G. Perrault

Workers' exposure to isocyanates.

A model of exposure to isocyanates, based on knowledge of industrial processes and starting materials and the results of industrial hygiene surveys, is proposed. This model of exposure suggests the concentration and physical form of airborne isocyanate monomers and oligomers. A new sampling and analytical system was developed that is capable of determining the physical and chemical characteristics of occupational exposure to a variety of aliphatic and aromatic isocyanates as required by the exposure model. The sampling system consisted of a dual-filter 37-mm cassette, in which the first filter captured aerosol phase contaminants and the second captured vapor phase isocyanates through derivatization with 9-(N-methylaminomethyl) anthracene (MAMA). Urea derivative recovery by the sampling system, isocyanate-MAMA reactivity, and linearity of the calibration curve were evaluated in the laboratory. The practicality of the system was evaluated during field trials. Sampling times are reduced to 15 min, and the detection limit for TDI, HDI, and MDI was 1.0 micrograms/m3. A partial validation of the new sampling system was performed for HDI vapor by comparison to a standard method in field trials and for TDI vapor in a controlled test atmosphere. The analytical system may also be used to measure the concentration of oligomeric isocyanates. Airborne concentrations of isocyanates were measured in two foam plants, nine paint shops, and two foundries to verify the usefulness of the model. Exposure in foam plants was predominantly to gaseous monomeric isocyanates. Exposure to oligomer isocyanates was higher than expected in paint shops. Both monomer and oligomer isocyanates were undetectable in foundries.

Evaluation of Occupational Exposure to Mixed Dusts and Polycyclic Aromatic Hydrocarbons in Silicon Carbide Plants

Workers in the silicon carbide industry have experienced occupational health diseases, particularly lung disorders such as silicosis. The silicon carbide production process mainly employs petroleum coke, sawdust, pure crystalline silica and graphite. Since crystalline silica is present in the occupational environment, the airborne dust content of various polymorphs of silica, especially quartz, cristobalite and tridymite, was determined by X-ray diffraction analysis. The analytical method was modified to eliminate graphite, since it overlaps with the main diffraction plane of quartz. Exploratory field surveys were conducted to identify the minerals present in that occupational environment and to evaluate the validity of the analytical method. The surveys provided information on the mineralogical nature of the dust, its respirable content and the concentration of silica polymorphs. Polycyclic aromatic hydrocarbons also were measured, and the effect of their adsorption on graphite was evaluated.

Retention of asbestos fibres in lungs of workers with asbestosis, asbestosis and lung cancer, and mesothelioma in Asbestos township.

OBJECTIVE: To conduct a mineralogical study on the particles retained in the necropsied lungs of a homogenous group of asbestos miners and millers from Asbestos township (and a local reference population) and to consider the hypothesis that there is a difference in size between fibres retained in the lungs of patients with asbestosis with and without lung cancer. METHODS: Samples of lung tissue were obtained from 38 patients with asbestosis without lung cancer, 25 with asbestosis and lung cancer, and 12 with mesothelioma, from necropsied Quebec chrysotile miners and millers from Asbestos township. Fibre concentrations in the lungs of these patients were compared with those in tissue from necropsies carried out on a local reference population: men who had died of either accidental death or acute myocardial infarction between 1990 and 1992. 23 were born before 1940 and 26 after 1940. RESULTS: Geometric mean (GM) concentrations were higher in cases than in the controls for chrysotile fibres 5 to 10 microns long in patients with asbestosis with or without lung cancer; for tremolite fibres 5 to 10 microns long in all patients; for crocidolite, talc, or anthophyllite fibres 5 to 10 microns long in patients with mesothelioma; for chrysotile and tremolite fibres > or = 10 microns long in patients with asbestosis; and crocidolite, talc, or anthophyllite fibres > or = 10 microns long in patients with mesothelioma. However, median concentrations of each type of fibre in the lungs did not show any significant differences between the three disease groups. Average length to diameter ratios of the fibres were calculated to be larger in patients with asbestosis and lung cancer than in those without lung cancer for crocidolite fibres > or = 10 microns long, for chrysotile, amosite, and tremolite fibres 5 to 10 microns long, and for chrysotile and crocidolite fibres < 5 microns long. However, there was no statistical difference in the median length to diameter ratios for any type of fibres across the disease groups when they were calculated in each patient. Cumulative smoking index (pack-years) was higher in the group with asbestosis and lung cancer but was not statistically different from the two other disease groups. CONCLUSION: Lung cancers occurred in workers with asbestosis from Asbestos township who had an equal concentration of retained fibres but a tendency to a higher length to diameter ratio of amphiboles. These workers had a 29% higher average cumulative smoking index.

Morphology and surface characteristics of particulates from silicon carbide industries

Faced with the lack of a correlation between health effects and exposures to known air contaminants in silicon carbide plants, an attempt was made to better characterize particles from these working environments with the use of electron microscopy with energy dispersive x-ray analysis and selected area electron diffraction, x-ray photoelectron spectroscopy and scanning Auger spectroscopy. The occurrence of SiC fibers was confirmed. SiC particulates were shown to be covered largely by silicon dioxide islets, heterogeneously distributed at the surfaces. These findings are discussed briefly in relation to the hypothesis on the toxicity of fibers and to the Altree-Williams and Sprogis risk function.

Characterization of Airborne Dust from Two Nonferrous Foundries by Physico-chemical Methods and Multivariate Statistical Analyses

Airborne particulate matter was sampled at a copper smelter and at an aluminum casting plant. Size, shape, quantity, and microlocalization of chemical species in the particulates were measured using closed cassettes, cascade impactors, scanning electron microscopy, X-ray diffraction, infrared and atomic absorption spectrophotometries, secondary ion mass spectrometry, and photoelectron spectroscopy. Cluster and principal components analyses were used in interpreting results. Aerosol chemistry varies as a function of size, and composition becomes more complex as the aerosol size drops into the respirable fraction and lower. Surface chemical properties are evidenced where, generally, volatile species are enriched. A few site-specific elements and characteristics were identified. The formation of particulates may often be related to process and practices, yet the actual distribution of species in the air remains an intricate matter.

Pulmonary Retention of of Ceramic Fibers in Silicon Carbide (SiC) Workers

The fibrous inorganic content of post-mortem lung material obtained from 15 men who worked in the primary silicon carbide (SiC) industry was evaluated. Five men had neither lung fibrosis nor lung cancer (NFNC), six had lung fibrosis (LF), and four had lung fibrosis and lung cancer (LFLC). The workers had 23 to 32 years of exposure. Mean duration of exposure was 23.4 (SD 6.9) years in the NFNC group, 28.8 (SD 5.5) in the LF, and 32.3 (SD 9.0) in the LFLC group. Concentrations of SiC ceramic fibers and other fibrous minerals and angular particles were determined by transmission electron microscopy and energy dispersive spectroscopy. The geometric mean and geometric standard deviation lung concentrations of SiC ceramic fibers < 5 microns were not statistically different for the three groups (Mann-Whitney, p > 0.1). Pulmonary retention of SiC fibers > or = 5 microns showed an excess in LF and LFLC cases combined versus NFNC that approached statistical significance (Mann-Whitney, p = 0.06). There was a somewhat greater difference for lung retention of ferruginous bodies between NFNC and either LF or LFLC cases (Mann-Whitney, p = 0.02). SiC fibers > or = 5 microns and angular particles containing Si and especially ferruginous bodies were found at higher concentrations in LF and LFLC than in NFNC cases.

Lanthanide particles in the lung of a printer.

Lanthanides were extracted from the lung tissue of a subject with a history of potential exposure to carbon-arc lamp emissions in printing shops. The characterization of inorganic particles was performed by energy dispersive X-ray spectroscopy (EDS) on a transmission electron microscope (TEM) and laser microprobe mass analysis (LAMMA). Both techniques showed the presence of elemental Ce, La and Nd at concentrations higher than the average concentration measured in 41 other workers who had died of cancer at various sites. The lung content of other prismatic and compact particles did not show any statistically significant differences between the case and the control group.

Presence of N-nitrosodiethanolamine contamination in Canadian metal-working fluids

N-Nitroso compounds are notorious mutagens, carcinogens and teratogens that can be seriously hazardous to human health. Metal-working fluids (MWFs) are used for lubricating and cooling the cutting and grinding surfaces of metal-working machines. Because a limited survey is available on MWFs used in Canada, this study was performed to assess the magnitude of the presence of N-nitroso compounds in these MWFs. N-nitrosodiethanolamine (NDELA) was found to be the major contaminant in different brands of MWFs. In the case of soluble oils, the concentrations of NDELA vary between 0.02 and 7.53 ppm, but it was absent in insoluble oils. The concentrations of nitrate in soluble oils vary between 1.6 and 67.0 ppm and in insoluble oils between 0.35 and 1.5 ppm. Nitrite was detected only in one sample of soluble oil (4.2 ppm) whereas it was absent in insoluble oils. By comparing the studies reported by two different Canadian groups in 1978 and 1990, concentrations of NDELA in the MWFs used in Canada were significantly reduced after a period of 12 years. The present study shows an additional significant decline in the concentrations of NDELA in MWFs.

Beryllium aerosol characteristics in the magnesium and aluminum transformation industry in Quebec: a comparison of four different sampling methodologies.

To examine the influence of the sampling method on beryllium (Be) exposure assessment, a study was conducted in foundries and smelters to contrast the performance of five different dust sampling devices. Six sampling surveys were conducted in four different settings, and both personal and fixed station samples were collected using the following sampling heads: IOM samplers (inhalable dust), 35-mm plastic cassettes (total dust), aluminum SKC cyclones (respirable dust), 8-stage Sierra cascade impactors, and 12-stage MOUDI impactors. In total, beryllium concentrations were determined for 66/68 inhalable dust samples, 62/62 total dust samples, 56/57 respirable dust samples, 54/64 8-stage Sierra samples, and 19/25 12-stage MOUDI samples. In the magnesium foundry and aluminum smelters, the concentrations obtained during specific tasks could exceed the actual permissible exposure limit of the province of Québec (0.15 μg/m 3 ) or of the ACGIH threshold limit value (TLV) (0.05 μg/m 3 ). The median of median dust concentration ratios computed from the sampling heads at the fixed station decreased as follows: IOM (1.00) > Sierra (0.76) > 37-mm cassette (0.61) > MOUDI (0.48) > respirable (0.12). The same trends were observed with the ratios of the median of median Be concentrations at the fixed station but with a larger scattering within sampling heads as follows: IOM (1.00) > Sierra (0.69) > 37-mm cassette (0.64) > MOUDI (0.54) > respirable (0.19). The median of median ratios of dust (IOM (1.00) > Sierra (0.56) > 37-mm cassette (0.35) > respirable (0.06)) and Be (IOM (1.00) > Sierra (0.66) > 37-mm cassette (0.48) > respirable (0.11)) in dust were lower, and there was less scattering for the 37-mm cassette and SKC cyclone used during breathing zone sampling than for the same sampling heads at the fixed station. Inhalable aerosol measurements should remain the tool for estimating the risk of exposure to beryllium in these settings until a clear dose response is established for these sampling heads.

Clearance of man made mineral fibres from the lungs of sheep.

OBJECTIVES: To compare the clearance rate, the related pathology, and the chemical and morphological changes of three man made mineral fibres (MMMFs) in the sheep model of pneumoconiosis. METHODS: Fibrous particles were extracted from lung parenchyma and analysed by transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS). RESULTS: The concentration of MMMF11, MMMF21, refractory ceramic fibre (RCF-1), and crocidolite asbestos fibres decreased with time according to a slow and a fast kinetic component. There was a statistical difference in the four regression lines as a function of time and the type of fibres (p < 0.001). The diameter of MMMFs decreased during the course of the time, whereas the crocidolite fibres did not seem to show any change. There was a statistical difference in the four regression lines as a function of time (p = 0.037) and type of fibres (p < 0.001). Ferruginous bodies were counted in the 40 sheep for which the latency period was 2 years. No typical ferruginous bodies were found in the groups exposed to MMMFs. The geometric mean concentration of asbestos bodies in the group exposed to crocidolite was 2421 bodies/g lung tissue (95% CI 385 to 15260). CONCLUSIONS: The number of initially retained fibres decreased with time according to a slow and a fast kinetic component. MMMF11 and MMMF21 have similar clearance, faster than RCF-1 and crocidolite. The geometric mean diameter and length of MMMF decreased with time, but crocidolite did not. After 2 years in the sheep tracheal lobe, ferruginous bodies were not found in all three MMMF groups but were substantial in the crocidolite group. Clearance is thought to proceed through dissolution and macrophage translocation.