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The paper by Thomsen et al 1 is a significant contribution to the now-substantial body of literature on the relationship between asbestos-related diseases and vehicle repair work. It is a large study, inclusive of all registered vehicle mechanics in the country for the designated years, with a mean follow-up time of 20 years and a maximum of 45 years. Several comprehensive administrative databases were linked for exposure and disease outcomes. The numbers of outcomes for the three main diseases of interest produced relatively narrow CIs. The authors present data indicating that reliance on administrative databases for health outcomes was unlikely to be a problem for mesothelioma and lung cancer; however, it is reasonable to question the validity of the diagnoses of asbestosis based on administrative data alone. As the authors point out, the statistically significant elevation in asbestosis mortality and morbidity is somewhat puzzling given the relatively high exposures required for asbestosis and the relatively low asbestos exposures experienced by vehicle mechanics. The existing literature does not support a positive relationship between asbestosis and vehicle repair work.2–5 The authors suggested that diagnostic bias may have played a role, but this is speculative. The result warrants further examination, possibly a nested case–control study with documentation of the diagnostic criteria supporting the database entries, blinded re-evaluation of the available diagnostic material, and further exploration of complete occupational histories. The investigators observed a slight elevation in lung cancer risk. The results are consistent with those from an earlier meta-analysis6 and are unremarkable. Studies of potential asbestos-related diseases among vehicle mechanics have focused primarily on risk of …

Background: We published a meta-analysis of the association between work as a motor vehicle mechanic and mesothelioma in 2004. Since then, several relevant studies on this topic have been published. Thus, to update the state-of-the-science on this issue, we conducted a new systematic review and meta-analysis. Methods: A comprehensive PubMed literature search through May 2014 was conducted to identify studies that reported relative risk estimates for mesothelioma among motor vehicle mechanics (in general), and those who were engaged in brake repair (specifically). Studies were scored and classified based on study characteristics. Random-effects meta-analyses generated summary relative risk estimates (SRREs) and corresponding 95% confidence intervals (CI). Heterogeneity of results was examined by calculating Q-test P-values (P-H) and I 2 estimates. Sub-group and sensitivity analyses were conducted for relevant study characteristics and quality measures. Results: Ten case-control studies, one cohort study, and five proportionate mortality ratio (PMR)/standardized mortality odds ratio (SMOR) studies were identified and included in the quantitative assessment. Most meta-analysis models produced SRREs below 1.0, and no statistically significant increases in mesothelioma were observed. The SRRE for all studies was 0.80 (95% CI: 0.61-1.05) with significant heterogeneity (P-H

BACKGROUND: It is postulated that children with asthma who receive an interactive, comprehensive education program would improve their quality of life, asthma management and asthma control compared with children receiving usual care.OBJECTIVE: To assess the feasibility and impact of ‘Roaring Adventures of Puff’ (RAP), a six-week childhood asthma education program administered by health professionals in schools.METHODS: Thirty-four schools from three health regions in Alberta were randomly assigned to receive either the RAP asthma program (intervention group) or usual care (control group). Baseline measurements from parent and child were taken before the intervention, and at six and 12 months.RESULTS: The intervention group had more smoke exposure at baseline. Participants lost to follow-up had more asthma symptoms. Improvements were significantly greater in the RAP intervention group from baseline to six months than in the control group in terms of parent’s perceived understanding and ability to cope with and control asthma, and overall quality of life (PCONCLUSION: A multilevel, comprehensive, school-based asthma program is feasible, and modestly improved asthma management and quality of life outcomes. An interactive group education program offered to children with asthma at their school has merit as a practical, cost-effective, peer-supportive approach to improve health outcomes.

The U.S. Environmental Protection Agency has begun discussions to consider its assessment of asbestos toxicity related to mineral form and fiber size. Brake workers are typically exposed to short chrysotile fibers. To explore the mesothelioma risk among brake workers, considering other occupational exposures to asbestos, data from a study that was published previously were obtained and the analysis was extended. The National Cancer Institute provided data from a case-control study of mesothelioma. Because many participants with a history of brake work also had employment in other asbestos-related occupations, mesothelioma cases and controls were compared for a history of brake work, controlling for employment in eight occupations with potential asbestos exposure. A stratified analysis was also performed excluding those with any of the eight occupations. Possible interactions between brake work and other occupational exposures related to risk of mesothelioma were also examined. The odds ratio (OR) for employment in brake installation or repair was 0.71 (95% CI: 0.30-1.60) when controlled for insulation or shipbuilding. When a history of employment in any of the eight occupations with potential asbestos exposure was controlled, the OR was 0.82 (95% CI: 0.36-1.80). ORs did not increase with increasing duration of brake work. Exclusion of those with any of the eight exposures resulted in an OR of 0.62 (95% CI: 0.01-4.71) for occupational brake work. There was no evidence of an interaction between brake work and other occupational exposures. These latter analyses were based on small numbers of exposed cases. The results are consistent with the existing literature indicating that brake work does not increase the risk of mesothelioma and adds to the evidence that fiber type and size are important determinants of mesothelioma risk.

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Background The study of near-fatal asthma (NFA) may provide a means to further our understanding of fatal asthma. Studies of NFA often are derived from a single ICU rather than from a defined population. We therefore aimed to identify factors distinguishing NFA patients (cases) from those persons treated in an emergency department (ED) [ED control subjects] and in the community (community control subjects [CCs]). Methods This was a population-based case-control study conducted over 20 months of 45 NFA patients (age range, 5 to 50 years), 197 ED control subjects treated in an ED, and 303 CCs, all of whom were residents of Alberta. Results The age distribution was similar between NFA patients and control subjects, with the majority being Conclusion NFA patients have many modifiable risk factors and many similarities to ED control subjects and CCs with asthma. General measures to improve asthma control and awareness of risks are required in all groups.

The relationship between crystalline silica and lung cancer has been the subject of many recent publications, conferences, and regulatory considerations. An influential, international body has determined that there was sufficient evidence to conclude that quartz and cristobalite are carcinogenic in humans. The present authors believe that the results of these studies are inconsistent and, when positive, only weakly positive. Other, methodologically strong, negative studies have not been considered, and several studies viewed as providing evidence supporting the carcinogenicity of silica have significant methodological weaknesses. Silica is not directly genotoxic and is a pulmonary carcinogen only in the rat, a species that seems to be inappropriate for assessing particulate carcinogenesis in humans. Data on humans demonstrate a lack of association between lung cancer and exposure to crystalline silica. Exposure-response relationships have generally not been found. Studies in which silicotic patients were not identified from compensation registries and in which enumeration was complete did not support a causal association between silicosis and lung cancer, which further argues against the carcinogenicity of crystalline silica.

Background Asthma mortality rates have increased in Canada and worldwide. Within Canada, the highest rates were seen in the prairie provinces. Objective The objective was to determine risk factors for fatal asthma by comparing those who died of an acute exacerbation with those who attended an emergency department for treatment of asthma. Methods The case-control study included all deaths from asthma among those aged 5 to 50 years in Alberta, Saskatchewan and Manitoba from November, 1992 through October, 1995 (cases). The 35 fatalities were matched to 209 controls by age, gender, time of the index event and residence. Results Cases were more likely than controls to have had severe asthma, an unscheduled physician visit in the past year, a past hospitalization for asthma, and to have been intubated. Both groups reported frequent, regular asthma symptoms. Beta-agonist bronchodilator use was more common among cases, as was use in excess of prescribed amounts. Use of inhaled steroids did not differ between groups. Prior to the index event controls were more likely to report a cold or flu (OR = 0.27; 95% CI: 0.10 to 0.72) and that medications were "not working" (OR = 0.30; 95% CI: 0.12 to 0.71). Cases were more often sad and depressed (OR = 2.88; 95% CI: 1.03 to 8.05). Time between onset/recognition of symptoms and the event was significantly shorter for cases than controls. Conclusions Both groups tolerated high levels of regular symptoms, suggesting poor management. Opportunities for intervention existed for both groups near the time of the event. The short time between recognition of symptoms and death suggests patients at increased risk should monitor their condition closely and take action in response to predetermined criteria.

Hepatitis C virus (HCV) is an emerging global public health issue with particular relevance in multiply transfused renal dialysis patients. This cross-sectional study evaluated the prevalence and risk factors for HCV infection among renal dialysis patients in northern Alberta, Canada. Ninety-two percent of eligible patients (n = 336) provided informed consent to participate. Participants were interviewed to gather risk factor information and, using multiple logistic regression analysis with exact inference, a predictive model for HCV infection in this population was developed. The prevalence of HCV infection in the population was 6.5%, and all positive patients had at least one identifiable risk factor. The multivariate analysis showed that the risk of HCV infection was greater for those in the 18-55 years age category (odds ratio (OR) = 4.9, 95% confidence interval (CI) 1.2-27.9), patients who had been on dialysis > 5 years (OR = 3.7, 95% CI 1.2-12.0), and patients who had > or = 2 high risk life-style behaviors (OR = 5.0, 95% CI 1.5-16.7). Transfusion prior to 1990 was marginally associated with HCV status (OR = 4.0, 95% CI 0.96-16.3). This study documented previously unreported life-style risk factors for HCV infection in patients with renal failure, confirmed the expected decline in transfusion-acquired HCV infection in this population, and provided evidence against nosocomial transmission of HCV.

Background Construction boilermakers may be exposed to a variety of substances, including asbestos and welding fumes. Past studies of boilermakers have shown increases in mortality from lung cancer and asbestosis and radiographic changes consistent with asbestos exposure. Methods Respiratory symptoms, lung function, and radiographic changes were compared for 102 actively employed boilermakers with 20 or more years of union membership and 100 telephone workers. Posteroanterior chest radiographs were evaluated by two experienced chest physicians, with a third arbitrating disagreed films. Union members were further categorized as boilermakers (n = 50) or welders (n = 52), based on longest service. Lung health was also compared with employment in a number of work sectors for time, and time-weighted exposure to dust and fumes. Results Boilermakers had more respiratory symptoms than telephone workers, but lung function did not differ. Radiographic changes were more common among the boilermakers (20% with any change, 8% circumscribed, and 9% diffuse pleural thickening). None of the boilermakers had small radiographic opacities. Several symptoms suggestive of bronchial responsiveness were associated with fume exposures in the gas and oil industry. Workers whose longest service was as a boilermaker demonstrated more symptoms than did welders. FEV1, FEV1/FVC, FEF25–75, and FEF50 were significantly lower among boilermakers compared with welders. Conclusion Health screening programs for these workers are warranted. Am. J. Ind. Med. 34:381–386, 1998. © 1998 Wiley-Liss, Inc.

To evaluate risk factors for asthma mortality, an unmatched case-control study was undertaken in the Canadian prairie provinces of Alberta, Saskatchewan, and Manitoba. Those between the ages of 5 and 50 (inclusive) who died from an acute exacerbation of asthma were compared to a control group of people with asthma from the same geographical areas who were contacted using random-digit dialing. Because no deaths occurred among residents less than 15 years old, this analysis was limited to cases and controls between 15 and 50 years old. Of the 38 deaths that occurred between November 1992 and October 1995, data were obtained from next of kin for 35 (92.1%). Of the 210 potential controls that were identified, 142 returned completed questionnaires (67.6%). Cases were more likely than controls to have asthma reported to be severe, to have experienced nocturnal symptoms, to have had cardiopulmonary resuscitation (CPR)/intubation, and to have had more healthcare utilization in the previous year. Medication use was also more common among cases compared to controls. Specific asthma triggers were reported more often for cases than controls; weather changes, excitement, depression, and stress showed the greatest case control differences. Although a number of very strong risk factors for death from asthma were identified, death from asthma is so rare in this age group that it is not possible to label an individual as "likely" to die from asthma. Nonetheless, patients, caregivers, and health professionals should be aware of indicators that would suggest greater risk.

A study was undertaken to assess pulmonary health effects of hydrogen sulfide (H2S) exposure in a group of workers (n = 175) extracting and processing oil and natural gas in west-central Alberta. Exposure to H2S was assessed by questioning the workers about “exposures strong enough to cause symptoms,” and exposures that resulted in loss of consciousness (a “knockdown”). Exposures strong enough to cause symptoms were reported by 34% of the workers. Fourteen workers (8%) reported having had a knockdown. Exposures severe enough to cause symptoms were not associated with lower spirometric values or excess symptoms. Knockdowns were not associated with lower spirometric values but were associated with statistically significant excesses of (1) shortness of breath while hurrying on the level or walking up a slight hill (OR = 3.55; 95% CI = 1.02–12.4); (2) wheeze with chest tightness (OR = 5.15; 95% CI = 1.29–20.6); (3) attacks of wheeze (OR = 5.08; 95% CI = 1.28–20.2). The pattern of excess respiratory symptoms is consistent with bronchial hyperresponsiveness, which has been documented in studies of high-level exposure to other irritant gases. Additional study is warranted and should include assessment of bronchial reactivity. Am. J. Ind. Med. 31:554–557, 1997. © 1997 Wiley-Liss, Inc.

Sixty-one individuals hospitalized for hip fractures received activities of daily living (ADL) assessments during the 3 days prior to discharge. Information was also collected regarding anticipated role loss, depression, mental status, health status, and social support. Independence in ADL at home was measured 3 weeks following discharge by telephone interviews. The concordance between predischarge and post discharge ADL scores was low but statistically significant (Kw= .223; p < .05). Approximately 50.8% of the subjects demonstrated greater dependence post discharge. More dependent ADL performance at home was not related to role loss, depression, mental status, health status, or social support. Predischarge ADL assessments are often taken into consideration when formulating discharge plans. However, these evaluations do not always accurately predict post discharge ADL independence. It is recommended, therefore, that community follow-up be carried out with patients who have fractured hips.

Controversy regarding the association between silicosis and lung cancer has been clouded by the fact that studies examining this association generally do not include information on smoking. A causal association between smoking and silicosis would seriously confound the association between silicosis and lung cancer. The current analysis assessed the association between silicosis and smoking using data on deceased white gold miners who underwent postmortem examination between 1976 and 1981. Smoking histories and exposure information were available. A subset analysis in a group of deceased miners for whom more detailed smoking and exposure information was available confirmed the findings of the larger analysis. Both analyses showed a slight inverse relationship between smoking and silicotic collagenization of the parenchyma and a stronger negative relationship between smoking and silicotic collagenization of the pleura, controlling for age and cumulative exposure to silica dust. No association between silicotic collagenization of the hilar glands and smoking was detected. The data should not be construed as advocating that workers exposed to silica dust should smoke. The hazards of cigarette smoking are likely to far outweigh the hazards of silicosis. The data suggest that the lack of smoking histories in studies of the association between silicosis and lung cancer probably does not seriously confound risk estimates. The distribution of silicotic collagenization in the lungs of smokers and nonsmokers is consistent with enhanced mucus interception, more central deposition in the lungs, and proportionally more lymphatic clearance to the hilum (as opposed to the pleura) of silica particles in smokers compared to nonsmokers.

Recent studies of the association between lung cancer and silicosis and silica dust have been inconclusive; some showing positive association and some showing none. The present study matched 231 cases of lung cancer with 318 controls by year of birth. Subjects were selected from the necropsy records of the National Centre for Occupational Health. Data on intensity and duration of exposure to silica dust were obtained from personnel records. Presence or absence of lung cancer and the presence and severity of silicosis of the parenchyma, pleura, and hilar glands were documented from necropsy reports. Smoking data were abstracted from records of routine examinations. No case-control differences were noted for any of the exposure indicators including cumulative dust exposure, total dusty shifts, weighted average intensity of exposure, total underground shifts, and shifts in high dust. Similarly, no association was found between lung cancer and the presence or severity of silicosis and any site. Stratified analyses showed neither significant nor suggestive trends when case-control comparisons for silicosis were examined by level of dust exposure or smoking. Reasons for disparity between these results and those of some other studies may include concomitant exposures to radon daughters, asbestos, diesel emissions, and cigarette smoking; idiosyncracies of the compensation process; and the possibility of a threshold in the relation(s).

BACKGROUND: Most children with asthma should be able to achieve acceptable control. However, are there differences between those with acceptable and poor control, and if so, how can health care approaches be modified accordingly?OBJECTIVE: To examine the characteristics of elementary school children aged five to 13 years with acceptable and poor levels of asthma control.METHODS: The present cross-sectional study of children with asthma used five indicators of control, as outlined by the Canadian Asthma Consensus Report, to categorize acceptable and poor asthma control.RESULTS: Of 153 children, 115 (75%) were rated as having poorly controlled asthma. Of those with poor control, 65 (64%) children were currently using inhaled corticosteroids, and 65% of those reported using inhaled corticosteroids daily versus as needed. Fifty-one per cent of the children with poorly controlled asthma had exposure to tobacco smoke, whereas 79% of the children with asthma under acceptable control were from households with no smokers (P=0.002). The poor control group also had significantly worse parental perceptions of the psychosocial impact of asthma on their child. No significant difference was found in the percentage of those who had written action plans in the poor control group (28%) compared with the acceptable control group (26%), and similar percentages in each group stated that they used the plans.CONCLUSIONS: Despite the high use of inhaled corticosteroids, the majority of children had poorly controlled asthma. The poor control group had more exposure to tobacco smoke and a worse psychosocial impact due to asthma. Few children had past asthma education and action plans, suggesting that there is a need to improve access to and tools for education.

We conducted a systematic review and analysis of the epidemiological literature that examines the risk of lung cancer and mesothelioma among motor vehicle mechanics who may have been engaged in brake repair and, thus, were potentially exposed to asbestos. All relevant studies were classified into three tiers according to their quality. Tier III (lowest quality) studies were cited for completeness, but were not included in the meta-analysis. Meta relative risks (meta-RRs) were calculated for mesothelioma and lung cancer using both fixed and random effects models for Tiers I and II, separately, followed by stratified analyses based on study design or exposure characterization (garage workers versus brake workers) and, for lung cancer studies, based on adequate adjustment for smoking. The meta-analysis for Tier I (higher quality) and Tier II (lower quality) studies of mesothelioma yielded RR estimates of 0.92 (95% CI 0.55-1.56) and 0.81 (95% CI 0.52-1.28), respectively. Further stratification according to exposure characterization did not affect the results. The meta-analysis for lung cancer produced RR estimates of 1.07 (95% CI 0.88-1.31) for Tier I and 1.17 (95% CI 1.01-1.36) for Tier II. When the lung cancer analysis was limited to studies that used adequate control for smoking, the resulting RR estimate was 1.09 (95% CI 0.92-1.28). Based on these findings, we conclude that employment as a motor vehicle mechanic does not increase the risk of developing mesothelioma. Although some studies showed a small increase in risk of lung cancer among motor vehicle mechanics, the data on balance do not support a conclusion that lung cancer risk in this occupational group is related to asbestos exposure.

Elevated prostate cancer incidence was found at a plant producing atrazine that had an intensive prostate screening program. This study tested the relationship among atrazine exposure, prostate cancer, and the screening program. Twelve cases and 130 control subjects were selected from the original cohort. Prostate screening and occupational histories were abstracted from company records and atrazine exposures were estimated. Hire date was comparable for cases and control subjects. Nearly half of the control subjects and no cases left before the prostate-specific antigen (PSA) screening program. Cases had more PSA tests than control subjects (odds ratio for > or =1 test, 8.54; 95% confidence interval, 1.69-82.20). There was no association between atrazine exposure and prostate cancer when those with > or =1 test were compared. There was no evidence for an association between atrazine and prostate cancer.

In an examination of the relationship between silicosis and lung function, relevant studies of silica-exposed workers were reviewed. Smoking, dust exposure, and emphysema are three important factors that can confound the association between silicosis and lung function. Despite the importance of smoking in relation to lung function, some studies did not control for smoking, or smoking was controlled inadequately. The data suggest a weak association between lung function (mainly obstruction) and dust exposure, although some studies had crude measures of exposure. In general, the lung function of those with radiographic silicosis in category 1 was indistinguishable from those in category 0. Those in category 2 had small reductions in lung function relative to those with category 0 and little difference in the prevalence of emphysema. There were slightly greater decrements in lung function with category 3 and more significant reductions with progressive massive fibrosis. Emphysema was related to higher categories of silicosis, as well as to smoking. Silica exposure was often inadequately controlled in studies examining silicosis and lung function. A few studies suggested that emphysema is an independent risk factor associated with significant reductions in lung function.

An evaluation of the relationship between silicosis and smoking is important in exploring the etiology of silicosis, and the relationship could have an impact on studies dealing with silicosis and lung cancer. Data addressing this relationship were found in studies designed explicitly to evaluate this association and studies that explored other questions. Studies based on compensation registers were excluded. Smoking data and methods varied across the studies considered. Of the 13 studies, 3 supported the hypothesis that smoking was positively associated with silicosis, 8 provided limited support (most included subpopulations showing positive associations), and 1 did not support the hypothesis. The only autopsy study suggested an inverse association. It is unclear whether the generally positive results indicate that smoking predisposes to silicosis or that nonspecific radiographic appearances from smoking were interpreted as silicosis in some studies. A positive association between radiographic silicosis and smoking would bias studies of silicosis and lung cancer, especially those lacking smoking data.

To evaluate the effectiveness of a comprehensive asthma management education program for 7- to 12-year-old children with asthma, entitled Roaring Adventures of Puff (RAP), 18 elementary schools in Edmonton were randomized to intervention and control groups. Participating in the program were 76 students with asthma in the intervention schools and 86 in the control schools. Children in the intervention schools had statistically significant improvements in unscheduled doctor visits, missed school days, moderate-to-severe parent rating of severity, severity of shortness of breath, limitations in the kind of play, and correct use of medications. Unscheduled doctor visits and missed school days were the only significant improvements in the control group; however, improvements were about half that of the intervention group. The results showed that a comprehensive, school-based asthma education program is feasible and improves outcomes.

BACKGROUND: Asthma can usually be controlled through allergen avoidance and/or appropriate medication. An emergency department visit for an acute exacerbation of asthma often represents a breakdown in asthma management. Emergency department treatment results in significant health care expenditures and reflects a compromised quality of life.OBJECTIVES: To identify risk factors associated with an emergency department visit for asthma.METHODS: This case-control study compared 299 people (76% of 390 cases contacted) who attended one of two emergency departments in Alberta in 1992 and 1993 for an acute exacerbation of asthma (cases) with 212 unmatched community controls with asthma who were located by random digit dialing. Cases and controls were asked to complete a mailed questionnaire to obtain data regarding severity, visits to doctors and emergency departments, medication use, allergies and other triggers, and smoking history. Data analysis included bivariate analysis of risk factors and multivariate model development using logistic regression.RESULTS: The response rate was similar between cases and controls. Cases were younger than controls (odds ratio [OR] 2.16, 95% CI 1.34 to 3.48) and more often reported their asthma to be severe (OR 4.25, 95% CI 2.24 to 8.06), and had experienced nocturnal symptoms (stratified OR range 1.36 to 6.82). Cases used more health care services in the previous year, had been admitted to hospital at some time for asthma (OR 1.62, 95% CI 1.10 to 2.38) and used more medication than controls.CONCLUSIONS: Physicians and other health care workers should be sensitive to the risk factors and target interventions to high risk individuals.

Workers exposed to a variety of wood dusts have been shown to exhibit occupational asthma, lung function deficits, and elevated levels of respiratory symptoms. Despite the popularity of pine and spruce, the health effects of exposures to these woods have not been extensively investigated. A study was undertaken to investigate the respiratory health of a group of sawmill workers processing pine and spruce (n = 94). Data collection included a respiratory symptom questionnaire, spirometry, and allergy skin testing. The sawmill workers were compared with a group of oil field workers from the same geographic area who underwent the same study protocol (n = 165). The results showed that the sawmill workers had significantly lower average values for FEV1 and FEV1/FVC (%), adjusted for age, height, and smoking. The largest differences were for current smokers. Significantly elevated age and smoking-adjusted odds ratios (OR) were detected for shortness of breath (2.83; 95% confidence interval [CI], 1.47 to 5.46) and wheeze with chest tightness (2.58; 95% CI, 1.18 to 5.62). Nonsignificant elevations were also seen for usual cough (1.47; 95% CI, 0.68 to 3.16), usual phlegm (1.94; 95% CI, 0.98 to 3.87), shortness of breath with exercise (1.45; 95% CI, 0.66 to 3.20), chest tightness (1.43; 95% CI, 0.80 to 2.57), and attacks of wheeze (1.70; 95% CI, 0.79 to 3.68). Sawmill workers were 2.5 times as likely as oil field workers to report current asthma (95% CI, 0.76 to 8.32). Workers employed more than 3 years showed significantly more asthma (OR = 3.67; 95% CI, 1.00 to 13.5) and bronchitis (OR = 2.14; 95% CI, 1.02 to 4.52). Sawmill workers were only 43% as likely to report a history of hay fever (95% CI, 0.20 to 0.94). These health effects were noted despite an average concentration of respirable dust of 1.35 mg/m3 (range, 0.1 to 2.2 mg/m3). These levels are below the present occupational standard.

The tendency for readers of chest films of the pneumoconioses to place films in the middle of the International Labour Office (ILO) categories of profusion (eg, 1/1, 2/2) was described by Morgan et al [1974], who saw this tendency as a possible source of bias. The present study reexamines the middling tendency in relation to bias and variability by comparing duplicate readings of chest films for pneumoconiosis. Readings of trained lay persons were compared to professional readings of the same films and readings of professional readers were compared with each other. Reasons for the middling tendency, which include the use of standard middle films and the instructions given to users of the classification, are suggested and possible solutions are proposed.

A cross-sectional radiological survey of 2 245 men who were employed in South African asbestos mines was conducted in 1976. Since 1976, the lungs of 172 of these men who died have been examined to establish the presence of asbestosis or other pneumoconiosis. The x-ray readings (ILO/UC 1971) were compared with the pathological findings. A high prevalence of false positive readings, particularly for two of the three readers, was found. False negative readings were also very prevalent. Detailed information about asbestos and other mining exposure, smoking habit, age, height, and weight were examined to determine what influence they may have had in inducing false positive findings. Other dust exposure and smoking appeared to be possible factors, whereas age and obesity were probably not. It is suggested that the term “small irregular opacities” requires more precise definition.

A case-control study was undertaken to assess the association between lung cancer and silicosis or silica dust exposure in white South African gold miners. Cases and controls were identified from deaths reported to the Gold Miners Provident Fund for the period January, 1979-October, 1983. Two controls were matched to each case by year of birth (+/- 2 years) and by smoking (+/- 5 cigarettes or equivalents per day) assessed 10 years (+/- 2 years) prior to death. One hundred thirty-three matched triplets were identified. The results showed no overall association between lung cancer and radiological silicosis (OR = 1.08, p = 0.92). Autopsy data indicated no overall associations between lung cancer and silicosis of the lung parenchyma (OR = 1.49, p = 0.11), the pleura (OR = 0.72, p = 0.30), or the hilar glands (OR = 0.85, p = 0.72). A trend toward increased severity of silicosis of the parenchyma was evident; however, this was not statistically significant (p = 0.08). Odds ratios for lung cancer and silicosis were higher at lower levels of cumulative silica dust exposure (ORs = 2.43, 1.72, 1.35 and 0.62 for lung cancer and autopsy silicosis of the parenchyma for the lowest, second, third, and highest quartiles of dust exposure, respectively; all p greater than 0.05). Cases did not differ from controls for total silica dust exposure, length of exposure, weighted average intensity of exposure, or number of shifts at high dust (all p greater than 0.20). The data do not support the hypothesis of a carcinogenic role for silica dust and no statistically significant associations were found between lung cancer and silicosis.(ABSTRACT TRUNCATED AT 250 WORDS)

To assess the feasibility of using the pathology automation system (PATHAUT) for research, the quality of the data was explored by examining who comes to autopsy, the quality of the autopsy material, interobserver variability, and repeatability of diagnoses. The data indicated that autopsy rates in the gold mining industry, especially for whites, are high and that even among blacks, gold miners are represented in proportions exceeding the relative size of the working population. Because of the perception of the autopsy service as a means of obtaining compensation, miners with occupational diseases fully compensated in life are probably underrepresented. The autopsy material submitted for full autopsy is generally better preserved than cardiorespiratory organs that are sent for examination. The gold mining industry has a high proportion of full autopsies as does the Iron and Steel Corporation of South Africa. Full autopsies are more commonly performed on older deceased miners. This was true for both blacks and whites. The allocation of material to pathologists for full autopsies and examinations of the cardiorespiratory organs were clearly not random, and this may affect comparisons among pathologists. Active tuberculosis, silicosis, and emphysema prevalences appeared fairly comparable across pathologists; however, there was wide variability in the prevalence of bronchiolitis as determined by the pathologists. Agreement between the diagnoses on PATHAUT and reclassifications by single pathologists was very good for the severity of emphysema and the histological type of bronchogenic carcinoma.

To determine whether certain temporal patterns of silica dust exposure, in addition to cumulative dose, and the dimensions of the lungs were related to elevated risk for silicosis, 168 silicotic cases were compared with 168 controls matched for cumulative dust exposure, year of birth and smoking. The data showed that the intensity of silica dust exposure was higher among cases when controlled for total cumulative dust exposure. Controls were found to have had significantly more time away from dust exposure during their mining careers. When cases and controls were compared for cumulative silica dust exposure and intensity of exposure for each decile of exposure time, the case-control differences were relatively constant throughout exposure time indicating that the timing of exposures was not an important risk factor. The height of the lungs was greater among cases compared with controls despite the fact that there were no differences in any of the other lung measurements or body length and after controlling for a significant difference in body mass index between cases and controls.

The progression of silicosis was measured for 631 South African gold miners to determine the effect of silica dust exposure on the rate of progression of simple silicosis and the development of progressive massive fibrosis (PMF). Silicosis was found to be a progressive disease regardless of whether exposure was continued after onset (94.6% progressed) or not (88.3% progressed). Cumulative dust exposure was significantly associated with the rate of progression ( p = 0.0014). When dust exposure before and after onset was considered, it was found that exposure after onset was significantly associated with progression ( p = 0.0001) whereas dust exposure before onset was not ( p = 0.95). Silicotics developing PMF had more exposure after onset of simple silicosis than silicotics who did not develop PMF. Progression appears to slow as the category of profusion increases; however, this cannot be stated with assurance given the study design used. The data suggest that the removal of silicotics from continued dust exposure will reduce the rate of progression of silicosis as well as the risk of developing PMF. It is also speculated that individual susceptibility to develop silicosis may not be related to the susceptibility to progress.