Respiratory disease and cardiovascular morbidity.

BACKGROUND: Work related dust exposure is a risk factor for acute and chronic respiratory irritation and inflammation. Exposure to dust and cigarette smoke predisposes to exogenous viral and bacterial infections of the respiratory tract. Respiratory infection can also act as a risk factor in the development of atherosclerotic and coronary artery disease. AIMS: To investigate the association of dust exposure and respiratory diseases with ischaemic heart disease (IHD) and other cardiovascular diseases (CVDs). METHODS: The study comprised 6022 dust exposed (granite, foundry, cotton mill, iron foundry, metal product, and electrical) workers hired in 1940-76 and followed until the end of 1992. National mortality and morbidity registers and questionnaires were used. The statistical methods were person-year analysis and Cox regression. RESULTS: Co-morbidity from cardiovascular and respiratory diseases ranged from 17% to 35%. In at least 60% of the co-morbidity cases a respiratory disease preceded a cardiovascular disease. Chronic bronchitis, pneumonia, and upper respiratory track infections predicted IHD in granite workers (rate ratio (RR) = 1.9; 95% CI 1.38 to 2.72), foundry workers (2.1; 1.48 to 2.93), and iron foundry workers (1.7; 1.16 to 2.35). Dust exposure was not a significant predictor of IHD or other CVD in any group. Dust exposure was related to respiratory morbidity. Thus, some respiratory diseases appeared to act as intermediate variables in the association of dust exposure with IHD. CONCLUSION: Dust exposure had only a small direct effect on IHD and other CVD. IHD morbidity was associated with preceding respiratory morbidity. A chronic infectious respiratory tract disease appeared to play an independent role in the development of IHD.

Exposure-response analysis and risk assessment for silica and silicosis mortality in a pooled analysis of six cohorts.

AIMS: To study the relation between exposure to crystalline silica and silicosis mortality. Although mortality is an important endpoint for regulators, there have been no exposure-response studies for silicosis mortality, because of the relative rareness of silicosis as an underlying cause of death, and the limited availability of quantitative exposure estimates. METHODS: Data from six occupational cohorts were pooled with good retrospective exposure data in which 170 deaths from silicosis were reported. Standard life table analyses, nested case-control analyses, and risk assessment were performed. RESULTS: The rate of silicosis mortality in the combined data was 28/100 000 py, increasing in nearly monotonic fashion from 4.7/100 000 for exposure of 0-0.99 mg/m(3)-years to 233/100 000 for exposure of >28.1 mg/m(3)-years. The estimated risk of death up to age 65 from silicosis after 45 years of exposure at 0.1 mg/m(3) silica (the current standard in many countries) was 13 per 1000, while the estimated risk at an exposure of 0.05 mg/m(3) was 6 per 1000. Both of these risks are above the risk of 1 per 1000 typically deemed acceptable by the US OSHA. CONCLUSION: The findings from this pooled analysis add further support to the need to control silica exposure and to lower the occupational standards. Our estimates of lifetime silicosis mortality risk are probably underestimates as, in addition to exposure misclassification, our study might have suffered from outcome misclassification in that silicosis deaths might have been coded to other related causes, such as tuberculosis or chronic obstructive pulmonary disease.

Factors predictive of ischemic heart disease mortality in foundry workers exposed to carbon monoxide.

The potential predictors of ischemic heart disease mortality were studied for 931 male foundry workers in Finland who participated in a health examination in 1973. These workers were followed up to 1993 through registers and by using a questionnaire. In 1973, the systolic and diastolic blood pressures of workers exposed to carbon monoxide (CO) were slightly higher than those of unexposed workers. The prevalence of angina pectoris showed a clear dose-response relation to CO exposure. Electrocardiogram (ECG) findings indicating past myocardial infarction or suggesting coronary artery disease as a function of smoking and/or CO exposure were not evident. In the 1987 follow-up, the rate ratio for ischemic heart disease mortality was estimated as 4.4 for CO-exposed smokers compared with unexposed nonsmokers. Ischemic heart disease mortality in 1973-1993 was analyzed by using the Cox proportional hazards model. The statistically significant predictors were age, pathologic ECG findings in 1973, regular CO exposure, and abundant alcohol drinking. Of the ECG findings, changes in Q or QS and ST-J or ST waves and in ventricular extrasystoles were statistically significant. The risk of mortality from ischemic heart disease was increased by working in iron foundries, by hypertension, and by smoking.

Mortality, morbidity and health selection among metal workers.

Workers are selected into and out of physically demanding jobs with regard to their health. The study of occupational mortality and morbidity is hampered by this selection. Furthermore, social selection and rapid turnover are involved in health selection. Because different stages of disease form only one continuum (dissatisfaction-death), the correct interpretation of the results also requires measures softer than mortality. Earlier studies have concluded that soft and hard measures of health follow one another as explanations for the termination-of-employment rate. The aim of this study was to determine which age and exposure categories are the most prone to health selection. Mortality and morbidity were studied on three different exposure levels defined primarily according to the physical demands of the work: heavy level (iron foundries); medium level (manufacture of metal products); and light level (manufacture of electrical devices). The population comprised 15,714 men hired in 1950-1976 to work in the three branches of the metal industry. Another cohort, a cross-sectional one, of 1292 workers (who had been hired earlier and were still working in 1950) in the three industrial branches was used to clarify selection due to disability and mortality. Data for the mortality and disability analyses were obtained from national death and disability registers. The period of follow-up was 1950-1978. A questionnaire on occupational history, morbidity, and the causes of turnover was sent to 400 current and 600 former workers from each industrial branch. A questionnaire concerning occupational history was also sent to the nearest relatives of a total of 450 decidents. The occupational histories of the current and former workers were compared for changes in the exposure level throughout their complete occupational histories. The occupations during the workers' life-times were also classified into three exposure levels on the basis of physical demands (heavy, medium, and light). The three exposure levels showed different patterns of change according to age throughout the workers' complete occupational histories. Selection into and out of jobs within and between different exposure levels appeared to be a continuous process, a chain of selection. This conclusion was ascertained when the complete occupational histories were analyzed according to the exposure levels (heavy, medium, light) of the occupations from which the workers came and to which they transferred. The foundry workers entered the industry from either heavy or medium-level occupations, and most of them sought lighter work in medium-level occupations. The metal product workers either began their work lives within the metal product industry or they transferred to it from work that entailed the same exposure level. After leaving a job, the metal product workers generally moved to medium (i.e., the same level) or light occupations. The electrical workers switched from medium-level work, or they began their worklives within that industrial branch. When they left a job, they chose medium or light work in the metal industry. Due to the chain of selection from one exposure level to another, the mortality and morbidity rates for a certain exposure level can be underestimated or overestimated if complete occupational histories are not available. The selection process was different for different diseases and was manifested as different stages of disease. Ache or pain in the musculoskeletal system within the last 12 months was more frequent among the foundry and metal product workers than among the electrical workers. Both the currently employed and former foundry workers had significantly more earlier-diagnosed musculoskeletal diseases than the electrical workers. The younger age classes of foundry workers (< 45 years) had a higher occurrence of musculoskeletal diseases than the metal product workers; in the older age classes the opposite was true. (ABSTRACT TRUNCATED)

Mortality among Finnish sea pilots 1956-85: a retrospective cohort study.

The National Board of Navigation in Finland employed 942 sea pilots in 1956-85, during which time 262 of them died (SMR = 77, 95% CI = 68-86). The male population in southwest Finland served as control. The causes of deaths were collected from death certificates. The mortality rate for all cardiovascular diseases and lung cancer was lower among sea pilots than in the comparison population (SMR = 83, 95% = CI 69-97 and SMR = 67, 95% CI = 37-97) while for ischaemic heart diseases, it was similar to that of the population as a whole (SMR = 96, 95% CI = 77-115). Health selection due to ischaemic heart disease was seen in the lower mortality rates among young pilots who started work in 1956-85. Otherwise, the slightly higher rates may indicate a possibility of adverse health effects of sea piloting.

Silica dust exposure and lung cancer.

OBJECTIVE: The study evaluated the possibility of a direct association between silica dust exposure and lung cancer. METHODS: Mortality and morbidity among 1026 granite workers was followed in 1940-1989. Regional census data for 1970-1985 and lung cancer incidence data were also linked. The cytotoxicity of different granite fractions and their capacity to induce reactive oxygen species (ROS) in human leukocytes was studied in vitro. RESULTS: Excess lung cancer mortality was found during several follow-up periods. The rate ratios were 1.6-3.8 for different latency periods. Lung cancer risk increased with the length of exposure and latency. Lung cancer morbidity in 1953-1987 showed an excess for the red and grey granite areas, the rate ratio being 2.5 for > or = 20-year latency. Only one lung cancer case came from the black granite area. The cancer cases from the grey area had a shorter latency than those from the red area. The mineral composition differed for each area. The strongest ROS-inducing activity of grey and red granite was seen in the quartz-containing fractions. In the cytotoxicity tests the quartz-containing fractions of the grey and red granite also caused the strongest lactic dehydrogenase (LDH) release. However, plagioclase, the main constituent of black granite (60%), had approximately the same ability to induce ROS as the quartz-containing fractions of red and grey granite. CONCLUSIONS: The cancer morbidity and mortality figures of the three different granite areas, combined with the found differences in biological activity of granite dusts and a hypothesis that there is a cancer-inducing mechanism for ROS, point to a direct role for quartz in cancer induction.

Cardiovascular diseases among foundry workers exposed to carbon monoxide.

OBJECTIVES: The study investigated long-term effects of carbon monoxide (CO) exposure on foundry workers' morbidity and mortality from cardiovascular diseases. METHODS: The study population comprised a cohort of 2857 men hired in 1950--1972 by 20 Finnish foundries and also 931 men who were still active in 1972, exposed for at least 4.2 years, took part in a health examination in 1973; 653 of the 931 had also been members of the cohort. These groups were followed to the end of 1987. RESULTS: The age-standardized incidence density rate (ID/1000 person-years) for compensated medication for hypertension was 4.7 for the unexposed workers and 9.4 for those exposed [rate ratio (RR) 2.0, 95% confidence interval (95% CI) 1.28--2.92]; for the iron foundry workers the rates were 4.7 and 9.9 (RR 2.1, 95% CI 1.24--3.38), respectively. During 1950--1987, 255 cardiovascular deaths were observed (284 expected according to national rates). The observed number of deaths due to ischemic heart disease was 183 (203 expected). The iron foundry workers' mortality rate for cardiovascular deaths was 99% of the national expected value. No remarkable differences were found between the CO-exposure categories. For the health-examination group, the age-standardized incidence rate for compensated medication for hypertension was 9.1 for the unexposed nonsmokers and 21.4 for the exposed smokers (RR 2.3, 95% CI 0.97-6.35); the difference originated among the iron foundry workers, for whom the rates were 8.1 and 24.0 (RR 3.0, 95% CI 0.96--9.78), respectively. The age-standardized mortality rate (ID/1000 person-years) was 2.7 for nonsmokers with no or slight CO exposure and 9.2 for exposed smokers (95% CI 1.13--12.11). This difference was mainly caused by ischemic heart disease. CONCLUSIONS: The results indicate that CO exposure increases the risk of cardiovascular morbidity and mortality.

Mortality among sulfide ore miners.

Lung cancer mortality was studied during 1965-1985 in Outokumpu township in North Karelia, where an old copper mine was located. Age-specific lung cancer death rates (1968-1985) were higher among the male population of Outokumpu than among the North Karelian male population of the same age excluding the Outokumpu district (p less than .01). Of all 106 persons who died from lung cancer during 1965-1985 in Outokumpu township, 47 were miners of the old mine, 39 of whom had worked there for at least three years and been heavily exposed to radon daughters and silica dust. The study cohort consisted of 597 miners first employed between 1954 and 1973 by a new copper mine and a zinc mine, and employed there for at least 3 years. The period of follow-up was 1954-1986. The number of person-years was 14,782. The total number of deaths was 102; the expected number was 72.8 based on the general male population and 97.8 based on the mortality of the male population of North Karelia. The excess mortality among miners was due mainly to ischemic heart disease (IHD); 44 were observed, the expected number was 22.1, based on the general male population, and the North Karelian expected number was 31.2 (p less than .05). Of the 44 miners who died from IHD, 20 were drillers or chargers exposed to nitroglycerin in dynamite charges, but also to several simultaneous stress factors including PAHs, noise, vibration, heavy work, accident risk, and working alone. Altogether 16 tumors were observed in the cohort. Ten of these were lung cancers, the expected number being 4.3. Miners who had died from lung cancer were 35-64 years old, and had entered mining work between 1954 and 1960. Five of the ten lung cancer cases came from the zinc mine (1.7 expected). Three of them were conductors of diesel-powered ore trains. The slight excess mortality from lung cancer could be explained by exposure to radon daughters and by the combined effect of silica dust and diesel exhaust gases in the zinc mine.

Mortality and disability among cotton mill workers.

The mortality and disability of cotton mill workers were studied in five Finnish cotton mills. The population under study comprised all 1065 women exposed to raw cotton dust who had been hired between 1950 and 1971. The minimum exposure period was five years. For the study on disability, the cohort was followed up until the end of 1981. The follow up period for the mortality analysis was from 1950 to 1985. At the end of 1981 the observed number of prevalent disability pensions for respiratory disease was 15, whereas 3.9 were expected (p less than 0.01) on the basis of the national figures for women. There were 46 musculoskeletal diseases (27.7 expected, p less than 0.01), of which 24 were osteoarthritis (14.5 expected) and 13 rheumatoid arthritis (6.6 expected). The incidence rates of disability pensions were calculated for the period 1969-81. Comparison of incidence rates between cotton mill workers and the Finnish female population showed excessive rates for both respiratory diseases (p less than 0.001) and musculoskeletal diseases (p less than 0.01), with an excess of new cases of rheumatoid arthritis (p less than 0.05). By the end of 1985 the number of person-years was 31,678 and the number of deaths 95. The standardised mortality ratios for the total period of follow up (1950-85) showed no excess for respiratory diseases. Mortality from cardiovascular diseases was also lower than expected. The observed number of tumours was 33, the corresponding expected number 32.0. Thirteen tumours were in the digestive organs (6.6 expected, p<0.05) and three were lung cancers (1.9 expected). Five workers had died from renal disease; the expected number was 1.5 (p<0.05).

Cancer mortality of granite workers 1940-1985.

A retrospective cohort study was undertaken to investigate the cancer mortality of granite workers. The study comprised 1026 workers who took up such work between 1940 and 1971. The number of person-years was 23,434, and the number of deaths was 296. During the total follow-up period, 59 tumours were observed as compared with 54.4 expected. An excess mortality from tumours was observed in workers followed up for 20 years or more. Of the 59 tumours, 31 were lung cancers (expected 19.9), and 18 gastrointestinal cancers (expected 11.6), nine of which were stomach cancers (expected 7.1). Mortality from lung cancer was excessive for workers followed up for at least 15 years (28 observed, 12.7 expected). The results indicate that granite exposure per se may be an etiological factor in the initiation or promotion of malignant neoplasms.

Silica exposure and rheumatoid arthritis: a follow up study of granite workers 1940-81.

The incidence and prevalence of subjects awarded disability pensions and the prevalence of subjects receiving free medicines because of rheumatoid arthritis were studied in a Finnish cohort of 1026 granite workers hired between 1940 and 1971 and followed up until 31 December 1981. The incidence of awards of disability pensions because of rheumatoid arthritis during 1969-81, the prevalence of rheumatoid arthritis on 31 December 1981, and the prevalence of subjects receiving free medicines for rheumatoid arthritis at the end of 1981 were significantly higher among the granite workers than in the general male population of the same age. Retrospective analysis of the records of all patients with rheumatoid arthritis in the cohort showed a predominance of a severe, serologically positive and erosive form of rheumatoid arthritis, usually with an age at onset of 50 or over. The possible aetiological or pathophysiological role of granite dust in rheumatoid arthritis may be based on the effects of quartz on the immune system.

Mortality and disability among granite workers.

The objective of the present study was to investigate the mortality, disability, and long-term morbidity of granite workers. The study included 1,026 workers hired between 1940 and 1971 and followed until the end of 1981. The total number of deaths was 235, and the expected number was 229.7. Excess mortality rates were observed for respiratory diseases (observed/expected = 28/13.9). The number of tumor deaths was 46 (expected 44.9). Excess lung cancer mortality was evident at 15 to 35 years of latency; the observed number of lung cancer deaths for the follow-up period of 25 to 29 years was 8, while 2.1 were expected. Mortality from cardiovascular diseases and violent deaths was slightly less than expected. The results for disability and long-term morbidity showed elevated incidence and prevalence rates for respiratory diseases and rheumatoid arthritis. The observed number of disability pensions due to rheumatoid arthritis in 1981 was 10 observed versus 1.8 expected, and the observed number of patients granted free medication was 19 versus 8.1 expected. The results indicate that granite dust exposure per se may be an etiologic and pathogenetic factor for lung cancer, cancer of the gastrointestinal tract, and some extrapulmonary nonmalignant chronic diseases.

Cancer mortality of granite workers.

A retrospective cohort study was undertaken to investigate the cancer mortality of granite workers. The study comprised 1,026 workers hired between 1940 and 1971. The number of person-years was 20,165, and the number of deaths 235. During the total follow-up 46 tumors were observed and 44.9 were expected. An excess mortality from tumors was observed for the workers followed for 20 years or more, the greatest excess occurring during the follow-up period of 25-29 years (observed 11, expected 5.2). Of the 46 tumors, 22 were lung cancers (expected 17.1) and 15 were gastrointestinal cancers (expected 9.7), nine of which were cancers of the stomach (expected 6.0). Mortality from lung cancer was excessive for workers with at least 15 years since entry into granite work (latency) (21 observed and 9.5 expected), being highest during the follow-up period of 25-29 years (observed 8, expected 2.1). The results indicate that granite exposure per se may be an etiologic factor in the initiation or promotion of malignant neoplasms.

Different stages of disease, changes in heaviness of work and life cycle.

The aim of this study was to determine which age and exposure categories are the most prone to health selection. Mortality and morbidity were studied on three different exposure levels defined primarily according to the physical demands of the work, heavy (iron foundries), medium (manufacture of metal products), and light (manufacture of electrical devices). The population comprised 15 714 men hired in 1950-1976 to work in the three branches of the metal industry. A questionnaire on occupational history, morbidity, and the causes of turnover was sent to 3 450 current and former workers. The occupational histories of current and former workers were compared for changes in heaviness throughout their complete occupational histories. Occupations during a lifetime were also classified into three levels of exposure on the basis of physical demand (heavy, medium, and light). The three levels of exposure showed different patterns of changes in heaviness of the work according to age throughout the workers' complete occupational histories. Selection into and out of jobs within and between different levels of exposure seemed to be some kind of continuous process, a chain of selection. Similarly as changes in the heaviness of the work formed a chain of selection during lifetime, the workers' health also changed to form a chain through their life cycle. Hard and soft measures formed a continuum (dissatisfaction - death), and they followed each other as explanations for termination of employment. The points of inflection in age, where the measures of different stages of disease turned from soft to hard, varied according to the level of exposure. The life-table technique was used to show the turning of the measures.

Completeness of occupational history and occurrences of work-related diseases.

The lack of complete occupational histories causes underestimates or overestimates of occupational mortality and morbidity. The problem is emphasized in cohorts with high turnover and in cross-sectional study designs. In the study of the effect of selective turnover on occupational mortality and morbidity complete occupational histories were acquired via questionnaire. The sample comprised 1 200 current and 1 800 alive former workers and the closest relatives of 450 deceased workers and was formed from three exposure-level cohorts (defined primarily according to the physical demands of the work) of 15 714 metal workers hired in 1950-1976. The occupational histories reported in the questionnaires were compared with those collected from employers' personnel records. The coverage of occupational histories was the most accurate for current and former workers with the longest duration of exposure and the least accurate for dead workers and the oldest age groups. The use of complete occupational histories and the combining of the similar levels of exposure through the lifetime produced clear differences in the occurrences of musculoskeletal, respiratory, and cardiovascular diseases between the three levels of exposure. The errors in person-years were smaller than the errors in the duration of exposure; the coverage varied from 51 to 94%. However, misclassification clearly caused cancer cases to be located in classes with too short a period of latency. About 30% of the deceased workers had reportedly entered the industry before the first follow-up year.

Effect of cohort definition and follow-up length on occupational mortality rates.

The purpose of this study was to clarify the effects of cohort formation, period of entry, and period of follow-up on occupational mortality figures. The study material comprised three cohorts of metal industry workers (6 415 iron foundry workers, 3 901 metal product workers, and 5 398 workers manufacturing electrical devices). The men, hired between 1950 and 1976, were followed until the end of 1978. The number of person-years was approximately 215 800. Different cohort formation criteria and variations in the follow-up modify the results of occupational mortality studies. A cross-sectionally based cohort (workers employed in a certain year or years) produces results different from those for an open cohort (new workers hired during a certain period of time) although the cohorts are formed from the same workplaces. The cohorts for retrospective cohort studies usually contain various periods of entry, periods of follow-up, and age structures. Increased or decreased mortality in a cohort depends on this internal structure. The structure of the cohort becomes especially important when a certain cause of death is concentrated in certain age classes and/or when a period of latency is required, as for tumors. In an attempt to reveal this internal structure the three cohorts were analyzed in five-year calendar periods and stratified according to the length of follow-up. The mortality pattern remained nearly unchanged when the number of periods of entry increased, and it was also comparable with the mortality pattern of the general male population.(ABSTRACT TRUNCATED AT 250 WORDS)

Health selection among metal workers.

The objective of the present study was to determine which age and exposure categories are the most prone to health selection. Mortality and morbidity were studied on three different exposure levels, defined primarily according to the physical demands of the work: heavy level (iron foundries), medium level (manufacture of metal products), and light level (manufacture of electrical devices). The population comprised about 15,700 men employed in 1950--1976 in the three branches of the metal industry. The number of person-years of follow-up was about 215, 800. During the period 1950--1978, 1,407 deaths occurred. Occupational history, morbidity, and turnover causes were studied by means of a questionnaire sent to 3,500 current and former workers. The survival curves showed no great differences between the three exposure levels. However the heavy level had the highest degree of mortality, and the medium level the lowest. Foundry workers had the highest overall rates of disability. But, in the older age groups, the disability rates of the metal product workers were the highest. Less social selection was suggested for foundry workers than for the two other cohorts. Metal product workers seemed to be selected by both social and health factors. Young electrical workers were occupationally trained. On the other hand older workers with poor health were selected to this light level (negative health selection).

Occupational mortality and morbidity in relation to selective turnover.

Because of the "healthy worker effect" most occupational cohorts, especially those of persons doing physically heavy work, are selected groups with regard to life expectancy. Health selection is also involved in turnover. Mortality and morbidity were studied on three different exposure levels, defined primarily according to physical demands: heavy level (iron foundries), medium level (manufacture of metal products), and light level (manufacture of electrical devices). The population comprised about 15,700 men who were employed in 1950-1976 in the three branches of the metal industry representing the different levels. The number of person-years of follow-up became about 215,800. During the period 1950-1978, there had occurred 1,407 deaths. Data for the mortality and disability analyses were obtained from the national death and disability registers. Occupational history, morbidity, and reasons for turnover were studied in a sample by means of questionnaire sent to 400 current and 600 former workers from each branch. In addition, a questionnaire concerning occupational history was sent to the next of kin of 450 dead persons. When the three cohorts were compared to the general male population of Finland, the standardized mortality ratio was 124 for the foundry workers, 92 for the metal product workers, and 107 for the electrical workers. The survival curves showed no great differences between the three exposure levels. However, the heavy level had the highest degree of mortality, and the medium level the lowest. Foundry workers showed less social selection than the two other cohorts. Metal product workers seemed to be socially and health selected. Economic fluctuations clearly regulated entries of new employees into the industries and thus introduced additional selective features.

Lung cancer mortality among iron foundry workers.

The present study was designed to test earlier findings of increased risk of lung cancer among iron foundry workers and to define the cause of the risk. The subjects were 3,425 workers with at least one year's employment in an iron foundry sometime between 1918 and December 31, 1972. The number (51) of cases of lung cancer which occurred prior to December 31, 1976 was statistically significantly higher than that expected, i.e., 35.3 based on proportional mortality. Molders and casters were determined to have the highest excess risk in a case-control study among the cohort. The worker groups with high exposure to polycyclic aromatic hydrocarbons (PAH) experienced a lung cancer risk higher than that of other groups, but the difference was not statistically significant.