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The association between low-level crystalline silica (silica) exposure and mortality risk is not well understood. We investigated a cohort of 44,807 Chinese workers who had worked in metal mines or pottery factories for at least 1 year from January 1, 1960, to December 31, 1974, and were followed through 2003. Low-level silica exposure was defined as having a lifetime highest annual mean silica exposure at or under a permissible exposure limit (PEL). We considered 3 widely used PELs, including 0.05 mg/m3, 0.10 mg/m3, and 0.35 mg/m3. Cumulative silica exposure was estimated by linking a job exposure matrix with each participant's work history. For the 0.10-mg/m3 exposure level, Cox proportional hazards models showed significantly increased risk of mortality from all diseases (for each 1-ln mg/m3-years increase in logged cumulative silica exposure, hazard ratio (HR) = 1.05, 95% confidence interval (CI): 1.03, 1.07), malignant neoplasms (HR = 1.06, 95% CI: 1.03, 1.09), lung cancer (HR = 1.08, 95% CI: 1.02, 1.14), ischemic heart disease (HR = 1.09, 95% CI: 1.02, 1.16), pulmonary heart disease (HR = 1.08, 95% CI: 1.00, 1.16), and respiratory disease (HR = 1.20, 95% CI: 1.14, 1.26). The 0.05-mg/m3 and 0.35-mg/m3 exposure levels yielded similar associations. Long-term exposure to low levels (PELs ≤0.05 mg/m3, ≤0.10 mg/m3, or ≤0.35 mg/m3) of silica is associated with increased total and certain cause-specific mortality risk. Control of ambient silica levels and use of personal protective equipment should be emphasized in practice., (© The Author(s) 2017. Published by Oxford University Press on behalf of the Johns Hopkins Bloomberg School of Public Health. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Background: Although occupational exposure is a known risk factor for Chronic Obstructive Pulmonary Disease (COPD), it is difficult to identify specific occupational contributors to COPD at the individual level to guide COPD prevention or for compensation. The aim of this study was to gain an understanding of how different expert clinicians attribute likely causation in COPD., Methods: Ten COPD experts and nine occupational lung disease experts assigned occupational contribution ratings to fifteen hypothetical cases of COPD with varying combinations of occupational and smoking exposures. Participants rated the cause of COPD as the percentage contribution to the overall attribution of disease for smoking, occupational exposures and other causes., Results: Increasing pack-years of tobacco smoking was associated with significantly decreased proportional occupational causation ratings. Increasing weighted occupational exposure was associated with increased occupational causation ratings by 0.28% per unit change. Expert background also contributed significantly to the proportion of occupational causation rated, with COPD experts rating on average a 9.4% greater proportion of occupational causation per case., Conclusion: Our findings support the notion that respiratory physicians are able to assign attribution to different sources of causation in COPD, taking into account both smoking and occupational histories. The recommendations on whether to continue to work in the same job also differ, the COPD experts being more likely to recommend change of work rather than change of work practice.

Objective: To establish the value of workplace spirometry monitoring methods for early recognition of long-term excessive lung function decline in individuals., Methods: Sensitivity, specificity, and positive likelihood ratio were calculated to determine the predictive value of the linear regression slope and limits of longitudinal decline for early prediction of long-term excessive forced expiratory volume in 1 second (FEV1) decline (> 90 mL/yr established over 9 to 11 years) in ongoing spirometry monitoring programs (firefighters and construction workers) and a historical program (paper-pulp mill workers). The longitudinal limits account for the expected FEV1 within-person variability., Results: The longitudinal limits achieved clinical "usefulness" (positive likelihood ratio 10 or higher) from the fourth to fifth year of follow-up, whereas the linear regression slope was less useful. The usefulness depended on data precision and measurement frequency., Conclusion: The limits of longitudinal decline are more useful for early recognition of long-term excessive FEV1 decline than the linear regression slope.

Objective: Effectiveness of periodic spirometry in medical monitoring depends on spirometry quality. We describe an intervention on spirometry quality and its impact on accuracy and precision of longitudinal measurements., Methods: The intervention was conducted from 2005 to 2010 in a monitoring program involving approximately 2500 firefighters. Intervention supported adherence to 2005 American Thoracic Society/European Respiratory Society recommendations through monitoring of spirometry quality and longitudinal data precision, technician training, change of spirometer, and quality control., Results: The percentage of forced vital capacity tests meeting the American Thoracic Society/European Respiratory Society criteria increased from 60% to 95% and the mean longitudinal forced expiratory volume in 1 second within-person variation decreased from 6% to 4%. The increased accuracy and precision of measurements and estimated rates of forced expiratory volume in 1 second decline were statistically significant., Conclusion: Monitoring of quality and data precision helped to recognize the need for intervention. The intervention improved accuracy and precision of spirometry measurements and their usefulness.

Objective: To evaluate methods for determining excessive short-term decline in forced expiratory volume in one second (FEV1) in diacetyl-exposed workers., Methods: We evaluated five methods of determining excessive longitudinal FEV1 decline in diacetyl-exposed workers and workers from a comparative cohort: American Thoracic Society (ATS), ACOEM an 8% limit, and a relative and absolute longitudinal limit on the basis of spirometry data variability. Relative risk and incidence of excess decline were evaluated., Results: Incidence of excessive FEV1 decline was 1% in the comparative cohort using ATS and ACOEM criteria, 4.1% using relative limit of longitudinal decline, 4.4% with absolute longitudinal limit of decline, and 5.6% by using the 8% limit. Relative risk of abnormal FEV1 decline in diacetyl-exposed workers was elevated in all evaluated methods., Conclusion: Alternative methods for respiratory surveillance in diacetyl-exposed workers may be preferable to ATS or ACOEM.

Aim: To investigate the risk of death associated with selected cut-off points for rate of decline of forced expiratory volume in one second (FEV(1))., Methods: Mortality rates of a cohort of 1730 coal miners who had performed two pulmonary function tests 12.8 years apart were followed up for an additional 12 years. Based on previous studies, cut-off points for FEV(1) rate of decline (ml/year) were selected as 30, 60 and 90 ml/year. Cox proportional hazard regression was used to estimate multivariate risk ratio of death in each category., Results: The risk ratios (compared to "below 30 ml/year") were 1.39 (95% CI 0.99 to 1.97) in the "60 to less than 90 ml/year" category and 1.90 (95% CI 1.32 to 2.76) in the "90 ml/year and above" category. Rates of decline above 90 ml/year were consistently related to excess mortality. In non-smokers and those with neither restrictive nor obstructive patterns at the first survey, rates of decline above 60 ml/year were significantly associated with increased mortality., Conclusions: Risk of death increases in individuals with rates of decline above about 60 ml/year and is statistically significant with declines of 90 ml/year or more. These results should be useful to healthcare providers in assessing lung function declines observed in individuals.

Background: The estimated number of US workers potentially exposed to asthmagens ranges from 8 to 20 million. This study was undertaken to estimate the US prevalence of asthma in adults by industry of employment and to identify industries with elevated risk of asthma., Methods: Prevalence analysis was performed on 20,991 adults, 18 years of age and older who participated in the 2001 National Health Interview survey. We used SUDAAN software to estimate the prevalence of self-reported physician diagnosed asthma by industry, and odds ratios (ORs) for asthma and industry adjusted for age, sex, race, and smoking status., Results: The overall prevalence of physician diagnosed asthma was 6.5% (95% CI 6.1-6.9); 4.7% (95% CI 4.1-5.3) for males and 8.5% (95% CI 7.9-9.1) for females. In whites, the prevalence and ORs were significantly elevated for printing, publishing, and allied industries (OR = 2.4, 95% CI 1.2-5.0) and health care (OR = 1.3, 95% CI 1.0-1.7). In blacks, ORs were elevated for furniture, lumber, and wood (OR = 5.9, 95% CI 1.4-25.4) and entertainment and recreation industries (OR = 4.1, 95% CI 1.1-15.9). Other industries with elevated ORs included automobile dealers and gasoline station; durable goods; elementary, secondary schools, and colleges; other personal services; eating and drinking places; entertainment and recreation services; and utility and sanitary., Conclusions: Industries with elevated prevalence of asthma are identified. This information helps to target workplaces where detailed investigations for prevention and control may be appropriate.

Objective: The authors conducted an investigation of a cluster of eight new-onset asthma cases identified in a chemical plant through the Sentinel Event Notification Systems for Occupational Risks (SENSOR) program., Methods: Workplace investigation involved interviews with the asthma cases, review of medical records, and medical and industrial hygiene surveys in the plant., Results: Altogether, 11 work-related asthma cases were identified among the plant workers-approximately 10% of the workers exposed to the potential causative agents: 3-amino-5-mercapto-1,2,4-triazole (AMT) or N-(2,6-difluorophenyl)-5-methyl-[1,2,4]triazolo[1,5-a]pyrimidine-2-sulfonamide (DE-498; trade name Flumetsulam). Of these cases, six had physician-diagnosed occupational asthma (OA) based on work-related respiratory symptoms and nonspecific bronchial hyperresponsiveness (NSBH), and of these, three had work-related expiratory peak flow changes., Conclusions: The findings of this investigation, together with findings from concurrent animal studies, suggest that this outbreak of new-onset asthma was associated with exposure to AMT., Clinical Significance: A cluster of eight new-onset asthma cases was identified in a chemical plant through the SENSOR program. Subsequent workplace investigation identified AMT, used in the production of a herbicide N-(2,6-difluorophenyl)-5-methyl- [1,2,4]triazolo[1,5-a]pyrimidine-2-sulfonamide, as the most likely causal agent.

During annual medical monitoring, some firefighters are found to have rates of decline in forced expiratory volume in one second (FEV1) far exceeding their peers. Interleukin-10 (IL-10) suppresses inflammation, and single nucleotide polymorphisms (SNPs) in the IL-10 gene may confer variable susceptibility to more rapid decline in lung function. In 1204 firefighters with at least six annual FEV1 measurements, increased age and greater initial FEV1 were associated with more rapid decline in lung function. DNA collected from 379 of these firefighters was screened for IL-10 SNPs at -1117, -854, 919, 1668, and 1812. A statistically significant difference in decline in lung function was found based on genotyping at the 1668 SNP. Evaluation of gene polymorphisms regulating lung inflammation may help to explain some of the variation in rate of decline in lung function in firefighters.

Background: The aim was to investigate the respiratory response of HDI-based paint aerosol within the context of the protection afforded by current exposure guidelines., Methods: A cross-sectional study of 240 painters spraying polyurethane enamels was undertaken at four aircraft maintenance plants. Questionnaire and spirometric data were related to gravimetric measures of cumulative total and respirable paint aerosol (TPA and RPA) and estimated isocyanate in total and respirable aerosols (TIA and RIA)., Results: Average cumulative exposures in mg/m(3)-years +/- SD were 159.0 +/- 115.2 TPA, 19.1 +/- 13.8 RPA, 15.8 +/- 11.5 TIA, and 1.9 +/- 1.4 RIA. After adjusting for smoking and asthma symptoms, higher exposures were associated with statistically significant reduction in expiratory flowrates. Significant smoking-related reductions were also observed, without exposure interactions., Conclusions: These results suggest important respiratory effects from exposures to spray paint aerosols at levels generally in compliance with existing standards for otherwise unregulated particulates and for the isocyanate component of the paint.

Objectives: To estimate the fraction of airflow obstruction attributable to workplace exposure by U.S. race/ethnic group., Methods: U.S. population-based third National Health and Nutrition Examination Survey (NHANES III) data on 4,086 Caucasians, 2,774 African-Americans, and 2,568 Mexican-Americans, aged 30-75, were studied. Airflow obstruction was defined as FEV1/FVC<75% and FEV1<80% predicted. Weighted prevalence, and prevalence odds ratios (OR) adjusted for the effect of age, smoking status, pack-years, body mass index, education, and socio-economic status were estimated using SUDAAN software., Results: Industries with the most cases of airflow obstruction attributable to workplace exposure include: armed forces; rubber, plastics, and leather manufacturing; utilities; textile mill manufacturing; health care; food products manufacturing; sales; construction; and agriculture. The fraction of cases with airflow obstruction associated with work in industry varied by race/ethnic group and was estimated as 22.2% (95% CI 9.1-33.4) among Caucasians, 23.4% (95% CI 2.2-40.0) among African-Americans, and 49.6% (32.1-62.6) among Mexican-Americans., Conclusions: This study found differences in the fraction of airflow obstruction cases associated with employment pattern among major U.S. race/ethnic population groups.

Chronic lower airway diseases, including chronic obstructive pulmonary disease (COPD) and asthma, are currently the third leading cause of death in the United States. We aimed to evaluate changes in prevalence of and risk factors for COPD and asthma among the US adult population. We evaluated changes in prevalence of self-reported doctor-diagnosed COPD (i.e. chronic bronchitis and emphysema) and asthma and self-reported respiratory symptoms comparing data from the 1988–1994 and 2007–2010 National Health and Nutrition Examination Surveys. To investigate changes in the severity of each outcome over the two periods, we calculated changes in the proportions of spirometry-based airflow obstruction for each outcome. Prevalence of doctor-diagnosed chronic bronchitis and emphysema decreased significantly mainly among males, while asthma increased only among females. The self-reported disease and the respiratory symptoms were associated with increased prevalence of airflow obstruction for both periods. However, the prevalence of airflow obstruction decreased significantly in the second period among those with shortness of breath and doctor-diagnosed respiratory conditions (chronic bronchitis, emphysema, and asthma). COPD outcomes and asthma were associated with lower education, smoking, underweight and obesity, and occupational dusts and fumes exposure. Chronic lower airway diseases continue to be major public health problems. However, decreased prevalence of doctor-diagnosed chronic bronchitis and emphysema (in males) and decreased prevalence of airflow obstruction in those with respiratory symptoms and doctor-diagnosed respiratory diseases may indicate a declining trend and decrease in disease severity between the two periods. Continued focus on prevention of these diseases through public health interventions is prudent. [ABSTRACT FROM PUBLISHER]

Data from the US population-based Third National Health and Nutrition Examination Survey, conducted from 1988 to 1994, were used to estimate the population prevalence, prevalence odds ratios, and attributable fractions for the association of chronic obstructive pulmonary disease (COPD) with employment by industry and occupation. The aim was to identify industries and occupations at increased risk of COPD. COPD was defined as forced expiratory volume in 1 second (FEV1)/forced vital capacity <70% and FEV1 <80% predicted. The authors used SUDAAN software (Research Triangle Institute, Research Triangle Park, North Carolina) to estimate the weighted population prevalence and odds ratios using 9,823 subjects aged 30-75 years who underwent lung function tests. Odds ratios for COPD, adjusted for age, smoking status, pack-years of smoking, body mass index, education, and socioeconomic status, were increased for the following industries: rubber, plastics, and leather manufacturing; utilities; office building services; textile mill products manufacturing; the armed forces; food products manufacturing; repair services and gas stations; agriculture; sales; construction; transportation and trucking; personal services; and health care. Occupations associated with increased odds ratios for COPD were freight, stock, and material handlers; records processing and distribution clerks; sales; transportation-related occupations; machine operators; construction trades; and waitresses. The fraction of COPD attributable to work was estimated as 19.2% overall and 31.1% among never smokers. [ABSTRACT FROM AUTHOR]

Objectives: Silica is one of the most common occupational exposures worldwide. In 1997 the International Agency for Research on Cancer (IARC) classified inhaled crystalline silica as a human carcinogen (group 1), but acknowledged limitations in the epidemiologic data, including inconsistencies across studies and the lack of extensive exposure–response data. We have conducted a pooled exposure–response analysis of 10 silica-exposed cohorts to investigate lung cancer. Methods: The pooled cohort included 65,980 workers (44,160 miners, 21,820 nominees), and 1072 lung cancer deaths (663 miners, 409 nonminers). Follow-up has been extended for five of these cohorts beyond published data. Quantitative exposure estimates by job and calendar time were adopted, modified, or developed to permit common analyses by respirable silica (mg/m3) across cohorts. Results: The log of cumulative exposure, with a 15-year lag, was a strong predictor of lung cancer ( p = 0.0001), with consistency across studies (test for heterogeneity, p = 0.34). Results for the log of cumulative exposure were consistent between underground mines and other facilities. Categorical analyses by quintile of cumulative exposure resulted in a monotonic trend with odds ratios of 1.0, 1.0, 1.3, 1.5, 1.6. Analyses using a spline curve also showed a monotonic increase in risk with increasing exposure. The estimated excess lifetime risk (through age 75) of lung cancer for a worker exposed from age 20 to 65 at 0.1 mg/m3 respirable crystalline silica (the permissible level in many countries) was 1.1–1.7%, above background risks of 3–6%. Conclusions: Our results support the decision by the IARC to classify inhaled silica in occupational settings as a carcinogen, and suggest that the current exposure limits in many countries may be inadequate. These data represent the first quantitative exposure–response analysis and risk assessment for silica using data from multiple studies. [ABSTRACT FROM AUTHOR]

Objectives: To investigate the following questions. (1) Is silica dust on its own, without the presence of silicosis, associated with an increased risk of pulmonary tuberculosis (PTB) in workers exposed to silica dust? (2) In the absence of silicosis is the excess risk dose related? (3) What is the predominant chronological sequence between the development of PTB and the development of silicosis after the end of exposure to dust?Methods: A cohort of 2255 white South African gold miners has been followed up from 1968 to 1971, when they were 45-55 years of age, to 31 December 1995 for the incidence of PTB. During the follow up 1592 (71%) men died. Of these, 1296 (81%) had a necropsy done at the National Centre for Occupational Health (NCOH) to determine the presence of silicosis and PTB. The incidence of PTB in the cohort was studied relative to cumulative exposure to dust and the onset of silicosis. For the miners with necropsy, the incidence for PTB was studied relative to the severity of silicosis found at necropsy.Results: There were 115 subjects who developed PTB. The total person-years of follow up was 39,319. For the whole cohort, the factors associated with increased risk of PTB were cumulative exposure to dust (mg/m3.y) (the adjusted rate ratio (RR) 1.07; (95% confidence interval (95% CI) 1.04 to 1.10)), silicosis diagnosed radiologically (3.96 (2.59 to 6.06)), and tobacco pack-years (1.02 (1.01 to 1.03)). The RR (95% CI) for PTB increased with increasing quartiles of cumulative exposure to dust 1.0, 1.51 (0.78 to 2.91), 2.35 (1.28 to 4.32), and 3.22 (1.75 to 5.90). In miners who did not have radiologically diagnosed silicosis (n = 1934, PTB = 74), the adjusted RR (95% CI) for PTB and cumulative exposure to dust was 1.10 (1.06 to 1.13), and increased with quartiles of cumulative exposure to dust as 1.00, 1.46 (0.70 to 3.03), 2.67 (1.37 to 5.23), and 4.01 (2.04 to 7.88). For the subjects who had a necropsy (n = 1296, PTB = 70), the adjusted RR (95% CI) for PTB increased with the severity of silicosis found at necropsy; 1.0 for no silicosis, 1.88 (0.97 to 3.64) for negligible, 2.69 (1.35 to 5.37) for slight, and 2.30 (1.16 to 4.58) for moderate or marked silicosis. For subjects who had a necropsy and no silicosis (n = 577, PTB = 18), the adjusted RR (95% CI) increased slightly with quartiles of cumulative dust 1.0, 1.11 (0.31 to 4.00), 1.42 (0.43 to 4.72), and 1.38 (0.33 to 5.62).Conclusion: Exposure to silica dust is a risk factor for the development of PTB in the absence of silicosis, even after exposure to silica dust ends. The risk of PTB increases with the presence of silicosis, and in miners without radiological silicosis, with quartiles of exposure to dust. The severity of silicosis diagnosed at necropsy was associated with increasing risk of PTB and even < 5 nodules--that is, undetectable radiologically--was associated with an increased risk of PTB. The diagnosis of PTB was on average 7.6 years after the end of exposure to dust, at around 60 years of age. The onset of radiological silicosis preceded the diagnosis of PTB in 90.2% of the cases with PTB who had silicosis. The results have implications for medical surveillance of workers exposed to silica dust after the end of exposure. [ABSTRACT FROM AUTHOR]