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Min-U-Sil5, a form of alpha quartz, has been shown to induce peripheral lung tumors in rats exposed to the dust by inhalation. The animals were exposed to a nominal particle concentration of 12.4 mg/m3 for 8 hr/day, 4 days/week, for 2 years. The induced tumors were large and peripheral, and, when examined by electron microscopy, were found to be composed predominantly of alveolar type II cells. These cells were found in papillary, acinar, and solid forms of the tumors and were characterized by lamellar inclusion bodies. This is in contrast to the mouse, in which the papillary form was associated with Clara cells and the acinar form was linked with the type II cell. In this study, the Clara cell was a minor component of the tumor mass. No clear risk is established in man linking silica exposure to increased lung tumor rates.

The kinetics of the bronchoalveolar response was assessed in rats exposed, at equal airborne mass concentration (10 mg/m3), to titanium dioxide--a non-pathogenic dust--and the two pathogenic mineral dusts quartz and chrysotile asbestos. Rats were killed at intervals over a 75 day exposure period and groups of rats exposed for 32 and 75 days after recovery for two months. Bronchoalveolar lavage was carried out and the lavage fluid characterised for cellular content, macrophage activation, and concentrations of free total protein, lactate dehydrogenase, and N-acetyl-beta-D-glucosaminidase. Inhalation exposure to the two pathogenic dusts resulted in an increased number of leucocytes, macrophage activation, and increased levels of free enzymes and total protein. The pattern and magnitude of the responses to quartz and chrysotile differed. Chrysotile caused less inflammation than quartz, and the main cellular response peaked around the middle of the period of dust exposure whereas the highest levels of enzymes occurred towards the end. The difference in timing suggests that macrophages were not available for lavage towards the end of the exposure, owing to their playing a part possibly in deposition of granulation tissue. Quartz caused a greater cellular and enzyme response than chrysotile, particularly towards the end of the dust exposure phase. There was a noticeable progression of inflammation in the quartz exposed groups left to recover for two months, but not in the chrysotile recovery groups.

The response of the rat lung to a range of doses of quartz at 50 and 100 days after its administration by intratracheal instillation has been assessed by bronchopulmonary lavage. The effects on the number of polymorphonuclear leukocytes (PMN), lymphocytes and macrophages are described. In addition the concentrations of soluble protein and hydroxyproline and the activities of lactate dehydrogenase, PZ peptidase and collagenase in lavage fluid supernatants were measured and an assessment of the hydroxyproline content of recovered cells was made. Finally PZ peptidase and collagenase were assayed in PMN-enriched cell fractions and in samples obtained from short-term culture of recovered macrophages. There was a dose-dependent increase in the recovery of all three cell types, and in the amounts of lactate dehydrogenase, protein and hydroxyproline in lavage fluids, which showed no signs of resolution over the 100-day period studied. Measurements of PZ peptidase and collagenase suggested that the PMN, not the macrophages, are the major source of these degradative enzymes. The relevance of these findings with regard to the importance of PMN in quartz-induced fibrosis is discussed.

Lactate Dehydrogenase Isoenzymes in Hamster Lung Lavage Fluid after Lung Injury. Beck, B. D., Gerson, B., Feldman, H. A., and Brain, J. D. (1983). Toxicol. Appl. Pharmacol. 71, 59-71. Lactate dehydrogenase (LD) levels and isoenzyme patterns were determined in the cell-free supernatant fractions of lung lavage fluid from hamsters exposed to alpha-quartz, iron oxide, Triton X-100, 100% O2, or 200 ppm SO2. The isoenzyme patterns were compared to those derived from hamster lung homogenates, serum, polymorphonuclear neutrophils (PMNs), pulmonary macrophages, and red blood cells. The isoenzyme patterns from alpha-quartz- and iron oxide-exposed animals resembled each other and were similar to that of PMNs. In contrast, the pattern seen after Triton X-100 exposure was similar to those of whole lung homogenates and of red blood cells. A 96-hr exposure to 100% O2 yielded an LD isoenzyme pattern in lung lavage fluid similar to that of serum. Exposure to SO2 did not alter LD levels, showing that upper airways damage is not reflected by changes in LD in lung lavage fluid. We conclude that LD isoenzyme patterns of lung lavage fluid can be used to differentiate among types of pulmonary injury and may help identify the sites of injury.

After inhalation of 222Ra at equilibrium with radon daughters, male Sprague-Dawley rats were inoculated intrapleurally with 2 mg of unleached or acid-leached asbestos fibres or glass fibres or quartz. The additive co-carcinogenic effects of this type of insult were demonstrated by the increased incidence of malignant thoracic tumours. In rats given mineral materials, bronchopulmonary carcinomas and mixed carcinomas were observed, as well as typical mesotheliomas and combined pulmonary pleural tumours, whereas in control rats inhaling radon alone, only bronchopulmonary carcinomas occurred. No significant differences in tumour incidence were observed between the groups of animals given the different types of dusts, but statistically significant differences were noted in survival times, according to the histological type of tumour. The co-carcinogenic effects of an insult of the pleura by mineral dusts following inhalation of radon are discussed in relation to a possible tumour-promoting effect by these agents.

Risks of developing abnormalities on chest X-rays differ widely between collieries in the Ruhr, despite comparable dust exposures. Simple pneumoconiosis hazard indices have been determined for thirteen collieries, taking into consideration variations in miners' individual cumulative dust exposures, their ages at start of dust exposure, the residence time of dust in their lungs, and the mineral content of the dust. Fine dust samples were taken in five collieries at places selected as representative of seams worked during the past 20 years. They were used for mineralogical and physical analyses and for cell and animal studies. Cytotoxicity of dusts with comparable composition increased with geological age and rank of coal seams. This finding is consistent with results from epidemiological studies.

Recent epidemiologic studies have suggested that some workers exposed to inorganic dusts develop air-flow obstruction independent of or greater than that produced by cigarette smoke; the morphologic basis of this effect is unknown. To investigate this problem, we administered saline alone, 10 mg iron oxide (an inert dust), or 10 or 30 mg of quartz to rats by intratracheal instillation. Animals were killed after 30 days, and pulmonary function and morphologic changes were examined. The iron oxide group was similar to the saline control group in all functional and morphometric parameters. However, both quartz-exposed groups showed evidence of air-flow obstruction, with more severe abnormalities in the high dose group. These findings correlated with morphometric observations of emphysema and thickened airway walls, with changes again more severe in the high dose group. Early silicotic nodules were also present in the latter animals. We conclude that in addition to the classic lesions of nodular silicosis, quartz can produce morphologic and functional changes of air-flow obstruction; no such changes are seen with iron oxide. These observations may explain the air-flow obstruction seen in workers exposed to mineral dusts.

Twelve baboons were exposed to a quartz dust cloud. Four of these were also given polyvinylpyridine-N-oxide (PVNO) by aerosol and four received PVNO by aerosol and injection. A prophylactic effect was demonstrated during the course of treatment, but when treatment stopped the silicosis progressed to the same degree of severity as in the untreated animals.

A protocol to provide a more rapid assessment of the fibrogenic potential of an inhaled particulate has been developed. Young rats are exposed nose-only for 6 h/day, 7 days a week for 28 days to a respirable aerosol of the test compound. After exposure the rats are kept for up to 1 year, followed by histopathological assessment of the lung. Interim sacrifices could allow an estimate of the rate and severity of the development of any fibrogenic lesion. The protocol has been evaluated for chrysotile asbestos, alpha-quartz and titanium dioxide using rats of both sexes and two different ages at first exposure. The results indicate that there are no significant differences in either the rate, type or extent of lesion provoked by a 28-day exposure period when compared with the more conventional 1-year exposure period studies. It can be concluded that neither sex nor age at first exposure cause any biologically significant differences in response, although young rats would be used in practice. Only one sex need be investigated. The protocol offers considerable benefits over conventional inhalation studies for fibrogenicity (where a 1-year exposure period followed by a further 1-year holding period is usual) by virtue of time, specificity (in the absence of continued exposure the development of any lesion can be studied free from initial inflammatory response) and cost, and could be incorporated into a standard subacute inhalation study design. The results obtained are also of more physiological relevance than studies based on intratracheal instillation.

The effects of quartz and sodium metasilicate on liposomes were studied in order to understand the mechanism of silicosis. 8-Hydroxyquinoline-5-sulfonic acid was tested for its in situ silicosis-prevention capacity. Two types of liposomes--(A) those incorporating cholesterol and (B) those without cholesterol--were used. The tests consisted of measuring permeability changes caused by the above-mentioned chemicals. Permeabilities were found to depend on membrane composition. Tests on quartz action led us to the conclusion that liposomes of this composition did not simulate the erythrocytes very well. It was also observed that absence or presence of cholesterol and the mode of contact altered the effect of quartz. Silicate destabilized type A liposomes, but this was less than that caused by quartz. This was explained by the concentration of monosilicic acid that dissolves out from quartz and silicate. When quartz was pretreated with the preventive, the type A liposomes were stabilized, but a slight destabilizing effect was observed on type B. 8-Hydroxyquinoline-5-sulfonic acid augmented the destabilizing effect of silicate, whereas it decreased the hemolytic activity of uncoated quartz, indicating a preventive potential in in vivo.

Aqueous suspensions of asbestos cement powder injected experimentally into the peritoneal cavity of mice act as a fibrogenic agent, as do chrysotile asbestos or chrysotile asbestos-containing soil samples. The fibrotic nodules caused by the dust resemble morphologically silicosis granulomas. In addition, asbestos cement has a characteristically strong cytotoxic effect during the first 2 weeks of the experiment. It is suggested that this is due to the chrysotile asbestos and/or the calcite component of the powder. Amosite and crocidolite, on the other hand, induce a diffuse peritoneal fibrosis with the appearance of numerous foreign body giant cells and asbestos bodies. Dust particles displaced to the regional lymph nodes are frequent in the animals treated with quartz, asbestos cement and asbestos-containing soil samples. A spindle cell type sarcoma arising from the visceral peritoneum is observed in animals injected with crocidolite or asbestos cement. In addition, dusts containing chrysotile asbestos induce considerable amyloidosis of the liver and spleen.

The methods of thermally stimulated luminescence (t.s.l), thermally stimulated exoelectron emission (t.s.e.e.), electron spin resonance (e.s.r), and infrared spectroscopy (i.r.) have been used to investigate whether the specific cytotoxic activities of SiO2 dust of various origins can be attributed to physical parameters. After interaction of toxic dusts with water an increase in the intensity of the t.s.l. peaks below room temperature has been detected whereas no effect could be observed in the case of inert materials. Dusts of weak cytotoxicity have been characterized by infrared absorption bands at 3610 cm-1 and 3685 cm-1. The results of the present studies emphasize the significance of silanol groups and adsorption properties in relation to the fibrogenic activity of quartz dusts.

The study of broncho-alveolar lavage harvested from rats intratracheally dusted with chrysotile (0.5 mg), leached chrysotile (0.5 mg), crocidolite (0.5 mg) and quartz (0.5 and 5 mg) indicated: 1. A cytotoxic lysis of alveolar macrophages in relation to phagocytosis of dust particles in the following decreasing order: quartz, crocidolite, chrysotile. 2. Regarding cell intensity and duration while asbestos, even leached chrysotile, gave merely an early and transient response. This cell recruitment concerned mostly PMN leukocytes and at a less extent alveolar macrophage. 3. Cell recruitment was associated with an increased protein and phospholipids alveolar content. The increase of proteins came probably mostly from an inflammatory serum exudation. However, an increase synthesis of complement C3 and phospholipids is not excluded.

The cytotoxic effect of quartz and coal on phagocytizing lung macrophages was studied by transmissive and scanning electron microscopy and histochemically (the detection of acid phosphatase). The level of phagocytic activity, the activity and localization of acid phosphatase, the number and state of organelles, and the type of macrophage surface processes were shown to represent the objective criteria of the morphofunctional state of macrophages and the cytotoxic effect of the particles phagocytized.

Wistar rats were injected intratracheally with pyrite particles and after 6 and 12 mo, lungs were evaluated for histological changes. Results were compared with rats that were given particles of galena, lead silicate, travertine, and quartz. Under the light microscope no significant changes were observed in the lungs from animals treated with galena, lead silicate, and travertine. In the lungs from animals that received quartz, a typical nodular fibrosis was observed. Moreover, both pyrite-treated rats and quartz-treated rats developed pulmonary alveolar lipoproteinosis; the lesions were much less prominent and severe in animals injected with pyrite than with quartz. These results indicate that pyrite, like only a few other types of dust that are different from quartz, can evoke the development of pulmonary alveolar lipoproteinosis in rats.

An evaluation of the biological activity of Bulgarian zeolite rocks was made by the methods in vivo and in vitro. The results pointed out to specific biological effect--cytotoxic and fibrogenic--most strongly expressed for clinoptilolite followed by mordenite and erionite. The clinoptilolite is characterized by strong cytotoxic effect in comparison with dust of calibrated quartz DQ-12 which confirms the lack of correlation between cytotoxicity and fibrogenicity for some types of dust. On the basis of the results a temporary hygienic norm for clinoptilolite dust--2 mg/m3 is proposed.

A high concentration of silica dust in the air many workstands in ceramic plants is a serious risk for the health of exposed workers. It can cause the development of silicosis. The aim of this paper is to evaluate a fibrogenic activity of dusts containing 98% crystalline silica. The ceramic masses have about 25% of Quartz. The samples of 2 lode quartz and 4 sand quartz originated from different mines in Poland were used for the experiment. Their physical properties were analysed by X-ray diffraction and SiO2 content was determined by colorimetry. Their biological aggresiveness was characterised by wet weight, hydroxyproline content, lipid level in the lungs and wet weight of mediastinal lymph nodes of rats which were intratracheally given of the dusts. The results show that the tested dusts have a moderated fibrogenic activity. At short time (3 months) after their administration the fibrogenic changes in lungs were different depending on the kind of dusts, but at the 6th month of the experiment they did not differ at all. The exposition of workers to silica dusts is a great occupational hazard.

The conditions which might favour development of the fibrotic or the lipid component of the pulmonary reaction to inhaled quartz were examined in rats. Smaller particle size and freedom from surface contamination by amorphous silica or iron oxide, status of the animals whether specific pathogen-free or conventional, and the resistance of cell membranes to damage appeared to bear on fibrogenesis. Increased membrane stability by treatment with polyvinylpyridine-N-oxide abolished not only the fibrosis but also the response of type II cells and hence lipidosis. The rate and intensity of quartz deposition may also affect the response, a low concentration inhaled over a long period favouring nodulation. No other manipulations, environmental or pharmacological, succeeded in inhibiting lipidosis to the benefit of fibrosis. Guinea pigs, however, behaved differently, their reaction being characterized by massive alveolar accumulation of dust-bearing macrophages and type II cell hyperplasia but not by lipidosis. The species variation is unexplained but macrophage predominance may represent a phase that later transforms to lipidosis. The experimental findings may have implications for forms of pneumoconiosis other than silicosis.

A short-term animal bioassay was used to assess the toxicity of occupational dusts. We quantified pulmonary responses in hamsters exposed to granite (12% quartz) and talc (quartz and asbestos-free) dust collected from worksites. Personal samples collected on workers showed similar quartz content and particle-size distributions to the high-volume samples collected for bioassays, thus demonstrating that the particulates were representative of worker exposure. We measured biochemical and cellular indicators of injury in bronchoalveolar lavage fluid (BAL) of animals exposed to dust suspensions by intra-tracheal instillation. The assays measured release of cytoplasmic and lysosomal enzymes into the cell-free supernatant of BAL; levels of albumin and red blood cells; changes in macrophage and polymorphonuclear neutrophil cell numbers; and in situ macrophage phagocytosis. Dose-response (0.15, 0.75, and 3.75 mg/100 g body wt) and time-course (1-14 days postexposure) studies were performed. One day after exposure, both talc and granite dust resulted in elevated enzyme levels, pulmonary edema, and increased cell numbers in BAL. Macrophage phagocytosis was also inhibited. Based on earlier studies, response levels were either intermediate between nontoxic iron oxide and toxic alpha-quartz or comparable with alpha-quartz. The response to granite dust diminished fairly rapidly over time. By contrast, after talc exposure, there was a more persistent elevation in enzyme levels, and macrophage phagocytosis remained depressed. These results indicate that, when a similar mass was deposited in the lungs, talc caused more lung injury than did granite. Better estimates of exposure-dose relationships in talc and granite workers as well as longer-term animal studies are required to evaluate the harmfulness of these work environments at present-day exposure levels.

A comparative study was made of the cytotoxic action of quartz dust in vitro on macrophages activated in vivo by intraperitoneal inoculation of physiological saline, thioglycolate and starch. The liberation of lactate dehydrogenase (LDH) into the supernatant culture medium, adherence to a plastic surface, extent of acid dye exclusion and ultrastructural alteration in the surface morphology of macrophages were taken as parameters of the cytotoxic action of the dusts. Thioglycolate and starch stimulated cells when exposed in vitro to quartz dust released more LDH into the supernatant culture medium and resulted in a greater decrease in macrophage adherence than similarly exposed cells derived from saline stimulated animals. No difference was observed between cells obtained from differently stimulated animals in increased acid dye uptake, loss of surface filopodia and rounding of cells which phagocytosed quartz particles. The results show that quartz is cytotoxic for macrophages, irrespective of their degree of activation and the extent of damage induced is related to the chemical agent used for activation of macrophages in vivo.

Recruitment of phagocytizing cells into the lower respiratory tract plays a very important role in the pulmonary dust clearance, depending both on the number of particles deposited therein and on their aggressiveness. The higher cytotoxicity of the particles, the greater the number of such cells recruited and the higher the contribution of the neutrophilic leukocytes (NL) into the free cellular population of airways which normally is represented chiefly by alveolar macrophages (AM). Adaptation of the alveolar dust phagocytosis to properties of inhaled particles operates through autoregulation of this process in which a key role is played by macrophage breakdown products (PMB). A series of experiments in vitro and in vivo showed that PMB stimulate AM and NL, enhance their recruitment into airways with a dose-dependent increase of the NL/AM ratio, promote recruitment of their precursors via blood and replenishment of such precursor reserves. The most active factor of the PMB appears to be lipidic by nature. The variability between individuals and between groups of alveolar phagocytosis response to particles of a given cytotoxicity may be due to differences of the host's neurohormonal status. It was shown that influencing the latter significantly shifts response to a standard dose of the PMB.

Two groups of rats were exposed to quartz dust for six months and in addition one group was given drinking water containing 1.5% sodium glutamate while the second received only water. In the rats receiving glutamate we observed (a) evidence for a considerably reduced cytotoxic effect of the quartz on cells obtained by bronchopulmonary lavage, (b) a reduction in dust retention in the lungs, especially in the tracheobronchial lymph nodes, (c) a considerable reduction in the weight gain in the lungs and in their hydroxyproline and lipid contents, and (d) the inhibition of the formation of silicotic nodules. Polarographic studies of the oxygen consumption of peritoneal macrophages from rats receiving glutamate showed that glutamate prevents the adverse effects of quartz on mitochondrial oxidative processes.

Twelve different groups of fine mine dusts were examined for their in vivo aggressivity by intraperitoneal injection. Twelve months after injection of the dust, quantitative morphometric analysis of the lymph nodes was carried out to determine (a) the extent of the typical quartz reaction, (b) the in vivo cytotoxicity, (c) the size of the lymph nodes. Different fine dusts showed significant variations in parameter (a) and (c). In the second part of the investigation, the results of the lymph node tests and of in vitro cytotoxicity tests, and also the quartz contents of the dusts were fed into a data matrix and subjected to correlation analysis and principal component analysis. The following hypotheses were arrived at to explain the effect of the fine dust in vivo: (1) The amount of fine dust which penetrates into the lymph nodes is dependent on its in vitro cytotoxicity (Factor A). This is not related to the quartz content of the dust and is not inhibited by PVNO. (2) The specific fibrogenic activity of the fine dust within the lymph node is primarily dependent on its quartz content (Factor B). It appears that this effect is inhibited by PVNO. (3) The total fibrogenic activity depends on a combination of Factor A and B.

Cytotoxicity and hemolysis were studied in chrysotile and quartz. The biological activity of the surface seemed to be different between chrysotile and quartz. Quartz lost its cytotoxicity on heating over about 500 degrees C. However chrysotile showed remarkable toxicity and induced hemolysis on heating between 650 and 800 degrees C, compared with the original unheated specimens. The mice injected intraperitoneally with minerals heated in this temperature range generally died within 48 hr after injection, while those injected with untreated chrysotile or chrysotile heated in the other heat ranges did not. The products in this range were highly disorded materials. It was assumed that the change of biological effects resulting from heat treatment may be related to the disordered state of chrysotile in the process of transformation into forsterite. The relationship between chemical character and cytotoxicity of the heated chrysotile specimens was also studied.

Lewis rats sensitized against peripheral nervous system antigens can be protected against experimental allergic neuritis (EAN) by the intraperitoneal injection of silica quartz dust. Two doses of 200 mg silica given 8 and 11 days post-inoculation (dpi) protected against the development of both clinical and pathological disease. A single dose of 200 mg silica 8 dpi gave significant protection against clinical disease but all animals developed pathological signs. A single injection of 200 mg silica 11 dpi, after the onset of early signs, protected against further progression of disease. The protection was long lasting. Given the known toxic effects of silica for macrophages, these results would support the conclusion that macrophages function during the effector stage in the clinical and pathological expression of EAN in the Lewis rat.

As a first step in the development of an animal model for determining the role of pulmonary fibrosis in the etiology and pathogenesis of lung cancer, the fibrogenic potential of quartz, quartz and ferric oxide administered together, fibrous glass, and hydrated alumina were studied by multiple intratracheal instillation in groups of male Lak:LVG Syrian golden hamsters. Dose-related decreases in survival were evident for the groups instilled with the two highest doses of quartz or quartz and ferric oxide. Instillation of quartz or quartz and ferric oxide induced the greatest pulmonary fibrosis in response to the materials tested. However, the dense fibrous tissue present in the lungs in classical human silicosis and in experimental silicosis of rats was not observed in this study. The results of this study indicate that the Syrian golden hamster is not a suitable species for studying the role of quartz-induced pulmonary fibrosis in pulmonary carcinogenesis.

Aluminium inhibits the harmful effect of quartz on the lungs. Current interest in such protective phenomena has lead us to consider a possible method of bonding aluminium to the crystal lattice, and to see if other atoms might have the same effect. A study of the structure of natural and artificial alumino-silicic compounds shows a surface state specific to quartz, namely the existence of vacancies in the three-dimensional SiO4 tetrahedral structure. Aluminium is a known inhibitor of the cytotoxic action of quartz, and can replace the missing silicon atoms in the crystal lattice. The result is the generation of finite numbers of heat-resistant acid sites. Thus it is not a question of a simple zeolite surface layer, but of the substitution of aluminium atoms for silicon atoms in the remaining crystal lattice. It can be shown that other atoms, such as sulphur and specially phosphorus, are capable of behaving in the same way as aluminium. There is reason to believe that the cytotoxic properties of quartz may be related to the crystal capturing atoms from the cell membrane. The large number of thermally stable acid sites detected after contact with alumina would then be a factor for assessing the cytotoxic properties of the various forms of quartz.

Lung tissue from rats that had inhaled U.I.C.C. crocidolite asbestos or quartz particles showed thickening of the interstitial tissue and the presence of collagen fibres. Aggregates of macrophages in the alveolar spaces were a dominant feature of all the sections examined from asbestos exposed rats. According to the ultrastructural studies described here, all the macrophages were mature cells, indicating that the ingested crocidolite asbestos was non-toxic. Lung sections of rats exposed to quartz particles were significantly different. Single cells were found in the alveolar spaces and many macrophages showed a characteristic pattern of vacuole formation. Other cells contained intracellular membranous lamellated bodies, similar to those found in Type II pneumocytes. Cells containing lamellated bodies were also found in the interstitial tissue. These findings suggest that the two mineral dusts have quite different biological effects on the macrophage and that the development of pulmonary fibrosis may, to some extent, be caused by a different mechanism in each instance.

It is unknown whether respirable dusts derived from the machining of composite fiber-epoxy materials pose a health risk. To evaluate the potential pulmonary toxicity of these materials, we studied the effects of six samples of dusts previously well characterized physically, chemically, and morphologically in the lungs of specific pathogen-free rats. A single intratracheal bolus of 5 mg of each sample was injected into separate groups of five rats each. For comparison, free crystalline silica (quartz) and aluminum oxide were used as positive and negative controls in additional animals. One month later, the lungs were fixed and sectioned for light microscopy. Histopathology scores for the six composite-epoxy samples showed a continuum of lung injury that was between the negative and positive controls. None of the composite dusts had effects that paralleled those of quartz; however, four of the composite dusts produced reactions that were more severe than that seen with aluminum oxide. Therefore, respirable fractions of some types of composite materials can induce pathological changes in lungs of experimental animals. The features responsible for the variation in host response between samples are, as yet, unclear.

Fly ash samples obtained from different coal combustors were tested for cytotoxicity to alveolar macrophages in vitro by measuring the release of dehydrogenase into the culture media. Fly ash samples obtained from the combustion of a variety of coals in several types of combustors were not found to be cytotoxic when compared to a quartz sample of known toxicity.

Preliminary pathological and mineralogical studies are reported on seventy-four sets of lungs from British coal miners who have been employed at the collieries included in the National Coal Boards's Pneumoconiosis Field Research. The degree of lung damage was considered in relation to the lung dust content and to the known dust exposures of the men concerned. Lungs were classified as having soft macules, fibrotic nodules or PMF. Those with soft macules had the lowest dust content but there was no significant difference between the dust contents of the lungs with fibrotic lesions and those with PMF. The percentage of non-coal minerals in the lung dust appeared to increase with the pathological classification from soft macules to PMF, and comparisons with the exposure data indicated a preferential retention of non-coal minerals, and especially of quartz, in the cases with the more severe lesions. Histological examination of the lesions showed the packing of dust was less close and the cellular response more vigorous with the lungs with the highest quartz content.

The toxicity of various minerals (kaolin, muscovite, illite) was compared by tracheal tests on rats to that of reference dusts (quartz, titanium dioxide, coal). These minerals have various degrees of toxicity. Owing to their sometimes very high concentration in the respirable dust, their toxicity should be taken into consideration. In order to define the aggravating role of quartz more accurately, dust inhalation tests were also conducted on rats with coal and a coal-quartz mixture containing about 10% quartz. The difference in the toxicity of these two types of dust which is practically not detectable up to 12 months, then increases progressively after that period. In addition, in rats having inhaled either coal or a quartz-coal mixture for 24 months, there appear tumoral lesions, principally of epidermoid type.

To evaluate the effects of volcanic ash and free crystalline silica on cells derived from the air space of the human lung, we compared the effects of these minerals on human alveolar macrophages and A549 cells, which are derived from human type II pneumocytes. The quartz was markedly cytotoxic to alveolar macrophages and A549 cells and stimulated the release of neutrophil chemotactic activity from alveolar macrophages. By contrast, volcanic ash was much less toxic to human alveolar macrophages and A549 cells and did not stimulate the release of neutrophil chemotactic activity from alveolar macrophages. The results with A549 cells were similar to findings with isolated type II pneumocytes recovered from rat lungs. Secretory IgA, IgG, and albumin, which are normally present in the air spaces of the lung, reduced the cytotoxicity of quartz in a dose-dependent manner. These results suggest that in the human lung quartz, but not volcanic ash, may cause direct damage to cells in the alveolar spaces and lead to the recruitment of phagocytes from the bloodstream to the lung.

The ultrastructural effects of mineral dusts on a macrophagelike cell line (P388D1) were studied by transmission electron microscopy. The cells were found to contain virus particles which probably did not exert a cytopathic effect toward the cells. During mitosis the asbestos fibers appeared to be pushed to the periphery of the cell. The distribution of the asbestos in the P388D1 cells was similar to that seen previously in cultured peritoneal macrophages, and it was concluded that the cytotoxic effect of asbestos towards the cells was due to mechanical effects, e.g., by penetrating structures such as the nucleus or phagosomes, by preventing the ordered movement of organelles with the cell or by disrupting the cytoskeletal framework of the cell.

Rats were exposed by inhalation to 5 or 50 mg/m3 Mount St. Helens volcanic ash, to 50 mg/m3 quartz (positive controls), or to filtered room air (sham-exposed controls), for 6 hr/day, 5 days/week, for up to 24 months to investigate biological effects of chronic inhalation exposure to volcanic ash under controlled laboratory conditions. Exposure-related lung changes comprised accelerated respiratory frequency; alveolar macrophage accumulation; interstitial reaction; lymphoreticular reaction in peribronchiolar regions and in mediastinal lymph nodes; alveolar proteinosis in the 50- mg/m3 ash- or quartz-exposed groups; increase in fresh lung weights; decreased body weight and increased mortality in the quartz-exposed group; and epidermoid carcinomas especially in the quartz-exposed females and, to a lesser extent, in the 50-mg/m3 ash-exposed females. The observed changes reflect significant dose-response and agent-response relationships.