Silicosis and lung cancer: a mortality study of compensated men with silicosis in New South Wales, Australia

BACKGROUND: Lung cancer mortality has been found to be in excess in several groups with silicosis, but allowance for smoking was not always possible. We investigated the lung cancer mortality in men with silicosis in New South Wales, Australia, who were compensated, making allowance for smoking habits. METHODS: A mortality study of 1467 men with silicosis in New South Wales who were compensated was carried out comparing observed mortality with that expected from the New South Wales death rates adjusting for age and period. Their smoking habits were compared with national survey smoking rates and the expected number of lung cancer deaths adjusted for smoking. Cases were coded for occupation and industry. RESULTS: The observed mortality was higher than expected, but the only site of cancer showing a significant excess was the lung. The group with silicosis had smoked more than the national rates. After adjusting for smoking the standardized mortality ratio for lung cancer was 1.9 (95% confidence interval 1.5-2.3). Although there were differences in lung cancer mortality between industries and occupations, these differences were not statistically significant. CONCLUSIONS: The excess lung cancer death rate may not be entirely due to silica exposure because compensation may have been influenced by the presence of chronic obstructive respiratory disease and there is some evidence that the presence of this disease increases lung cancer risk independently of smoking.     

Case-control study of silicosis, silica exposure, and lung cancer in white South African gold miners

A case-control study was undertaken to assess the association between lung cancer and silicosis or silica dust exposure in white South African gold miners. Cases and controls were identified from deaths reported to the Gold Miners Provident Fund for the period January, 1979-October, 1983. Two controls were matched to each case by year of birth (+/- 2 years) and by smoking (+/- 5 cigarettes or equivalents per day) assessed 10 years (+/- 2 years) prior to death. One hundred thirty-three matched triplets were identified. The results showed no overall association between lung cancer and radiological silicosis (OR = 1.08, p = 0.92). Autopsy data indicated no overall associations between lung cancer and silicosis of the lung parenchyma (OR = 1.49, p = 0.11), the pleura (OR = 0.72, p = 0.30), or the hilar glands (OR = 0.85, p = 0.72). A trend toward increased severity of silicosis of the parenchyma was evident; however, this was not statistically significant (p = 0.08). Odds ratios for lung cancer and silicosis were higher at lower levels of cumulative silica dust exposure (ORs = 2.43, 1.72, 1.35 and 0.62 for lung cancer and autopsy silicosis of the parenchyma for the lowest, second, third, and highest quartiles of dust exposure, respectively; all p greater than 0.05). Cases did not differ from controls for total silica dust exposure, length of exposure, weighted average intensity of exposure, or number of shifts at high dust (all p greater than 0.20). The data do not support the hypothesis of a carcinogenic role for silica dust and no statistically significant associations were found between lung cancer and silicosis.(ABSTRACT TRUNCATED AT 250 WORDS)     

Lung cancer among tin miners in Southeast China: Silica exposure,silicosis, and cigarette smoking

The Dachang Tin Mine is an industrial facility with high rates of lung cancer compared to the resident population in Guangxi province in southern China. Historically, exposure to silica dust was very high in the 1950s, falling in recent years to levels in keeping with international standards. Radon levels in the mine are low. We report the findings of a case-control study nested into a cohort study on miners working in Dachang. Cases of lung cancer among miners incident from 1973–1989 were obtained from local comprehensive medical records covering workers employed at the mine. These were matched approximately 3 to 1 with miners randomly chosen from the district surrounding the mine within the same birth decade. Matched odds ratios of 2.42 (95% confidence limit [CL] 1.3, 4.4) for underground employment, 3.52 (95% CL 1.7, 7.5) for smoking, and 2.04 (95%) CL 1.2, 3.7) for silicosis as determined on chest film were noted. Multi-factor analysis of unconditional logistic regression showed that among the risk factors for excess mortality from lung cancer only the years spent drilling underground and the cumulative smoking index (product of daily cigarette consumption and number of years smoking) were independent contributors to risk and there was no interaction observed. The presence of silicosis did not contribute to predicting risk independently of the years spent underground.     

Observed and predicted silicosis risks in heavy clay workers

BACKGROUND: There is increasing pressure to tighten the regulation of workers' exposures to airborne silica, which can lead to severe and in some cases rapid development of disease. However, estimated risks from respirable silica vary greatly across industries. AIM: To clarify differences in risks between workers in the heavy clay and coal industries with documented exposures to respirable silica, in order to assist decisions on whether further investigation of possible differences might be justified. METHODS: We applied a published equation for radiological risks from exposure to respirable silica, from a study of Scottish coalworkers (with unusually high exposures) to exposure estimates from an epidemiological study of heavy clay workers, by the same research team and using similar methods. RESULTS: The equation based on coalworkers' risks predicted in the heavy clay workers 31 cases of abnormalities at grade 2/1+ on the International Labour Organization scale, greatly in excess of the eight cases observed. Statistical variation is an implausible explanation (P < 0.0001). CONCLUSIONS: While there were some methodological differences between the studies, the disparity in risks provides some support for the case for further investigation of possible differences.     

Enzyme exposure, smoking and lung function in employees in the detergent industry over 20 years

This study was undertaken to examine the long term relationshipbetween lung function, smoking and exposure to enzymes in thedetergent industry. A total of 731 male workers from five locationsin the United Kingdom were subject to respiratory health surveillanceincluding lung function testing over a period of 4–20years. Exposure groups were defined by job history. Significantlydifferent rates of fall in FEV1 and FVC with time were fourtdby geographical location and by smoking habit, but there wereno consistent trends with enzyme exposure.     

Lung cancer risk, silica exposure, and silicosis in Chinese mines and pottery factories: the modifying role of other workplace lung carcinogens.

BACKGROUND: Aims of our study were to explore whether and to what extent exposure to other lung carcinogens, or staging and clinical features of silicosis modify or confound the association between silica and lung cancer. METHODS: We used data from a nested case-control study, conducted in the late 1980s in 29 Chinese mines and potteries (10 tungsten mines, 6 copper and iron mines, 4 tin mines, 8 pottery factories, and 1 clay mine), that included 316 lung cancer cases and 1,356 controls, matched by decade of birth and facility type. The previous analysis of these data presented results by type of mine or factory. RESULTS: In our study, pooling all 29 Chinese work sites, lung cancer risk showed a modest association with silica exposure. Risk did not vary after excluding subjects with silicosis or adjusting the risk estimates by radiological staging of silicosis. Strong correlation among exposures prevented a detailed evaluation of the role of individual exposures. However, lung cancer risk was for the most part absent when concomitant exposure to other workplace lung carcinogens, such as polycyclic aromatic hydrocarbons (PAHs), nickel or radon-daughters, was considered. The cross classification of lung cancer risk by categories of exposure to respirable silica and total respirable dust did not show an independent effect of total respirable dust. Silicosis showed a modest association with lung cancer, which did not vary by severity of radiological staging, or by radiological evidence of disease progression, or by level of silica exposure. However, among silicotic subjects, lung cancer risk was significantly elevated only when exposure to cadmium and PAH had occurred. CONCLUSIONS: Our results suggest that, among silica-exposed Chinese workers, numerous occupational and non-occupational risk factors interact in a complex fashion to modify lung cancer risk. Future epidemiological studies on silica and lung cancer should incorporate detailed information on exposure to other workplace lung carcinogens, total respirable dust, and on surface size and age of silica particles to understand whether and to what extent they affect the carcinogenic potential of silica.     

Continued exposure to silica after diagnosis of silicosis in Brazilian gold miners

BACKGROUND: There is a paucity of studies analyzing the effect of continued silica exposure after the onset of silicosis with regard to disease progression. The present study investigates differences in clinical and radiological presentation of silicosis among former workers with a diagnosis of silicosis, and compares workers who continued to be exposed to silica with those who stopped silica exposure after having received their diagnosis. METHODS: A sample of 83 former gold miners with a median of 21 years from the first diagnoses of silicosis, had their clinical and occupational histories taken and underwent both chest radiography (International Labor Organization standards) and spirometry. Their silica exposure was assessed and an exposure index was created. The main outcome was the radiological severity of silicosis and tuberculosis (TB). The statistical analysis was done by multiple logistic regression. RESULTS: Among the 83 miners, 44 had continued exposed to silica after being diagnosed with silicosis. Continuation of silica exposure was associated with advanced radiological images of silicosis (X-ray classification in category 3, OR = 6.42, 95% CI = 1.20-34.27), presence of coalescence and/or large opacities (OR = 3.85, CI = 1.07-13.93), and TB (OR = 4.61, 95% CI = 1.14-18.71). CONCLUSIONS: Differential survival is unlikely to explain observed differences in silicosis progression. Results reinforce the recommendation that silica exposure should be halted at an early stage whenever X-ray is suggestive of the disease.     

Radiographic silicosis and lung cancer risk among workers in Ontario

A case-control study, nested in a cohort of workers under surveillance for silicosis in 1979 or later, was undertaken to assess lung cancer risk in relation to the ILO coding scheme for the pneumoconioses. The subjects of this study are from the 41 matched quartets, consisting of one worker with silicosis and three age-matched controls, in which a lung cancer case was diagnosed. The odds ratio for lung cancer among subjects with ILO classification 1/0 or more, in comparison to subjects with category ≤ 0/1, was 3.27 (95%CI = 1.32–8.2). Adjustment of the radiographic risk for the effect of cumulative radon exposure had the effect of increasing the odds ratio for the association between ILO category ⩾1/0 and lung cancer. Although small smoking differences could account for the increased lung cancer odds ratio among workers with silicosis, the empirical evidence suggests that these smoking differences do not exist. It is concluded on the basis of two North American studies of silica exposed workers that radiographic silicosis is a marker for an increased risk of lung cancer. Am. J. Ind. Med. 34:244–251, 1998. © 1998 Wiley-Liss, Inc.     

Joint effects of smoking, noise exposure and age on hearing loss

BACKGROUND: Smoking has been shown to have adverse effects on hearing, but it's unclear whether smoking interacts with known causes of hearing loss such as noise exposure and ageing. AIMS: To examine the hypothesis that smoking, noise and age jointly affect hearing acuity. METHODS: This cross-sectional study was carried out in 535 male adult workers of a metal processing factory. Pure-tone audiometric tests were utilized to assess hearing loss. Noise exposure assessment was based on a job exposure matrix constructed with industrial hygienist scoring and job titles. Each participant answered questionnaires about socio-demographic, life-style, occupational and health-related data. Analysis of the possible underlying biological model was undertaken assessing departures from additivity using measures of the size of the interaction present. RESULTS: Age and occupational noise exposures were, separately, positively associated with hearing loss. For all the factors combined the estimated effect on hearing loss was higher than the sum of the effects from each isolated variable, especially for smoking and noise among those 20-40 years of age, and for smoking and age among those non-exposed to occupational noise. CONCLUSIONS: The synergistic effect of smoking, noise exposure and age on hearing loss, found in this study, is consistent with the biological interaction. Furthermore, it is possible that distinct ototoxic substances in the chemical composition of mainstream smoke may synergistically affect hearing when in combination with noise exposure, which needs to be examined in future studies.     

钨矿矽尘,矽肺与肺癌关系再探讨

同济医科大学、美国国家癌症研究所进行的矽尘、矽肺与肺癌研究,１９８９年曾作初步结论。因上述研究观察时间尚嫌稍短,全队列成员平均年龄才５０．９岁,尚未完全进入肺癌发病的高峰期,为了进一步论证这个课题,在原有基础上对队列成员继续观察到１９９４年底为止。此时全队列成员７２％超过５０岁,平均年龄５５．４岁,已经超过肺癌发病的平均年龄。统计资料表明,按所接触的低、中、高等不同浓度的粉尘,矽肺死亡的ＳＭＲ分别     

Silica exposure, silicosis, and lung cancer: a necropsy study

Recent studies of the association between lung cancer and silicosis and silica dust have been inconclusive; some showing positive association and some showing none. The present study matched 231 cases of lung cancer with 318 controls by year of birth. Subjects were selected from the necropsy records of the National Centre for Occupational Health. Data on intensity and duration of exposure to silica dust were obtained from personnel records. Presence or absence of lung cancer and the presence and severity of silicosis of the parenchyma, pleura, and hilar glands were documented from necropsy reports. Smoking data were abstracted from records of routine examinations. No case-control differences were noted for any of the exposure indicators including cumulative dust exposure, total dusty shifts, weighted average intensity of exposure, total underground shifts, and shifts in high dust. Similarly, no association was found between lung cancer and the presence or severity of silicosis and any site. Stratified analyses showed neither significant nor suggestive trends when case-control comparisons for silicosis were examined by level of dust exposure or smoking. Reasons for disparity between these results and those of some other studies may include concomitant exposures to radon daughters, asbestos, diesel emissions, and cigarette smoking; idiosyncracies of the compensation process; and the possibility of a threshold in the relation(s).     

Silica exposure, silicosis, and lung cancer: a necropsy study.

Recent studies of the association between lung cancer and silicosis and silica dust have been inconclusive; some showing positive association and some showing none. The present study matched 231 cases of lung cancer with 318 controls by year of birth. Subjects were selected from the necropsy records of the National Centre for Occupational Health. Data on intensity and duration of exposure to silica dust were obtained from personnel records. Presence or absence of lung cancer and the presence and severity of silicosis of the parenchyma, pleura, and hilar glands were documented from necropsy reports. Smoking data were abstracted from records of routine examinations. No case-control differences were noted for any of the exposure indicators including cumulative dust exposure, total dusty shifts, weighted average intensity of exposure, total underground shifts, and shifts in high dust. Similarly, no association was found between lung cancer and the presence or severity of silicosis and any site. Stratified analyses showed neither significant nor suggestive trends when case-control comparisons for silicosis were examined by level of dust exposure or smoking. Reasons for disparity between these results and those of some other studies may include concomitant exposures to radon daughters, asbestos, diesel emissions, and cigarette smoking; idiosyncracies of the compensation process; and the possibility of a threshold in the relation(s).     

One agent, many diseases: exposure-response data and comparative risks of different outcomes following silica exposure

BACKGROUND: Evidence in recent years indicates that silica causes lung cancer, and probably renal disease, in addition to its well-known relationship to silicosis. There is also suggestive evidence that silica can cause arthritis and other auto-immune diseases. Silica has, therefore, joined a handful of other toxic exposures such as tobacco smoke, dioxin, and asbestos which cause multiple serious diseases. METHODS: The available exposure-response data for silica and silicosis, lung cancer, and renal disease are reviewed. We compare the corresponding excess risks (or absolute risks in the case of silicosis) of death or disease incidence by age 75 for these three diseases, subsequent to a lifetime (45 years) of exposure to silica at current US standard (0.1 mg/m(3) respirable crystalline silica). RESULTS: The absolute risk of silicosis, as defined by small opacities greater than or equal to ILO classification 1/1 on an X-ray, ranges from 47% to 77% in three cohort studies with adequate follow-up after employment. The absolute risk of death from silicosis is estimated at 1.9% (0.8%-2.9%), based on a pooled analysis of six cohort studies. The excess risk of lung cancer death, assuming US male background rates, is 1.7% (0.2%-3.6%), based on a pooled analysis of ten cohort studies. The excess risk of end-stage renal disease (assuming male background rates) is 5.1% (2.2%-7.3%), based on a single cohort. The excess risk of death from renal disease is estimated to be 1.8% (0.8%-9.7%), based on a pooled analysis of three cohorts. CONCLUSIONS: Keeping in mind that the usual OSHA acceptable excess risk of serious disease or death for workers is 0.1%, it is clear that the current standard is far from sufficiently protective of workers' health. Perhaps surprisingly, kidney disease emerges as perhaps a higher risk than either mortality from silicosis or lung cancer, although the data are based on fewer studies.     

Silica exposure and silicosis among Ontario hardrock miners: I. Methodology

An epidemiological investigation was undertaken to determine the relationship between silicosis in hardrock miners in Ontario and cumulative exposure to silica (crystalline silica--alpha quartz) dust. This first report describes the cohort, the method of classifying the radiographs, and the identification of a case of silicosis.     

Silica exposure and silicosis among Ontario hardrock miners: II. Exposure estimates

An epidemiological investigation was carried out to determine the relationship between silicosis in hardrock miners in Ontario and cumulative exposure to silica (free crystalline silica--alpha quartz) dust. This second report describes a side-by-side air-sampling program used to derive a konimeter/gravimetric silica conversion curve. A total of 2,360 filter samples and 90,000 konimeter samples were taken over 2 years in two mines representing the ore types gold and uranium, both in existing conditions as well as in an experimental stope in which dry drilling was used to simulate the high dust conditions of the past. The method of calculating cumulative respirable silica exposure indices for each miner is reported.     

Occupational lung diseases and global occupational health on the Net

Occupational lung disease is a major area of concern in occupationalhealth, exhibiting a diverse panorama across countries. Whilepneumoconiosis is deemed to be the most common occupationaldisease in many developing countries, emphasis is shifting towardsasbestos-related lung diseases and occupational asthma in industrializedcountries. Following the Occupational Health for All strategiesset forth by the World Health Organization, we propose thata model system based upon the Global Health Network can serveas an effective vehicle towards the prevention of occupationallung diseases on a global scale. It has the potential to: (1)enhance transmission of data and collaboration with the primaryhealth care system in disease surveillance; (2) strengthen researchand information transfer and (3) promote education and trainingat all levels of prevention, with a possible application tothe interpretation of chest radiograms.