Nuisance Dust Research Articles

Exposure to fibres, crystalline silica, silicon carbide and sulphur dioxide in the norwegian silicon carbide industry.

Objectives: The aim of this study was to assess personal exposure to fibres, crystalline silica, silicon carbide (SiC) and sulphur dioxide in the Norwegian SiC industry.Methods: Approximately 720 fibre samples, 720 respirable dust samples and 1400 total dust samples were collected from randomly chosen workers from the furnace, processing and maintenance departments in all three Norwegian SiC plants. The respirable dust samples were analysed for quartz, cristobalite and non-fibrous SiC content. Approximately 240 sulphur dioxide samples were collected from workers in the furnace department.Results: The sorting operators from all plants, control room and cleaning operators in Plant A and charger, charger/mix and payloader operators in Plant C had a geometric mean (GM) of fibre exposure above the Norwegian occupational exposure limit (OEL) (0.1 fibre cm−3). The cleaner operators in Plant A had the highest GM exposure to respirable quartz (20 μg m−3). The charger/mix operators in Plant C had the highest GM exposure to respirable cristobalite (38 μg m−3) and the refinery crusher operators in Plant A had the highest GM exposure to non-fibrous SiC (0.65 mg m−3). Exposure to the crystalline silica and non-fibrous SiC was generally low and between 0.4 and 2.1% of the measurements exceeded the OELs. The cleaner operators in Plant A had the highest GM exposure to respirable dust (1.3 mg m−3) and total dust (21 mg m−3). GM exposures for respirable dust above the Norwegian SiC industry-specific OEL of 0.5 mg m−3 were also found for refinery crusher operators in all plants and mix, charger, charger/mix and sorting operators in Plant C. Only 4% of the total dust measurements exceeded the OEL for nuisance dust of (10 mg m−3). Exposure to sulphur dioxide was generally low. However, peaks in the range of 10–100 p.p.m. were observed for control room and crane operators in Plants A and B and for charger and charger/mix operators in Plant C.Conclusion: Workers in the SiC industry are exposed to a mixture of several agents including SiC fibres, quartz, cristobalite, non-fibrous SiC and sulphur dioxide. Exposure levels were generally below the current Norwegian OELs; however, high exposure to fibres and respirable dust still occurs in the furnace department.

Nitric Oxide Scavenging by Environmental Particles and Engineered Nanoparticles: Size and Composition Dependency

Inhaled particulate matter (PM) elicits systemic biological responses such as impaired arteriolar dilation and increased venular leukocyte adhesion. One mechanism that may contribute to such effects is NO scavenging by pulmonary translocated particles. The purpose of this study was to determine if PM scavenges NO in vitro, and also determine if PM size or composition influences any such activity. PM was classified as combustion source particles, engineered nanoparticles or nuisance dusts. NO solutions were generated by SNAP and were measured with a NO sensor. A concentration of 1–2.5 μg/ml was used for each particle, and responses were normalized to a bolus SNAP dose, [NO]=841 nm. Among fly ashes, residual oil fly ash was the most potent scavenger, decreasing the signal by 67%. Coal fly ash from Western Kentucky and Montana, as well as Mt. St. Helens ash did not significantly alter NO levels. Diesel exhaust particles attenuated the NO signal by 19%. Among nanoparticles, TiO2 decreased the NO signal by 39%. Single and multi‐walled carbon nanotubes did not produce an effect. These findings suggest that air particulate pollution as well as some engineered nanoparticles have the potential to scavenge NO, and this ability is heavily dependent upon particle size, composition and/or surface properties.Support: HEI #4730 and NIH RO1 ES015022 to TRN(This abstract does not necessarily reflect EPA policy)

A review of carcinogenicity studies of asbestos and non-asbestos tremolite and other amphiboles

Experimental animal studies comparing asbestos and non-asbestos varieties of tremolite indicate tremolite asbestos is markedly more carcinogenic. By direct analogy, the differences in carcinogenicity between tremolite asbestos and non-asbestos prismatic tremolite should be the same for the other types of amphibole that also crystallize in the asbestos and non-asbestos habits. The earliest of the experiment animal studies, done more than 25 years ago, have design limitations by modern standards including the use of injection or surgical implantation as the route of administration rather than the more relevant route of inhalation. However, the differences in the carcinogenicity of amphibole asbestos and non-asbestos amphiboles are sufficiently large to be clearly discernable even with the study limitations. Together with later studies on these and related minerals, there is strong evidence of a much lower hazard associated with the shorter, thicker fibers of the non-asbestos amphiboles, than is found for the asbestos analogues of the same mineral. It is possible that the non-asbestos amphiboles are no more hazardous than other silicate minerals widely considered nuisance dusts.

Grain Dust and Lung Health: Not Just a Nuisance Dust

The invitation to contribute to the present issue of the Journal, celebrating the 50th anniversary of the Canadian Thoracic Society (CTS), provides me with an opportunity to document what, in my view, is one of the most effective collective interventions in the field of epidemiology and occupational health. The present essay gives the reasons why the Society addressed the question of whether grain dust is not just a nuisance dust, and how it did so. My main source of information is from a 1978 report in the Canadian Lung Association Bulletin (1). Grain growing, handling and processing have long been major Canadian industries. In the 1971 census of Canada, there were in Canada approximately 253,000 farmers, farm managers and farm workers; approximately 5000 small elevator workers and 7200 large elevator workers; and approximately 15,000 workers in the flour, feed and seed mills. The dust to which grain workers are exposed is complex, whether it be wheat, barley, rye, oats or corn. It consists of the grain, hairs from the epicarp and the germ. Plant contaminants include weeds and pollens. Fungi grow in grain depending on its freshness. Rodents may infest it, leaving their spoor. Chemicals may be added to control fungi, arthropods and rodents. Free silica from the soil may be present or incorporated into the plant as phytoliths. Finally, grain workers often handle oil seeds such as sunflower, flax and mustard. Grain dust had been classified as a ‘nuisance’ dust; it does not, in the view of the influential American Conference of Government and Industrial Hygienists, require regulation because of its ill health effects on exposed workers. This, however, was contrary to the experience of several members of the CTS, who had been involved in an impressive number of epi-demiological research studies of workers in different branches of the grain handling industry before 1977.

Nanoparticles: Health Effects—Pros and Cons

With the advent of nanotechnology, the prospects for using engineered nanomaterials with diameters of < 100 nm in industrial applications, medical imaging, disease diagnoses, drug delivery, cancer treatment, gene therapy, and other areas have progressed rapidly. The potential for nanoparticles (NPs) in these areas is infinite, with novel new applications constantly being explored. The possible toxic health effects of these NPs associated with human exposure are unknown. Many fine particles generally considered “nuisance dusts” are likely to acquire unique surface properties when engineered to nanosize and may exhibit toxic biological effects. Consequently, the nuisance dust may be transported to distant sites and could induce adverse health effects. In addition the beneficial uses of NPs in drug delivery, cancer treatment, and gene therapy may cause unintentional human exposure. Because of our lack of knowledge about the health effects associated with NP exposure, we have an ethical duty to take precautionary measures regarding their use. In this review we highlight the possible toxic human health effects that can result from exposure to ultrafine particles (UFPs) generated by anthropogenic activities and their cardiopulmonary outcomes. The comparability of engineered NPs to UFPs suggests that the human health effects are likely to be similar. Therefore, it is prudent to elucidate their toxicologic effect to minimize occupational and environmental exposure. Highlighting the human health outcomes caused by UFPs is not intended to give a lesser importance to either the unprecedented technologic and industrial rewards of the nanotechnology or their beneficial human uses.

Will pulmonary insulin delivery help improve type 1 and type 2 diabetes care?

Will pulmonary insulin delivery help improve type 1 and type 2 diabetes care?

HSE warns against nuisance dust masks

HSE warns against nuisance dust masks

The Biopersistence of Canadian Chrysotile Asbestos Following Inhalation

Chrysotile asbestos is often included with other asbestos materials in evaluation and classification. However, chrysotile is a serpentine with markedly different physical and chemical characteristics in comparison to amphiboles (e.g., crocidolite, amosite, tremolite). In contrast to amphiboles, which are solid, rodlike fibers, chrysotile is composed like a rope of many fine fibrils, which tend to unwind. In order to quantify the dynamics and rate by which chrysotile is removed from the lung, the biopersistence of a sample of commercial chrysotile from the Eastern Townships area of Quebec, Canada, labeled QS Grade 3-F, which is the longest commercial grade intended for textile use, was studied. As the long fibers have been shown to have the greatest potential for pathogenicity, the chrysotile samples were specifically chosen to have more than 200 fibers/cm3 longer than 20 µm present in the exposure aerosol. This publication presents the results of this study through 3 mo postexposure. The study design included: (1) Fiber clearance (lung digestions): At 1 day, 2 days, 7 days, 14 days, 1 mo, 3 mo, and 12 mo (to be reported) following a 5-day (6 h/day) inhalation exposure, the lungs from groups of animals were digested by low-temperature plasma ashing and subsequently analyzed by transmission electron microscopy for total chrysotile fibers number in the lungs and chrysotile fiber size (length and diameter) distribution in the lungs. (2) Fiber distribution (confocal microscopy): This procedure was included in order to identify the location of the fibers in the lung. At 1 day, 2 days, 7 days, 14 days, 1 month, and 3 months (to be reported) postexposure, the lungs from groups of animals were analyzed by confocal microscopy to determine the anatomic fate, orientation, and distribution of the retained chrysotile fibrils deposited on airways and in the parenchymal region. Chrysotile was found to be rapidly removed from the lung. Fibers longer than 20 µm were cleared with T1/2 = 16 days, most likely by dissolution and disintegration into shorter fibers. The shorter fibers were also rapidly cleared from the lung, with fibers 5–20 µm clearing even faster (T1/2 = 29.4 days) than those <5 µm in length. The fibers <5 µm in length cleared at a rate (T1/2 = 107 days) that is within the range of clearance for insoluble nuisance dusts. The breaking apart of the longer fibers would be expected to increase the short fiber pool and therefore could account for this difference in clearance rates. The short fibers were not found clumped together but appeared as separate, fine fibrils, occasionally unwound at one end. Short free fibers appeared in the corners of alveolar septa, and fibers or their fragments were found within alveolar macrophages. The same was true of fibers in lymphatics, as they appeared free or within phagocytic lymphocytes. Neutrophil-mediated inflammatory response did not occur in the presence of chrysotile fibers at the time points examined. Taken in context with the scientific literature to date, this report provides new robust data that clearly support the difference seen epidemiologically between chrysotile and amphibole asbestos.

Exposure to cooking fumes in restaurant kitchens in norway.

The purpose of this study was to assess exposure to fat aerosols and aldehydes in kitchens and to study the variations in exposure between different types of kitchen. Measurements were made in four hotel kitchens, two hamburger chain restaurants, 10 à la carte restaurants and three small local restaurants serving mostly fried food. The measurements were performed as personal measurements and each person carried two sampling devices connected to pumps. One pump was connected to a filter cassette with a 37 mm glassfibre filter and the other to a sampling device for aldehydes. The measurements were repeated on 3 days in each kitchen. Variables which could influence the level of exposure were recorded by the occupational hygienist. The level of fat aerosols varied between the different types of kitchen. The highest measured level of fat aerosol was 6.6 mg/m(3), in a small local restaurant. The arithmetic mean for all the kitchens was 0.62 mg/m(3). The highest level of the sum of the aldehydes was 186 micro g/m(3) (0.186 mg/m(3)), while the arithmetic mean was 69 micro g/m(3). The exposure to fat aerosols was modest, but could be up to 50% of the Norwegian threshold limit value (TLV) for nuisance dust (10 mg/m(3)). Fat aerosols from frying will, however, contain a mixture of heat- and water-treated fat from the meat which is being fried, hydrolysed vegetable fat and other degradation products, such as fatty acids, other organic acids and aldehydes. As a consequence of this, cooking fumes should be regarded as harmful to the lungs. The levels of formaldehyde, acetaldehyde and acrolein were well below the TLVs.

PULMONARY TOXICITY OF SIMULATED LUNAR AND MARTIAN DUSTS IN MICE: I. HISTOPATHOLOGY 7 AND 90 DAYS AFTER INTRATRACHEAL INSTILLATION

NASA is contemplating sending humans to Mars and to the moon for further exploration. Volcanic ashes from Arizona and Hawaii with mineral properties similar to those of lunar and Martian soils, respectively, are used to simulate lunar and Martian environments for instrument testing. Martian soil is highly oxidative; this property is not found in Earth's volcanic ashes. NASA is concerned about the health risk from potential exposure of workers in the test facilities. Fine lunar soil simulant (LSS), Martian soil simulant (MSS), titanium dioxide, or quartz in saline was intratracheally instilled into groups of 4 mice (C57BL/6J) at 0.1 mg/mouse (low dose, LD) or 1 mg/mouse (high dose, HD). Separate groups of mice were exposed to ozone (0.5 ppm for 3 h) prior to MSS instillation. Lungs were harvested for histopathological examination 7 or 90 days after the single dust treatment. The lungs of the LSS-LD groups showed no evidence of inflammation, edema, or fibrosis; clumps of particles and an increased number of macrophages were visible after 7 days but not 90 days. In the LSS-HD-7d group, the lungs showed mild to moderate alveolitis, and perivascular and peribronchiolar inflammation. The LSS-HD-90d group showed signs of mild chronic pulmonary inflammation, septal thickening, and some fibrosis. Foci of particle-laden macrophages (PLMs) were still visible. Lung lesions in the MSS-LD-7d group were similar to those observed in the LSS-HD-7d group. The MSS-LD-90d group had PLMs and scattered foci of mild fibrosis in the lungs. The MSS-HD-7d group showed large foci of PLMs, intra-alveolar debris, mild-to-moderate focal alveolitis, and perivascular and peribronchiolar inflammation. The MSS-HD-90d group showed focal chronic mild-to-moderate alveolitis and fibrosis. The findings in the O 3 -MSS-HD-90d group included widespread intra-alveolar debris, focal moderate alveolitis, and fibrosis. Lung lesions in the MSS groups were more severe with the ozone pretreatment. The effects of O 3 and MSS coexposure appeared to be more than additive. Results for the TiO 2 and quartz controls were consistent with the known pulmonary toxicity of these compounds. The overall severity of lung injury was TiO 2 < LSS < MSS < O 3 + MSS < quartz. Except for TiO 2, the increased duration of dust presence in the lung from 7 to 90 days transformed the acute inflammatory response to a chronic inflammatory lesion. This study showed that LSS and MSS are more hazardous in the lungs than nuisance dusts.

Composition and particle size of and exposure to coal fly ash

Nuisance of dust caused by handling and blown away of coal and ash can be find at coal-fired power stations. A research program was accomplished in order to map the exposure and effects of workers and people living in the neighbourhood. In this program, the following aspects were researched: exposure, particle size distribution, chemical composition, emission factors and fugitive dust calculations. Due to different standards for population and workers, the exposure to three dust fractions has to be established. For the population it is the fine dust fraction (PM 10 ) and for the workers it is the inhalable (PM 50 ) and respirable fraction (PM 4 ). Due to co-combustion of biomass and other secondary fuels in coal-fired power plants, a good knowledge about composition of these combustion aerosols is necessary. For that purpose by KEMA an empirical model (KEMA Trace Model) is developed, in which the composition of the various particle size, based on the fuel composition, can be predicted. Next a methodology was developed by which it can be determined whether the formed ash is a nuisance dust or not (KEMA-DAM: KEMA Dust Assessment Methodology). Furthermore KEMA has developed their own fugitive dust model with much more possibilities than the existing models (KEMA 3D; 3D=dust, dispersion and deposition).

Protection of Breathing Zone by Uniform Velocity Blowing

A system of work site ventilation that blows clean air around a worker's nose and mouth was studied. The characteristics of the blowing flow were examined experimentally and then for a practical application. Field tests were performed to confirm the effectiveness of the blowing equipment during concrete chipping at a building construction site. This type of ventilation was found to be useful for contaminants with relatively low toxicity (e.g., nuisance dust); however, the technique may increase the exposure of workers in adjacent areas, since the dust is not captured or filtered. It became evident that the worker's dust exposure during the chipping could be decreased by using the air-blowing equipment.

The Occurrence of Quartz in Coal Fly Ash Particles

In spite of the presence of quartz, coal fly ash can be considered as a nuisance or inert dust. Respirable crystalline silica (e.g., quartz) is notorious for the induction of, for example, progressive massive fibrosis (PMF); besides, in 1997 the IARC stated that crystalline silica in the form of quartz or cristobalite from occupational sources is carcinogenic to humans. Quartz is present in both coal and residual ash. Ash originates from combustion of pulverised coal and, once removed from the flue gases by electrostatic precipitators (ESPs), it is called pulverized fuel ash (PFA). Thus, occupational exposure to PFA could also include exposure to silica. However, epidemiological studies did not show evidence of progressive massive fibrosis (PMF). In vitro tests demonstrated that PFA is less toxic than silica, and in vivo data of PFA did not support the importance of silica content for toxicity. Commissioned by the Dutch coal-fired power plants, KEMA has started a research project to determine the quartz content in coal and the corresponding PFA. It appears that on average 50% of the a-quartz in coal is found again in the total fraction of PFA (D50(ae) 31 µm, where Dsotae) is the aerodynamically mass median diameter), whereas 16% is found in an even finer fraction (D50(ae) 10 µm). The remaining part of the quartz is embedded in a glass phase. Scanning electron microscopy (SEM) with x-ray microanalyses (XMA) of cross-sections of 11,130 ash particles showed that quartz in PFA is present as unmelted sand particles. These quartz particles are angularly shaped. However, two types are to be distinguished: free coarse angular quartz particles (not respirable) and small angular quartz particles within the PFA particles. From the SEM/XMA results, it has to be concluded that the quartz in the respirable fraction is predominantly present within the original molten PFA particle. Since the effects of quartz are surface related, this elucidates the negative results of quartz-related effects of PFA in epidemiological, in vitro and in vivo studies. Besides, the amount of the total α-quartz in the respirable fraction of the ashes studied is less than 0.2%, so probably the Dutch occupational quartz standard of 0.075 mg m−3 will not be exceeded.

Current Exposure Guidelines for Particulates Not Otherwise Classified or Regulated: History and Rationale

Abstract Exposure limits and guidelines for particles not otherwise classified or regulated (PNOC/R) evolved from several important studies of pneumoconiosis performed early in the 20th century. These studies indicated that exposure to dust concentrations of less than 50 million particles per cubic foot (mppcf) and with low crystalline silica concentrations did not appear to lead to the development of disabling lung disease. Consequently, dusts containing less than 5 percent crystalline silica were termed “nuisance dusts,” and an exposure limit of 50 mppcf was recommended. With the advent of mass sampling technology and the ability to sample directly for respirable dust, exposure limits migrated to total and respirable nuisance dust exposure limits of 15 and 5 mg/m3, respectively, for dusts containing less than 1 percent crystalline silica. Regulatory exposure limits were established by incorporating these exposure guidelines that were in existence when the enabling legislation was enacted. Changes to regulatory limits have lagged behind threshold limit values adopted by the American Conference of Governmental Industrial Hygienists (ACGIH), which have been updated based on current research. Current ACGIH recommendations for inhalable and respirable dusts are 10 and 3 mg/m3, respectively. Recent studies of ultrafine particulate and toxicological investigation of the pulmonary overload phenomena from exposure to PNOC/R indicate that exposure to these materials at sufficiently high concentrations can cause irreversible changes to the airways. The term “nuisance dust” was inaccurate, so the terminology of PNOC/R was substituted as a better descriptor for dusts without component-specific exposure limits. Further reductions in exposure limits and guidelines have been proposed for control of occupational exposure to PNOC/R. These proposals are motivated by increasing recognition that clinically significant chronic airways obstruction is caused by occupational dust exposure.

Nuisance Dust Deposition and Soiling Rate Measurements

Changes in soiling rate of clean clear microscope slides have mean measured at four sites in central London and two to the south-west of London. The study was conducted over the course of a year to sample a wide range of weather conditions. The purpose of the study was to investigate the variation in soiling rates over time at busy roadside, sheltered roadside and non-roadside situations. Measurements were made using a Diffusion Systems Ltd Nuisance Dust Meter. Soiling rates in central London, where traffic flows are more dense, were found to be greater than outside London, and roadside sites were found to be dirtier than non-roadside ones. The closer proximity of high density traffic with a greater proportion of diesel engined vehicles in central London is likely to be an important contributory factor to this. Over the course of a year, weekly soiling rates at a particular site could vary by a factor of two. At all sites soiling levels increased approximately linearly with time for the first week, after which the rate of increase tended to fall off with time. These results show that if the soiling characteristics of a site are to be compared, it is necessary to standardise the time over which measurements are made, and that it is necessary to carry out measurements over a number of months in order to experience a typical range of weather conditions. A standard averaging time of one week is proposed for individual soiling measurements.

Performance of respiratory filters and surgical masks against bacterial aerosols

A laboratory test system has been designed and built to measure the efficiency of filter material from several commonly used respirator filter cartridges, approved disposable dust masks, nuisance dust masks, single-use surgical procedure masks and a resuscitation mask against aerosols of the bacteria Bacillus subtilis subspecies globigii, Micrococcus luteus and Pseudomonas alcaligenes. All tests were carried out at a flow rate of 301min−1. The same materials were also tested with monodisperse urea aerosols in the size range 1.5–9 μm and with the British Standard BS 4400 sodium chloride aerosol, which has a mass geometric mean diameter of 0.6 μm and a geometric standard deviation of 2.3. One type of surgical mask allowed penetration of up to 83% of a microbiological aerosol and 87% of a non-biological aerosol, and nuisance dust masks allowed penetrations of up to effectively 100% for a microbiological aerosol and 91% for a non-biological aerosol. The materials of the other surgical masks and the resuscitation mask, all of which were electrically charged, performed better against all the test aerosols. Penetration of microbiological aerosols through the respirator filter materials was no greater than 0.88%, and penetration of non-biological aerosols no greater than 1.72%. The results for microbiological aerosols generally corresponded to those for the non-biological aerosols in the same size range.

Localization of intercellular adhesion molecule-1 (ICAM-1) in the lungs of silica-exposed mice.

Intercellular adhesion molecule-1 (ICAM-1) is expressed on a variety of cells including endothelial cells, alveolar epithelial cells, and alveolar macrophages. Endothelial/epithelial cell ICAM-1 participates in the migration of leukocytes out of the blood in response to pulmonary inflammation, whereas alveolar macrophage ICAM-1 may represent cell activation. Our previous studies have shown that there is increased expression of ICAM-1 in lung tissue during acute inflammation following intratracheal injection with silica particles (2 mg/mouse). This increased expression was shown to play a role, in part, in the migration of neutrophils from the circulation into the tissue parenchyma. The aim of the current work is to localize expression of ICAM-1 during acute inflammation in lungs of mice exposed to either silica or the nuisance dust, titanium dioxide. In silica-exposed mice, a significant increase in ICAM-1 was detected on day-1 and localized by immunohistochemistry to aggregates of pulmonary macrophages and to type II epithelial cells. Areas of the lung with increased ICAM-1 expression also showed increased tumor necrosis factor alpha expression. Immunocytochemical staining of bronchoalveolar lavage (BAL) cells demonstrated increased ICAM-1 expression associated with alveolar macrophages 3, 5, and 7 days following silica exposure. Finally, soluble ICAM-1 levels in the BAL fluid were significantly increased in mice exposed to silica on the same days. Titanium dioxide exposure elicited a minimal increase in expression of ICAM-1 in the lungs. These data demonstrate that exposure to the toxic particle silica specifically increases ICAM-1 expression localized to pulmonary macrophages and type II epithelial cells.

COMPARISON OF INDUCIBLE NITRIC OXIDE SYNTHASE GENE EXPRESSION AND LUNG INFLAMMATION FOLLOWING INTRATRACHEAL INSTILLATION OF SILICA, COAL, CARBONYL IRON, OR TITANIUM DIOXIDE IN RATS

The pulmonary toxicity of the respirable dusts silica, coal, carbonyl iron, and titanium dioxide on alveolar macrophage (AM) and neutrophil (PMN) inducible nitric oxide syn thase (iNOS) gene expression and nitric oxide (NO) production was investigated. Rats were intratracheal^ instilled with 5 mg/100 g body weight of silica, coal, carbonyl iron, or titanium dioxide. The dust particles averaged less than 5 pm in diameter. Bronchoalveolar lavage was performed 24 h later. Bronchoalveolar lavage cell (BALC) differentials, iNOS gene expression and NO production by BALC (measured indirectly as NO-dependent chemiluminescence), and lavageable lung protein levels were measured. Analyzed on an equal mass basis, silica, coal, and titanium dioxide dusts increased the production of iNOS-dependent NO by AM. Silica and titanium dioxide both increased the levels of iNOS mRNA while carbonyl iron and coal did not. Each dust caused an increase in PMN, indicating an inflammatory response. Carbonyl iron and titanium dioxide decreased the numbers of AM. Levels of acellular lavageable lung protein were increased by silica, car bonyl iron, and titanium dioxide. When exposure was normalized for an equal number of particles, the pneumotoxic dusts, silica and coal, caused more inflammation and NO pro duction than the nuisance dusts, carbonyl iron and titanium dioxide. Therefore, it appears that particle number is a more appropriate metric of exposure than mass when comparing the relative pathogenicity of dusts of different sizes. Furthermore, since the potency of these dusts (on a particle number basis) to increase iNOS gene expression reflects their inflammatory and pathogenic potential, it is proposed that NO may contribute to the early inflammatory damage observed in the lung following dust exposure.

N-acetyl-beta-D-glucosaminidase activity within BAL from macaques exposed to generic coal dusts

N-acetyl-beta(beta)-D-glucosaminidase is a lysosomal enzyme secreted by alveolar macrophages in response to phagocytosis of particulate material. Alveolar macrophages participate in the degradation and fibrosis of pulmonary tissue that results in pneumoconiosis. Known quantities of four characterized respirable dusts were bronchoscopically placed into the right caudal lung lobe of macaque monkeys. Bronchoalveolar lavage (BAL) samples were collected from dust-exposed right lung and unexposed left lung of the same individuals at 2-week intervals for 12 weeks after dust instillation. The samples were tested for N-acetyl-beta-D-glucosaminidase activity to determine if the enzyme levels could serve as an indicator of pulmonary injury induced by generic coal dusts when compared to known fibrogenic and nuisance dusts. Installation of generic quartz, anthracite, or TiO2 dusts produced significant elevations of enzyme activity and increased numbers of macrophages in the dust-exposed lobes. Elevations in enzymatic activity and macrophage numbers were greatest in response to generic quartz dust. These results suggest that quantitative levels of N-acetyl-beta-D-glucosaminidase activity may be a useful indicator of acute and chronic lung injury following exposure to fibrogenic and nonfibrogenic dusts.

Nuisance dust fall-out monitoring in the vicinity of Kelvin Power Station

Nuisance dust fall-out monitoring in the vicinity of Kelvin Power Station