[Risk of myocardial infarction is increased among transportation and industry workers].
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Biomedical subjects
Publications and source records attributed to C Hogstedt.
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In a previous cohort study by our group, certain industry-related chemicals were judged as warranting further attention as possible urothelial carcinogens. In this paper, the epidemiologic literature of cancer of the lower urinary tract is evaluated for these substances. We would like to add combustion gases/soot from coal to the substances considered as increasing the risk of urothelial cancer. It is, however, uncertain whether this risk is due to contaminants of aromatic amines in tar volatiles or whether it depends on other agents, such as nitroarenes or polycyclic aromatic hydrocarbons. Furthermore, we find some support for the hypothesis that exposure to chlorinated aliphatic hydrocarbons increases the risk of urothelial cancer. For creosote, cutting fluids and cutting oils, hair dyes, and polychlorinated biphenyls, data are scarce. Available data do not support the hypothesis that asbestos is associated with urothelial cancer. "Publication bias," such that only limited information was available, was judged to be a potential problem in the review for many, but not all, of the substances investigated.
The influence of heavy lifting during pregnancy on gestational age, birthweight and the risk of fetal death (spontaneous abortion or stillbirth) was investigated in a prospective study of 3906 occupationally active women. Information on exposure was collected at the women's first contact with the antenatal care centres in Orebro County from October 1980 to June 1983. Logistic and linear regression were used to analyse the data, allowing for several non-occupational factors in the models. Women who reported heavy lifting did not have in general more unfavourable outcomes than other women, although the risk estimates varied between different occupational categories. Lifting of weights greater than or equal to 12 kg more than 50 times per week increased the risk of pre-term birth (less than 37 weeks of gestation--odds ratio 1.7), but only among women who stopped working before the 32nd week of pregnancy. Unfavourable outcomes were more common among those who reported chemical exposure during pregnancy. The preventive routines and regulations in Sweden may have helped to reduce possible risks from heavy lifting during pregnancy.
Neuropsychiatric symptoms in 65 welders exposed to aluminium and 217 railroad track welders were studied with the aid of a previously validated questionnaire. Semiquantitative data on exposure to the metals aluminium, chromium, lead, manganese, and nickel were also recorded by questionnaire. Logistic regression was employed to study the relation between exposure and the prevalence of symptoms. Welders exposed to aluminium, lead, or manganese for a long period had significantly more neuropsychiatric symptoms than welders not exposed to these metals. The results indicate that detailed psychometric studies should be performed on welders exposed long term to specific metals as such exposures might affect their nervous system.
Mortality and cancer incidence was investigated among the 695 bus garage workers employed as mechanics, servicemen, or hostlers for at least six months in five bus garages in Stockholm between 1945 and 1970. The exposure to diesel exhaust and asbestos was estimated by industrial hygienists. A small excess of lung cancer mortality was found in the cohort when occupationally active men in Stockholm were used as the reference group. A case-referent study was performed within the cohort, six referents being selected for each of the 20 lung cancer cases. The lung cancer risk increased with increasing cumulative exposure to diesel exhaust, but not with cumulative asbestos exposure. The relative risk for lung cancer among the highly exposed men was 2.4 (95% CI 1.3-4.5) as compared with those with low exposure. The study indicates that exposure to diesel exhaust increases the risk for lung cancer.
Two criteria for an interpretation of noneffect are that the relative risk estimate be near unity and that the confidence interval be narrow; lack of statistical significance has no bearing on this issue. A further requirement is that the relative risk estimate not be near the null value as an effect of non-differential exposure misclassification, negative confounding, or some other systematic error. Occasionally, when results are unexpected or difficult to accept, studies are "underinterpreted" as negative or inconclusive on the basis of arguments such as "confounding," "crude exposure assessment," or "lack of a known mechanism." The present paper supports the position that these arguments are commonly invalid. Scientific standards should be used to separate causal associations from noncausal ones, but in public health decisions this practice has to be balanced by the principle that the "benefit of the doubt" should be given to the persons subject to potential risk.
Several studies of pulp and paper workers have demonstrated increased risks for certain cancer sites, e.g. tumours of the lymphatic and haematopoietic system as well as stomach cancer. An impressive lung cancer excess was found among paper and board mill workers in Finland, but not in studies elsewhere. Individual exposures have not been estimated, neither has a job-exposure matrix been applied in any of the studies. Therefore, it is impossible to link any of the excesses to specific single compounds or mixtures, of which there are a multitude in the pulp and paper industries. Although there are high quantities of organic chlorine compounds in the process mixtures and waste, the compounds have low volatility and occupational exposures are not necessarily high. Estimations of individual occupational exposure should be mandatory in future epidemiological studies in this industry.
The incidence of lung cancer among 280 silicotic men working in the ceramics industry and notified to the Swedish Silicosis Registry has been investigated. During the study period 1958-83, the risk of lung cancer (nine cases) was double that expected based on national rates. There was no increased incidence of cancer at any other site. The results are in agreement with those of both animal and epidemiological studies of quartz exposure and point to an increased risk of lung cancer, especially among silicotics. Various possible explanations of this increased risk are discussed, but further studies are required.
The influence of occupational factors on the outcome of pregnancy was investigated in a prospective study of 3901 women who worked during their pregnancy and received prenatal care in Orebro County from October 1980 to June 1983. Data on occupational factors, social circumstances, and life-style factors were obtained from questionnaires. There were no significant differences in the incidence of adverse pregnancy outcome (spontaneous abortion, perinatal death, birth defects, or low birthweight) between the nine occupational categories used when nonoccupational factors were accounted for. No increased risk was found for exposure to organic solvents, but the adjusted risk ratio of adverse outcome was 1.28 (95% CI 0.91-1.80) for "other chemical exposures." The work conditions in this county have been generally favorable in recent years, and the results therefore cannot be generalized to conditions with higher exposures. Methodological problems such as misclassification of exposure and the possible bias resulting from different rates of legal abortions among occupational groups are discussed.
The incidence of cancer was investigated among 5266 Swedish chimney sweeps employed for any period between 1918 and 1980. An analysis of the mortality has been reported earlier and showed an increased number of deaths from coronary heart disease, respiratory diseases, and lung, oesophageal, and liver cancer. Excess risks for cancer of the lung and oesophagus were confirmed in this analysis. Among the lung cancers, both squamous cell carcinoma and oatcell/undifferentiated carcinoma were in excess. In addition, a more than doubled risk for bladder cancer (23 observed v 9.8 expected cases) and an increase of malignancies of the haematopoietic system was found. There were, however, no cases of scrotal cancer, the classic occupational hazard among chimney sweeps. Chimney sweeps are exposed to polycyclic aromatic hydrocarbons generated by the combustion of organic material (coal, wood, coke, and oil). They are also exposed to cancerogenic metals (arsenic, nickel, and chromium). These results support the need for improved working conditions.
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In a cohort study of 5464 union organised Swedish chimney sweeps employed at any time between 1918 and 1980 mortality was studied from 1951 to 1982 with national statistics used as a reference. Follow up was possible for 98.6% of the individuals: 717 deaths were observed against 540 expected. There was an increased mortality from coronary heart disease, respiratory diseases, and several types of malignant tumours. Lung cancer mortality was significantly increased and positively correlated to the number of years employed. A fivefold risk increase for oesophageal cancer and liver cancer was found. The increased mortality could be attributed to exposure to combustion products in the work environment but not to smoking habits.
An excess of lung cancer among butchers and slaughterhouse workers has been reported in several record-linkage studies. In this case-referent investigation on the possibility of occupational exposures being related to the lung cancer excess, cases and referents were selected from butchers and slaughterhouse workers registered in the Swedish national census of 1960. The case group comprised all men in the study population dying from lung cancer between 1971 and 1982. Two reference groups were formed, ie, all individuals dying from other cancers and a random sample of all dead men in the study population during the same time period. The history of occupations, occupational exposures, and smoking habits was obtained from the next-of-kin by questionnaire. None of the occupational exposures that were studied (work with live animal care, in the bleeding area, on the killing floor, or with meat cutting, processing, curing, smoking, chilling and packaging) were associated with an increased lung cancer rate. Tobacco smoking habits may have contributed to the overall excess of lung cancer found previously for this occupational group.
Exposure to combustion engine exhaust and its effect on crews of roll-on roll-off ships and car ferries and on bus garage staff were studied. The peak concentrations recorded for some of the substances studied were as follows: total particulates (diesel only) 1.0 mg/m3, benzene (diesel) 0.3 mg/m3, formaldehyde (gasoline and diesel) 0.8 mg/m3, and nitrogen dioxide (diesel) 1.2 mg/m3. The highest observed concentration of benzo(a)pyrene was 30 ng/m3 from gasoline and diesel exhaust. In an experimental study volunteers were exposed to diesel exhaust diluted with air to achieve a nitrogen dioxide concentration of 3.8 mg/m3. Pulmonary function was affected during a workday of occupational exposure to engine emissions, but it normalized after a few days with no exposure. The impairment of pulmonary function was judged to have no appreciable, adverse, short-term impact on individual work capacity. In the experimental exposure study, no effect on pulmonary function was observed. Analyses of urinary mutagenicity and thioether excretion showed no sign of exposure to genotoxic compounds among the occupationally exposed workers or among the subjects in the experimental study.
The mortality and incidence of cancer in three groups of workers with occupational exposure to ethylene oxide have been assessed. Eight cases of leukemia have occurred among 733 ethylene oxide-exposed workers compared with an expected 0.8 cases. Six cases of stomach cancer have been reported compared with 0.65 cases expected. These epidemiologic results provide support for an increased risk of malignancy in individuals with extended and intermittent exposure to low concentrations of ethylene oxide.
A cohort study of 142 male Swedish capacitor manufacturing workers was performed. PCB had been used as a dielectricum in power capacitors between 1960 and 1978. Mortality was investigated for the period 1965 to 1982 and cancer incidence from 1965 to 1980. Twenty-one deaths and seven cancers were observed, which was in agreement with the anticipated numbers calculated from national statistics. One person had developed two rare tumors, a slow growing mesenchymal tumor (desmoid) and a malignant lymphoma. The results cannot rule out the possibility of a carcinogenic risk from PCB exposure because of the small size of the cohort and relatively brief follow-up period, but they do not indicate any excess mortality or cancer incidence in this factory so far.