Pulmonary clearance and toxicity of respirable gallium arsenide particulates intratracheally instilled into rats

Gallium arsenide (GaAs) is an intermetallic compound that is recognized as a potential toxicological risk to workers occupationally exposed to its dust. Previous results have shown that rats intratracheally instilled with a fraction of GaAs particulates, characterized with a mean count diameter of 8.30 microns and a mean volume diameter of 12.67 microns, developed signs of systemic arsenic intoxication, pulmonary inflammation, and pneumocyte hyperplasia. The results of the present study confirm these findings and also show that a significantly smaller fraction of GaAs is a relatively more severe pneumotoxicant. Decreasing the particle mean count and mean volume diameter to 1.63 micron and 5.82 microns, respectively, increased the in vivo dissolution rate of GaAs, increased the severity of pulmonary lesions previously associated with GaAs exposure, and resulted in unique pathological sequelae in affected lung tissue. Pulmonary fibrosis, as indicated by analysis of lung 4-hydroxyproline content, was not considered statistically significant although histological examination of lung tissue revealed a mild fibrotic response. These results provide additional evidence that pulmonary exposure to respirable GaAs particulates is a potential health hazard in the semiconductor industry.     

煤工尘肺院内获得性肺感染的诊断与治疗

煤工尘肺 (CWP)院内获得性肺部感染常见者有慢性支气管炎急性发作、支气管扩张继发感染、急性或慢性肺炎、肺大泡感染、霉菌和厌氧菌感染等几种常见形式。CWP患者大都进入老年 ,具有老年肺炎的特点 :临床表现为发病隐匿 ,常无咳嗽、发热、胸痛等症状 ,老年人基础体温低 ,对感染发热反应能力差 ,具统计存活者 2 8%有发热 ,非存活者 13 %有发热[1] 。此外 ,CWP患者除广泛的、不同程度的肺组织纤维化外 ,大都合并有尘源性或慢性支气管炎 ,部分病人合并不同程度的慢性阻塞性肺部疾病 (COPD)、肺结核等 ,平时就有不同程度的呼吸困难 ,咯痰…     

2011年三明市新发尘肺病的肺功能分析

为探讨尘肺病患者肺功能损伤特点及影响因素,对2011年三明市新发的尘肺病患者体检资料进行分析。结果显示,104例新发尘肺病人肺功能损伤率达34.6%,肺功能损伤主要以限制性通气功能障碍为主;掘进工肺功能损伤率明显高于采煤工和采掘工,差异有统计学意义(P<0.05);工龄>30年的患者肺功能损伤率明显高于其他组别,差异有统计学意义(P<0.05);肺功能损伤率随着年龄的增长而升高,差异有统计学意义(P<0.05);≥60岁患者的肺功能损伤率明显高于其他组别,差异有统计学意义(P<0.05)。提示新发尘肺病人肺功能损伤率仍然较高,工种、工龄、年龄对尘肺病患者肺功能有影响。应采取切实有效的措施阻止或延缓肺功能的损伤,提高患者生存质量、延长寿命。     

A relationship between the molar proportion of propionic acid and the clearance rate of the liquid phase in the rumen of the sheep.

1. Four rumen-cannulated sheep were given a forage mixture (F) of chopped hay-ground, pelleted, dried grass (92:8, w/w) and two concentrate mixtures (C and S) of ground barley-ground hay-flaked maize (46:24:30 and 56:24:20, by wt respectively) in twenty-four hourly meals each day. Each of the diets was offered in successive periods of 16 d to give a feeding sequence F-S-C-S for one pair of sheep and C-S-F-S for the other pair. 2. The average composition (mol/100 mol) of the mixture of short-chain fatty acids, acetic, propionic and butyric, in the rumen was respectively 70-1, 18-5 and 7-5 with diet F, and 55-8, 24-8 and 13-6 with diet C. With diet S, the pattern of fermentation varied both between animals and in the same animal for different periods having either 'high' (28-39 mol/100 mol) or 'low' (16-21 mol/100 mol) proportions of propionic acid. On average when diet S followed diet F there was less propionic acid in the fermentation mixture than when diet S followed diet C (59-3 acetic, 22-2 propionic and 14-1 butyric as compared with 52-7, 29-4 and 13-1 respectively) but this trend was not significant and there was evidence of interactions between the feeding sequences and the individual sheep. 3. The mean concentrations of ammonia, sodium, potassium and chloride were similar for all diets but the pH and concentrations of calcium, magnesium and phosphorus tended to be higher and the buffering capacity lower for diet F than for diets C or S. In animals receiving diet S there was no relationship between the concentrations of minerals, the pH or buffering capacity and the pattern of fermentation except for ammonia, the concentration of which was high when the molar proportion of propionic acid was low. 4. Rumen volume, outflow rate and clearance rate, determined using polyethylene glycol, were higher for diet F than for diets C and S but within each diet, particularly for diet S, values varied considerably between sheep and between periods. 5. There was evidence of an interrelationship between the molar proportion of propionic acid in the fermentation products and the clearance rate, which indicated that the clearance rate may be an important factor influencing the pattern of fermentation in the rumen.     

兔尘肺模型制备与肺灌洗方法的研究

目的 为尘肺的发病机制研究、治疗提供无损伤的家兔尘肺动物模型和肺灌洗方法。方法 采用气管插管向家兔气管内注入直径≤5μm的粉尘，用改进的灌洗导管进行肺灌洗。结果 染煤尘家兔全肺多处出现点状和片状黑色尘斑，成纤维细胞增生；染矽尘家兔全部发现矽结节且有多处融合。X线摄征片证实染尘家兔两肺非不规则小阴影或片状融合阴影及类圆形阴影等。灌洗液回收率为89％－94％。结论 采用气管插管和改进的灌洗导管制备尘肺模型和进行肺灌洗，方法简便、安全、无损伤。     

Studies on the deposition of inhaled fibrous material in the respiratory tract of the rat and its subsequent clearance using radioactive tracer techniques. 1. UICC crocidolite asbestos

Radioactive tracer methods were used to study the distribution of crocidolite between the upper and lower respiratory tracts after single short inhalation exposures of the “nose only” type. With the UICC standard reference sample of crocidolite, it was found that 50 ± 5% of the deposited asbestos was in the lower respiratory tract. After 30 days the lung content of crocidolite had been reduced to 73% of the initial value. Autoradiography was used to study the distribution of asbestos within the lung immediately after exposure and after 30 days. The clearance of crocidolite from the respiratory tract was also followed by the measurement of radioactivity in faeces.     

Evaluation of the phase contrast microscopy method for the detection of fibrous and other elongated mineral particulates by comparison with a STEM technique

The USPHS/NIOSH Membrane Filter Method is used to monitor for asbestos in occupational and mining atmospheres, and employs the phase-contrast optical microscope (PCM) that under optimum conditions has a resolution of approximately 0.25 micron. While amphibole cleavage fragments are usually visible by PCM, asbestos fibers (such as amosite and chrysotile) have finer widths that may render them invisible by PCM. In this study, personal air-monitoring filters containing chrysotile, amosite and amphibole cleavage fragments from various sources have been analyzed by PCM in accordance with the USPHS/NIOSH Method and scanning transmission electron microscopy (STEM) to assess the effectiveness of the PCM technique. Each STEM specimen was prepared using a direct-transfer technique to ensure that particle size distribution and concentration were not altered. STEM results for chrysotile samples are highly variable, with 9% to 81% of regulatory particles having widths smaller than 0.25 micron--the resolution of the optical microscope. Amosite samples have 27% to 38% of regulatory particles with widths below microscope resolution, indicating that routine particle counts by PCM on these samples would underestimate true fiber content by approximately one-third. All amphibole cleavage fragment samples had regulatory particles that would be observed by PCM. Multiplication factors have been suggested for application to routine counts by PCM to more accurately assess true particle content for mineral particulates on personal air-monitoring filters.     

Energy dispersive x-ray analysis in the study of pneumoconiosis.

Identification of inorganic substances in the lung is an important step towards the establishment of a cause and effect relationship in the study of pneumoconiosis. The conventional methods for this identification usually require an ashing which makes it difficult to study the localisation of these substances in relation to pathology. A method is described to identify foreign substances in the tissue obtained either on biopsy or autopsy without destroying them. The technique employs scanning electron microscopy together with energy dispersive x-ray analysis. This method not only allows simultaneous multi-elemental analysis of over 80 elements, but also permits detailed morphological examination while the tissue is being analysed.     

Pulmonary deposition and clearance of a coal fly ash aerosol by inhalation

Wistar male rats were exposed to coal fly ash aerosols at average exposure concentration of 10.4 mg/m3 for 7 hr/day, 5 days/week for 1 month. Some rats were sacrificed just after the exposure, while others were kept for 6 or 10 months clearance time before sacrifice. There were no differences in body weight gain between fly ash exposure groups and controls. The burden of fly ash was estimated by the measurement of aluminum contents in rat organs. Aluminum concentrations in lungs of exposure groups were much higher than those of controls. No apparent deposition of fly ash was observed in the liver, kidneys, spleen, and blood, but lung burdens of up to about 0.7 mg of fly ash were found. The apparent deposition fraction was 5.1% after the 1-month exposure. The clearance rate of fly ash deposited in rat lungs may be very slow.     

Progressive massive fibrosis and simple pneumoconiosis in ex-miners.

A group of 17 738 working miners, medically examined during 1953-8, were followed up from 1974 to 1980. Of the 7118 men re-examined, 2547 were still working miners and 4526 had left the industry (45 were of unrecorded status). The incidence of progressive massive fibrosis (PMF) over an average follow up period of 22 years among men who had remained in the industry was 27 per 1000, but 94 per 1000 among men who had left. This difference was only partly related to the difference in age between the groups; for men without simple pneumoconiosis at the start of the period, and for similar age groups (45-64), the attack rate in miners was 20 per 1000 and in the ex-miners 41 per 1000. In a group of 1902 leavers who did not have PMF at a medical examination conducted at most four years before leaving, 172 had developed PMF by the time of the follow up examination. Of these, 116 had had simple pneumoconiosis at the earlier examination. Cumulative exposure to respirable dust, category of simple pneumoconiosis, and age were each found to influence the probability of developing PMF in a subgroup of the 1902 men. Among the 1902 leavers, there was no overall progression or regression of simple pneumoconiosis.     

Variation in the ratio of respirable particulates over inhalable particulates by type of dust workplace

Objective: The aim of the present study was to clarify the quantitative relationship between respirable particulates and inhalable particulates in various dust workplaces. Methods: Both respirable particulate and inhalable particulate concentrations were measured in 1644 dust workplaces by means of elutriation, and the ratio of respirable particulate mass over that of inhalable particulate (R/I ratio) was calculated for each workplace. Results: Statistical analyses showed that the R/I ratio varied substantially, depending on the type of dust work. The ratio was highest in welding workplaces (mean ± SD: 53 ± 19%) and lowest in foundries (23 ± 16%); the former value suggests that respirable particulate exposure may be underestimated in substantial parts of welding work when only the occupational exposure limit for inhalable particulates is taken for compliance testing. Conclusions: Simple compliance with the limit for inhalable particulates is not sufficient, and the limit for respirable particulates should also be simultaneously cleared. Received: 21 February 1997 / Accepted: 17 July 1997     

The relationship between coal rank and the prevalence of pneumoconiosis.

As part of the Periodic X-ray Scheme of the National Coal Board (NCB), a comparison is made between the previous and new films of all miners who were face-workers on the former occasion, five years earlier. This assessment is made by distributing the films randomly to all the NCB readers. This paper compares the rank of coal mined in each colliery with each colliery's percentage prevalence of pneumoconiosis of at least ILO category 1 in the films of previous face-workers obtained during the third survey round (1969-73). Of the NCB's 291 collieries in Britain, information enabling a rank classification to be made was available for 250, employing 62 362 face-workers. In these 250 mines a progressive and five-fold increase in prevalence was observed from collieries mining low-rank (bituminous) coal to those mining coal of high ranks (anthracite and high-grade steam and coking coal). A possible reason for this is that, in the past, high-rank collieries may have had the highest mass-concentrations of respirable dust.