Relation between exposure to asbestos and smoking jointly and the risk of lung cancer.
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OBJECTIVES: To review evidence about the joint relation of exposure to asbestos and smoking on the risk of lung cancer to answer three questions: (1) does asbestos increase risk in non-smokers; (2) are the data consistent with an additive model; and (3) are the data consistent with a multiplicative model? METHODS: Analysis of 23 studies reporting epidemiological evidence on the joint relation. Comparison of risk of lung cancer in subjects unexposed to asbestos or smoking, exposed to asbestos only, to smoking only, or to both. Estimation of the relative risk associated with asbestos exposure in non-smokers and of statistics testing for additivity and multiplicativity of risk. RESULTS: Eight of the 23 studies provided insufficient data on the risk of lung cancer in non-smokers to test for possible effects of asbestos. Asbestos exposure was associated with a significantly (p<0.05) increased risk in non-smokers in six of the remaining studies and with a moderately increased, but not significant, increase in a further six. In two of the three studies that found no increase, asbestos exposure was insufficient to increase risks in smokers. In 30 of 31 data sets analysed, risk in the combined exposure group was greater than predicted by the additive model. There was no overall departure from the multiplicative model, the proportional increase in risk of lung cancer with exposure to asbestos being estimated as 0.90 (95% confidence interval (95% CI) 0.67 to 1.20) times higher in smokers than non-smokers. For two studies significant (p<0.05) departures from a multiplicative relation were found in some, but not all, analyses. Reasons are presented why these may not indicate true model discrepancies. CONCLUSIONS: Asbestos exposure multiplies risk of lung cancer by a similar factor in non-smokers and smokers. The extent to which it multiplies risk varies between studies, no doubt depending on the type of asbestos involved, and the nature, extent, and duration of exposure. (+info)
Small area estimation of incidence of cancer around a known source of exposure with fine resolution data.
(42/710)
OBJECTIVES: To describe the small area system developed in Finland. To illustrate the use of the system with analyses of incidence of lung cancer around an asbestos mine. To compare the performance of different spatial statistical models when applied to sparse data. METHODS: In the small area system, cancer and population data are available by sex, age, and socioeconomic status in adjacent "pixels", squares of size 0.5 km x 0.5 km. The study area was partitioned into sub-areas based on estimated exposure. The original data at the pixel level were used in a spatial random field model. For comparison, standardised incidence ratios were estimated, and full bayesian and empirical bayesian models were fitted to aggregated data. Incidence of lung cancer around a former asbestos mine was used as an illustration. RESULTS: The spatial random field model, which has been used in former small area studies, did not converge with present fine resolution data. The number of neighbouring pixels used in smoothing had to be enlarged, and informative distributions for hyperparameters were used to stabilise the unobserved random field. The ordered spatial random field model gave lower estimates than the Poisson model. When one of the three effects of area were fixed, the model gave similar estimates with a narrower interval than the Poisson model. CONCLUSIONS: The use of fine resolution data and socioeconomic status as a means of controlling for confounding related to lifestyle is useful when estimating risk of cancer around point sources. However, better statistical methods are needed for spatial modelling of fine resolution data. (+info)
The design of hazard risk assessment matrices for ranking occupational health risks and their application in mining and minerals processing.
(43/710)
Two hazard risk assessment matrices for the ranking of occupational health risks are described. The qualitative matrix uses qualitative measures of probability and consequence to determine risk assessment codes for hazard-disease combinations. A walk-through survey of an underground metalliferous mine and concentrator is used to demonstrate how the qualitative matrix can be applied to determine priorities for the control of occupational health hazards. The semi-quantitative matrix uses attributable risk as a quantitative measure of probability and uses qualitative measures of consequence. A practical application of this matrix is the determination of occupational health priorities using existing epidemiological studies. Calculated attributable risks from epidemiological studies of hazard-disease combinations in mining and minerals processing are used as examples. These historic response data do not reflect the risks associated with current exposures. A method using current exposure data, known exposure-response relationships and the semi-quantitative matrix is proposed for more accurate and current risk rankings. (+info)
An investigation of heavy metal exposure and risks to wildlife in the Kafue flats of Zambia.
(44/710)
Exposure and ecological risks to heavy metals (copper, zinc, manganese, iron) at Lochnivar and Blue Lagoon National Parks in wildlife dependent on the Kafue river contaminated with mining waste was evaluated. Samples included water, fish, grasses and Kafue Lechwe (Kobus leche kafuensis) liver. At both parks copper ranged from 0.03-0.04 mg/l; 3.0-6.0 mg/kg; 11.0-44.0 mg/kg; trace -199.0 mg/kg; while zinc was 0.01 mg/l; 32.0-82.0 mg/kg; 15.0-21.0 mg/kg; and 52.0-138.0 mg/kg; in water, fish, grasses and lechwe, respectively. Manganese ranges were 0.15-0.16 mg/l; 7.0-18.0 mg/kg; 51.0-145.0 mg/kg; and 40.0-53.0 mg/kg while iron ranges were 0.13-0.14 mg/l; 26.0-134.0 mg/kg; 1766.0-1797.0 mg/kg; and 131.0-856.0 mg/kg; in water, fish, grasses and lechwe, respectively. Levels in all samples except water were high indicating potential for adverse effects. (+info)
Lung cancer in a nonsmoking underground uranium miner.
(45/710)
Working in mines is associated with acute and chronic occupational disorders. Most of the uranium mining in the United States took place in the Four Corners region of the Southwest (Arizona, Colorado, New Mexico, and Utah) and on Native American lands. Although the uranium industry collapsed in the late 1980s, the industry employed several thousand individuals who continue to be at increased risk for developing lung cancers. We present the case of a 72-year-old Navajo male who worked for 17 years as an underground uranium miner and who developed lung cancer 22 years after leaving the industry. His total occupational exposure to radon progeny was estimated at 506 working level months. The miner was a life-long nonsmoker and had no other significant occupational or environmental exposures. On the chest X-ray taken at admission into the hospital, a right lower lung zone infiltrate was detected. The patient was treated for community-acquired pneumonia and developed respiratory failure requiring mechanical ventilation. Respiratory failure worsened and the patient died 19 days after presenting. On autopsy, a 2.5 cm squamous cell carcinoma of the right lung arising from the lower lobe bronchus, a right broncho-esophageal fistula, and a right lower lung abscess were found. Malignant respiratory disease in uranium miners may be from several occupational exposures; for example, radon decay products, silica, and possibly diesel exhaust are respiratory carcinogens that were commonly encountered. In response to a growing number of affected uranium miners, the Radiation Exposure Compensation Act (RECA) was passed by the U.S. Congress in 1990 to make partial restitution to individuals harmed by radiation exposure resulting from underground uranium mining and above-ground nuclear tests in Nevada. (+info)
Influence of exposure concentration or dose on the distribution of particulate material in rat and human lungs.
(46/710)
Differences among species in the anatomic sites of particle retention could influence responses to inhaled particles. In this study, we used morphometric techniques to examine the influence of exposure concentration on particle retention in histologic sections from rats and humans. The rats had been exposed for 24 months to diesel exhaust at 0.35, 3.5, or 7.0 mg soot/m(3). The human subjects were nonsmokers who did not work as miners, nonsmoking coal miners who worked under the current standard of 2 mg dust/m(3) for 10-20 years (mean = 14 years), and nonsmoking coal miners who worked under the former standard of < 10 mg dust/m(3) for 33-50 years (mean = 40 years). The distribution of retained particles within the lung compartments was markedly different between species. In all three groups of rats, 82-85% of the retained particulate material was located in the alveolar and alveolar duct lumens, primarily in macrophages. In humans, 57, 68, and 91% of the retained particulate material was located in the interstitium of the lung in the non-miners, coal miners under the current standard, and coal miners under the former standard, respectively. These results show that chronically inhaled diesel soot is retained predominantly in the airspaces of rats over a wide range of exposures, whereas in humans, chronically inhaled particulate material is retained primarily in the interstitium. In humans, the percentage of particles in the interstitium is increased with increased dose (exposure concentration, years of exposure, and/or lung burden). This difference in distribution may bring different lung cells into contact with the retained particles or particle-containing macrophages in rats and humans and may account for differences in species response to inhaled particles. (+info)
Retrospective view of airborne dust levels in workplace of a chrysotile mine in Ural, Russia.
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The Bazhenovskoye chrysotile asbestos deposit has been exploited for 115 years. All the technological operations in the quarry are accompanied by the formation of high-dispersion asbestos-containing aerosols. The dust concentrations at the miner's working places for the last 30 years (1970-2000) were at or below the Russian MACs(m.s.) level (4.0 mg/m3). The seasonal precipitation amount in the deposit area causes a rise in dust content in certain periods. The maximum density of asbestos respirable fibres exceeded 2.7 f/cm3. All the identified fibres belonged to chrysotile asbestos, and no amphibole asbestos, such as tremolite asbestos, has been identified. An excessive dust level remains, despite the dust content level decrease, at the work sites of oversized lump drillers and unloaders, and oncopathology heightened risk remains in these occupational groups, as a result. (+info)
Heavy mining vehicle controls and skidding accidents.
(48/710)
This paper examines various control locations in heavy mining vehicles. Three trucks have been tested on a skid pad in both clockwise and anticlockwise directions. The skid lengths were measured after each trial. The primary focus of the study was the positioning of various controls and their relevance to various skid lengths. Some additional measures such as NASA-TLX scales were also used to make subjective evaluations. The results are presented in this paper. The findings clearly indicate the relevance of control locations to actual skid lengths. The poorly located controls resulted in greater skid lengths. This is an important finding as skid lengths are related to greater reaction times in a skidding situation and hence greater risk of accidents on relevant trucks. Such accidents can incur large repair bills for damaged equipment whereas more importantly, jeopardizing the life and safety of heavy mining vehicle drivers. (+info)