不同类型厂矿接尘工人肺癌病因学研究──矽尘或矽肺与肺癌的关系

为评价游离二氧化硅（简称矽尘或ＳｉＯ２）是否致肺癌？矽肺是否是肺癌前变基础？选择四类接尘厂矿进行队列和队列内病例对照研究。队列对象６８２８５人。有矽肺６４８７例，肺癌３３０例（男３１９，女１１），配对照１３５８例。根据厂矿历年工业卫生记录和近期对已知致癌物监测结果，定量评估了每个对象的接尘水平及每个病例对照的累积接触量。研究对象追访到１９８９年底，死亡６１９２人。与全国居民死亡平均数计算的期望值近似。全死因中癌症是第一死因，但全癌低于国家居民死亡率。分析结果说明：（１）矽尘单独存在时不是肺致癌剂。肺癌不超高，与接尘关系不明显；（２）在６４８７名矽肺队列中，肺癌相对危险度仅比非矽肺高０．２２倍，主要反应在铜铁矿工人中（Ｒ＝２．２），而矽肺患病率最严重的钨矿工人，其肺癌危险度反而随接尘水平上升而下降，再则肺癌死亡率与矽肺期别不呈正比；形态学上观察也不支持肺癌病变与矽肺纤维化病变相关。本研究结果难以支持矽尘或矽肺与肺癌病因学相关的假说。     

职业接触粉尘及吸烟对死亡影响的前瞻性队列研究

目的 研究接尘和吸烟对死亡的影响。方法 以1989－1992年广州实施并建立的职工职业健康监护档案为基础资料，选年龄≥30岁的接尘工人和无任何粉尘及其他有害物质接触的职工（对照组）61648名为研究对象，进行前瞻性队列研究。结果 （1）队列失访28例，死亡1186例，以恶性肿瘤死亡为主；（2）本队列男性多于女性，年龄35－44岁，主要为工人，中学文化，已婚，率42．2％，饮酒率32．8％；（3）调整相应混杂因素后，全死因、恶性肿瘤和呼吸系疾病死亡接尘者相对危险度（RR）分别为1．24、1．34和1．96，与对照组比较，差异均有显著性（P＜0．01），吸烟者RR分别为1．16、1．37和1．63，与不吸烟者比，前二者差异有显著性（P＜0．01）；既接尘又吸烟者上述相应死因死亡1RR分别为1．48、1．85和3．12，明显高于单纯接尘或单纯吸烟者，差异有显著性（P＜0．01）；（4）接尘对死亡的影响主要表现在职业接触矽尘和木尘。结论 接尘与吸烟均可致死亡危险性增加，并存在协同作用。     

接尘、吸烟者死亡危险度比较的前瞻性队列研究

目的 比较接尘、吸烟对死亡的影响。方法 以1989～1992年广州市实施并建立的职工职业健康监护档案为基础资料，选年龄≥30岁的80987名接尘和无接尘职工为研究对象，进行前瞻性队列研究。结果 (1)队列平均43．5岁，主要为工人、中学文化程度、已婚，接尘率16．3％，吸烟率43．7％，饮酒率335%。(2)队列平均随访8年，失访35人，死亡1539人，以恶性肿瘤死亡为主。(3)调整相关混杂因素后，全死因、恶性肿瘤、心脑血管疾病等死亡相对危险度(RR)，接尘者和吸烟者基本一致，但鼻咽癌、呼吸系统疾病死亡RR值，接尘者高于吸烟者，而肺癌、胃癌死亡RR值，吸烟者分别是接尘者的2．2倍和1．5倍；接尘可协同吸烟致死亡危险性明显增加。(4)男性总死因、恶性肿瘤和呼吸系统疾病死亡RR值，矽尘接触者高于吸烟者，心脑血管疾病死亡RR值，木尘接触者也高于吸烟者。(5)人群死亡归因危险度百分比(PARP)吸烟者是接尘者的2．5倍。(6)男吸烟者全死因、恶性肿瘤、肺癌、胃癌的死亡危险随日吸烟量、烟龄的增加而明显递增，冠心病、呼吸系统疾病的死亡危险则分别随日吸烟量、烟龄的增加而增加。结论 接尘、吸烟者死亡RR值基本一致，接尘与吸烟存在协同作用，某些死因死亡危险吸烟者较明显，某些接尘者较明显；吸烟者PARP较接尘者高；吸烟与死亡危险存在明显的剂量效应关系。     

某矿区接尘工人30年恶性肿瘤发病情况调查

目的调查某矿区接尘工人３０年恶性肿瘤的发病情况。方法采用回顾性队列研究，对该矿区１６７１１名接尘工人和７５９８名非接尘工人恶性肿瘤的发病情况进行调查。结果接尘组中肺癌居首，对非接尘组的标化发病比为２．６４８；接尘工人比非接尘工人恶性肿瘤发病率明显增高；４０岁以上接尘工人中，高接尘工龄段肺癌发病率显著高于低接尘工龄段；湿式作业工人肺癌发病率显著低于干式作业工人。结论接尘工人的恶性肿瘤（特别是肺癌）高发，粉尘可能是致病的重要危险因素之一。     

职业接尘及吸烟致呼吸系统疾病死亡危险度比较的队列研究

目的 比较接尘、吸烟对呼吸系统疾病死亡的影响.方法 在1989年至1992年广州建立职业健康监护档案的基础上对30岁以上、职业接触粉尘和无粉尘接触的80 987名工人进行前瞻性队列研究.结果 （1）队列平均年龄43.5岁,职业性粉尘接触率16.3%,吸烟率43.7%,饮酒率33.5%.（2）队列平均随访8年,35人失访,失访率0.04%,总死亡1 593人中,219人死于肺癌,90人死于非恶性肿瘤性呼吸系统疾病.（3）调整相关因素后,相对于不吸烟者,吸烟者肺癌死亡相对危险度（RR）为3.32,是粉尘接触者相对于无粉尘接触者肺癌死亡RR（1.53）的2.2倍.粉尘接触者非恶性肿瘤性呼吸系统疾病死亡RR为2.41,是吸烟者（1.89）的1.28倍.尤其是矽尘接触者,其非恶性肿瘤性呼吸系统疾病死亡RR为5.72,是吸烟者的3.03倍.既接触粉尘又吸烟,呼吸系统疾病死亡RR增加更明显.（4）男性吸烟者呼吸系统疾病死亡危险分别随日吸烟量、烟龄的增加而增加.结论 职业接触粉尘和吸烟均可引致超额的呼吸系统疾病死亡,两者存在协同作用.吸烟致肺癌死亡RR高于接尘,而致非恶性肿瘤性呼吸系统疾病死亡RR则低于接尘.吸烟与呼吸系统疾病死亡危险存在明显的剂量-效应关系.     

职业接触粉尘与死亡相关的前瞻性队列研究

目的探讨职业接触粉尘对死亡的影响,为现代职业卫生政策法规的制定以及相关工作提供科学依据。方法以1989～1992年广州市实施并建立的职工职业健康监护档案为基础资料,选年龄≥30岁的80987名接尘和无接尘职工为研究对象,进行前瞻性队列研究。结果(1)队列平均43．5岁,主要为工人,中学文化,已婚,接尘率16．3％,吸烟率43．7％,饮酒率33．5％;(2)队列平均随访8年,失访35例,死亡1539人,以恶性肿瘤死亡为主。接尘、无接尘全死因粗死亡率分别为男380．14／10万和314．56／10万,女95．72／10万和98．33／10万。(3)调整相关混杂因素后,接尘者全死因、恶性肿瘤、呼吸系统疾病死亡相对危险度(RR)分别为1．24、1、34和2．41,其中男性矽尘接触者分别为1．57、1．61和5、72,男接尘者肺癌和鼻咽癌死亡相对危险度分别为1、67和1．81,与无接尘者比,RR的增加均有显著性意义。(4)调整相关混杂因素后,接尘者全死因、恶性肿瘤死亡归因危险度百分比(AR％)和人群归因危险度百分比(PAR％)分别为19．5％、3．8％、25．4％和5．3％。结论职业接触粉尘可致全死因死亡尤其是恶性肿瘤和呼吸系统疾病死亡危险性增加。     

矽肺对肺癌及总死亡影响的回顾性队列研究

目的 利用香港矽肺患者队列的资料进行分析,探讨矽尘、矽肺与肺癌的关系.方法 选择1981年1月1日至1998年12月31日期间在香港尘肺诊所登记的2789例男性矽肺病例为研究对象,取用同时期一般男性人群作为对照.用人年的方法估计各死因的标化死亡比(SMR),用Axelson's法间接调整吸烟的混杂影响.矽尘与肺癌的剂量-效应关系采用多因素p-spline平滑法模型来拟合最佳风险模型.结果 该组研究队列人数为2789,共观察24 992.6人年,失访率仅为2.9%.该队列主要工种为建筑工人(5 1.09%)和地下沉箱操作工人(37.54%).队列总死亡人数为853人,平均死亡年龄为(63.8±10.27)岁,整个队列中86例死于肺癌.全死因及全癌的SMR均明显上升,首位死因是呼吸道疾病,肺癌的5MR明显增加(SMR:1.69,95%CI:1.35～2.09).去除年龄、时期和吸烟的混杂因素的影响,矽肺对肺癌的相对危险度下降到1.12(95%CI:0.89～1.38).间接调整吸烟的混杂影响后建筑工人及地下沉箱工人肺癌的相对危险度分别为1.09(95%CI:0.82～1.42)和1.56(0.98～2.36).多因素p-spline平滑法风险模型分析显示,肺癌与累积呼吸性矽尘总量或平均矽尘浓度的关系无剂量-效应关系.结论 队列研究未发现接触矽尘或矽肺能增加肺癌死亡的危险,平滑法模型拟合的风险模型并不支持矽尘与肺癌死亡之间存在剂量-效应关系.     

铁矿工人队列死因研究

目的 探索危害铁矿作业工人健康的主要疾患及职业有害因素对工人寿命的影响.方法 用流行病学队列研究方法,对武钢大冶铁矿7 469名职工从1972年开始随访30余年,以全国城市居民年龄别死亡率为参照,用标化死亡比（SMR）作为统计指标,并计算95%可信区间.结果 自1972年至2003年底,共计199 108.0人年,死亡1 752人,累积死亡率为23.5%.影响铁矿工人寿命的主要疾病按累积死亡率从高到低排序分别是：肿瘤（7.8%）、脑血管疾病（3.9%）、心血管系疾病（3.4%）和呼吸系疾病（2.9%）,恶性肿瘤以肺癌和肝癌最多,分别占总死亡数的10%和7.4%.全死因SMR为1.06,高于全国平均水平.死亡率明显升高的疾病有鼻咽癌、肝癌、肺癌、尘肺和意外事故,SMR分别为1.84、1.51、1.83、14.94和1.25.队列中接尘工人与非接尘工人比较,接尘工人全死因、胃癌、肺癌、呼吸系统疾病、心血管疾病和意外事故的累积死亡率明显升高（相对危险度分别为1.35、1.83、1.61、2.27、1.34和1.69）.结论 以粉尘为主的职业有害因素明显影响铁矿工人健康和寿命.     

景德镇瓷厂工人死因分析

目的 探索危害陶瓷工人健康的主要疾患及职业有害因素对工人寿命的影响.方法 采用流行病学队列研究方法,对景德镇3个瓷厂1972年到1974年在册且工作一年以上所有陶瓷工人建立队列,随访至2003年底.队列中对死者均查询死因,陶工尘肺由当地疾病控制中心诊断小组确诊,肺癌均收集医院诊断病例.以全国城市居民年龄别死亡率为参照计算标化死亡比(SMR).结果 队列成员共4957名,随访至2003年底,共计130 783.6人年,死亡1636人,死亡率为1250.9/10万,累计死亡率为33.1%.影响陶瓷工人寿命的主要疾病按累计死亡率从高到低排序分别是:恶性肿瘤、心血管疾病、呼吸系统疾病、传染性疾病.与全国平均水平比较,陶瓷工人全死因死亡率基本持平,标化死亡比为1.01,死亡率明显升高的疾病有呼吸系统疾病(SMR=1.30)、陶工尘肺(SMR=36.35)、传染性疾病(SMR=5.08)和肺结核(SMR=4.06).陶瓷粉尘对工人寿命的影响十分明显,接尘工人多种疾病的死亡率均高于非接尘组,除陶工尘肺外,接尘组肺癌(RR=1.9,95%CI:1.2～3.1)、呼吸系统疾病(RR=2.4,95%CI:1.8～3.2)、肺结核(RR=1.6,95%CI:1.2～2.1)明显高于非接尘组,差异有统计学意义.研究还发现全死因、肠癌、肺癌、呼吸系统疾病、肺结核危险度均随接尘严重程度而明显增加,呈现接触一反应关系.结论 陶瓷行业主要职业危害为粉尘,卫生工作重点应是控尘和预防肺结核.     

矽尘,煤矽尘和石棉作业工人MTTp对比研究

本文采用“简易计算法”对７３６接尘工人、尘肺病人和对照人群的肺气部分平均通过时间（ＭＴＴｐ）进行对比研究，以探讨ＭＴＴｐ在评价接尘工人和尘肺病人通气功能变化中的应用价值．结果表明三组ＦＶＣ、ＦＥＶ１、Ｖ（７５）、Ｖ（５０）和Ｖ（２５）测值从大到小序位为对照组、接尘组、尘肺组，而ＭＴＴｐ测值从小到大序位为对照组、接尘组、尘肺组。接尘组内比较，煤矽尘组的时气流速和ＭＴＴｐ与矽尘肺组、石棉尘组比，均有显著差异（Ｐ＞０．０５）．提示ＭＴＴｐ在评价接尘工人肺通气功能变化中有一定实用价值，尤其是对煤矽尘工人，ＭＴＴｐ指标的应用更有实际意义．     

Non-malignant respiratory diseases and lung cancer among Chinese workers exposed to silica

The objective of this study was to explore whether a medical history for non-malignant respiratory disease contributes to an increased lung cancer risk among workers exposed to silica. We analyzed data from a nested case-control study in 29 dusty workplaces in China. The study population consisted of 316 lung cancer cases and 1356 controls matched to cases by facility type and decade of birth who were alive at the time of diagnosis of the index case and who were identified in a follow-up study of about 68,000 workers. Age at first exposure and cigarette smoking were accounted for in the analysis. Smoking was the main risk factor for both lung cancer and chronic bronchitis. Lung cancer risk showed a modest association with silicosis and with cumulative silica exposure, which did not vary by history of previous pulmonary tuberculosis. Among subjects without a medical history for chronic bronchitis or asthma, lung cancer risk was associated with silicosis (odds ratio [OR], 1.6; 95% confidence interval [CI], 1.1 to 2.2), and it was increased in each quartile of cumulative silica exposure. However, risk was not elevated in the highest quartile (OR, 1.3, 1.6, 1.8, 1.4). Among subjects with a medical history for chronic bronchitis or asthma, lung cancer risk was associated with neither silicosis (subjects with chronic bronchitis: OR, 0.6; subjects with asthma: OR, 0.4) nor with silica exposure. In this study population, we observed a modest association of both silicosis and cumulative exposure to silica with lung cancer among subjects who were not previously diagnosed with chronic bronchitis or asthma, but not among subjects who had a medical history for either disease. Risk of lung cancer associated with silicosis or cumulative exposure to silica did not vary by previous medical history of pulmonary tuberculosis.     

An update of a mortality study of talc miners and millers in Italy

BACKGROUND: While talc containing asbestiform fibers is considered a human carcinogen, only limited animal and human data are available on non-asbestiform talc. To provide further evaluation on the issue, we updated the analysis of an Italian cohort of talc miners and millers in Val Chisone; talc found here is free from asbestiform fibers. METHODS: The cohort was comprised of 1,795 men who had worked for at least 1 year in the mine and/or in the factory between 1946 and 1995. Vital status and death certificates were obtained from registration offices in the municipality of death or of birth. Employment, termination of employment, and detailed job history were obtained from personnel records at the plant. RESULTS: No excess was found for total cancer mortality, nor mortality for lung cancer. No case of mesothelioma was reported. There was a significant excess mortality from non-neoplastic respiratory diseases (SMR 228.2, 95% CI 190.2-271.5). Mortality excess for non-neoplastic respiratory diseases was mainly due to silicosis. CONCLUSIONS: This study provides additional support for an association between talc in mining and milling and non-neoplastic respiratory diseases, while showing no significant excess risk for lung cancer and mesothelioma. The results also provide additional information of interest to evaluate the potential association between silica and lung cancer.     

Indirect validation of a retrospective method of exposure assessment used in a nested case-control study of lung cancer and silica exposure.

Validations of retrospective methods of assessment used in occupational epidemiological studies have rarely been published. This study is an indirect validation of a quantitative retrospective assessment of exposure to silica used in a nested case-control study of lung cancer among workers at 29 metal mines and pottery factories in China. Indices of cumulative total dust and cumulative respirable dust were calculated by merging work histories with the historical exposure profile for each subject. To validate indirectly the methods of exposure assessment used in the study of lung cancer, trends for exposure response relation between the two indices of exposure to silica and risk of silicosis were evaluated with 376 patients with silicosis from the study population as the cases, and 1262 controls without silicosis for comparison. Age adjusted odds ratios (ORs) as a measure of risk of silicosis showed striking trends with both indices of exposure to silica. For cumulative respirable dust, the OR (95% confidence interval) rose from 7.6 (5.1-11.4) for low exposure to 20.0 (13.2-30.6) for medium exposure, and to 51.7 (31.0-86.8) for high exposure. The strength of the association between exposure to silica and risk of silicosis suggests that the retrospective assessment of exposure used in the case-control study of lung cancer would accurately reflect an exposure response relation between silica and lung cancer, if it existed.     

Mortality of workers compensated for silicosis during the period 1959-1963 in the Veneto region of Italy

After reports appeared from other countries indicating an excess risk of lung cancer among silicotics, a cohort of workers compensated for silicosis during the period 1959-1963 in the Veneto region of Italy was constructed and followed for mortality through 1984. The results of the study showed a large mortality excess for infectious diseases (180 observed versus 9.5 expected), due to silicotuberculosis, and for diseases of the respiratory system (270 observed versus 33.5 expected) due to silicosis. An elevated standardized mortality ratio of 239 (70 observed versus 29.3 expected) from lung cancer was also detected. An increasing pattern was observed with time since first exposure, while the relationship with employment category and duration of exposure was less clear-cut. The lung cancer excess was also strongly associated with cigarette smoking, there being a dose-response relationship with daily cigarette consumption. The study confirms the results from other epidemiologic studies on silicotics which show this pathological condition to be associated with increased lung cancer mortality.     

Mortality from lung cancer and respiratory disease among pottery workers exposed to silica and talc

A cohort mortality study of white men employed for at least one year between 1939 and 1966 at three plants of a single United States company was conducted to evaluate the risk of lung cancer and nonmalignant respiratory disease among workers exposed to silica dust and nonfibrous (nonasbestiform) talc in the manufacture of ceramic plumbing fixtures. Follow-up of 2,055 men through January 1, 1981, indicated a substantial excess of nonmalignant respiratory disease among those with high levels of exposure to silica dust (standardized mortality ratio = 2.26). The risk of nonmalignant respiratory disease rose with the number of years exposed, was not further enhanced by talc exposure, and appeared to be appreciably lower among those exposed in more recent time periods. For lung cancer, men exposed to high levels of silica dust with no talc exposure had a nonsignificant standardized mortality ratio of 1.37. However, those exposed to nonfibrous talc in addition to high levels of silica had a significant 2.5-fold excess risk of lung cancer. Among this group, the lung cancer standardized mortality ratio rose with increasing years of talc exposure to 3.64 among those exposed for 15 or more years. Although the role of silica as a cofactor cannot be ruled out, these data suggest that nonfibrous talc exposure is associated with excess lung cancer risk.     

Mortality experience of haematite mine workers in China

The mortality risk of iron ore (haematite) miners between 1970 and 1982 was investigated in a retrospective cohort study of workers from two mines, Longyan and Taochong, in China. The cohort was limited to men and consisted of 5406 underground miners and 1038 unexposed surface workers. Among the 490 underground miners who died, 205 (42%) died of silicosis and silicotuberculosis and 98 (20%) of cancer, including 29 cases (5.9%) of lung cancer. The study found an excess risk of non-malignant respiratory disease and of lung cancer among haematite miners. The standardised mortality ratio for lung cancer compared with nationwide male population rates was significantly raised (SMR = 3.7), especially for those miners who were first employed underground before mechanical ventilation and wet drilling were introduced (SMR = 4.8); with jobs involving heavy exposure to dust, radon, and radon daughters (SMR = 4.2); with a history of silicosis (SMR = 5.3); and with silicotuberculosis (SMR = 6.6). No excess risk of lung cancer was observed in unexposed workers (SMR = 1.2). Among current smokers, the risk of lung cancer increased with the level of exposure to dust. The mortality from all cancer, stomach, liver, and oesophageal cancer was not raised among underground miners. An excess risk of lung cancer among underground mine workers which could not be attributed solely to tobacco use was associated with working conditions underground, especially with exposure to dust and radon gas and with the presence of non-malignant respiratory disease. Because of an overlap of exposures to dust and radon daughters, the independent effects of these factors could not be evaluated.     

A case-control study of malignant and non-malignant respiratory disease among employees of a fiberglass manufacturing facility. II. Exposure assessment.

A case-control study of malignant and non-malignant respiratory disease among employees of the Owens-Corning Fiberglas Corporation's Newark, Ohio plant was undertaken. The aim was to determine the extent to which exposures to substances in the Newark plant environment, to non-workplace factors, or to a combination may play a part in the risk of mortality from respiratory disease among workers in this plant. A historical environmental reconstruction of the plant was undertaken to characterise the exposure profile for workers in this plant from its beginnings in 1934 to the end of 1987. The exposure profile provided estimates of cumulative exposure to respirable fibres, fine fibres, asbestos, talc, formaldehyde, silica, and asphalt fumes. Employment histories from Owens-Corning Fiberglas provided information on employment characteristics (duration of employment, year of hire, age at first hire) and an interview survey obtained information on demographic characteristics (birthdate, race, education, marital state, parent's ethnic background, and place of birth), lifetime residence, occupational and smoking histories, hobbies, and personal and family medical history. Matched, unadjusted odds ratios (ORs) were used to assess the association between lung cancer or non-malignant respiratory disease and the cumulative exposure history, demographic characteristics, and employment variables. Only the smoking variables and employment characteristics (year of hire and age at first hire) were statistically significant for lung cancer. For non-malignant respiratory disease, only the smoking variables were statistically significant in the univariate analysis. Of the variables entered into a conditional logistic regression model for lung cancer, only smoking (smoked for six months or more v never smoked: OR = 26.17, 95% confidence interval (95% CI) 3.316-206.5) and age at first hire (35 and over v less than 35: OR = 0.244, 95% CI 0.083-0.717) were statistically significant. There were, however, increased ORs for year of employment (first hired before 1945 v first hire after 1945: OR = 1.944, 95% CI 0.850-4.445), talc (cumulative exposure >1000 fibres/ml days v never exposed: OR = 1.355, 95% CI 0.407-5.515), and asphalt fumes (cumulative exposure >0.01 mg/m(3) days v never exposed: OR 1.131, 95% CI 0.468-2.730). For non-malignant respiratory disease, only the smoking variable was significant in the conditional logistic regression analysis (OR = 2.637, 95% CI 1.146-6.069). There were raised ORs for the higher cumulative exposure categories for respirable fibres, asbestos, silica, and asphalt fumes. For both silica and asphalt fumes, ORs were more than double the reference groups for all exposure categories. A limited number of subjects were exposed to fine fibres. The scarcity of cases and controls limits the extent to which analyses for fine fibre may be carried out. Within those limitations, among those who had worked with fine fibre, the unadjusted, unmatched OR for lung cancer was (1.0 (95% CI 0.229-4.373) and for non-malignant respiratory disease, the OR was 1.5 (95% CI 0.336-6.702). The unadjusted OR for lung cancer for exposure to fine fibre was consistent with that for all respirable fibre and does not suggest an association. For non-malignant respiratory disease, the unadjusted OR for fine fibre was opposite in direction from that for all respirable fibres. Within the limitations of the available data on fibre, there is o suggestion that exposure to fine fibre has resulted in an increase in risk of lung cancer. The increased OR for non-malignant respiratory disease is inconclusive. The results of this population, in this place and time, neither respirable fibres nor any of the substances investigated as part of the plant environment are statistically significant factors for lung cancer risk although there are increased ORs for exposure to talc and asphalt fumes. Smoking is the most important factors in risk for lung cancer in this population. The situation is less clear for non-malignant respiratory disease. Unlike lung cancer, non-malignant respiratory represents a constellation of outcomes and not a single well defined end point. Although smoking was the only statistically significant factor for non-malignant respiratory disease in this analysis, the ORs for respirable fibres, asbestos, silica, and asphalt fumes were greater than unity for the highest exposure categories. Although the raised ORs for these substances may represent the results of a random process, they may be suggestive of an increased risk and require further investigation.     

Mortality experience of haematite mine workers in China.

The mortality risk of iron ore (haematite) miners between 1970 and 1982 was investigated in a retrospective cohort study of workers from two mines, Longyan and Taochong, in China. The cohort was limited to men and consisted of 5406 underground miners and 1038 unexposed surface workers. Among the 490 underground miners who died, 205 (42%) died of silicosis and silicotuberculosis and 98 (20%) of cancer, including 29 cases (5.9%) of lung cancer. The study found an excess risk of non-malignant respiratory disease and of lung cancer among haematite miners. The standardised mortality ratio for lung cancer compared with nationwide male population rates was significantly raised (SMR = 3.7), especially for those miners who were first employed underground before mechanical ventilation and wet drilling were introduced (SMR = 4.8); with jobs involving heavy exposure to dust, radon, and radon daughters (SMR = 4.2); with a history of silicosis (SMR = 5.3); and with silicotuberculosis (SMR = 6.6). No excess risk of lung cancer was observed in unexposed workers (SMR = 1.2). Among current smokers, the risk of lung cancer increased with the level of exposure to dust. The mortality from all cancer, stomach, liver, and oesophageal cancer was not raised among underground miners. An excess risk of lung cancer among underground mine workers which could not be attributed solely to tobacco use was associated with working conditions underground, especially with exposure to dust and radon gas and with the presence of non-malignant respiratory disease. Because of an overlap of exposures to dust and radon daughters, the independent effects of these factors could not be evaluated.     

Exposures to silica mixed dust and cohort mortality study in tin mines: exposure-response analysis and risk assessment of lung cancer

BACKGROUND: Mineral dusts that contain crystalline silica have been associated directly or indirectly with the development of pneumoconiosis or silicosis, non-malignant respiratory diseases, lung cancer, and other diseases. The health impacts on workers with silica mixed dust exposure in tin mines and dose-response relationships between cumulative dust exposure and the mortality from lung cancer are investigated. METHODS: A cohort of 7,837 workers registered in the employment records in 4 Chinese tin mines between 1972 and 1974 was identified for this study and the mortality follow-up was traced through 1994. Of the cohort, the cause of death was ascertained for 1,061 (97%) of the 1,094 deceased workers. Standardized mortality ratios (SMRs) were calculated for all workers, non-exposed workers, and dust-exposed workers with different exposure levels, silicotics, and non-silicotics based on Chinese national rates. RESULTS: The mortality from all causes in four tin mines was nearly the same as the national mortality. Malignant neoplasm, cerebrovascular disease, and cardiovascular disease accounted for 68.6% of all deaths. Mortality excess from lung cancer, liver cancer, all malignant diseases, and non-malignant respiratory diseases was observed among dust-exposed workers; a 50-fold excess of pneumoconiosis was observed. There was an upward trend for SMRs of lung cancer was noted from no exposure to low, medium, and high exposure levels (SMRs=1.29, 2.65, 2.66, 3.33). The shape of the exposure-response curve for risk of lung cancer at high exposure levels was inconsistent in these four mines. CONCLUSIONS: The findings indicated a positive dose-response relation between exposure to cumulative dust and the mortality of lung cancer. High arsenic content in dust particles, together with crystalline silica, may play an important role in causing increased mortality from lung cancer.