Dust exposure, dust recovered from the lung, and associated pathology in a group of British coalminers

The relation between dust exposure, retained lung dust, and pneumoconiosis have been examined in 430 dead coalminers who had participated in a large scale epidemiological survey of respiratory health. The men were divided into three groups depending on the presence of particular lesions in their lungs. Lungs containing no fibrotic lesions in excess of 1 mm were included in the "M" group, those with fibrotic lesions of between 1 mm and 9 mm in diameter were included in the "F" group, and those with any lesion 10 mm or more were categorised as having progressive massive fibrosis (PMF). The men were further divided into four groups according to the rank of coal mined at the colliery of employment. The mean weight of lung dust increased over the pathological range (M----F----PMF) regardless of the rank of coal mined. The men with PMF had not received unusually high exposures to dust in life but were found to have accumulated more dust in their lungs per unit of dust exposure than men without PMF, providing further evidence for differences in the patterns of deposition or clearance, or both, of dust in these men compared with those who do not develop PMF. For men who had mined the higher rank coals there was no difference in the composition of the lung dust between the pathological groups. Lungs from men mining low rank coal, however, showed a striking increase in the proportion of ash over the pathological groups (M, F, and PMF). In men who had mined low rank coal the proportion of ash in the airborne dust to which they had been exposed and in the dust retained in their lungs was, as expected, greater than in men who had worked with higher rank coals. For the same men, and particularly associated with the presence of some dust related fibrosis, the proportion of ash in retained dust was higher than that in the dust to which the men were exposed suggesting the occurrence of selective deposition or retention of the mineral components of dust in this group.     

Exposure to oxides of nitrogen: respiratory symptoms and lung function in British coalminers

Five hundred and sixty British coalminers with relatively high or relatively low exposures to oxides of nitrogen, based on measurements of concentrations of these gases at nine collieries over four years, and records of the men's places of work and colliery mining conditions over a total of eight years have been studied. Data on these men's respiratory symptoms and ventilatory capacity (FEV1), obtained as part of an epidemiological study of British coalminers, have been used to investigate possible adverse effects of exposure to oxides of nitrogen. Exposures to oxides of nitrogen were generally well below threshold limit values, though occasional peaks after shotfiring and during diesel locomotive use did exceed short term limits. No relationship was found between exposure and respiratory symptoms or decline in FEV1 nor was there any evidence of differences in symptoms of FEV1 between 44 pairs of men matched for age, dust exposure, smoking habit, coal rank, and type of work, but differing in respect of exposure to oxides of nitrogen. It has not been possible to detect any adverse effects on the health of this working population of the levels of nitrogen oxides that have occurred in British mines over the past decade. With the current levels of these gases, any long term effects on respiratory health are so small as to be undetectable in the presence of smoking and dust exposure.     

Dust exposure, dust recovered from the lung, and associated pathology in a group of British coalminers.

The relation between dust exposure, retained lung dust, and pneumoconiosis have been examined in 430 dead coalminers who had participated in a large scale epidemiological survey of respiratory health. The men were divided into three groups depending on the presence of particular lesions in their lungs. Lungs containing no fibrotic lesions in excess of 1 mm were included in the "M" group, those with fibrotic lesions of between 1 mm and 9 mm in diameter were included in the "F" group, and those with any lesion 10 mm or more were categorised as having progressive massive fibrosis (PMF). The men were further divided into four groups according to the rank of coal mined at the colliery of employment. The mean weight of lung dust increased over the pathological range (M----F----PMF) regardless of the rank of coal mined. The men with PMF had not received unusually high exposures to dust in life but were found to have accumulated more dust in their lungs per unit of dust exposure than men without PMF, providing further evidence for differences in the patterns of deposition or clearance, or both, of dust in these men compared with those who do not develop PMF. For men who had mined the higher rank coals there was no difference in the composition of the lung dust between the pathological groups. Lungs from men mining low rank coal, however, showed a striking increase in the proportion of ash over the pathological groups (M, F, and PMF). In men who had mined low rank coal the proportion of ash in the airborne dust to which they had been exposed and in the dust retained in their lungs was, as expected, greater than in men who had worked with higher rank coals. For the same men, and particularly associated with the presence of some dust related fibrosis, the proportion of ash in retained dust was higher than that in the dust to which the men were exposed suggesting the occurrence of selective deposition or retention of the mineral components of dust in this group.     

Exposure to oxides of nitrogen: respiratory symptoms and lung function in British coalminers.

Five hundred and sixty British coalminers with relatively high or relatively low exposures to oxides of nitrogen, based on measurements of concentrations of these gases at nine collieries over four years, and records of the men's places of work and colliery mining conditions over a total of eight years have been studied. Data on these men's respiratory symptoms and ventilatory capacity (FEV1), obtained as part of an epidemiological study of British coalminers, have been used to investigate possible adverse effects of exposure to oxides of nitrogen. Exposures to oxides of nitrogen were generally well below threshold limit values, though occasional peaks after shotfiring and during diesel locomotive use did exceed short term limits. No relationship was found between exposure and respiratory symptoms or decline in FEV1 nor was there any evidence of differences in symptoms of FEV1 between 44 pairs of men matched for age, dust exposure, smoking habit, coal rank, and type of work, but differing in respect of exposure to oxides of nitrogen. It has not been possible to detect any adverse effects on the health of this working population of the levels of nitrogen oxides that have occurred in British mines over the past decade. With the current levels of these gases, any long term effects on respiratory health are so small as to be undetectable in the presence of smoking and dust exposure.     

Health risks in wastewater irrigation: comparing estimates from quantitative microbial risk analyses and epidemiological studies

The combination of standard quantitative microbial risk analysis (QMRA) techniques and 10,000-trial Monte Carlo risk simulations was used to estimate the human health risks associated with the use of wastewater for unrestricted and restricted crop irrigation. A risk of rotavirus infection of 10(-2) per person per year (pppy) was used as the reference level of acceptable risk. Using the model scenario of involuntary soil ingestion for restricted irrigation, the risk of rotavirus infection is approximately 10(-2) pppy when the wastewater contains < or =10(6) Escherichia coli per 100ml and when local agricultural practices are highly mechanised. For labour-intensive agriculture the risk of rotavirus infection is approximately 10(-2) pppy when the wastewater contains < or = 10(5) E. coli per 100ml; however, the wastewater quality should be < or = 10(4) E. coli per 100ml when children under 15 are exposed. With the model scenario of lettuce consumption for unrestricted irrigation, the use of wastewaters containing < or =10(4) E. coli per 100ml results in a rotavirus infection risk of approximately 10(-2) pppy; however, again based on epidemiological evidence from Mexico, the current WHO guideline level of < or =1,000 E. coli per 100ml should be retained for root crops eaten raw.     

Health risks in wastewater irrigation: Comparing estimates from quantitative microbial risk analyses and epidemiological studies

The combination of standard quantitative microbial risk analysis (QMRA) techniques and 10,000-trial Monte Carlo risk simulations was used to estimate the human health risks associated with the use of wastewater for unrestricted and restricted crop irrigation. A risk of rotavirus infection of 10^-2 per person per year (pppy) was used as the reference level of acceptable risk. Using the model scenario of involuntary soil ingestion for restricted irrigation, the risk of rotavirus infection is ~10^-2 pppy when the wastewater contains 10⁶ Escherichia coli per 100 ml and when local agricultural practices are highly mechanised. For labour-intensive agriculture the risk of rotavirus infection is ~10^-2 pppy when the wastewater contains 10⁵ E. coli per 100 ml; however, the wastewater quality should be 10⁴ E. coli per 100 ml when children under 15 are exposed. With the model scenario of lettuce consumption for unrestricted irrigation, the use of wastewaters containing 10⁴E. coli per 100 ml results in a rotavirus infection risk of ~10^-2 pppy; however, again based on epidemiological evidence from Mexico, the current WHO guideline level of 1,000 E. coli per 100 ml should be retained for root crops eaten raw.     

Factors associated with the development of progressive massive fibrosis in British coalminers: a case-control study.

Possible associations between the incidence of progressive massive fibrosis (PMF) over periods of average length 11 years during 1963-80 and a range of explanatory variables, both environmental and medical, were examined in a study group of 4772 miners and ex-miners using case-control methods. Cases were members of the study group who developed PMF during the study period; controls were men who remained free of the disease. Cases and controls were matched on cumulative dust exposure to the start of the study period, colliery of employment, and whether or not employment before and during the study period had been at a single colliery only. Of 257 cases of PMF, 142 were matched to four controls each, 39 to three controls, 33 to two controls, and 31 to a single control only. Twelve cases could not be matched. Age and category of simple pneumoconiosis were each found to be associated with the incidence of PMF, confirming the results of many previous studies. Quetelet's index of body mass (a measure of weight, normalised for height) was found to differ considerably between cases and controls, cases tending to be lighter for their height. The difference did not vary significantly between three groups of collieries, defined by coal rank. Regression analysis confirmed the high level of statistical significance of the difference (p less than 0.001), allowing for the effects of age and prior category of simple pneumoconiosis. Of the environmental factors considered, an index of residence time of dust in the lungs was found to have the most statistically significant association with the incidence of PMF. The crudeness of the measure used, however, together with unreliability in estimates of early exposure to dust for some of the men studied, means that further work is necessary to investigate the magnitude and significance of this apparent association. In low and medium rank collieries there were large differences between the proportion of cases and controls showing a range of respiratory symptoms, cases consistently displaying a higher prevalence. In the high rank collieries of south Wales, however, symptoms occurred with equal frequency in cases and controls, the prevalence at these collieries being the same as among cases generally. Regression analysis (low and medium rank collieries only) showed that the presence of breathlessness was the symptom most strongly associated with the risk of attack of PMF, allowing for the effects of age and Quetelet's index.     

Contribution of follow-up of nonresponders to prevalence and risk estimates: a Norwegian respiratory health survey

Achieving a high response rate is often expensive and time consuming. Does an extensive survey effort change prevalence estimates and exposure-disease relations? In 1998-1999, the authors conducted a population-based respiratory health survey in two Norwegian counties (Oslo, n = 20,000; Hordaland, n = 5,000) of a random sample of the adult population aged 15-70 years. A postal questionnaire was mailed, with as many as two reminder letters. A 25% random sample of postal nonresponders was contacted by ordinary or cellular telephone. Cumulative response rates after the first mailing, first reminder, second reminder, and telephone follow-up were 42.7%, 60.7%, 68.3%, and 79.9%, respectively. Compared with initial postal responders, responders at later stages were younger, and more were male. Late responders had a lower educational level, were more often smokers, and were occupationally exposed to dusts or gases more frequently. After the authors adjusted for these factors, late responders were found to have less asthma, attacks of breathlessness, and hay fever. Hardly any changes in prevalences and odds ratios were noted when initial responders were compared with all responders. The additional contribution of sending reminder letters and conducting a telephone follow-up to prevalence estimates and the exposure-disease relation was small. A single letter would have produced nearly the same prevalence estimates and risk factor associations.     

Pneumoconiosis and respiratory problems in dental laboratory technicians: Analysis of 893 dental technicians

Objectives

To explore the rate of pneumoconiosis in dental technicians (DTP) and to evaluate the risk factors.

Material and Methods

Data of 893 dental technicians, who were admitted to our hospital in the period January 2007–May 2012, from 170 dental laboratories were retrospectively examined. Demographic data, respiratory symptoms, smoking status, work duration, working fields, exposure to sandblasting, physical examination findings, chest radiographs, pulmonary function tests and high-resolution computed tomography results were evaluated.

Results

Dental technicians’ pneumoconiosis rate was 10.1% among 893 cases. The disease was more common among males and in those exposed to sandblasting who had 77-fold higher risk of DTP. The highest profusion subcategory was 3/+ (according to the International Labour Organization (ILO) 2011 standards) and the large opacity rate was 13.3%.

Conclusions

To the best of our knowledge, it was the largest DTP case series (N = 893/90) in the literature in English. Health screenings should be performed regularly for the early diagnosis of pneumoconiosis, which is an important occupational disease for dental technicians.     

Risk scores from logistic regression: Unbiased estimates of relative and attributable risk

In epidemiology, the risk of disease in terms of a set of covariates is often modelled by logistic regression. The resulting linear predictor can be used to define the extent of risk between extremes, and to calculate an attributable risk for the covariates taken together. As is well known, straightforward use of the linear predictor, on the sample from which it was derived, to obtain estimates the relative and attributable risk will be biased, often seriously. Use of the jack-knife technique is extended to produce asymptotically unbiased estimates of relative and attributable risks. The asymptotic variances associated with these estimates are derived by using the formulae of conditional variances. They are applied to the results of a case-control study of stomach cancer.     

某机械制造企业粉尘作业人员尘肺危害现状调查

[目的]调查某机械制造企业粉尘作业人员尘肺危害状况,对尘肺发病的风险进行评估,探讨有效的职业病防控对策。[方法]2009年对粉尘作业车间进行现场职业卫生调查、对216名粉尘作业接触工人进行职业健康检查及问卷调查。[结果]粉尘作业地点工程防护设施不完善,作业工人个人呼吸防护情况不佳。职业健康检查结果显示,未发现尘肺患者,胸片有异常表现者66人,占总人数的30.56%,其中观察对象有6人。与上年胸片对比,有16人肺部损害呈现加重的趋势。随着接尘工龄的延长,粉尘作业工人胸片有异常表现的比例明显增高(P<0.001)。[结论]该企业粉尘作业工人尘肺发病的风险增加,应及早建立职业病防控管理体系,通过多种技术手段加强职业病预防控制。对胸片表现异常,包括出现小阴影改变,未达到观察对象标准的粉尘作业人员进行监测和动态观察,可以早期评估尘肺发病的风险。     

Effect of follow-up time on risk estimates: a longitudinal examination of the relative risks of leukemia and multiple myeloma in a rubber hydrochloride cohort

BACKGROUND: Choice of follow-up time for an occupational cohort can influence risk estimates. We examined the effects of follow-up time on relative risk estimates for leukemia and multiple myeloma in a cohort of 1,845 rubber hydrochloride workers. MATERIALS AND METHODS: We generated standardized mortality ratios (SMRs) for yearly follow-ups, beginning each study in 1940 and increasing study end dates from 1950 through 1996. We used Cox proportional hazards modeling to explore the effects of follow-up time on the exposure-response relationship. RESULTS: The SMR for leukemia rose to 13.55 in 1961 and fell nearly monotonically to 2.47 by 1996. Cox modeling suggested interaction between cumulative exposure and time since exposure. A longer time to peak risk was seen for multiple myeloma. CONCLUSIONS: Because summary risk estimates change with follow-up time, exposure limits set using these estimates may not adequately protect workers. Consideration of appropriate follow-up time and use of more complex temporal models are critical to the risk assessment process.     

Pet birds and risks of respiratory disease in Australia: a review

Objective: Exposure to birds has long been associated with disease in humans. Three respiratory diseases (psittacosis, allergic alveolitis and asthma) were reviewed in association with pet bird ownership with the aim to clarify the spectrum of avian-related respiratory illnesses.
Approach: Nineteen studies were selected for review based on recreational bird exposure in relation to psittacosis, allergic alveolitis and asthma.
Conclusion: Literature reveals little consensus on the relationship between pet bird ownership and respiratory illness.
Implications: Future studies should aim to clarify the spectrum of avian-related illnesses, and to direct the dissemination of public health information to clinicians and members of the public who keep birds as pets.     

Low plasma retinol concentrations increase the risk of developing bronchopulmonary dysplasia and long-term respiratory disability in very-low-birth-weight infants

BACKGROUND: The effect of inadequate vitamin A during the neonatal period on lung status is still unknown. OBJECTIVE: We tested the hypothesis that low plasma retinol concentrations during the first month of life are independently associated with bronchopulmonary dysplasia (BPD) and long-term respiratory morbidity at 6 mo gestationally corrected age (ie, the age the infant would be had the pregnancy gone to term). DESIGN: Respiratory outcome information was obtained to 6 mo corrected age for a historical cohort of very-low-birth-weight neonates (<1250 g) who were admitted to intensive care over a 7-y period. Neonates with one or more plasma measurements of retinol concentrations < 0.35 micromol/L (<100 microg/L) on days 1-28 were classified as having low vitamin A. BPD was defined at day 28 by clinical and radiologic criteria and by use of supplemental oxygen at 36 wk postmenstrual age (PMA). Dependence on supplemental oxygen was used to identify long-term respiratory disability at 6 mo corrected age. Multivariate logistic regression analyses were conducted. RESULTS: Of the 350 study infants, 192 (55%) had low vitamin A status. BPD occurred in 52% of survivors at day 28 (173/331) and at 36 wk PMA (147/285). Fourteen percent (33/244) required oxygen support at 6 mo corrected age. Adjusted odds ratios of BPD with low vitamin A were 3.5 (95% CI: 1.7, 7.2) at day 28 and 1.7 (1.0, 2.7) at 36 wk PMA. At 6 mo corrected age, the adjusted odds ratio was 2.6 (1.1, 6.4) for respiratory disability with low vitamin A. CONCLUSION: Poor vitamin A status during the first month of life significantly increased the risk of developing BPD and long-term respiratory disability.