OBJECTIVE: The aim of the study was to investigate the ability of two organic dusts, wool and grain, and their soluble leachates to stimulate secretion of tumour necrosis factor (TNF) by rat alveolar macrophages with special reference to the role of lipopolysaccharide (LPS). METHODS: Rat alveolar macrophages were isolated by bronchoalveolar lavage (BAL) and treated in vitro with whole dust, dust leachates, and a standard LPS preparation. TNF production was measured in supernatants with the L929 cell line bioassay. RESULTS: Both wool and grain dust samples were capable of stimulating TNF release from rat alveolar macrophages in a dose-dependent manner. The standard LPS preparation caused a dose-dependent secretion of TNF. Leachates prepared from the dusts contained LPS and also caused TNF release but leachable LPS could not account for the TNF release and it was clear that non-LPS leachable activity was present in the grain dust and that wool dust particles themselves were capable of causing release of TNF. The role of LPS in wool dust leachates was further investigated by treating peritoneal macrophages from two strains of mice, LPS responders (C3H) and LPS non-responders (C3H/HEJ), with LPS. The non-responder mouse macrophages produced very low concentrations of TNF in response to the wool dust leachates compared with the responders. CONCLUSIONS: LPS and other unidentified leachable substances present on the surface of grain dust, and to a lesser extent on wool dust, are a trigger for TNF release by lung macrophages. Wool dust particles themselves stimulate TNF. TNF release from macrophages could contribute to enhancement of inflammatory responses and symptoms of bronchitis and breathlessness in workers exposed to organic dusts such as wool and grain.

https://oem.bmj.com/content/oemed/53/6/387.full.pdf

Wool and grain dusts stimulate TNF secretion by alveolar macrophages in vitro

Respiratory symptoms and ventilatory capacity were studied in 97 women carpet weavers in a hand-made carpet weaving industry in Umtata, Transkei, South Africa. The controls were from a bottling plant in the same city. Both groups were Black Africans from the Xhosa-speaking population. The population we studied were non-smokers and there was no significant difference in age, race or height between the groups. The exposed weavers had significantly lower forced expiratory indices than the control group. Mean forced expiratory volume in 1 second (FEV1), forced mid-expiratory flow (FEF 25-75%), forced expiratory flow between 200 ml and 1200 ml of forced vital capacity (FEF 200-1200), and peak expiratory flow (PEF) were: 26.0%, 39.0%, 36.4% and 28.5% lower respectively in the exposed group compared with the controls. Mean forced vital capacity (FVC) and forced expiratory ratio (FEV1/FVC x 100) were 22.0% and 6.6% lower respectively in the exposed group compared with the controls. The percentage predicted (%pred) values of FVC, FEV1, FEV1/FVC ratio, FEF 25-75%, FEF 200-1200, and PEF in the exposed group were 82.9%, 77.1%, 95.6%, 64.6%, 72.2% and 82.8%, respectively. The prevalence of FEV1/FVC ratio less than 70% in the exposed group was 37.2%, while in the controls it was 12%. The exposed group reported a significantly higher prevalence of respiratory symptoms compared to the control. The prevalence of nasal symptoms and cough was 62.8% and 58.1%, respectively in the weavers. Weavers who reported cough, breathlessness, and wheezing had significantly (p < 0.01) lower pulmonary function than those who did not report these symptoms. The present study demonstrates that the continual exposure to dust in weavers in this industry is associated with significantly lower pulmonary function, higher prevalence of respiratory symptoms, and weavers show signs of airway obstruction compared to workers not exposed to this type of dust. Women in the weaving industry have a significant occupationally related respiratory impairment.

Respiratory symptoms and pulmonary function in a group of women weavers in South Africa.

Assessment of health implications related to processing and use of natural wool insulation products.

Epidemiological studies of workers in weaving units in carpet industries have shown relationships between the airborne dust concentrations and pulmonary ill health. Therefore, to predict the health risk of carpet weavers, this preliminary experiment was conducted to evaluate the effect of carpet dust (knotted, tufted) on cellular and biochemical mediators considered as potential biological markers of lung injury. Lung cytoplasmic (lactate dehydrogenase, LDH), lysosomal (acid phosphatase, ACP), type II (alkaline phoshatase, ALP) and Clara-cell marker enzymes (gamma-glutamyl transferase, GGT) were monitored in rat cell-free lung lavage (BAL) during postexposure days 1, 4, 8, and 16. Furthermore, lung microsomal cytochrome P-450 (CYP450) and Clara-cell secretory protein (CC16) content in BAL was also evaluated. These pulmonary marker enzymes were significantly elevated during the postexposure period over the respective untreated control; however, tufted carpet dust shows more responses than knotted carpet dust. Lung CYP450 content was reduced significantly at early days; the pattern shows the reoccurrence of CYP450 content in the later stage of postexposure to carpet dust. Clara-cell secretory protein in BAL shows decline in the carpet-treated group; however, tufted carpet shows more decline than knotted carpet. Thus, reduction in CC16 level may have important implication in the development of chronic lung inflammation and diseases. Present investigation found that modulation of these cellular marker enzymes is clear evidence of pulmonary damage caused by exposure to carpet dust.

Alteration in Cellular and Biochemical Markers of Pulmonary Toxicity in Rat Lung Exposed to Carpet Dusts

Epidemiological studies of workers in wool textile mills have shown a direct relation between the concentration of wool dust in the air and respiratory symptoms. Injurious effects of wool dust on the bronchial epithelium could be important in causing inflammation and irritation. A pulmonary epithelial cell line in vitro was therefore used to study the toxic effects of wool dust. Cells of the A549 epithelial cell line were labelled with 51Cr and treated with whole wool dusts and extracts of wool, after which injury was assessed. Also, the effects of grain dust, which also causes a form of airway obstruction, were studied. The epithelial injury was assessed by measuring 51Cr release from cells as an indication of lysis, and by monitoring cells which had detached from the substratum. No significant injury to A549 cells was caused by culture with any of the dusts collected from the air but surface "ledge" dust caused significant lysis at some doses. Quartz, used as a toxic control dust, caused significant lysis at the highest concentration of 100 micrograms/well. To determine whether any injurious material was soluble the dusts were incubated in saline and extracts collected. No extracts caused significant injury to epithelial cells. A similar lack of toxicity was found when 51Cr labelled control alveolar macrophages were targets for injury. Significant release of radiolabel was evident when macrophages were exposed to quartz at concentrations of 10 and 20 micrograms/well, there being no significant injury with either wool or grain dusts. These data suggest that neither wool nor grain dust produce direct injury to epithelial cells, and further studies are necessary to explain inflammation leading to respiratory symptoms in wool and grain workers.

https://oem.bmj.com/content/oemed/48/3/196.full.pdf

Injurious effects of wool and grain dusts on alveolar epithelial cells and macrophages in vitro.

In a previous study assessing respiratory symptoms in individuals employed in wool textile mills in the north of England relations between symptoms of chronic bronchitis, breathlessness and wheeze, and rhinitis and current exposure to airborne mass concentration of dust were shown. As preliminary steps in defining the potential hazard associated with dust from the air of wool mills the ability of inspirable dust, collected from the air of wool textile mills, to cause inflammation when injected into the lungs of rats was determined. Dusts were collected from the beginning of wool processing (opening) in one factory and from the middle (combing) and late (backwinding) stages of the process in two other factories. Ability of the dusts to cause inflammation was assessed by instillation into the lungs of rats followed by bronchoalveolar lavage. All the dusts caused some inflammation which peaked on day 1 and did not persist beyond one week. A distinctive aggregation response of mononuclear cells in the lavage, however, had a different time course, peaking at day 7. An attempt was made to determine how the wool mill dusts caused inflammation and experiments showed that the dusts themselves had no inherent chemotactic activity but that they did have a pronounced ability to generate chemotaxins in serum and so could activate complement in lung fluid. In addition, dust collected from ledges in the mills had the ability to injure epithelial cells in vitro which could also contribute to inflammation. A role for endotoxin in the inflammatory activity of the dusts was not discounted and a leachate of the dust had the ability to cause inflammation when injected into the lungs of rats. Wool mill dust is likely to be a complex mixture of materials and these experiments represent a preliminary approach to understanding the biological activity of the whole unfractionated dust and further studies are in progress to define more accurately the toxic material(s) in the dust.

https://oem.bmj.com/content/oemed/47/4/231.full.pdf

Inflammation in the lungs of rats after deposition of dust collected from the air of wool mills: the role of epithelial injury and complement activation.

R G Love

Papers

Inflammation in the lungs of rats after deposition of dust collected from the air of wool mills: the role of epithelial injury and complement activation.