident in human nasal mucosa in response to the regimen of ozone exposure employed during these studies. Although these investigations were completed under highly controlled circumstances and with the constraints attendant to research on humans subjects, they may provide a fundamental base for future examinations of the potential injurious effects of ozone on human respiratory epithelium under conditions more relevant to habitual environmental exposure.     

A study of the prevalence of ventilatory obstruction in textile workers exposed to cotton dust

A study was conducted in a cotton spinning mill to assess the prevalence of respiratory impairment in 189 asymptomatic workers and 133 byssinotics drawn from various sections of the plant exposed to airborne cotton dust in the work environment. Eight-four healthy controls belonging to the same socioeconomic status and ethnic group having never been exposed to cotton dust or any other pollutant was also studied for the purpose of comparison. Of the 189 asymptomatic workers, 13 (6.8%) suffered from bronchial obstruction whereas only 2 (2.3%) among the control showed obstructive pulmonary impairment. The byssinotics showed a significantly higher prevalence (15.7%) of bronchial obstruction than that (6.8%) observed among the asymptomatic cotton workers (P less than 0.005). Byssinotics (grade II) showed significantly higher prevalence (31.5%) of bronchial obstruction than that (9.4%) observed in acute byssinotics (grade I). The effect of smoking on the prevalence of bronchial obstruction in the asymptomatic and byssinotics was quite discernible as smokers showed significantly higher prevalence than that observed among the nonsmokers (P less than 0.05). The asymptomatic cotton workers and those with different grades of byssinosis having more than 10 years of exposure showed significantly higher prevalence of bronchial obstruction than that observed in the group with less than 10 years of exposure (P less than 0.005). The healthy cotton workers and byssinotics engaged in the preparatory section (card, blow, and waste plant rooms) showed an insignificant higher prevalence of bronchial obstruction (11.3 and 24.4%, respectively) than among those who worked in the spinning, reeling, and winding sections of the mill. The mechanism responsible for causing ventilatory obstruction in the textile workers is discussed.     

Subacute inhalation toxicity of benzaldehyde in the Sprague-Dawley rat.

Benzaldehyde was administered by inhalation to female and male Sprague-Dawley rats for 14 consecutive days (low level: 500 ppm; medium level: 750 ppm; high level: 1000 ppm). Effects of this chemical were investigated during and at the end of the exposure period. Throughout the experiment, significant hypothermia and a reduction of motor activity were observed in all rats exposed to benzaldehyde and were accompanied in high-level rats by a severe impairment of the central nervous system, as evidenced by abnormal gait, tremors, and a positive Straub sign. Histopathologic examination of tissues from exposed rats showed a goblet cell metaplasia that was largely confined to the respiratory epithelium lining the nasal septum in male rats. No other abnormal microscopic changes were observed. A no effect level was not observed in these studies.     

Noise exposure reduction aboard an oceangoing hopper dredge

Reported industrial hygiene surveys aboard seagoing vessels are few, despite the presence of many potentially hazardous chemical and physical agents aboard ships. This investigation focused on crew noise exposure aboard an oceangoing hopper dredge. Noise exposure criteria were adopted based on the 24-hr equivalent continuous sound level (Leq(24)) because of the absence of standards for U.S. shipboard noise exposure. Personal noise dosimeters were used to measure the noise exposure of watchstanders, whose duties were predictable and repetitive. Watchstanders with high noise doses were asked to estimate their duration of exposure in specific areas of the vessel to enable calculation of noise dose per space. Noise sources within spaces associated with high noise dose were identified by sound pressure and surface vibration analysis in octave bands. Almost all accommodation spaces (cabins, recreation rooms, dining rooms, and hospital) were sufficiently quiet (sound pressure levels [SPLs] less than 65 dBA) to permit hearing threshold recovery. Machinery space SPLs ranged from 85 to 108 dBA, and engineering personnel noise exposure exceeded the selected criterion of Leq(24) = 80 dBA. Selective noise abatement and use of an enclosed operating station in the engine room were recommended to control engineering personnel noise exposure. This approach to noise exposure assessment and reduction should be applicable to other oceangoing ships where personnel may be exposed to noise 24 hr per day for weeks at a time.     

Respiratory disease in a textile factory in Nicaragua

This is the first epidemiologic study conducted in a textile mill in Nicaragua using techniques and diagnostic criteria similar to those used in the United States and England. The prevalence of byssinosis and nonspecific respiratory symptoms were studied in 194 workers in a cotton mill in Managua. Limited environmental sampling, performed using a vertical elutriator in yarn preparation and weaving areas, indicated that exposures were similar to those reported in other parts of the developing world. A modified translated version of the Medical Research Council respiratory questionnaire was administered. Pulmonary function tests were performed before and after the Monday workshift to measure across-shift change in ventilatory function. The prevalence of byssinosis was 5.9% and all the cases occurred among exposed women. Nonspecific respiratory symptoms were also more prevalent among exposed workers. After adjusting for age, gender, smoking habit, and work tenure, the exposure odds ratios for usual cough and usual phlegm were 3.3 and 2.2, respectively. The association between exposure and across-shift decrement in FEV1 was not significant. Byssinotic workers, however, had greater decrements in FEV1% than those without byssinosis: 5.5% versus 1.8%. A consistent gender effect was observed in which both exposed and unexposed women were found to have greater across-shift decrements in FEV1 than men. The gender difference existed among long-term workers as well as workers who had been employed less than 2 years. Results are related to cotton dust exposure, as has been documented elsewhere. The poorer health status of the women in this study population deserves follow-up.     

Toxic effects of cadmium on ciliary activity using a tracheal ring model system

Experiments were performed to measure the effect of trace metals on ciliary activity using isolated hamster tracheal rings in an in vitro organ culture system. Dose—time response studies for various Cd concentrations and for lengths of exposure were conducted. Statistically significant reductions in ciliary activity occurred at concentrations as low as 0.006 mm of Cd. Validation of these in vitro results occurred when hamsters were exposed in vivo to a CdCl₂ aerosol of 2 μm particles at concentrations of 50 to 1420 μg/m³. The length of time required for complete recovery was also studied following various exposure regimens.Since the effectiveness of the mucociliary escalator depends on normal functioning of the ciliated epithelium, it follows from the data presented that inhalation of this metal can inhibit the normal mucociliary function vital for clearance of agents from the respiratory tract.     

A study of the ciliar tracheal epithelium on passerine birds and small mammals subjected to air pollution: Ultrastructural study

A study was made of the ciliar tracheal epithelium on passerine birds and small mammals subjected to NO_x, SO₂ emissions and particulates from a coal-fired power plant. The results were compared to those of a non-polluted area, very similar in vegetation, relief, and climatology. We studied Carduelis carduelis (goldfinch), Emberiza cia (rock bunting), Parus major (great tit), Turdus merula (blackbird), and Apodemus sylvaticus (wood mouse). All animals were captured in the wild. We also used goldfinch (Carduelis carduelis) captured in the wild and mice (Mus musculus) from our laboratory. These species were placed in protected cages near the source of pollution for 5 and 12 months. The images of the tracheal epithelium surface and the observation of tracheal sections at transmission and scanning electron microscopy showed a variation in the percentage of ciliated and non-ciliated cells, and a variation in the organization, orientation, and morphology of the cilia in animals from the polluted zone.     

Cooperation Brings Safer Foundry Work Environment

The effects of tobacco cigarette smoke residues on rings of rabbit tracheal epithelium in organ culture were examined. Residue from cigarette smoke was collected through continuous suction and the residue from one cigarette was used for each two tracheal rings. Epithelium exposed to residue showed cellular desquamation, initially of only scattered columnar cells. As exposure time increased the entire columnar cell layer was lost, resulting in exposure of basal cells to residue. Columnar cell loss occurred through breakdown of intercellular junctions. Alteration was also observed in columnar cell mitochondria, cilia, and microvilli. Loss of columnar cells and subsequent exposure of basal cells to tobacco smoke residue may account for the hyperplasia and metaplasia observed by other investigators after long-term in vivo exposure of tracheal epithelium to cigarette smoke.     

Pulmonary cell reactions after exposure to cotton dust extract

Rylander, R. and Nordstrand, Annie (1974).British Journal of Industrial Medicine,31, 220-223. Pulmonary cell reactions after exposure to cotton dust extract. Free lung cells were studied in guinea-pigs exposed to a water extract of cotton mill dust. An increase in the number of leucocytes was found 5 hours after exposure with a peak after about 20 hours. The response was related to the concentration of the extract and was equal in conventional and infection-controlled animals. The reaction provides a useful tool for further studies of the toxicity of various fractions of cotton dust.     

Thymidine incorporation by lung fibroblasts as a sensitive assay for biological activity of asbestos

Three groups of Syrian golden hamsters were exposed to NO₂ for 6, 24, or 48 hr to determine acute effects on intercellular junctional morphology in distal airways and alveolar epithelium. A fourth group, exposed for 48 hr, was allowed to recover for 2 days prior to sacrifice. Light and transmission electron microscopy of bronchiolar epithelium show ciliary loss and surface membrane damage, loss of ciliated cells, and epithelial flattening at 24 and 48 hr. Moderate to marked epithelial hyperplasia and nonciliated cell hypertrophy are noted after 48 hr. Some restoration of normal histoarchitecture is noted in bronchioles of animals allowed a 48-hr recovery period. Freeze fracture platinum-carbon replicas of bronchiolar epithelium show the gradual evolution of a severe disruption of tight junctional networks after 6, 24, and 48 hr of exposure. Following 2 days of “recovery,” bronchiolar tight junctions from animals exposed for 48 hr remain fragmented. The wide distribution of the junctional material present suggests a regenerative process. Freeze fracture replicas of bronchial epithelium show similar fragmentation of tight junctions following 6-hr exposures. After longer intervals, however, there is a return to more normal appearances. Duration of NO₂ exposure has no systematic effect on the integrity of tight junctions in alveolar epithelium. The findings suggest that disruption of tight junctions may be an important specific determinant of increased bronchiolar epithelial permeability following brief exposures to nitrogen dioxide.     

Respiratory disorders and atopy in cotton, wool, and other textile mill workers in Denmark.

A cross-sectional study of respiratory disorders and atopy in Danish textile industry workers was conducted to survey respiratory symptoms throughout the textile industry, to estimate the association of these disorders with atopy, and to study dose-response relationships within the cotton industry. Workers at cotton mills, a wool mill, and a man-made fiber (MMF) mill were examined. Four hundred nine (90%) of the 445 workers participated in this survey, i.e., 253, 62, and 94 workers at the cotton mills, the wool mill, and the MMF mill, respectively. An interview designed to assess the prevalence of common respiratory and allergic symptoms was given to all workers willing to participate, and blood samples were drawn. Lung function measurements determined a baseline FEV1, FVC and the change in FEV1 and FVC during work hours on a Monday. The working environment was examined for dust, bacteria, endotoxins, and molds, and the exposure was estimated for each participant. The mean personal samples of airborne respirable dust and respirable endotoxin were highest in the cotton industry, i.e., 0.17-0.50 mg/m3 and 9.0-126 ng/m3 respectively, whereas mold spores were found in the highest concentrations in the wool mill: 280-791 colony-forming units (cfu)/m3. Only small concentrations of microorganisms were found in the MMF mill. The mean change in FEV1% and FVC% was greatest among atopic individuals in both cotton and wool industry and other textile industries although the differences were not significant. FEV1% and FVC% in the cotton workers were significantly associated with the cumulative exposure to respirable endotoxin. Byssinosis was diagnosed only in the cotton industry. We found a dose-response relationship between endotoxin exposure and byssinosis, and a significant association between A-1-A serum concentrations less than or equal to 35 mumol/liter and byssinosis, a finding we are further evaluating in subsequent studies.     

The Effect of Viscose Rayon Fibers on Lung Function in Rats

Experiments have been performed to determine the effect of viscose rayon fibers upon the pulmonary mechanics of a group of rats. Daily intratracheal injection of synthetic fiber suspension for 20 days produced an increase in index of alveolar pressure and a decrease in tidal volume, respiratory rate, and minute volume. In control animals there was no significant change in pulmonary function after intratracheal injection of normal saline. Comparison of the values after the first exposure of rayon fibers with those after intra tracheal injection of histamine did not show significant difference except in higher respiratory rate after histamine. In both exposed and control groups, infection was present when the animals were killed at the end of the experiment. The significant changes in lung function in control animals with approximately the same histological findings indicated that the changes in dust-exposed animals were mostly related to the rayon fibers.     

Detection of leishmanial activity in nature by means of sentinel animals

In order to assess the usefulness of the sentinel-animal study method for field investigations on cutaneous leishmaniasis in tropical forested areas, several series of laboratory animals were exposed to the bite of sandflies in the forest of 2 distinct geographical regions of Panama. The golden hamster, Mesocricetus auratus, the cotton rat, Sigmodon hispidus, and the domestic dog, Canis familiaris were used in these investigations.A high proportion of sentinel rodents died during the exposure period, especially in the first trials. From animals that completed their exposure period, 1 of 5 dogs, and 1 of 52 hamsters proved to be infected. All 29 cotton rats simultaneously exposed were negative.The use of sentinel animals seems a promising method to investigate leishmanial activity in nature. Nevertheless, to obtain final results requires the expenditure of considerable time for the exposure period and the post-exposure observations of the sentinels in the laboratory. A knowledge of the local sandfly species composition and their feeding habits is a prerequisite in every area under study. Further comparisons with newer techniques are needed to determine the best single or combination of methods for the detection of natural leishmaniasis.Cotton rats challenge inoculated with Leishmania braziliensis were readily infected, showing the importance of this rodent for studies on experimental cutaneous leishmaniasis.     

Across-shift lung function variation in cottonseed oil workers

BACKGROUND: The effects of cotton dust on pulmonary function among workers employed in cotton-spinning mills are well known. However, little data exist on the prevalence of this disorder in 'non-textile' cotton industries, including cottonseed oil mills, where high levels of exposure to dust have been demonstrated. AIMS: This study was performed in order to determine the across-shift and across-week decline of FEV(1) and respiratory symptoms among workers in a cottonseed oil mill. METHODS: Sixty-six exposed and 48 unexposed workers of a cottonseed oil mill in Turkey were investigated by questionnaire and lung function test (LFT). LFTs were performed before and after shift on all the working days of the week. Acute airway response was defined as an across-shift decline in FEV(1) of 5% or more on the first working day. RESULTS: Smoking was the only risk factor for having respiratory symptoms. Acute airway response was more frequently observed in the exposed group as compared to the unexposed group (OR = 6.2, 95% CI = 2.3-16.7). The median across-shift decline in FEV(1) on the first day (120 ml) significantly improved on the following days (10, 50, 60 and -30 ml). CONCLUSION: Smoking appears to be the main risk factor for having respiratory symptoms. Cottonseed dust may cause an acute pulmonary function decline on the first working day, but not on the following days of the week. This decline is associated with respiratory symptoms in exposed workers.     

Monocyte CD14 response following endotoxin exposure in cotton spinners and office workers

BACKGROUND: Monocyte cell surface CD14 acts as the major lipopolysaccharide (LPS) binding structure, and as such is of interest in the etiology of LPS induced disease. METHODS: The objective was to assess change in monocyte cell surface CD14 and CD4+ CD25+ lymphocytes in a group of cotton workers exposed to LPS over a working week, and to compare this to changes in office workers. Twenty-five cotton workers and nine office workers were studied. Monocyte CD14 fluorescence was measured by flow cytometry, on samples taken pre-shift on a Monday morning (baseline/pre-exposure), and subsequently after 6 and 72 hr. The majority of cotton workers were exposed to at least 1 EU/m(3) of endotoxin over a working shift, and some highly exposed (between 100 and 400 EU/m(3)). RESULTS: After 6 hr of work in the mill, cotton workers developed a significant upregulation in CD14 in comparison to office workers (P = 0.016), whereas CD14 expression had returned to levels not significantly differing from the office workers at 72 hr after first work exposure (P = 0.426). CONCLUSIONS: We propose that CD14 expression on monocytes may help to determine the mechanism of action of lipopolysaccharide in producing respiratory ill health, and may ultimately play a role in monitoring the health effect associated with LPS exposure in the workplace.