Trichloroethylene Induced Cancer in animals and its relevance to Humans: Trevor GREEN. Zeneca Central Toxicology Laboratory—Trichloroethylene has been manufactured on an industrial scale since the beginning of this century. During that time widespread human exposure has occurred in industry and in the general population through the environment and from its uses in medicine, food and consumer products. Following the discovery in 1976 that trichloroethylene was an animal carcinogen, there have been numerous animal toxicology and human epidemiology studies evaluating the risks associated with exposure to this chemical. Trichloroethylene has been shown to cause tumours in both rats and mice in lifetime bioassays, principally liver and lung tumours in the mouse and kidney tumours in the rat. The mechanisms involved in the development of these tumours have been studied in detail and have been shown to be either species specific or a result of the use of cytotoxic dose levels. There is little or no evidence for genotoxicity playing a major role in these mechanisms. In mice, liver tumours are associated with peroxisome proliferation and increased cell division, the lung tumours are linked to cell damage and increased cell division. None of these effects are seen in rats due to metabolic and pharmacokinetic differences nor can they be replicated in human tissues. The low incidences of rat kidney tumours seen in some cancer bioassays appear to be linked to high dose toxicity. Human epidemiology studies based on large well defined cohorts support the findings of the mechanistic studies in animals and the overall conclusions that trichloroethylene is not a cancer hazard at current occupational and environmental levels.
A Research in the Effects of Active Listening on Corporate Mental Health Training: Shinya KuBOTA, et al. Department of Mental Health, Institute of Industrial Ecological Sciences, University of Occupational and Environmental Health—The effects of mental health training for corporate administrators, using Active Listening (Experiential Listening) as a major method was investigated. Sixty subjects took part in the mental health training program which consisted of 2 two-day workshops (a total of 30 hr). The workshop program consisted of a lecture on stress, techniques of relaxation, the practice of Active Listening, and sharing of personal communication experiences in the workplace. Questionnaires which measured the Type A behavior pattern and the effects of Active Listening were collected in the first and last training sessions. The results showed significant differences in the degree of listening in the workplace in six of 27 items in the listening questionnaire and significant differences in three of seven items in the Type A questionnaire. Active Listening training seems to promote the attitudes of "listening genuinely" or "listening seriously" to workers. The practice of better listening may decrease the characteristics of the Type A behavior pattern such as "being busy" or "making others busy." The mental health method focusing on Active Listening is discussed as a useful training technique for corporate mental health.
The Relationship between the White Blood Cell Count and Cigarette Smoking among Japanese Males: Yoshito MOMOSE, et al. Department of Hygiene and Preventive Medicine, School of Medicine, Fukuoka University—The cross-sectional data for 1, 155 men aged 20-59 years obtained during annual health checkups in 1993 were used to study factors related to the WBC count. Current smokers have a WBC count averaging 10-15 percent higher than those of both ex-smokers and those who never smoked. The current number of cigarettes smoked per day and the Brinkman index were also positively related to the WBC count after adjusting for such risk factors as the BMI, diastolic blood pressure, and HDL-C level by means of a covariance analysis. We thus confirmed that an elevated WBC count is independently associated with the amount and duration of cigarette smoking among Japanese males.
A Meta-Analysis on the Relationship between Pneumoconiosis and Lung Cancer: Toshihide TSUDA, et al. Department of Hygiene and Preventive Medicine, Okayama University Medical School—An excess of lung cancer deaths among pneumoconiosis patients has been noted for many years but there has not been agreement on the excess of lung cancer deaths among pneumoconiosis patients in Japan. A meta-analysis on the relationship between silicosis/pneumoconiosis and lung cancer mortality was conducted, by using 36 mortality studies published from 1980 to 1994. MEDLINE and other information sources were used for the information retrieval. After the critical appraisal, 32 eligible studies were identified. Study estimates were then pooled by using both the fixed effect model and the random effect model. An excess of lung cancer mortality among people with silicosis/pneumoconiosis was shown in all 32 studies. Although homogeneity among the studies was rejected (p<0.05) because the shape of the funnel plots assumed a symmetrical pyramidal shape, the summary rate ratio was estimated. The estimated rate ratio was 2.74 (95 percent confidence interval 2.60-2.90) in all 32 studies, and 2.77 (2.61-2.94) in 25 cohort studies. The random effect model results were almost the same as the fixed model results. The estimates in the Japanese studies were a little higher than the overall estimates, which indicated that lung cancer mortality was about three times higher among silicotic patients than among people in the control. This indicated a causal-relationship between silicosis and lung cancer. This means that lung cancer should be regarded as one of the important complications of silicosis/pneumoconiosis. We recommend further research on the relationship between silica exposure and lung cancer.
Trends in Major Occupational Injuries in Different Industrial Divisions in Taiwan during 1983-1993: Yu-Chen CHANG, et al. Department of Family Medicine, Tainan Municipal Hospital—Objectives: The purpose of this study was to examine the time trend in occupational injuries in main industrial divisions in Taiwan from 1983 through 1993 with newly developed quantification methods. Methods: Data concerning deaths and permanent disabilities caused by occupational injuries were retrieved from the computer files of Taiwan''s Labor Insurance Bureau and statistical analyses were performed by using the indices of the cumulative injury rate for from 15 to 64 years of age (CIR15-64), modified severity index (MSI), proportion of potential workdays lost (PPWDL) and foregone earnings lost. Results: Mining and quarrying was the most risky industry, when expressed in both frequency and severity. The mean rates over the 1 1 year period were as follows: disabling frequency rate, 24.0; incidence rate, 0.012 (yr -1); CIR15-64, 0.491 ; disabling severity rate, 7, 591.7; modified severity index, 22.5; and the PPWDL, 3.72 (10-3). In terms of frequency, incidence rate and CIR15-64, manufacturing was second and agriculture third. With regard to severity, MSI and PPWDL, agriculture ranked second and construction ranked third. The overall trend in occupational injuries in Taiwan has steadily improved in the past decade. All indicators of human capital loss in 1993 were nearly down to one third of those reported in 1983. The estimated potential salary lost in all industries of 1993 was 584.6 million US dollars. Conclusions: Mining and quarrying was still ranked the most risky industry during 1983-93. We have demonstrated that CIR15-64, MSI, PPWDL and foregone earnings lost supplemented disabling frequency and severity rates in the aspect of human capital loss. There was a consistently improved trend in occupational injuries in Taiwan during 1983-93.
A Retrospective Cohort Study on Digestive Cancer in the Rubber Tire Industry in Shanghai: Jigang CHEN, et al. Shanghai Institute of Industrial Hygiene and Occupational Diseases—8, 316 subjects, who had been employed in three tire factories in Shanghai for more than 1 year before December 31, 1972, were investigated in a retrospective cohort study to ascertain the relationship between digestive cancer and the job types in the rubber tire industry in Shanghai. Every subject was assigned to one of 27 jobs grouped into 8 types. The observation period was from January 1, 1967 to December 31, 1988. The Results show that several sites of cancer in the digestive system were associated with some main jobs in factories for both sexes. For example, stomach and liver cancers in workers in milling (SIR=202.8 and 229.2), inner tube curing (SIR=231.3 and 252.3) and material handling (SMR=209.6 for stomach cancer) in males; pancreatic cancer in tire curing (SIR=349.4) in males and in inner tube and tire buildings (SMR=372.5) in females; esophageal cancer in the production of non-tire products (SMR=275.31) in males; and rectal cancer in Building and Multiple jobs for non-tire work in males (SMR=483.7) and females (SMR=245.0). The authors thought the high incidence of cancer in the digestive system was a prominent phenomenon in several types of jobs in the rubber product manufacturing industry.
Pulmonary Function in Jute Dust- Exposed Workers: A Dose-Response Relationship: Jie CHEN, et al. Department of Pneumoconiosis, China Medical University School of Preventive Medicine—Pulmonary function tests were carried out on 488 jute-exposed workers in a jute mill and 332 control workers. An industrial hygiene survey was also conducted. Most workers in the mill were exposed to dusts containing less than 6% silica, whereas a few workers were exposed to dusts containing approximately 10-16% silica. The cumulative dose of dust exposure [dust level (mg/m3)× exposure year (yr)] was used as an exposure index to relate pulmonary function injury in jute workers. The results showed that jute workers had lower percentages of predicted pulmonary function than those of control workers. As the cumulative dose of dust exposure increased, average levels of pulmonary function (FVC, FEV1, MMF, V50, V25) in smoking male jute workers and V50, V25 in nonsmoking female jute workers significantly declined, and pulmonary function abnormalities (less than 80% of predicted FEV1 or less than 70% of predicted V50) significantly increased as the cumulative dose of dust exposure increased. Examination of the effects of dust exposure and smoking on pulmonary function injury showed that not smoking but jute dust exposure was a factor associated with the decline in pulmonary function; Moreover, smoking interacted with dust exposure in causing declines in FEV1. Our results demonstrated that there is a dose-response relationship between dust exposure and pulmonary function injury in jute workers. Based on this dose-response relationship and by using the life-table method, an exposure limit for jute dust was proposed as 4 mg/m3.
Effects of Styrene on Peripheral Nerve Conduction Velocities in Rats: Tadashi YAMAMOTO, et al. Department of Preventive Medicine and Environmental Health, Osaka City University Medical School—The effects of styrene on the peripheral nerves were studied by measuring conduction velocities of the tail nerve in 24 male Wistar rats which had been exposed to 0 (control), 200 and 2, 000 ppm of styrene (8 rats for each concentration) for 32 wk (8 h/d × 5 d/wk), from the age of 8 wk, and in the same number of rats which received the same treatment since they were 4 wk of age. Motor nerve conduction velocity (MCV), distal latency (DL) and sensory nerve conduction velocity (SCV) were determined at 2-wk intervals from the age of 8 wk to 16 wk after the end of exposure. Body weight in the 2, 000 ppm (start at 4 and 8 wk of age) and 200 ppm (start at 4 wk of age) exposure groups were significantly lower than in the control group. MCV and DL in the all exposure groups were not significantly different from the control group. SCV in the 2, 000 ppm (start at 4 and 8 wk of age) and 200 ppm (start at 8 wk of age) exposure groups were significantly lower than in the control group during the styrene exposure. After discontinuation of exposure, SCV remained small in the 2, 000 ppm group (start at 4 wk) compared with that in the controls, but showed recovery in the other exposure groups. The effects on the decrease in SCV were greater in the distal than in the proximal area.
Cancer Mortality among Carbon Workers in China: Retrospective Cohort Study: Ning Liu, et al. Institute of Industrial Health Anshan Iron & Steel Complex—A retrospective cohort study was performed on a group of 6, 635 male workers employed for more than 15 years during the period 1970-1985 in seven factories including the carbon plants and the potroom and carbon department in an aluminium reduction plant. The SMRs for lung cancer and liver cancer among the workers highly exposed to coal tar pitch volatiles (CTPV) were 4.30 (p<0.01) and 2.25 (p<0.01), respectively. The SMRs for lung cancer and cancer of the esophagua among moderately CTPV-exposed workers were 1.52 (p>0.05) and 5.46 (p<0.01) respectively. Results showed that the numerous deaths from lung cancer were correlated with CTPV in the carbon-producing process in carbon plants.
Validation of a Self-Administered Questionnaire on Asthmatic Symptoms and Atopy it House Painters: Gunilla WIESLANDER, et al. Department of Occupational and Environmental Medicine, Uppsala University—The aim of this study was to validate questions on asthmatic symptoms and atopy among Swedish house painters. Clinical investigations were performed in 44 male painters, selected by stratified sampling from a larger group of 415 painters. Symptoms were recorded by means of a self-administered questionnaire. Clinical examinations were performed after an exposure free weekend, and included dermal prick test to nine common allergens, dynamic spirometry, and methacholine challenge test (MCT). Atopy was defined as at least one positive skin prick test to common allergens. A forced expiratory volume in one second (FEV1) below 80% of normal values were considered a sign of impaired lung function. A cumulative dose of methacholine below 8 mg causing a 20% decrease in FEV1 (PD20) was considered a sign of bronchial hyperresponsiveness (BHR). Sensitivity and specificity for different questions was calculated. Most single airway symptom had a good sensitivity for severe BHR, defined as a PD20 below 0.5 mg of methacholine. For milder BHR, however, sensitivity was below 50% for most single symptoms, except the question on nonspecific hyperreactivity symptoms. By combining the symptoms to a symptom score predicable of BHR, a high sensitivity could be obtained for both mild BHR and severe BHR Most single questions on respiratory symptoms had high specificity, but low sensitivity, as predictors of impaired FEV1. Sensitivity for impaired FEV1 was improved by constructing another symptom score, predictable of FEV1. The assessment of a history of atopy by five questions on asthma, hay fever and eczema in childhood was significantly related to atopy verified by a positive dermal prick test (79% sensitivity and 75% specificity). There was also a significant relation between self-reported hay fever and positive prick test to pollen extracts (52% sensitivity and 90% specificity). In conclusion, our questions on airway symptoms and atopy are related to clinical signs of BHR, impaired FEV1, and atopy respectively. By combining different symptoms to symptom scores, the problem with low sensitivity of single questions on airway symptoms and atopy can be reduced.
Assessment of Workers'' Exposure to Antimony Trioxide in Korea: Ki-Woong KIM, et al. Industrial Health Research Institute, KISCO—The assessment of workers'' exposure to antimony trioxide was conducted for the workers at three antimony trioxide factories located in Kyeonggi-do, Chungnam, Cheonnam, Korea during the period of September 4 to October 28, 1995. The objective of this study was to investigate any exposure of workers to antimony. The results were as follows: 1. Mean of the total antimony concentration in the air near the workplace was 0.0223 mg/m3 in the oxidation part and 0.2806 mg/m3 in the packing part (p<0.05). 2. Mean of the respirable antimony concentration in air near the workplace was 0.0028 mg/m3 in oxidation and 0.0034 mg/m3 in packing (p>0.05). 3. The average urinary antimony level in the oxidation part was 0.1827 mg/g creatinine and that of packing part was 0.1371 mg/g creatinine. But they were not statistically significant (p>0.05).