Silica exposure, smoking, silicosis and lung cancer--complex interactions

Background Establishing a clear relationship between workplaceexposures and cancer is often difficult. The latent period forcancer development can make it difficult to establish a definitecause–effect relationship. The picture is further complicatedby variable job histories, concomitant exposure to other carcinogensand other factors such as genetic susceptibility and poor nutrition.The lack of accurate and detailed record keeping may potentiallymask informative differences among group of workers. Removingor reducing exposures to probable and known carcinogens, however,can prevent workplace cancer. Aim This paper gives an overview of the literature reportinginvestigations of the relationship between exposure to silicaand development of lung cancer with a focus on the controversyconcerning the roles of silicosis and smoking in the developmentof cancer. Method A literature search was conducted to identify epidemiologicpapers on silica, silicosis and lung cancer using electronicdatabases (MEDLINE, PubMed, Web of Science) from 1996 onwardsand paper bibliographies. Results If silicosis were the necessary step leading to lungcancer, enforcing the current silica standards would protectworkers against lung cancer risk as well. Alternatively, a directsilica–lung cancer association that has been suggestedimplies that regulatory standards should be revised accordingly. Conclusion Further research is needed in order to understandthe complex pattern of interactions leading to lung cancer amongsilica-exposed workers (and cancers and workplace exposuresin general) and to understand whether and to what extent otherworkplace lung carcinogens, total respirable dust and totalsurface size and age of silica particles affect the carcinogenicpotential of silica. In addition, the apparent paradox of alower lung cancer risk in some workplaces with high-level silicaexposure needs further investigation.     

Exposures to blood and body fluids in Brazilian primary health care

Background Primary health care workers (HCWs) represent a growingoccupational group worldwide. They are at risk of infectionwith blood-borne pathogens because of occupational exposuresto blood and body fluids (BBF). Aim To investigate BBF exposure and its associated factors amongprimary HCWs. Methods Cross-sectional study among workers from municipal primaryhealth care centres in Florianópolis, Southern Brazil.Workers who belonged to occupational categories that involvedBBF exposures during the preceding 12 months were interviewedand included in the data analysis. Results A total of 1077 workers participated. The mean incidencerate of occupational BBF exposures was 11.9 per 100 full-timeequivalent worker-years (95% confidence interval: 8.4–15.3).The cumulative prevalence was 7% during the 12 months precedingthe interview. University-level education, employment as a nurseassistant, dental assistant or dentist, higher workload score,inadequate working conditions, having sustained a previous occupationalaccident and current smoking were associated with BBF exposures(P 0.05). Conclusions Primary Health Care Centres are working environmentsin which workers are at risk of BBF exposures. Exposure surveillancesystems should be created to monitor their occurrence and toguide the implementation of preventive strategies.     

Solar ultraviolet radiation and skin cancer

Background Incidence rates of skin cancer, both non-melanomaskin cancer and (malignant/cutaneous) melanoma, are rising inGreat Britain. It is widely accepted that solar ultravioletradiation (UVR) is the main causal factor for these neoplasms.Many people are occupationally exposed to solar UVR, includingfarmers, construction workers and some public service workers. Aim The aim of this article is to review the key epidemiologicpapers on occupational solar exposure and skin cancer and discussthe relationships found. Method A literature search was conducted using online databasesand article bibliographies. A full review of all available studieswas not carried out, as only key studies on occupational exposurewere required. Results There is a clear association between solar radiationand skin cancer. The mechanisms for induction vary between thetypes of skin cancer and these cannot be solely attributed tooccupational exposures. Conclusions There is great difficulty in separating the effectsof occupational and recreational solar UVR exposure; therefore,any results discussed in this review should be interpreted withcaution. However, it is clear that solar UVR exposure does induceskin cancer and protective measures should be taken in an attemptto reduce the burden of occupational skin cancer in Great Britain.     

Health care workers' exposure to blood-borne pathogens in Lebanon

Background Accidental exposure to blood-borne pathogens (BBPs)is a risk for health care workers (HCWs). Aim To study the pattern of occupational exposure to blood andbody fluids (BBFs) at a tertiary care hospital. Methods This study reports a 17-year experience (1985–2001)of ongoing surveillance of HCW exposure to BBFs at a 420-bedacademic tertiary care hospital. Results A total of 1590 BBF exposure-related accidents werereported to the Infection Control Office. The trend showed adecrease in these exposures over the years with an average ±standard error of 96 ± 8.6 incidents per year. In thelast 6 years, the average rate of BBF exposures was 0.57 per100 admissions per year (average of needlestick injuries alonewas 0.46 per 100 admissions). For 2001, the rates of exposurewere found to be 13% for house officers, 9% for medical student,8% for attending physicians, 5% for nurses, 4% for housekeeping,4% for technicians and 2% for auxiliary services employees.The reason for the incident, when stated, was attributed toa procedural intervention (29%), improper disposal of sharps(18%), to recapping (11%) and to other causes (5%). Conclusions The current study in Lebanon showed that exposureof HCWs to BBPs remains a problem. This can be projected toother hospitals in the country and raises the need to implementinfection control standards more efficiently. Similar studiesshould be done prospectively on a yearly basis to study ratesand identify high-risk groups.     

Role of occupational asbestos exposure in Hungarian lung cancer patients

Objective: What is the frequency of occupational asbestos exposure among patients suffering from malignant respiratory tumours and how many of these tumours are associated with asbestos in Hungary? Methods: An internationally established questionnaire with 29 questions, covering the most characteristic activities of asbestos exposure at the workplace was completed for 300 patients with respiratory malignancies, i.e. 297 patients with lung cancer and three with mesothelioma of the pleura. From the questionnaire, the smoking habits were estimated and cumulative asbestos exposure was assessed in fibre-years. Additionally, lung X-rays were classified and the national data on the incidence of malignant pleura mesothelioma were analysed. Results: A cumulative asbestos exposure of 25?fibre-years or more was detected in 11 patients with lung cancer (4%) and in each of the three patients with pleural mesothelioma (100%). In a further 72 patients (24%), cumulative occupational asbestos exposure was assessed as below 25?fibre-years (between 0.01 and 23.9?fibre-years). In this group, car and truck mechanics, and installation and construction workers using asbestos-cement were registered. Among patients with an asbestos exposure of 25?fibre-years or more, six asbestos-cement production workers were observed, among them the three mesothelioma cases. A weak but significant association between positive X-ray findings and exposure estimates could be demonstrated. Additionally, results of the lung tissue fibre counts by scanning transmission electron microscopy were available for 25 of the lung cancer patients. A good correlation was observed between the asbestos fibre counts and the assessment of cumulative asbestos exposure. In Hungary, 84 cases of pleural mesothelioma were registered in 1997 and 73 in 1998. These numbers correspond to an annual incidence of about one new case per 100,000 inhabitants older than 15?years. Conclusions: The annual incidence of lung cancer in Hungary is about 6,000. Since in our series of lung cancer patients about 4% were observed, which could be accepted as representing occupational disease because of a cumulative exposure to 25?fibre-years or more, the annual asbestos related lung tumour incidences may be estimated to be approximately 150 or more. The proportion of nearly two estimated cases of lung cancer per case of pleural mesothelioma corresponds to international experience. Up to now, lung cancer cases only exceptionally have been registered as occupational diseases, i.e. they were seriously under-diagnosed in Hungary. For improving this situation, diagnostic assistance by a self-interview with a questionnaire covering the working history for all newly diagnosed lung cancer patients would be helpful.     

Occupational respiratory cancer and exposure to asbestos: A case-control study in a cohort of workers in the electricity and gas industry

Cancers of the pleura, lung, and larynx between 1978 and 1989 among active male workers of Electricité de France-Gaz de France were studied in association with asbestos exposure using a case-control design nested within the cohort of workers of the company. The cohort included about 1,400,000 person-years, corresponding to a mean of 117,000 men per year. Exposure to asbestos and to some potential occupational confounders selected among agents from groups I, IIa, and IIb of the International Agency for Research on Cancer was assessed by a job-exposure matrix specific to the company. During the observation period, 12 cases of pleural cancer, 310 cases of lung cancer, and 116 cases of larynx cancer were registered in the cancer register of the company social security department. Four controls per case, matched for year of birth, were randomly selected among the cohort. Conditional logistic regression was used to estimate the odds ratios. A first analysis was conducted in order to assess the validity of the job-exposure matrix by investigating already known relationships between asbestos exposure and asbestosis. For asbestosis, a strong exposure-response relation was found with an odds ratio (OR) of 57.4 [95% confidence interval (CI): 17.0–194.0] in the highest exposure group. There was an elevated risk of pleural cancer (OR, 4.8, CI, 1.2–19.8). For lung cancer, significant ORs of 2.0 (CI, 1.3–3.2) and 1.9 (CI, 1.2–3.0) were found among the two highest cumulative exposure groups; adjustement for confounders slightly decreased the ORs. Squamous cell neoplasm of the lung was associated with asbestos exposure. The association between larynx cancer and asbestos exposure showed a tendency towards a nonsignificant increase in ORs in the highest cumulative exposure categories; this tendency disappeared when adjusting for occupational confounders. This study showed that occupational exposure to asbestos could increase the risk of pleural and lung cancer in a sector in which exposure levels are not considered to be high compared with other industrial settings.     

Exposure and mineralogical correlates of pulmonary fibrosis in chrysotile asbestos workers.

OBJECTIVES: The relation between lifetime cumulative exposure to asbestos, pathological grade of pulmonary fibrosis, and lung burden of asbestos at death, was explored in a necropsy population of former workers in a chrysotile asbestos textile plant in South Carolina. METHODS: Estimates of cumulative, mean, and peak exposures to asbestos were available for 54 workers. Necropsy records and lung tissue samples were obtained from hospital files. Matched control cases were selected from consecutive necropsies performed at the same hospitals. The extent and severity of pulmonary fibrosis was graded on tissue sections. Mineral fibres in lung tissue were characterised by transmission electron microscopy combined with x ray spectroscopy. RESULTS: A significant positive correlation (r = 0.67, P < 0.0001) was found between lifetime cumulative exposure to asbestos and total lung burden of asbestos fibres. This relation was also found for the individual types of asbestos associated with the exposure: chrysotile and tremolite. Pulmonary fibrosis was correlated with both cumulative exposure to asbestos (r = 0.60, P < 0.01) and the concentration of asbestos fibres in the lung (r = 0.62, P < 0.0001). The concentration of tremolite fibres in the lung provided a better estimate of lung fibrosis than did the concentration of chrysotile. Asbestosis was usually present in asbestos textile workers with more than 20 fibre-years cumulative exposure. The lengths and aspect ratios of chrysotile asbestos, but not amphibole asbestos, were greater in the lungs of asbestos fibre workers than in the control population. Textile workers with lung cancer had significantly greater cumulative exposures and fibrosis scores than workers without lung cancer. CONCLUSIONS: Both cumulative exposure to asbestos and lung fibre burden are strongly correlated with severity of asbestosis. The data also support the hypothesis that the high prevalence of asbestosis and lung cancer in this population resulted from exposure to long fibres of chrysotile asbestos in the workplace.     

Acute respiratory symptoms among sisal workers in Tanzania

Background Few studies have focused on respiratory health effectsamong sisal workers. Aim To report on the prevalence of acute respiratory symptomsamong sisal processors. Methods We interviewed 163 dust-exposed brushing and decorticationworkers and 31 low-exposed security workers from six sisal estatesin Tanzania using a modified symptom score questionnaire todetermine the prevalence of acute respiratory symptoms duringwork. Groups were compared using chi-square tests, Fisher'sexact tests, t-tests and logistic regression, adjusting forconfounding factors. Results After the first working day of the week, 73% of thebrushing workers reported dry cough, 66% sneezing, 65% productivecough, 63% running nose and 34% stuffy nose. Brushing workershad a significantly higher prevalence of these symptoms thandecortication workers. Brushing and decortication workers hadsignificantly more dry cough and sneezing than the control groupof security workers, when adjusting for age, smoking, past respiratorydiseases and residence. Conclusion Processors of sisal fibre have a high prevalenceof acute respiratory symptoms. More detailed studies on workand health in sisal estates are needed, including exposure studies.     

Exposure to asbestos and lung and pleural cancer mortality among pulp and paper industry workers

We studied the mortality from lung and pleural cancers in a cohort of 62,937 male workers employed for at least 1 year in the pulp and paper industry in 13 countries during 1945 to 1996. Mill departments were classified according to probability and level of exposure to asbestos on the basis of available dust measurements and mill-specific information on exposure circumstances. Thirty-six percent of workers were classified as ever exposed to asbestos. Standardized mortality ratios of lung cancer were 0.99 (95% confidence interval [CI], 0.90 to 1.08) among unexposed and 1.00 (95% CI, 0.90 to 1.11) among ever exposed workers. The number of pleural cancer deaths among unexposed workers was 10; that among exposed workers was 14, most of which occurred among maintenance workers. In internal analyses, a trend in mortality from either neoplasm was suggested for estimated cumulative exposure to asbestos, weighted for the individual probability of exposure within the department and for duration of exposure (relative risk for lung cancer for 0.78+ f/cc-years, as compared with < or = 0.01 f/cc-years: 1.44; 95% CI, 0.85 to 2.45; corresponding relative risk for pleural cancer: 2.43; 95% CI, 0.43 to 13.63). Despite a possible nondifferential misclassification of exposure and outcome, this study suggests that the carcinogenic effect of asbestos can be detected among workers employed in industries such as the pulp and paper industry, in which it is not considered to be a major hazard.     

Lung cancer and occupation: results of a multicentre case-control study.

The objective of the current study was to estimate the risk of lung cancer attributable to occupational factors and not due to tobacco. At 24 hospitals in nine metropolitan areas in the United States, 1793 male lung cancer cases were matched for race, age, hospital, year of interview, and cigarette smoking (never smoker, ex-smoker, smoker (1-19 and > or = 20 cigarettes per day)) to two types of controls (cancer and non-cancer hospital patients). Information on usual occupation, exposure to specific potential carcinogens, and cigarette smoking was obtained by interview. Risk of lung cancer was increased significantly for electricians; sheetmetal workers and tinsmiths; bookbinders and related printing trade workers; cranemen, derrickmen, and hoistmen; moulders, heat treaters, annealers and other heated metal workers; and construction labourers. All of these occupations are potentially exposed to known carcinogens. Odds ratios (ORs) were increased for exposure to coal dust (adjusted OR = 1.5; 95% confidence interval (95% CI) 1.1-2.1). After stratification, this association was statistically significant only after 10 or more years of exposure. Lung cancer was also related to exposure to asbestos (adjusted OR = 1.8; 95% CI 1.5-2.2). The ORs increased with increasing duration of exposure to asbestos for all smoking categories except for current smokers of 1-19 cigarettes per day. The statistical power to detect ORs among occupations that were previously reported to be at increased risk of lung cancer but that failed to show an OR of at least 1.5 in the current study was small. The cumulative population attributable risk (PAR) of lung cancer due to occupation was 9.2%. It is concluded that occupational factors play an important part in the development of lung cancer independently of cigarette smoking. Because occupations at high risk of lung cancer were under-represented, the cumulative PAR of the present study is likely to be an underestimate of the true contribution of occupation to risk of lung cancer.     

The effect of asbestosis on lung cancer risk beyond the dose related effect of asbestos alone

Aims: To determine if the presence of asbestosis is a prerequisite for lung cancer in subjects with known exposure to blue asbestos (crocidolite). Methods: Former workers and residents of Wittenoom with known amounts of asbestos exposure (duration, intensity, and time since first exposure), current chest x ray and smoking information, participating in a cancer prevention programme (n = 1988) were studied. The first plain chest radiograph taken at the time of recruitment into the cancer prevention programme was examined for radiographic evidence of asbestosis according to the UICC (ILO) classification. Cox proportional hazards modelling was used to relate asbestosis, asbestos exposure, and lung cancer. Results: Between 1990 and 2002 there were 58 cases of lung cancer. Thirty six per cent of cases had radiographic evidence of asbestosis compared to 12% of study participants. Smoking status was the strongest predictor of lung cancer, with current smokers (OR = 26.5, 95% CI 3.5 to 198) having the greatest risk. Radiographic asbestosis (OR = 1.94, 95% CI 1.09 to 3.46) and asbestos exposure (OR = 1.21 per f/ml-year, 95% CI 1.02 to 1.42) were significantly associated with an increased risk of lung cancer. There was an increased risk of lung cancer with increasing exposure in those without asbestosis. Conclusion: In this cohort of former workers and residents of Wittenoom, asbestosis is not a mandatory precursor for asbestos related lung cancer. These findings support the hypothesis that it is the asbestos fibres per se that cause lung cancer, which can develop with or without the presence of asbestosis.     

Relationship between job, lifestyle, age and occupational injuries

Background Physical job demands (PJD), age, disability and lifestylemay influence the risk of occupational injury. Aim To assess the relationships between PJD, lifestyle and injuryin workers of various ages. Methods A total of 2888 randomly selected workers from northeasternFrance, aged 15, completed a postal questionnaire. The PJD scorewas defined as the total number of the following reported jobdemands: using pneumatic tools, other vibrating hand tools,hammers, machine tools or vibrating platforms and exposure tomanual handling tasks, awkward postures, high pace of work,high physical workload, work at heights, work in adverse climatesor exposure to noise, cold or heat. Data were analysed usinglogistic regression. Results Nine per cent of subjects reported an injury duringthe previous 2 years. The PJD score was related to the injuryrate for workers aged 45: crude odds ratio (OR) 3.5 (95% confidenceinterval = 1.5–8.0) for PJD = 1, 5.0 (2.2–11.3)for PJD = 2–3 and 14.5 (6.5–32.2) for PJD 4, versusPJD = 0. Lower ORs were found for those aged <30 (1.4, 4.2and 9.9, respectively) and 30–44 (1.5, 4.4 and 6.5, respectively).The differences between age groups remained when controllingfor all factors studied. Obesity, smoking and musculoskeletaldisorders were associated with injury risk in workers aged 45(adjusted ORs 1.7–2.6). Smoking was also an injury riskfactor for workers aged <30. Conclusions PJD and lifestyle have a higher impact on injuryrates among older workers than among younger ones. Injury preventionshould address reducing PJD and improving relevant lifestylefactors, especially for older workers.     

Occupational dental erosion from exposure to acids: a review

Objective Dental erosion is characterized as a disorder witha multifactorial aetiology including environmental acid exposure.The purpose of this article was to summarize and discuss theavailable information concerning occupational dental erosion. Methods Information from original scientific papers, case reportsand reviews with additional case reports listed in PubMed, Medlineor EMBASE [search term: (dental OR enamel OR dentin) AND (erosionOR tooth wear) AND (occupational OR worker)] were included inthe review. References from the identified publications weremanually searched to identify additional relevant articles. Results The systematic search resulted in 59 papers, of which42 were suitable for the present review. Seventeen papers demonstratedevidence that battery, galvanizing and associated workers exposedto sulphuric or hydrochloric acid were at higher risk of dentalerosion. For other industrial workers, wine tasters and competitiveswimmers, only a few clinical studies exist and these do notallow the drawing of definitive conclusions. Conclusion Occupational acid exposure might increase the riskof dental erosion. Evidence for occupational dental erosionis limited to battery and galvanizing workers, while data forother occupational groups need to be confirmed by further studies.     

Cold haemagglutinin disease misdiagnosed as hand-arm vibration syndrome

Abstract A patient with a diagnosis of hand–arm vibrationsyndrome was referred for a second opinion. He worked as a multi-skilledoperative in the housing department of a local authority, ajob not normally associated with high levels of exposure tohand-transmitted vibration (>2.5 m/s² A(8)). He describedblanching of his fingers and a blue discolouration of his extremitiesin cold weather. On examination, his fingertips, toes and pinnaewere acrocyanotic, the fingers were patchily pale and sensationwas subjectively impaired in all of the digits. Investigationsrevealed a haemolytic anaemia and haemagglutination. He wasdiagnosed with idiopathic cold haemagglutinin disease. Exposureto vibration may confound with exposure to cold in which casethe differential diagnoses of cold haemagglutinin disease orcryoglobulinaemia should be excluded before diagnosing hand–armvibration syndrome.     

Salivary acetylcholinesterase as a biomarker for organophosphate exposure

Background Workers exposed to organophosphate (OP) pesticidesare required to undergo periodic statutory medical surveillancein several countries. Aim To study the relationship between serum, erythrocyte andsaliva acetylcholinesterase (AChE) levels and to explore theuse of salivary AChE as potential biomarker for OP exposure. Methods A cross-sectional study was conducted on 19 healthyadult male lead-exposed workers who were undergoing six monthlystatutory medical examination. Passive drool saliva sampleswere collected from each worker. Each blood sample was testedfor serum and erythrocyte AChE, and each saliva sample was testedfor AChE. Results Among the 19 subjects, the mean (±standard deviation)of salivary, erythrocyte and serum AChE/cholinesterase were22.7 (±17.4), 17171 (±1467), 8861 (±1876)U/l, respectively. There was a moderate correlation betweensalivary and erythrocyte AChE (r = 0.42, P = 0.071), but notsalivary and serum AChE (r = –0.17, P = 0.48). The levelof AChE in saliva was 1820 times lower than AChE in erythrocytes. Conclusion It is probably not feasible to use saliva as a replacementfor blood for the measurement of AChE levels. This is becauseof the much lower levels of AChE in saliva relative to erythrocytes,the weak correlation between the two measurements and the previouslyreported high intra-individual variation of salivary AChE.     

Lung cancer mortality at a UK tin smelter

BACKGROUND: An earlier study of mortality among male former employees at a tin smelter in Humberside, UK, had identified excess mortality from lung cancer, which appeared to be associated with occupational exposure. AIMS: The aim of the present study was to investigate the relationship between lung cancer mortality and quantitative measures of exposure. METHODS: Using available records of occupational hygiene measurements, we established exposure matrices for arsenic, cadmium, lead, antimony and polonium-210 ((210)Po), covering the main process areas of the smelter. We established work histories from personnel record cards for the previously defined cohort of 1462 male employees. Three different methods of extrapolation were used to assess exposures prior to 1972, when no measurement results were available. Lung cancer mortality was examined in relation to cumulative inhalation exposure by Poisson regression analysis. RESULTS: No significant associations could be found between lung cancer mortality and simple cumulative exposure to any of the substances studied. When cumulative exposures were weighted according to time since exposure and attained age, significant associations were found between lung cancer mortality and exposures to arsenic, lead and antimony. CONCLUSIONS: The excess of lung cancer mortality in the cohort can most plausibly be explained if arsenic is the principal occupational carcinogen (for which the excess relative risk diminishes with time since exposure and attained age) and if there is a contribution to excess mortality from an enhanced prevalence of smoking within the cohort. The implications of the dose-response for arsenic exposure for risk estimation merit further consideration.     

Reanalysis of mortality from lung cancer among diatomaceous earth industry workers, with consideration of potential confounding by asbestos exposure.

OBJECTIVE: To evaluate the potential for confounding from asbestos exposure, primarily chrysotile, on the relation between crystalline silica and mortality from lung cancer among diatomaceous earth (diatomite) workers. METHODS: A reanalysis of a cohort mortality study of diatomite workers was performed to take into account quantitative estimates of asbestos exposure. The reanalysis was limited to a subset of the original cohort, comprising 2266 white men for whom asbestos exposure could be reconstructed with greatest confidence. Comparisons between mortality from lung cancer (standardised mortality ratios (SMR)) were made between rates for 1942-87 for United States white men, and workers cross classified according to cumulative exposures to crystalline silica and asbestos. Comparisons of internal rates, involving Poisson regression modeling, were conducted for exposure to crystalline silica, with and without adjustment for asbestos exposure. Exposures were lagged by 15 years to take into account disease latency. RESULTS: There was an overall excess of lung cancer (SMR 1.41; 52 observed). The SMRs for four categories of increasing crystalline silica among the workers not exposed to asbestos were 1.13, 0.87, 2.14, 2.00. An SMR of 8.31 (three observed) was found for workers with the highest cumulative exposure to both dusts. Internal analysis, after adjustment for asbestos exposure, yielded rate ratios for categories of exposure to crystalline silica: 1.00 (reference), 1.37, 1.80, and 1.79. CONCLUSIONS: Asbestos exposure was not an important confounder of the association between crystalline silica and mortality from lung cancer in this cohort. Although based on a small number of deaths from lung cancer, the data suggest possible synergy between these exposures. An extended follow up of this cohort is in progress and should enable better assessments of independent and combined effects on risk of lung cancer.     

Asbestos fibreyears and lung cancer: a two phase case-control study with expert exposure assessment

Aims: To assess the cumulative effect of asbestos on lung cancer risk where the exposure is assessed by an expert rating.

Methods: 1678 male cases and controls were enrolled in a population based matched case–control study, focused on occupational risk factors, carried out in West Germany. The exposure to asbestos was computed as lifelong working hours. For a validation subsample of 164 matched pairs from this study the intensity of asbestos exposure was further assessed by a panel of experts in order to obtain an estimate of the cumulative exposure on a time by intensity scale (fibreyears). The information on duration of asbestos exposure in the original study was combined with the fibreyears following the two phase case control study paradigm.

Results: The number of exposed subjects in the validation subsample was 75 cases and 71 controls. The percentage of subjects with a cumulative exposure ≤1, 1 to ≤10, and >10 fibreyears was 16%, 15%, and 15% for the cases and 18%, 16%, and 9% respectively for the controls. The smoking adjusted odds ratios for the fibreyears based on an unconditional logistic regression were 0.81, 1.02, and 1.60 respectively with increasing exposure categories (not significant). The coefficient (beta) for a log transformed trend was 1.156. Applying the two phase paradigm, these odds ratios became 0.86, 1.33, and 1.94; the latter reached significance and the beta coefficient was 1.178.

Conclusions: The two phase paradigm allowed us to obtain a more precise estimate of the effect of asbestos on lung cancer. Results are consistent with a doubling of the lung cancer risk with 25 fibreyears asbestos exposure.

     

Asbestosis as a precursor of asbestos related lung cancer: results of a prospective mortality study

A prospective mortality study of 839 men employed in the manufacture of asbestos cement products in 1969 examined lung cancer risk in relation to lung fibrosis seen on chest x ray film, controlling for age, smoking, and exposure to asbestos. Twenty or more years after hire, no excess of lung cancer was found among workers without radiographically detectable lung fibrosis, even among long term workers (greater than or equal to 21.5 years); nor was there a trend in risk by level of cumulative exposure to asbestos among such workers. By contrast, employees with small opacities (greater than or equal to 1/0; ILO classification) experienced a significantly raised risk of lung cancer (nine observed deaths v 2.1 expected), even though their exposures to asbestos were similar to the exposures of long term workers without opacities. In this population, excess risk of lung cancer was restricted to workers with x ray film evidence of asbestosis, a finding consistent with the view that asbestos is a lung carcinogen because of its fibrogenicity.     

Overtime work and stress response in a group of Japanese workers

Background Working long overtime hours is considered a causeof mental health problems among workers but such a relationshiphas yet to be empirically confirmed. Aim To clarify the influence of overtime work on response tostress and to assess the role of other stress-related factorson this relationship. Methods The study was conducted among 24 685 employees of acompany in Japan. Stress response, job stressors and socialsupports were assessed by the Brief Job Stress Questionnaire.Participants were divided into five categories of overtime (0–19,20–39, 40–59, 60 h of overtime per month and exemptedemployees). Results The nonadjusted odds ratios for stress response for40–59 and 60 overtime hours per month in reference to0–19 overtime hours were 1.11 [95% confidence interval(CI) 1.03–1.19] and 1.62 (95% CI 1.50–1.76), respectively.After adjustment for self-assessed amount of work, mental workloadand sleeping time, the association between overtime work andstress response disappeared. Conclusions This large cross-sectional study shows that overtimework appears to influence stress response indirectly throughother stress factors such as self-assessed amount of work, mentalworkload and sleeping time.