Comparison of radiographic appearances with associated pathology and lung dust content in a group of coalworkers

The pathology and dust content of lungs from 261 coalminers in relation to the appearances of their chest radiographs taken within four years of death were examined. Radiological opacities of coalworkers' pneumoconiosis were more profuse the more dust was retained in lungs. Among the men who had mined low rank coal--that is, with a relatively high proportion of ash--the increase in profusion was most closely related to the ash component of the dust, whereas in men who had mined high rank coal both coal and ash increased in the lungs in relation to radiological profusion. The fine p type of opacity was found to be associated with more dust and a higher proportion of coal and less ash than the nodular r opacity, and was also more likely to be associated with emphysema. The pathological basis of the different types of opacity found on the radiographs of coalminers related to the number, size, and nodularity of the dust lesions. Larger fibrotic lesions were likely to appear as r opacities, whereas fine reticular dust deposition was most likely to present as p opacities, q opacities showing a mixture of appearances. The study has shown that the composition of dust retained in the lung, as well as its amount, makes an important contribution to the radiographic appearances of pneumoconiosis. In particular, the r type of lesion on the radiograph of a low rank coalminer indicates the possibility of a silicotic like lesion.     

Dust exposure, dust recovered from the lung, and associated pathology in a group of British coalminers

The relation between dust exposure, retained lung dust, and pneumoconiosis have been examined in 430 dead coalminers who had participated in a large scale epidemiological survey of respiratory health. The men were divided into three groups depending on the presence of particular lesions in their lungs. Lungs containing no fibrotic lesions in excess of 1 mm were included in the "M" group, those with fibrotic lesions of between 1 mm and 9 mm in diameter were included in the "F" group, and those with any lesion 10 mm or more were categorised as having progressive massive fibrosis (PMF). The men were further divided into four groups according to the rank of coal mined at the colliery of employment. The mean weight of lung dust increased over the pathological range (M----F----PMF) regardless of the rank of coal mined. The men with PMF had not received unusually high exposures to dust in life but were found to have accumulated more dust in their lungs per unit of dust exposure than men without PMF, providing further evidence for differences in the patterns of deposition or clearance, or both, of dust in these men compared with those who do not develop PMF. For men who had mined the higher rank coals there was no difference in the composition of the lung dust between the pathological groups. Lungs from men mining low rank coal, however, showed a striking increase in the proportion of ash over the pathological groups (M, F, and PMF). In men who had mined low rank coal the proportion of ash in the airborne dust to which they had been exposed and in the dust retained in their lungs was, as expected, greater than in men who had worked with higher rank coals. For the same men, and particularly associated with the presence of some dust related fibrosis, the proportion of ash in retained dust was higher than that in the dust to which the men were exposed suggesting the occurrence of selective deposition or retention of the mineral components of dust in this group.     

Dust exposure, dust recovered from the lung, and associated pathology in a group of British coalminers.

The relation between dust exposure, retained lung dust, and pneumoconiosis have been examined in 430 dead coalminers who had participated in a large scale epidemiological survey of respiratory health. The men were divided into three groups depending on the presence of particular lesions in their lungs. Lungs containing no fibrotic lesions in excess of 1 mm were included in the "M" group, those with fibrotic lesions of between 1 mm and 9 mm in diameter were included in the "F" group, and those with any lesion 10 mm or more were categorised as having progressive massive fibrosis (PMF). The men were further divided into four groups according to the rank of coal mined at the colliery of employment. The mean weight of lung dust increased over the pathological range (M----F----PMF) regardless of the rank of coal mined. The men with PMF had not received unusually high exposures to dust in life but were found to have accumulated more dust in their lungs per unit of dust exposure than men without PMF, providing further evidence for differences in the patterns of deposition or clearance, or both, of dust in these men compared with those who do not develop PMF. For men who had mined the higher rank coals there was no difference in the composition of the lung dust between the pathological groups. Lungs from men mining low rank coal, however, showed a striking increase in the proportion of ash over the pathological groups (M, F, and PMF). In men who had mined low rank coal the proportion of ash in the airborne dust to which they had been exposed and in the dust retained in their lungs was, as expected, greater than in men who had worked with higher rank coals. For the same men, and particularly associated with the presence of some dust related fibrosis, the proportion of ash in retained dust was higher than that in the dust to which the men were exposed suggesting the occurrence of selective deposition or retention of the mineral components of dust in this group.     

Classification of progressive massive fibrosis of coalminers by type of radiographic appearance.

In a pilot study the chest radiographic appearances of 112 coalminers who developed progressive massive fibrosis (PMF) over an 11 year period have been classified into six types based on the appearances of the large radiographic opacities. The most common type of PMF was one or more large shadows of homogeneous radiodensity. Less common types included markedly rounded shadows usually less than 3 cm in diameter, non-homogeneous shadows appearing to consist of conglomerations of small rounded opacities, and condensations of linear or streaky shadows. Good reproducibility by one reader between two readings were obtained. The lifetime exposures to mixed respirable coal mine dust, and to its quartz component, of these 112 men were compared with those of control subjects matched for age and starting category of simple pneumoconiosis but without PMF. Overall, the men with PMF had been exposed to more mixed dust than controls, confirming that one of the reasons some men with simple pneumoconiosis develop PMF is that they have inhaled more dust than others. Eleven of the 112 cases had large opacities that were not homogeneous and appeared to consist of conglomerations of "r" type small rounded opacities. The average quartz exposures of these men were much higher than in control subjects, suggesting that in this type of PMF quartz was an important causative factor.     

Irregularly shaped small shadows on chest radiographs, dust exposure, and lung function in coalworkers' pneumoconiosis.

The predominant shapes of small opacities on the chest radiographs of 895 British coalminers have been studied. The aims were to determine whether irregular (as distinct from rounded) small opacities can be identified reproducibly, whether their occurrence is related to dust exposure, and whether they are associated with excess prevalence of respiratory symptoms or impairments of lung function. Six of the doctors responsible for regular radiological surveys of all British coalminers each classified all 895 radiographs twice and independently, using the International Labour Organisation's 1980 classification system. The majority view was that 39 films showed predominantly irregular small opacities, 131 showed predominantly small rounded opacities, and 587 showed no small opacities. Readers' opinions varied about the presence and shapes of shadows on the other 138 films. In general, consistency between readers (and within readers on repeated viewings) was satisfactory. The occurrence and profusion of irregular shadows were related significantly both to the men's ages and additionally to their cumulative exposure to respirable coalmine dust as determined from 15 years' dust monitoring close to where the miners had worked. For any given level of exposure, the average level of profusion of the small irregular opacities was less than the corresponding profusion of small rounded opacities. The prevalence rates of chronic cough and phlegm, and of breathlessness, were higher in those with small irregular opacities than in those with no small opacities (category 0/0), but the differences were not statistically significant after adjustment for other factors including smoking habits. The presence of irregular (but not rounded) small shadows was associated with an impairment in respiratory function averaging about 190 ml deficits in both FEV1 and FVC. These deficits were not explicable in terms of the men's ages, body sizes, and smoking habits and they were in addition to the lung function losses attributable to the miners' dust exposure as such. It is concluded that the presence and profusion of small irregular opacities should be taken into consideration when assessing the severity of coalworkers' simple pneumoconiosis.     

Irregularly shaped small shadows on chest radiographs, dust exposure, and lung function in coalworkers' pneumoconiosis

The predominant shapes of small opacities on the chest radiographs of 895 British coalminers have been studied. The aims were to determine whether irregular (as distinct from rounded) small opacities can be identified reproducibly, whether their occurrence is related to dust exposure, and whether they are associated with excess prevalence of respiratory symptoms or impairments of lung function. Six of the doctors responsible for regular radiological surveys of all British coalminers each classified all 895 radiographs twice and independently, using the International Labour Organisation's 1980 classification system. The majority view was that 39 films showed predominantly irregular small opacities, 131 showed predominantly small rounded opacities, and 587 showed no small opacities. Readers' opinions varied about the presence and shapes of shadows on the other 138 films. In general, consistency between readers (and within readers on repeated viewings) was satisfactory. The occurrence and profusion of irregular shadows were related significantly both to the men's ages and additionally to their cumulative exposure to respirable coalmine dust as determined from 15 years' dust monitoring close to where the miners had worked. For any given level of exposure, the average level of profusion of the small irregular opacities was less than the corresponding profusion of small rounded opacities. The prevalence rates of chronic cough and phlegm, and of breathlessness, were higher in those with small irregular opacities than in those with no small opacities (category 0/0), but the differences were not statistically significant after adjustment for other factors including smoking habits. The presence of irregular (but not rounded) small shadows was associated with an impairment in respiratory function averaging about 190 ml deficits in both FEV1 and FVC. These deficits were not explicable in terms of the men's ages, body sizes, and smoking habits and they were in addition to the lung function losses attributable to the miners' dust exposure as such. It is concluded that the presence and profusion of small irregular opacities should be taken into consideration when assessing the severity of coalworkers' simple pneumoconiosis.     

Coalworkers' pneumoconiosis: correlation between opacity profusion and number and type of dust lesions with special reference to opacity type.

The relation between the profusion and predominant type of small rounded opacities on chest radiographs taken within four years of death and the postmortem counts of dust lesions in four classes (macules, "pinhead" fibrotic nodules, nodules 1-3 mm, and nodules greater than 3-9 mm in diameter) has been examined for 71 coalworkers without progressive massive fibrosis. The radiographs were categorised by four readers independently, according to the ILO classification. For subjects considered by each reader to present predominantly p type opacities, increasing opacity profusion was exclusively and significantly associated with an increase in the number of pinhead fibrotic nodules. Numbers of nodules measuring 1-3 mm and greater than 3-9 mm in diameter both showed significant linear associations with opacity profusion category in subjects presenting predominantly q opacities, the closer association being observed with the smaller lesions. These observations held true for all readers. Opacities of type r were rarely considered to be the predominant type. For the reader who recorded the maximum number of such cases, opacity profusion was not significantly related to the numbers of dust lesions in any of the lesion classes. Nevertheless, the closest association was observed with nodules measuring greater than 3-9 mm in diameter. An overall significant linear association between total lung dust content and opacity profusion was found to be due mainly to subjects presenting predominantly p type opacities and to a lesser extent to those with predominantly q opacities.     

直读数字式摄影应用于尘肺病诊断的可行性研究

[目的]研究直读数字式摄影（DR）和传统胶片-增感屏（FSR）摄影对尘肺病小阴影形态和密集度辨识的可比性与一致性,评估直接读出DR胸片摄影技术在尘肺病诊断中的可行性和技术关键。[方法]以204名尘肺病人和31名粉尘作业工人为研究对象,同期拍摄FSR片和DR片,对FSR片和从显示器直接读取DR片的胸片质量、小阴影形态、肺区小阴影密集度和大阴影的检出率进行比较分析。[结果]FSR废片率明显较DR高（P〈0.001）;两种胸片在判定肺区小阴影密集度上有较好的一致性（κ=0.77）,从上肺区（κ=0.82）、中肺区（κ=0.75）到下肺区（κ=0.68）一致性略有降低;两种胸片对小阴影形态的判定没有明显差异（FSR 93.2%,DR 90.0%,P〉0.05）;对大阴影的识别表现一致（22.9%,44/192）。[结论]DR胸片质量优于FSR胸片,在尘肺病小阴影形态、密集度的判定和大阴影的识别上与FSR相似。     

尘肺诊断中读片差异的分析

目的 研究尘肺诊断中由于X射线胸片读片者的个体差异对诊断的影响及产生差异的主要原因,为提高尘肺病诊断质量提供依据。方法 选择240张不同尘肺期别的高仟伏X射线胸片制作5套复制片,在规范一致的读片条件下由7位有多年尘肺病诊断经验的医师阅凑,读片结果按统一格式记录于读片记录表内,将小阴影密集度与尘肺病诊断期别分别量化计分,分析7位读片者读片结果的差异。结果 7位读片者间在小阴影总体密集度、肺区平均密集度、尘肺诊断期别判定上的变异系数分别为15.17％、15.91％、12.06％;对有无小阴影、有无大阴影和小阴影聚集的判断,读片者之间的一致性较高,分别为91.09％、91.93％和76.41％。胸片技术质量一级或二级对于读片结果没有明显影响。形态判定一致的圆形小阴影或不规则小阴影,在总体密集度和分期上判定的一致性较好;形态判断差异较大的小阴影,则对密集度和期别判断的差异均较大。结论 在不同读片者间存在着读片差异。在控制了外部条件后,读片者之间的读片差异主要来自于对小阴影形态判断的差异。     

CT和高分辨CT对煤工尘肺小阴影和阴影融合及肺气肿诊断的价值

目的 探讨CT和高分辨CT(HRCT)早期检测煤工尘肺小阴影、阴影融合与肺气肿的敏感性和准确性.方法 77例煤工尘肺患者、36例无尘肺煤工和37例健康非煤工接受多层螺旋CT机无间隔胸部容积扫描及HRCT扫描,对所获得的CT图像进行煤工尘肺小阴影密集度分级、平均肺密度值和肺气肿指数测定,并与其X线胸片诊断结果对照.结果 对77例煤工尘肺患者CT和HRCT诊断的尘肺小阴影密集度分级与X线胸片尘肺分期一致性较好(Kappa=0.771,P＜0.01).CT和HRCT诊断尘肺的敏感性达到98.70％,在X线胸片确诊的77例煤工尘肺患者中,CT和HRCT评估76例为煤工尘肺,可疑1例.CT和HRCT从36例X线胸片无尘肺煤工中检出8例(22.22％)达到小阴影密集度1级;从73例Ⅰ～Ⅱ期煤工尘肺患者中,检出26例(35.62％)阴影密集度≥3级,其中3级密集度阴影20例,4级密集度阴影6例;对4例X线胸片Ⅲ期煤工尘肺患者,CT和HRCT与X线胸片诊断结果相同.从113例煤工中,X线胸片检出肺气肿7例(6.19％),CT检出36例(31.86％).CT尘肺小阴影密集度1～2级组的CT平均肺密度值最高,明显高于健康对照组、无尘肺组和小阴影密集度4级组,差异有统计学意义(F1=-45.73、F2=-23.00和F3=57.72,P＜0.01或P＜0.05).结论 从多层螺旋CT获得的CT和HRCT影像,与X线胸片比较,对煤工尘肺小阴影、阴影融合与肺气肿识别的敏感性和准确性均较高,可为煤工尘肺及其并发症的早期诊断提供更先进的手段.     

Relation between content and composition of coalworkers'' lungs and radiological appearances

Rossiter, C. E. (1972).Brit. J. industr. Med.,29, 31-44. Relation between content and composition of coalworkers' lungs and radiological appearances. The relation between radiological category of simple pneumoconiosis and dust content of the lung has been studied on a mixed group of 221 miners, of whom 76 had progressive massive fibrosis radiologically.

The average radiological scores based on 11 independent readings for the films showing simple pneumoconiosis only were related, by multiple regression, to the coal, mineral, quartz, and iron contents of the lungs. Three subgroups were found which showed differing relations. Films of poor technique tended to be read in the middle categories whatever the content of the lungs. The lungs of Scottish miners all contained soot, from working in naked light pits, and their radiological scores were much higher than expected from the lung dust contents. The few films showing nodular sized small opacities were also over-read, suggesting that nodularity may be some response to dust other than simple accumulation. There were 98 subjects in the resulting homogeneous group of cases with simple pneumoconiosis only. On a revised scale to correct for slight non-linearity, the regression coefficients of radiological score on the total mineral and coal contents of the lung were in the ratio of 3·8 to 1. The iron content did not add much to this regression relation even though by itself it correlated well with the amount of simple pneumoconiosis. Probably most of the variation of radiological appearance with iron reflects variation with coal and mineral. The mineral and quartz contents were highly correlated (r = 0·96), but relations including quartz were not as close fitting as those including mineral. There was a small, but significant, residual relation of radiological score to years in coalmining.

The background categories of simple pneumoconiosis in the 76 radiographs showing some evidence of progressive massive fibrosis were generally read higher than expected from the relation to dust content derived from the simple pneumoconiosis cases only. This was most true for those showing most evidence of progressive massive fibrosis.

     

Lung disorders of workers exposed to rush smear dust in China

The aim of this study was to evaluate the lung disorders of the workers exposed to rush smear dust. A cross sectional study was carried out on 1,709 current workers (788 male, 921 female) in 80 factories. All subjects were asked by questionnaire, and health examination including chest X-ray was conducted for 661 workers in 35 factories. Lung function test was also examined for 119 non-smoking males among 661 subjects. Dust samplings were collected and total and respirable dust concentrations at 127 spots in 35 factories were measured. The geometric mean dust concentration in the workshops was up to 20.00 mg/m(3), and the geometric mean respirable dust concentration reached 8.22 mg/m(3). The mean quartz concentration of accumulated dust was 29.2%. The prevalence of radiographic small opacities profusion category > or = 1/0, according to the ILO 1980 Classification System, was 2.6% among 661 employees. One worker was found to have pneumoconiotic findings of 2/2 profusion accompanied with large opacity. The prevalence of pneumoconiosis (1/0 or more) correlated with cumulative dust exposure (r=0.192, p<0.0001). The similar relationship was found between the prevalence rate of cough or sputa and worksite dust concentration. In non-smokers, a positive association was found between the prevalence of cough and occupational exposure duration (r=0.080, p=0.004). Approximately 19.3% and 34.5% of employees suffered from respiratory impairment for FVC and FEV1.0, respectively. This is the first report of "rush" pneumoconiosis in China. Rush mat workers were found to be at high risk for pneumoconiosis, a preventable disease. Our results showed a dose-response relationship between rush-mat dust level and the prevalence of pneumoconiosis. Similar relationship between the prevalence of cough and sputum and the work duration was found for non-smoking workers but not for smoking workers.     

Relationship between type of simple coalworkers'' pneumoconiosis and lung function. A nine-year follow-up study of subjects with small rounded opacities.

One hundred and twenty-five men who were identified in 1968 as having the simple pneumoconiosis of coalworkers were re-examined nine years later when their mean age was 59.6 years. On both occasions the lung function and response to exercise were assessed. There was no evidence for progression of simple pneumoconiosis between the surveys, but 14 had developed small irregular opacities on their chest radiographs and 28 showed early changes of progressive massive fibrosis (PMF). After allowing for the effects of smoking and of exposure to coal dust, subjects with both p and r types of simple pneumoconiosis exhibited a reduced transfer factor compared with subjects having q-type opacities; subjects with r-type opacities also showed an increased pulmonary elastic recoil pressure. The presence of irregular opacities, independent of rounded opacities, was associated with a low transfer factor and decreased slope of phase III of the single breath oxygen test. Subjects who developed PMF between 1968 and 1978 had p or r opacities more often than q opacities: these subjects had an increase pulmonary elastic recoil pressure. The development of PMF was also associated with physiological evidence of airways obstruction. The changes in subjects with r opacities are consistent with the presence of space occupying lesions that may progress to PMF. Subjects with p opacities have physiological evidence of emphysema as do some subjects with established PMF. Irregular opacities may reflect the presence of both emphysema and diffuse fibrosis. There is need for more morbid anatomical evidence on the underlying pathology.     

Radiographic abnormalities among construction workers exposed to quartz containing dust

Background: Construction workers are exposed to quartz containing respirable dust, at levels that may cause fibrosis in the lungs. Studies so far have not established a dose-response relation for radiographic abnormalities for this occupational group.

Aims: To measure the extent of radiographic abnormalities among construction workers primarily exposed to quartz containing respirable dust.

Methods: A cross sectional study on radiographic abnormalities indicative of pneumoconiosis was conducted among 1339 construction workers mainly involved in grinding, (jack)-hammering, drilling, cutting, sawing, and polishing. Radiological abnormalities were determined by median results of the 1980 International Labour Organisation system of three certified "B" readers. Questionnaires were used for assessment of occupational history, presence of respiratory diseases, and symptoms and smoking habits.

Results: An abnormality of ILO profusion category 1/0 and greater was observed on 10.2% of the chest radiographs, and profusion category of 1/1 or greater on 2.9% of the radiographs. The average duration of exposure of this group was 19 years and the average age was 42. The predominant type of small opacities (irregularly shaped) is presumably indicative of mixed dust pneumoconiosis. The prevalence of early signs of nodular silicosis (small rounded opacities of category 1/0 or greater) was low (0.8%).

Conclusions: The study suggests an elevated risk of radiographic abnormalities among these workers with expected high exposure. An association between radiographic abnormalities and cumulative exposure to quartz containing dust from construction sites was observed, after correction for potentially confounding variables.

     

Correlation of Radiological Category with Lung Pathology in Coal-workers' Pneumoconiosis

The relation between the macroscopic pathology of the lungs of coal-workers and the radiological category of pneumoconiosis on a chest film taken not more than two years before death has been investigated in 238 coal-miners in South Wales. Large lung sections were shown to provide more accurate and convenient material than wet lungs for this comparison and were used to assess the number and character of dust foci and the degree of emphysema. The profusion of dust foci was classified into four grades—very sparse, sparse, moderate, and numerous—using standard lung sections. Emphysema was graded slight, moderate, and severe. The chest radiographs were categorized according to the I.L.O. Classification, 1953.     

蔺草染土粉尘对工人健康影响的研究

目的　研究蔺草染土粉尘对工人健康的影响。方法　采用横断面整群抽样 ,对所选工厂进行劳动卫生学调查 ,并对 6 6 1名作业工人进行问卷和健康检查。结果　蔺草加工业主要引起严重的粉尘污染 ,总尘平均浓度为 2 0 .0 0mg/m3 ,呼吸性粉尘平均浓度为 8.2 2mg/m3 。车间积尘平均游离SiO2 含量为 2 5 .6 %。在作业工人中发现Ⅰ期及以上蔺草染土尘肺 9例 [其中Ⅱ期 1例 (小阴影聚集 ) ]、0 + 8例 ;X线胸片阳性 (1/0以上 )检出率为 2 .5 7%,与接尘工龄、粉尘浓度密切相关 (分别为r =1.15 6 ,P <0 .0 0 1;r =0 .10 6 ,P =0 .0 0 6 ) ;咳嗽、咯痰等症状与接触蔺草染土粉尘有趋势相关 (分别为r=0 .0 85 ,P =0 .0 2 8;r=0 .0 94,P =0 .0 16 )。结论　蔺草染土尘肺在我国首次报道 ,作业工人肺X线胸片阳性检出率与接触蔺草染土粉尘存在一定的剂量 -效应关系 ;工人咳嗽、咯痰与粉尘接触有关。蔺草染土致尘肺的机制有待于进一步调查。     

Radiological progression and its predictive risk factors in silicosis

OBJECTIVES—To investigate the risk factors predicting radiological progression in silicosis in a prospective cohort study of patients with silicosis who were previously exposed to silica from granite dust.METHODS—From among a total of 260 patients with silicosis contracted from granite work, 141 with available serial chest x ray films of acceptable quality taken over a period of 2 to 17 (mean 7.5) years, were selected for study. Ninety four (66.7%) had ended exposure 5 or more years perviously (mean 10.1 years, maximum 28 years). Radiological progression was assessed by paired comparison of the initial and most recent radiographs, with two or more steps of increase in profusion of small opacities according to the 12 point scale of the International Labour Organisation (ILO) classification of radiographs of pneumoconiosis, taken from the majority reading by a panel of three independent readers.RESULTS—Overall, 37% of patients with silicosis had radiological evidence of progression. From the initial radiographs, 24 (31.6%) of those with radiological profusion category 1, 15 (37.5%) of those with radiological profusion category 2, and 13 (52%) of those with complicated silicosis (including all seven with category 3 profusion of small opacities) showed radiological progression. As expected, progression was more likely to be found after longer periods of follow up (the interval between the two chest x ray films) with a 20% increased odds of progression for every additional year of follow up. After adjustment for varying intervals of follow up, the probability of radiological progression was found to be significant if large opacities were present in the initial chest x ray film. Progression was also less likely to be found among those who had ended exposure to silica longer ago, although the result was of borderline significance (p=0.07). Tuberculosis was also associated with increased likelihood of progression (borderline significance).CONCLUSIONS—There is a high probability of radiological progression in silicosis after high levels of exposure to granite dust among workers who were followed up for up to 17 years. A significant risk factor is the extent of radiological opacities in the initial chest x ray film. The probability of progression is also likely to be reduced with longer periods after the end of exposure.     

尘肺诊断标准中小阴影密集度的应用价值

目的探讨尘肺诊断标准中小阴影密集度的应用价值。方法采用职业流行病学的方法,参照1980ILO国际尘肺X线影像分类指南,分析比较了太钢耐火厂不同时期接尘工人X线胸片小阴影密集度小级的发生率、发生密度及其与工龄的关系。同时,选择了接触煤矽尘工人的X线胸片与之比较其胸片小阴影密集度小级的发展速度和特点。结果①不同时期接尘工人胸片小阴影密集度小级的发生率不同,统计学检验P＜0．05。②胸片小阴影密集度随工龄延长而呈现出由低到高的上升趋势。③接触不同性质粉尘的工人其小阴影密集度小级的晋级速度不同。结论小阴影密集度是观察尘肺发生发展、评价生产环境的质量和估测接触粉尘性质的指标。