The cytotoxic and hemolytic potential of coal fly ash derived from a number of thermal power stations in India was investigated on guinea pig macrophages and mammalian erythrocytes respectively. The cytotoxic studies were carried out using graded concentrations of fly ash. Fly ash‐macrophage interaction resulted in increased release of LDH into the supernatant culture medium. Acid dye uptake was enhanced only when the interaction ensued in a serum free milieu. Both the extent of enzyme release and dye uptake were significantly more in quartz exposed cultures than in those exposed to fly ash. In hemolytic assay all fly ash samples produced only a meagre hemolysis of erythrocytes, irrespective of the mammalian species from which the erythrocytes were obtained. Concentrations which produced more than 75 percent hemolysis of quartz exposed erythrocytes produced less than 10 percent hemolysis when erythrocytes were exposed to fly ash. These results reveal a weak membranolytic activity of coal fly ash.

Urban suspended particulate pollutants differ with place of occurrence, meteorological conditions, physicochemical compositions, and the response of the bronchopulmonary apparatus. Lung injury following intratracheal instillation of respirable suspended particulate matter (RSPM) collected in an urban setting in India was investigated in rats. The animals were killed 15 days after exposure to 2.5, 5.0, and 10.0 mg of RSPM. We examined the changes in lung histology, enzymatic activity in the bronchoalveolar lavage (BAL), and the oxidant/ antioxidant status in lung homogenates. The alterations in these parameters were compared with those in rats instilled with quartz particulates, which were used as positive controls. Exposure to RSPM resulted in an increase in the relative weight of lungs and inflammatory changes evidenced by an increase in the total cellularity of the lungs, predominantly polymorphonuclear cells, demonstrable both in the lungs sections and in the bronchoalveolar lavage of the exposed animals. An increase in the protein content and in the lactate dehydrogenase activity in the BAL was found in the RSPM-exposed rats. A marked increase in the output of lipid peroxides and a dose-dependent increase in the formation of reactive nitrogen species (NO) in lung homogenates and BAL, respectively, was found in the RSPM-exposed rats. A significant decrease in the enzymatic lung antioxidants, superoxide dismutase, and catalase was observed. However, the alterations in the levels of glutathione in the lungs of the RSPM-exposed animals were not significant. The inflammatory reaction, oxidative changes, and enzyme release, were more marked in quartz-exposed animals in comparison to the RSPM-exposed rats.

With an aim to evaluate the antifibrotic action of colchicine in experimental model of pulmonary silicosis, the effect of colchicine on developing and developed pulmonary silicosis induced by quartz was studied in rats in vivo and on alveolar macrophages exposed to quartz particulates in vitro. A progressive increase in wet and dry weight of lungs exposed to quartz dust alone, and quartz dust and colchicine injected orally was investigated. An increase in collagen contents, with lapse in time, in animals exposed intratracheally to quartz dust, or exposed similarly to quartz dust but receiving colchicine simultaneously through oral route was observed. A blindfold evaluation of histological sections of lungs of silicotic animals with or without colchicine administration during development of lesions did not reveal any difference between two groups of silicotic rats. Administration of colchicine for 4 weeks after the lesions were developed neither inhibited nor retarded the laying down of collagen. The studies were extended to investigate the effect of colchicine on quartz-induced alveolar macrophage cytotoxicity. The presence of varying concentrations of colchicine in the culture medium did not significantly alter cytotoxic potential of quartz. The results reveal that colchicine administration during the development of and on developed silicosis does not significantly alter pathogenesis of silicotic lesions. At the cellular level colchicine does not modulate quartz-induced alveolar macrophage cytotoxicity, believed to be a significant event for the onset of pulmonary silicotic fibrogenesis.

Rats were exposed for 1 h to increasing concentrations of cadmium (Cd) through inhalation of cadmium chloride aerosol using nose-only inhalation chambers and depositions of Cd in lungs, liver and kidneys were measured. Changes in spontaneous locomotor activities were recorded 2 and 7 d after cessation of exposure. A concentration dependent increase in Cd in lungs, liver and kidneys was accompanied by significant alterations in spontaneous locomotor response that was dependent on the air Cd concentrations and the postexposure duration. The study shows decreased spontaneous locomotor activity due to Cd accumulation in tissues.

The neurobehavioural effects of trichloroethylene (TCE) were studied in rats following administration of the solvent orally (350, 700 and 1400 ppm in drinking water for 90 days) and through inhalation (376 ppm for 4 h a day, 5 days per week for 180 days). Various aspects of spontaneous locomotor activity were assessed at different periods after exposure through either of the routes. Oral exposure to TCE had no significant effect on spontaneous locomotor activity or cognitive ability, whereas inhalation to the solvent resulted in an increase in the distance travelled and horizontal activity counts at day 30 but a decrease at day 60 of exposure. The time spent in ambulatory and stereotypic movements as well as the number of stereotypic movements were enhanced significantly only at day 30. The resting time was decreased at day 30 but enhanced at day 60 of exposure. The learning ability was not affected significantly up to day 180. The results highlight the neurotoxic potential of inhalation exposure to TCE.

The potential of nickel as nickel chloride, native fly ash and Ni-coated fly ash to alter pulmonary and systemic immune response was evaluated upon intratracheal (I/T) exposure of rats. The animals were sensitised with sheep red blood cells (SRBC) through I/T and intraperitoneal (I/P) routes. Nickel exposure resulted in a decrease in the number of antibody forming cells (AFC) in lung associated lymph nodes (LALN) and spleen. In rats exposed to native fly ash there was a reduction in the number of AFC in LALN but not in spleen. The results did not demonstrate any significant difference in the immunosuppression of fly ash and Ni-coated fly ash exposed rats. The decrease in AFC formation in Ni-coated fly ash exposed animals was of a lesser magnitude than in rats exposed to Ni-alone.

Pulmonary toxicity of cadmium and nickel was evaluated in rat lungs following intratracheal instillation of their chlorides. Concentration of both the metals varied from 0.2-5 mM. Both the metals increased total number of cells, number of polymorphonuclear neutrophils, total protein, sialic acid and the activity of lactate dehydrogenase and beta-glucuronidase in bronchoalveolar lavage 3 days after exposure. Increase in the levels of the selected parameters was more following Cd exposure than in Ni exposed rats. Histologically there was an inflammatory response and interstitial fibroblastic proliferation in the lungs of Cd exposed animals. These changes were mild in Ni-exposed animals and higher concentrations of Ni were needed to produce changes similar to those produced by smaller concentrations of Cd.

The viability of Candida albicans was tested at various intervals in the lungs of rats following single intratracheal inoculation of the yeast cells. Most of the inoculated cells were cleared from lungs within 48 hr after exposure. Clearance was enhanced in lungs exposed to metal-coated fly ash than in those exposed to native fly ash. The validity of these studies was verified in vitro using peritoneal macrophages of mice exposed in vivo to native and metal-coated fly ash. An increase in phagocytic and intracellular killing of macrophages harvested from animals exposed to native or metal-coated fly ash was observed.

The effect of intratracheally injected fly ash on the development of pulmonary and systemic immunity was studied in rats. Following intratracheal and intraperitoneal immunisation with sheep red blood cells (SRBC) there was an appearance of antibody forming cells (AFC) in lung associated lymph nodes (LALN) of animals exposed to either fly ash or physiological saline. Enumeration of AFC in LALN after immunisation by either of the routes, revealed a reduction in the number of AFC in LALN of fly ash exposed rats in comparison to saline exposed animals. The reduction in the number of AFC was more pronounced after exposure of Cd-coated fly ash. The AFC appeared in the spleen only after immunisation through intraperitoneal route and the number of AFC in spleen of the fly ash and saline exposed group of animals did not show any significant difference. These results demonstrate that fly ash burden of lungs results in an impairment of the local immune response of the lungs without an associated effect on the systemic immunity.

Pulmonary reaction to fly ash coated with cadmium (Cd) or nickel (Ni) and to native fly ash was studied in rats after intratracheal inoculation of dust suspensions. The histopathological alterations and changes in biochemical and cellular constituents of the bronchoalveolar lavage were correlated with the metal content in lungs and kidneys. More Ni was adsorbed than Cd on fly ash particulates. Metal-coated fly ash was more toxic than uncoated fly ash. Cd-coated fly ash produced significantly more histopathological and biochemical changes than Ni-coated fly ash. A high concentration of Cd was detected in the kidneys of rats exposed to Cd-coated fly ash.

By virtue of its antioxidant property butylated hydroxytoluene (BHT) is extensively used to prevent rancidity of food materials on storage. Recently pulmonary effects of BHT ingestion have been reported. Present studies were aimed at exploring the effect of BHT on the lungs of mice. Cellular, biochemical and histopathological changes were studied. Male mice (25-30 g) were given BHT intraperitoneally in doses of 200, 400 or 800 mg/kg bw in olive oil. The controls received olive oil alone. The animals were sacrificed at 24 h, 48 h and 7 day intervals and the bronchoalveolar lavage fluid (BALF) was collected for cellular and biochemical studies. Lungs from separate groups of animals were fixed in formal-saline for histopathological studies. The total number of cells in BHT-exposed mice increased in a dose-dependent manner. Total protein content and the activity of LDH also increased significantly as compared with controls. The histopathological results correlated with the biochemical and cellular alterations. It can, therefore, be concluded that BALF analysis can be used to quantify the acute pulmonary toxicity following extrapulmonary exposure to BHT.

We examined the morphological and functional characteristics of goat alveolar macrophages exposed in a serum-free medium in vitro for up to 20 hr to cadmium as CdCl2 and nickel as NiCl2. The concentration of these metals varied from 0.04 to 1.00 mM. Cadmium reduced the viability and phagocytosis of macrophages and increased the release of lactate dehydrogenase from cells into the culture medium at all the concentrations tested. Alterations in macrophage surface morphology, evaluated by scanning electron microscopy, consisted of withdrawal of pseudopodia and rounding of cells exposed to 0.20 and 1.00 mM of CdCl2. In nickel-exposed macrophages these changes were marked only at higher concentrations of the metal. Higher concentrations of Ni were necessary to produce effects similar to those produced by lower Cd concentrations. Our results demonstrated that the higher toxicity of cadmium as compared to that of nickel for alveolar macrophages is related to a difference in the alterations in the morphology and function of the exposed cells.

1 Studies were carried out to explore the acute pulmonary effects of equal, split-dose, multiple inhalation exposures of rats to methyl isocyanate (MIC), (0.32 mg l-1, 8 min x 10 exposures) as reflected by alterations in bronchoalveolar lavage fluid (BALF) constituents and to evaluate recovery, if any, following survival in a MIC-free environment, 10 d after the last MIC exposure.2 In the BALF of MIC-exposed rats, there was an increase in the total number of cells and the number of cells showing enhanced dye uptake and reduction of nitroblue tetrazolium chloride. The cell-free BALF showed increases in total protein, sialic acids and lactic acid contents and lactate dehydrogenase activity.3 In rats exposed to MIC and sacrificed 1 0 d after survival in a MIC-free environment, there was a reduction in the cellular and biochemical constituents of BALF, The phagocytic potential of macrophages was, however, also decreased under this regime.

Peritoneal macrophages and quartz dust interaction was studied in vitro. Quartz dust inhibited lactate production and the degree of inhibition was more in glucose free condition. There was no substantial uptake of glucose and the pyruvate was present in negligible amounts. In glucose free culture, protein values were 1.6 fold higher than cultures supplemented with glucose. Results suggest that quartz exerts its effect on metabolism at a point between protein catabolism and lactate production.

The deposition of particles in lungs is governed by aerodynamic diameter of particles, anatomical features of the respiratory tract, breathing pattern and body habitus. The clearance of the dust is facilitated by mucociliary escalator activity and phagocytosis by alveolar microphages. The clinical aspects have been presented to show the significance of symptoms, radiological features and lung function tests in the diagnosis of dust-related pulmonary diseases. An analysis of the mechanism of cytotoxicity has been discussed which reveals that dust-cell interaction results in the secretion from cells of a number of materials responsible for tissue injury. The significance of alterations in different components of immune system and immunoregulatory mechanisms in the pathogenesis of dust-induced toxicity has been outlined. An evaluation of the studies demonstrating an association between increased incidence of lung cancer and exposure to mineral dusts has been made.

Female wistar rats were inoculated intratracheally with 10 mg/ml suspensions of various dusts, viz: quartz, fly ash, mica and corundum in physiological saline. Biochemical markers of bronchoalveolar lavage fluid (BALF) were analysed 8 days after the instillation of the dusts. Elevated levels of proteins, sialic acid and phospholipid contents and the activity of lactate dehydrogenase correlated well with the degree of the known fibrogenic potential of different dusts in the lungs in the following order, quartz greater than fly ash greater than mica greater than corundum. beta-glucuronidase activity, was however, only elevated in the quartz inoculated group of rats. It is suggested that biochemical constituents of BALF analysed shortly after the exposure to different dusts can be useful to mirror alterations in the tissue response to mineral dusts.

Acute pulmonary injury in rats following a single inhalation exposure to methyl isocyanate (3.2 mg l-1) was reflected by alterations in the biochemical and cytological constituents of bronchoalveolar lavage fluid (BALF) over a period of 30 days. Total protein, sialic acid and lactic acid contents of BALF were increased followed by a gradual decline to normalcy between day 3 and day 30 post-exposure. The activity of lactic dehydrogenase also increased progressively with time. The cellularity of BALF was increased significantly and primarily comprised of polymorphonuclear neutrophils at 8 days. The adherence of macrophages was unchanged but their viability was lowered at 30 days post-exposure. The results indicate the significance of bronchoalveolar lavage analysis in monitoring pulmonary toxicity by methyl isocyanate, which is characterized by the hypoxic condition and reduced cellular defence. Some toxic manifestations are potentially reversible with time after cessation of exposure.

Studies were carried out to further localize pulmonary tissue lipid peroxidation inhibitor reported earlier to be present in whole lung homogenate in rat. A major portion of the inhibitory material could be lavaged from bronchoalveolar region using various wash media. The material was heat labile and exhibited higher degree of inhibition when recovered from the lungs of mature and aged rats.

Quartz exposure resulted in an increase in the wet weight, dry weight and collagen contents of lungs. Animals inoculated comparable amounts of fly ash revealed a statistically insignificant increase in these parameters. In silicotic rats exposed to fly ash the increase in the wet weight, dry weight and collagen contents of lungs was reduced in comparison to silicotic animals unexposed to coal fly ash. Histological examination of lungs revealed the development of silicotic granulomata with reticulin and collagen fibre formation. The difference in the development of these lesions was less pronounced when a blindfold comparison was made between the silicotic animals, exposed or unexposed to coal fly ash. The increased activity of LDH in the bronchoalveolar lavage (BAL) of rats exposed to quartz alone was mitigated significantly in silicotic animals subsequently exposed to coal fly ash. The protein content of the BAL increased significantly more in quartz-fly ash exposed animals than in rats exposed to either dust alone. The total cellular elements of the BAL were increased in rats exposed to quartz alone (p less than 0.005). The results demonstrate that fly ash exposure can significantly modify the development of a silicotic pulmonary reaction.