Occupational causes of chronic obstructive pulmonary disease

Association between Crystalline Silica Dust Exposure and Silicosis Development in Artificial Stone Workers

Occupational exposure to respirable crystalline silica (SiO₂) is one of the most common and serious risks because of the health consequences for the workers involved. Silicosis is a progressive, irreversible, and incurable fibrotic lung disease caused by the inhalation of respirable crystalline silica dust. A cross-sectional epidemiological study was carried out to assess the occupational risk factors that may contribute to the onset of silicosis in workers carrying out work activities with the inhalation of silica compact dust. The study population consisted of 311 artificial stone workers from the province of Almeria (southeast of Spain). Among them, 64 were previously diagnosed with silicosis and the rest of the participants (n = 247 workers) were not diagnosed with such a disease. The workers showing a greater risk of developing silicosis were those who installed kitchen worktops at consumers’ homes, as they did not use face-masks or were not provided with personal protective equipment (PPE) by their business. The results of this study provide support for the evidence indicating that silicosis is a major emerging health concern for workers in the artificial stone sector. Exposure to crystalline silica dust thus can influence the development of silicosis in those cases where individual and collective protection measures are not used or adequately applied.

Global and regional burden of chronic respiratory disease in 2016 arising from non-infectious airborne occupational exposures: a systematic analysis for the Global Burden of Disease Study 2016

OBJECTIVES

This paper presents detailed analysis of the global and regional burden of chronic respiratory disease arising from occupational airborne exposures, as estimated in the Global Burden of Disease 2016 study.

METHODS

The burden of chronic obstructive pulmonary disease (COPD) due to occupational exposure to particulate matter, gases and fumes, and secondhand smoke, and the burden of asthma resulting from occupational exposure to asthmagens, was estimated using the population attributable fraction (PAF), calculated using exposure prevalence and relative risks from the literature. PAFs were applied to the number of deaths and disability-adjusted life years (DALYs) for COPD and asthma. Pneumoconioses were estimated directly from cause of death data. Age-standardised rates were based only on persons aged 15 years and above.

RESULTS

The estimated PAFs (based on DALYs) were 17% (95% uncertainty interval (UI) 14%-20%) for COPD and 10% (95% UI 9%-11%) for asthma. There were estimated to be 519 000 (95% UI 441,000-609,000) deaths from chronic respiratory disease in 2016 due to occupational airborne risk factors (COPD: 460,100 [95% UI 382,000-551,000]; asthma: 37,600 [95% UI 28,400-47,900]; pneumoconioses: 21,500 [95% UI 17,900-25,400]. The equivalent overall burden estimate was 13.6 million (95% UI 11.9-15.5 million); DALYs (COPD: 10.7 [95% UI 9.0-12.5] million; asthma: 2.3 [95% UI 1.9-2.9] million; pneumoconioses: 0.58 [95% UI 0.46-0.67] million). Rates were highest in males; older persons and mainly in Oceania, Asia and sub-Saharan Africa; and decreased from 1990 to 2016.

CONCLUSIONS

Workplace exposures resulting in COPD, asthma and pneumoconiosis continue to be important contributors to the burden of disease in all regions of the world. This should be reducible through improved prevention and control of relevant exposures.

Respiratory Symptoms and Lung Function among Greek Cotton Industry Workers: A Cross-Sectional Study

Background:

Workers in cotton industry are occupationally exposed to various dust-related hazards. The nature of these agents and the respective exposure levels depend on the cotton industry specific sector. These exposures could be associated with respiratory symptoms and changes in lung function parameters.

Objective:

To evaluate associations between occupational exposure and respiratory function as well as reported symptoms in several groups of workers at different stages of the cotton industry in a vertical approach that covers all the major sectors—from cotton ginning to weaving and fabric production.

Methods:

A questionnaire on respiratory symptoms and individual as well as workplace characteristics was completed by 256 workers at the cotton industry and 148 office workers (control group). Both groups underwent spirometry.

Results:

Workers in cotton industry reported a higher prevalence of severe dyspnea (p=0.002) and wheezing (p=0.004) compared to the control group. Also they were found to have a lower predicted FEV1% (p<0.029) and lower FEV1/FVC (p<0.001) values. In addition, a higher prevalence of FEV1% <80% (p<0.001) and FEV1/FVC <70% (p=0.041) were found among textile workers. Similar results were found for non-smoker textile workers compared to non-smoker control group workers. Those working in cotton ginning mills recorded the highest decrease of spirometric values. Duration of employment in cotton industry and smoking use were found to be predictors of lung function decline for cotton industry workers.

Conclusion:

Occupational exposure to cotton dust was associated with increased prevalence of respiratory symptoms and obstructive pattern in pulmonary function test.

DIAGNOSTICS OF CHRONIC OBSTRUCTIVE PULMONARY DISEASE IN REAL CLINICAL PRACTICE: HYPODIAGNISTICS OR HYPERDIAGNOSTICS

According to the data of the world statistics there is observed the continuous growth of chronic obstructive pulmonary disease (COPD). According to the last data of the World health organization (WHO), for today there is near 250 mln persons with chronic obstructive pulmonary disease (COPD), and this disease becomes as cause of death of near 3 mln persons annually. Aim: to establish the prevalence of undiagnosed chronic pulmonary disease (COPD) among persons, who consider themselves as healthy ones and regularly undergo medical check-ups; to estimate the frequency of chronic obstructive pulmonary disease (COPD) according to the data of medical documentation. Methods and materials: 525 persons, older than 35, who did not have in an anamnesis any chronic diseases of respiratory tract, were interrogated. At the following stage, persons, who had taken 18 points or more underwent a spirography with bronchodilatation test, using 400 mcg of salbutamol and were interrogated by the modified questionnaire of short breath by the medical research council (MRC) and test of the chronic obstructive pulmonary disease estimation (COPD) (TEC). There were examined 136 patients, mean age (51,5±0,8), men were 81(59,5 %) mean age (52,2±1,1) and women – 55(40,4 %) mean age (50,7±0,9). There were analyzed 56 medical stories of patients, treated at therapeutic departments of the city clinic because of internal organs diseases with the concomitant diagnosis of chronic obstructive pulmonary disease (COPD). Among persons with first revealed chronic obstructive pulmonary disease у 21 (26,6 %) was reveled І severity degree according to GOLD, in 26 persons (32,9 %) – GOLD ІІ, in 28 (35,4 %) – GOLD ІІІ, in 4 (5,1 %) – GOLD ІV severity degree, so 32 patients did not receive basic treatment at all. At the same time among patients with COPD diagnosis in medical documentation only in 38,4 % this diagnosis was spirographically verified, the hyperdiagnostics of disease on the base of complaints and age characteristic took place in other cases.

Augmenting autophagy for prognosis based intervention of COPD-pathophysiology

Chronic obstructive pulmonary disease (COPD) is foremost among the non-reversible fatal ailments where exposure to tobacco/biomass-smoke and aging are the major risk factors for the initiation and progression of the obstructive lung disease. The role of smoke-induced inflammatory-oxidative stress, apoptosis and cellular senescence in driving the alveolar damage that mediates the emphysema progression and severe lung function decline is apparent, although the central mechanism that regulates these processes was unknown. To fill in this gap in knowledge, the central role of proteostasis and autophagy in regulating chronic lung disease causing mechanisms has been recently described. Recent studies demonstrate that cigarette/nicotine exposure induces proteostasis/autophagy-impairment that leads to perinuclear accumulation of polyubiquitinated proteins as aggresome-bodies, indicative of emphysema severity. In support of this concept, autophagy inducing FDA-approved anti-oxidant drugs control tobacco-smoke induced inflammatory-oxidative stress, apoptosis, cellular senescence and COPD-emphysema progression in variety of preclinical models. Hence, we propose that precise and early detection of aggresome-pathology can allow the timely assessment of disease severity in COPD-emphysema subjects for prognosis-based intervention. While intervention with autophagy-inducing drugs is anticipated to reduce alveolar damage and lung function decline, resulting in a decrease in the current mortality rates in COPD-emphysema subjects.

Carbon nanotubes stimulate synovial inflammation by inducing systemic pro-inflammatory cytokines

Carbon nanotubes (CNTs) have promising applications in a wide range of biomedical fields, including imaging, drug/gene delivery and other therapeutics; however, the biosafety concerns of CNTs should be addressed. To date, many reports have documented the toxicological effects on the cells, tissue or organs that are in direct contact with the tubes; however, there is limited evidence to unravel the secondary toxicity upon CNT treatment. Moreover, more effort is needed to gain a definitive understanding of the adverse outcome pathway (AOP) for CNTs, and a pragmatic framework for risk assessment has not been established yet. In the current study, we aimed to decipher the secondary toxicity to joints under CNT exposure. We demonstrated that carboxylated multi-wall CNTs (MWCNTs-COOH) significantly provoked systemic pro-inflammatory responses, leading to synovial inflammation within knee joints, as evidenced by the infiltration of pro-inflammatory cells in the synovium and meniscus. Mechanistic studies showed that MWCNTs-COOH stimulated pro-inflammatory effects by activating macrophages, and the secreted pro-inflammatory cytokines primed the synoviocytes and chondrocytes, resulting in enhanced production of a large array of enzymes involved in articular cartilage degeneration, including matrix metalloproteinase (MMP) members and cyclooxygenase (COX) members, and increased enzymatic activity of MMPs was demonstrated. Blockade of the cytokines by antibodies significantly attenuated the production of these enzymes. Our current study thus suggests that there is a novel secondary toxicity of CNTs, namely a new AOP to understand the indirect effects of carbon nanotubes: synovial inflammation due to the alteration of the priming state of synoviocytes and chondrocytes under CNT-induced systemic inflammatory conditions.

Occupational Risk Factors for COPD: A Case-Control Study

OBJECTIVES

The aim of this research was to examine the occupational risk factors for Chronic Obstructive Pulmonary Diseases (COPD) in a range of occupations.

METHODS

Eleven occupations involving different types of exposure were observed in this multicenter case-control study. Controls and cases were matched for sex, age and smoking. Multiple logistic regression analyses were used to estimate odds ratios (ORs).

RESULTS

A total of 1,519 participants were initially recruited between September 2004 and September 2012. After matching, 547 pairs were obtained. The mean age was 56.3 +/- 10.4 years. Smelter workers were the only ones with an increased risk of COPD in this study (OR = 7.6, p < 0.0001, 95% CI [4.5, 12.9]). Physical activity was protective (OR = 0.7), while living in the city was a risk (OR = 1.6). The main used metals were cast iron, aluminum and alloys. Molds and cores were mainly made from sand and synthetic resins. Machine maintenance (65.2%), molding (49.6%), finishing (41.1%) and casting (41.0%) were the most common activities. Almost all workers (95.1%) cleaned the floors and machines with a brush or compressed air.

CONCLUSIONS

This study demonstrates the importance of occupational factors in the genesis of COPD, especially among smelter workers. As with the fight against smoking-related disease, the removal or substitution of recognized hazardous agents is the best way of preventing the onset of COPD. This is why it is essential to continue research on its occupational risk factors.

Are welders more at risk of respiratory infections?

Inhalation of metal fume from welding is known to produce a reversible increase in susceptibility to infectious lobar pneumonia caused by Streptococcus pneumoniae and possibly other microorganisms. However, the mechanism underlying the hazard is uncertain, as is the relationship of risk to level of exposure. A new study at a shipyard in the Middle East suggests that welders also have higher rates of respiratory infections than other manual occupations. If confirmed, this finding could lead to a better understanding of pathogenesis, and possibly the development of biomarkers that could be used to elucidate exposure-response relationships. This in turn could guide limits on levels of exposure.

The need to increase awareness of the risk factors of COPD

COPD is a heterogeneous disease responsible for a major burden on public and individual health. A wide variety of intrinsic and environmental risk factors are involved, and exert their influence at various time points during the life span of individuals. Knowledge of these factors is of utmost importance to develop appropriate screening and prevention programs, and may help improving the pathophysiological knowledge of the disease. Accordingly, there are multiple targets of information and education on risk factors for COPD, including the general population and patients, workers and employers, doctors and other healthcare professionals, researchers, policy-makers, payers, etc. Gender and socioeconomic factors need to be specifically considered. Importantly, it is likely that increasing the specific knowledge of COPD risk factors among the above-mentioned targets cannot not be obtained without increasing the general knowledge of COPD in the population, which at present is dramatically low.

A case-control study of airways obstruction among construction workers

BACKGROUND

While smoking is the major cause of chronic obstructive pulmonary disease (COPD), occupational exposures to vapors, gases, dusts, and fumes (VGDF) increase COPD risk. This case-control study estimated the risk of COPD attributable to occupational exposures among construction workers.

METHODS

The study population included 834 cases and 1243 controls participating in a national medical screening program for older construction workers between 1997 and 2013. Qualitative exposure indices were developed based on lifetime work and exposure histories.

RESULTS

Approximately 18% (95% CI = 2-24%) of COPD risk can be attributed to construction-related exposures, which are additive to the risk contributed by smoking. A measure of all VGDF exposures combined was a strong predictor of COPD risk.

CONCLUSIONS

Construction workers are at increased risk of COPD as a result of broad and complex effects of many exposures acting independently or interactively. Control methods should be implemented to prevent worker exposures, and smoking cessation should be promoted.

Redemption of asthma pharmaceuticals among stainless steel and mild steel welders: a nationwide follow-up study

PURPOSE

The purpose was to examine bronchial asthma according to cumulative exposure to fume particulates conferred by stainless steel and mild steel welding through a proxy of redeemed prescribed asthma pharmaceuticals.

METHODS

A Danish national company-based historical cohort of 5,303 male ever-welders was followed from 1995 to 2011 in the Danish Medicinal Product Registry to identify the first-time redemption of asthma pharmaceuticals including beta-2-adrenoreceptor agonists, adrenergic drugs for obstructive airway diseases and inhalable glucocorticoids. Lifetime exposure to welding fume particulates was estimated by combining questionnaire data on welding work with a welding exposure matrix. The estimated exposure accounted for calendar time, welding intermittence, type of steel, welding methods, local exhaustion and welding in confined spaces. Hazard ratios (HRs) with 95% confidence intervals (CIs) were calculated using a Cox proportional hazards model adjusting for potential confounders and taking modifying effects of smoking into account.

RESULTS

The average incidence of redemption of asthma pharmaceuticals in the cohort was 16 per 1,000 person year (95% CI 10-23 per 1,000 person year). A moderate nonsignificant increased rate of redemption of asthma medicine was observed among high-level exposed stainless steel welders in comparison with low-level exposed welders (HR 1.54, 95% CI 0.76-3.13). This risk increase was driven by an increase risk among non-smoking stainless steel welders (HR 1.46, 95% CI 1.06-2.02). Mild steel welding was not associated with increased risk of use asthma pharmaceuticals.

CONCLUSION

The present study indicates that long-term exposure to stainless steel welding is related to increased risk of asthma in non-smokers.

Performing a lung disability evaluation: how, when, and why?

OBJECTIVES

The objective of this review is to present a case-based clinical discussion on this topic.

METHODS

The article represents part of the proceedings of the Occupational and Environmental Lung Disease conference held by the American College of Chest Physicians at Toronto, Ontario, Canada, in 2013, and is based upon a nonsystematic review of the current literature by the author.

RESULTS

Although the American Medical Association Guides to the Evaluation of Permanent Impairment is the mainstay for evaluating respiratory impairment, many other impairment schemata are currently available in the United States. Impairment evaluation for a case with chronic respiratory disease and a separate case with asthma is discussed.

CONCLUSIONS

Pulmonary function tests are the cornerstone for evaluating respiratory impairment. Impairment values differ between various impairment schemata. Impairment evaluation for asthma may be particularly difficult.

Toenail metal concentration as a biomarker of occupational welding fume exposure

In populations exposed to heavy metals, there are few biomarkers that capture intermediate exposure windows. We sought to determine the correlation between toenail metal concentrations and prior 12-month work activity in welders with variable, metal-rich, welding fume exposures. Forty-eight participants, recruited through a local union, provided 69 sets of toenail clippings. Union-supplied and worker-verified personal work histories were used to quantify hours welded and respirator use. Toenail samples were digested and analyzed for lead (Pb), manganese (Mn), cadmium (Cd), nickel (Ni), and arsenic (As) using ICP-MS. Spearman correlation coefficients were used to examine the correlation between toenail metal concentrations. Using mixed models to account for multiple participation times, we divided hours welded into three-month intervals and examined how weld hours correlated with log-transformed toenail Pb, Mn, Cd, Ni, and As concentrations. Highest concentrations were found for Ni, followed by Mn, Pb and As, and Cd. All the metals were significantly correlated with one another (rho range = 0.28-0.51), with the exception of Ni and As (rho = 0.20, p = 0.17). Using mixed models adjusted for age, respirator use, smoking status, and BMI, we found that Mn was associated with weld hours 7-9 months prior to clipping (p = 0.003), Pb was associated with weld hours 10-12 months prior to clipping (p = 0.03) and over the entire year (p = 0.04). Cd was associated with weld hours 10-12 months prior to clipping (p = 0.05), and also with the previous year's total hours welded (p = 0.02). The association between Ni and weld hours 7-9 months prior to clipping approached significance (p = 0.06). Toenail metal concentrations were not associated with the long-term exposure metric, years as a welder. Results suggest Mn, Pb, and Cd may have particular windows of relevant exposure that reflect work activity. In a population with variable exposure, toenails may serve as useful biomarkers for occupational metal fume exposures to Mn, Pb, and Cd during distinct periods over the year prior to sample collection.

Biopersistent granular dust and chronic obstructive pulmonary disease: a systematic review and meta-analysis

Objective

Applying a systematic review to identify studies eligible for meta-analysis of the association between occupational exposure to inorganic dust and the development of chronic obstructive pulmonary disease (COPD), and conducting a meta-analysis.

Data Sources

Searches of PubMed and Embase for the time period 1970–2010 yielded 257 cross-sectional and longitudinal studies on people exposed to inorganic dust at the workplace with data on lung function. These studies were independently abstracted and evaluated by two authors; any disagreement was resolved by a third reviewer. Of 55 publications accepted for meta-analysis, 27 investigated the effects of occupational exposure to biopersistent granular dust (bg-dust).

Methods

A random effects meta-analysis allowed us to provide an estimate of the average exposure effect on spirometric parameters presented in forest plots. Between-study heterogeneity was assessed by using I² statistics, with I²>25% indicating significant heterogeneity. Publication bias was investigated by visual inspection of funnel plots. The influence of individual studies was assessed by dropping the respective study before pooling study-specific estimates.

Results

The mean FEV1 of workers exposed to bg-dust was 160 ml lower or 5.7% less than predicted compared to workers with no/low exposure. The risk of an obstructive airway disease—defined as FEV1/FVC < 70%—increased by 7% per 1 mg· m^-3 respirable bg-dust.

Conclusion

Occupational inhalative exposure to bg-dust was associated with a statistically significant decreased FEV1 and FEV1/FVC revealing airway obstruction consistent with COPD.

Chronic bronchitis in the cohort of Mayak workers first employed 1948-1958

Incidence of chronic bronchitis has been studied in a cohort of 12,210 workers first employed at one of the main plants of the Mayak nuclear facility during 1948-1958 and followed up to 31 December 2005. Information on external gamma doses is available for virtually all of these workers; in contrast, plutonium body burden was measured only for 30% of workers. During the follow-up period in the study cohort 1,175 incident cases of chronic bronchitis were verified. The analyses of nonradiation factors revealed that the underlying risk of chronic bronchitis incidence increased with increasing attained age and was higher among smokers compared with never-smokers as would be expected. The most interesting finding in relationship to nonradiation factors was a sharp increase in the baseline chronic bronchitis risk before 1960. The cause of this is not clear but a number of factors may play a role. Based on the follow-up data after 1960, the analysis showed a statistically significant linear dose response relationship with cumulative external gamma-ray dose (ERR/Gy = 0.14, 95% CI 0.01, 0.32). Based on the same subset but with an additional restriction to members with cumulative internal lung dose below 1 Gy, a statistically significant linear dose response relationship with internal alpha-radiation lung dose from incorporated plutonium was found (ERR/Gy = 2.70, 95% CI 1.20, 4.87). In both cases, adjustment was made for nonradiation factors, including smoking and either internal or external dose as appropriate. At present there are no similar incidence studies with which to compare results. However, the most recent data from the atomic bomb survivor cohort (the Life Span Study) showed statistically significant excess mortality risk for respiratory diseases of 22% per Gy and this value is within the confidence bounds of the point estimate of the risk from this study in relation to external dose.

Obstructive pulmonary function impairment among Korean male workers exposed to organic solvents, iron oxide dust, and welding fumes

We evaluated spirometric obstructive pulmonary function impairment among workers who were occupationally exposed to organic solvents, iron oxide dust, or welding fumes. Data were collected from records of periodic health examinations of workers. In total, 448 Korean male workers were enrolled and classified into three exposure groups: exposure to organic solvents, iron oxide dust, or welding fumes. Logistic regression analysis was performed to evaluate the association between occupational exposure and pulmonary function. Compared to exposure to organic solvents, exposure to iron oxide dust was significantly associated with obstructive pulmonary function impairment (odds ratio [OR], 9.61; 95% confidence interval [CI], 2.20-41.97). The group exposed to welding fumes did not show a significantly higher OR compare to those exposed to organic solvents (OR, 2.83; 95% CI, 0.74-10.8). These results suggest that exposure to iron oxide dust has a greater association with obstructive pulmonary function impairment than exposure to organic solvents or welding fumes.

Occupational cancer burden in Great Britain

A sound knowledge base is required to target resources to reduce workplace exposure to carcinogens. This project aimed to provide an objective estimate of the burden of cancer in Britain due to occupation. This volume presents extensive analyses for all carcinogens and occupational circumstances defined as definite or probable human occupational carcinogens by the International Agency for Research on Cancer. This article outlines the structure of the supplement – two methodological papers (statistical approach and exposure assessment), eight papers presenting the cancer-specific results grouped by broad anatomical site, a paper giving industry sector results and one discussing work-related cancer-prevention strategies. A brief summary of the methods and an overview of the updated overall results are given in this introductory paper. A general discussion of the overall strengths and limitations of the study is also presented. Overall, 8010 (5.3%) total cancer deaths in Britain and 13, 598 cancer registrations were attributable to occupation in 2005 and 2004, respectively. The importance of cancer sites such as mesothelioma, sinonasal, lung, nasopharynx, breast, non-melanoma skin cancer, bladder, oesophagus, soft tissue sarcoma and stomach cancers are highlighted, as are carcinogens such as asbestos, mineral oils, solar radiation, silica, diesel engine exhaust, coal tars and pitches, dioxins, environmental tobacco smoke, radon, tetrachloroethylene, arsenic and strong inorganic mists, as well as occupational circumstances such as shift work and occupation as a painter or welder. The methods developed for this project are being adapted by other countries and extended to include social and economic impact evaluation.

[Alveolar epithelial cell injury as an etiopathogenic factor in pulmonary fibrosis]

Idiopathic pulmonary fibrosis (IPF) is characterized by a progressive accumulation of extracellular matrix and an imbalance between profibrotic and antifibrotic mediators. In the last few years, understanding of the mechanisms of the biology of IPF has increased. One of the most significant discoveries is the finding that alveolar epithelial cell injury plays an important role in the pathogenesis of this disease. In this review, we describe some of the mechanisms involved in alveolar cell injury and their contribution to the development of IPF.

Occupation and chronic obstructive pulmonary disease (COPD)

INTRODUCTION

There is growing interest in preventable, non-smoking causes of chronic obstructive pulmonary disease (COPD), among which are chronic exposures to respiratory irritants in the workplace.

SOURCES OF DATA

Reviews of occupational COPD in specific occupations and industries and in general populations; supplemented with other or more recently published material.

AREAS OF AGREEMENT

There is good evidence for an increased risk of COPD from certain specific exposures (coal mine dust, silica, welding fume, textile dust, agricultural dust, cadmium fume).

AREAS OF CONTROVERSY

Less clear is the causal role of non-specific dusts or fumes/gases in general populations where the available literature is notably uncritical.

GROWING POINTS

Other specific exposures, such as diesel fume; interactions between specific exposures and cigarette smoking; the development of safe working limits.

AREAS TIMELY FOR DEVELOPING RESEARCH

Occupations with large numbers of exposed employees, particularly in low-income countries.

EXPLANATIONS FOR EDUCATION GRADIENTS IN DEPRESSION-THE CASE OF KOREA

OBJECTIVES

We examine gender differences in educational gradients in depressive symptoms of married couples and identify what accounts for education gradients for husbands and wives.

METHODS

We use a nationally representative sample of married couples from the 2006 Korean Longitudinal Study of Aging, which collected information about depressive symptoms and risk factors for both spouses.

RESULTS

For married couples, we find significant education gradients in depressive symptoms for both husbands and wives. Economic resources, physical health, children, and the relationship of spouse explain educational gradients of both husbands and wives. On the other hand, work and organized social activities are important pathways for husbands, but not for wives. In contrast, spouse's educational attainment accounts for wives' educational gradient, but not husbands'.

CONCLUSIONS

Education is a strong predictor of depressive symptoms, but the pathways linking education to depressive symptoms differ between men and women.

Sensory detection and responses to toxic gases: mechanisms, health effects, and countermeasures

The inhalation of reactive gases and vapors can lead to severe damage of the airways and lung, compromising the function of the respiratory system. Exposures to oxidizing, electrophilic, acidic, or basic gases frequently occur in occupational and ambient environments. Corrosive gases and vapors such as chlorine, phosgene, and chloropicrin were used as warfare agents and in terrorist acts. Chemical airway exposures are detected by the olfactory, gustatory, and nociceptive sensory systems that initiate protective physiological and behavioral responses. This review focuses on the role of airway nociceptive sensory neurons in chemical sensing and discusses the recent discovery of neuronal receptors for reactive chemicals. Using physiological, imaging, and genetic approaches, Transient Receptor Potential (TRP) ion channels in sensory neurons were shown to respond to a wide range of noxious chemical stimuli, initiating pain, respiratory depression, cough, glandular secretions, and other protective responses. TRPA1, a TRP ion channel expressed in chemosensory C-fibers, is activated by almost all oxidizing and electrophilic chemicals, including chlorine, acrolein, tear gas agents, and methyl isocyanate, the highly noxious chemical released in the Bhopal disaster. Chemicals likely activate TRPA1 through covalent protein modification. Animal studies using TRPA1 antagonists or TRPA1-deficient mice confirmed the role of TRPA1 in chemically induced respiratory reflexes, pain, and inflammation in vivo. New research shows that sensory neurons are not merely passive sensors of chemical exposures. Sensory channels such as TRPA1 are essential for maintenance of airway inflammation in asthma and may contribute to the progression of airway injury following high-level chemical exposures.

Reduction in cotton dust concentration does not totally eliminate respiratory health hazards: the Greek study

A number of epidemiological studies have shown that byssinosis is associated with exposure to high levels of cotton dust. In this first survey, the prevalence of respiratory symptoms in cotton workers under low concentration of cotton dust was investigated. A respiratory questionnaire consisting of 47 questions was given to 443 cotton workers. Their lung function was measured with spirometry. Breathing zone cotton dust concentration was measured by personal samplers and static sampling was used to define the level of the work area concentration. Workers with abnormalities in the pulmonary function parameters, including forced expiratory volume in 1 second (FEV₁), forced vital capacity (FVC) and peak expiratory flow rate (PEFR), were 5.9%. In this group of operatives 7.7% had symptoms compatible with byssinosis, 65.4% of them were smokers, 69.2% of them had symptoms of allergic rhinitis, while 72.2% of them were smokers. Asthma, which appeared after the age of 30, was reported by 57.7%, while 60% of them were smokers. Mean breathing zone cotton dust concentration was 0.16 mg/m³ and the mean work area cotton dust concentration 0.14 mg/m³. Despite the reduction in cotton dust concentration, byssinosis symptoms, allergic rhinitis, asthma and impaired pulmonary function are the most common findings in our cotton workers depending on the duration of exposure, whether they are smokers or not and the nature of the cotton dust.

Endotoxin exposure and inflammation markers among agricultural workers in Colorado and Nebraska

The adverse respiratory effects of agricultural dust inhalation are mediated in part by endotoxin, a constituent of gram-negative bacterial cell walls. This study quantified personal work-shift exposures to inhalable dust, endotoxin, and its reactive 3-hydroxy fatty acid (3-OHFA) constituents among workers in grain elevators, cattle feedlots, dairies, and on corn farms. Exposures were compared with post-work-shift nasal lavage fluid inflammation markers and respiratory symptoms. Breathing-zone personal air monitoring was performed over one work shift to quantify inhalable dust (Institute of Medicine samplers), endotoxin (recombinant factor C [rFC] assay), and 3-OHFA (gas chromatography/mass spectrometry). Post-shift nasal lavage fluids were assayed for polymorphonuclear neutrophils (PMN), myeloperoxidase (MPO), interleukin 8 (IL-8), albumin, and eosinophilic cation protein (ECP) concentrations. The geometric mean (GSD) of endotoxin exposure (rFC assay) among the 125 male participants was 888 +/- (6.5) EU/m(3), and 93% exceeded the proposed exposure limit (50 EU/m(3)). Mean PMN, MPO, albumin, and ECP levels were two- to threefold higher among workers in the upper quartile of 3-OHFA exposure compared to the lowest exposure quartile. Even numbered 3-OHFA were most strongly associated with nasal inflammation. Symptom prevalence was not elevated among exposed workers, possibly due to endotoxin tolerance or a healthy worker effect in this population. This is the first study to evaluate the relationship between endotoxin's 3-OHFA constituents in agricultural dust and nasal airway inflammation. More research is needed to characterize the extent to which these agents contribute to respiratory disease among agricultural workers.

Elastase- and LPS-exposed mice display altered responses to rhinovirus infection

Viral infection is associated with approximately one-half of acute exacerbations of chronic obstructive pulmonary disease (COPD), which in turn, accelerate disease progression. In this study, we infected mice exposed to a combination of elastase and LPS, a constituent of cigarette smoke and a risk factor for development of COPD, with rhinovirus serotype 1B, and examined animals for viral persistence, airway resistance, lung volume, and cytokine responses. Mice exposed to elastase and LPS once a week for 4 wk showed features of COPD such as airway inflammation and obstruction, goblet cell metaplasia, reduced lung elastance, increased total lung volume, and increased alveolar chord length. In general, mice exposed to elastase or LPS alone showed intermediate effects. Compared with rhinovirus (RV)-infected PBS-exposed mice, RV-infected elastase/LPS-exposed mice showed persistence of viral RNA, airway hyperresponsiveness, increased lung volume, and sustained increases in expression of TNFalpha, IL-5, IL-13, and muc5AC (up to 14 days postinfection). Furthermore, virus-induced IFNs, interferon response factor-7, and IL-10 were deficient in elastase/LPS-treated mice. Mice exposed to LPS or elastase alone cleared virus similar to PBS-treated control mice. We conclude that limited exposure of mice to elastase/LPS produces a COPD-like condition including increased persistence of RV, likely due to skewing of the immune response towards a Th2 phenotype. Similar mechanisms may be operative in COPD.

Lessons from ecological and spatial studies in relation to occupational lung disease

PURPOSE OF REVIEW

The majority of epidemiological research into occupational lung disease has been advanced by the study of individuals, typically in a workplace setting. This review examines how recent advances in ecological and spatial study methodology and in the information held in routine databases could be used to enhance occupational health studies.

RECENT FINDINGS

Ecological studies often use routinely collected data, and this is becoming much more extensive and better validated with potential for increasing use in occupational health research. Improvements in computing power and statistical and geographical information systems methodology have led to more sophisticated mapping techniques and greater use of spatial information when investigating lung diseases usually related to occupational exposures. Ecological study methodology is experiencing a radical overhaul with supplementation of group-level data with information from small-scale individual-level studies. This hybrid design can be used to reduce bias and increase power and is directly applicable to the enhancement of aggregate information from job exposure matrices.

SUMMARY

Studies of occupational lung disease can be enhanced by incorporating methodological innovations from ecological and spatial studies.

Chronic obstructive pulmonary disease and occupational exposure to silica

Prolonged exposure to high levels of silica has long been known to cause silicosis This paper evaluates the evidence for an increased risk of chronic obstructive pulmonary disease (COPD) in occupations and industries in which exposure to crystalline silica is the primary exposure, with a focus on the magnitude of risks and levels of exposure causing disabling health effects. The literature suggests consistently elevated risks of developing COPD associated with silica exposure in several occupations, including the construction industry; tunneling; cement industry; brick manufacturing; pottery and ceramic work; silica sand, granite and diatomaceous earth industries; gold mining; and iron and steel founding, with risk estimates being high in some, even after taking into account the effect of confounders like smoking. Average dust levels vary from about 0.5 mg.m3 to over 10 mg.m3 and average silica levels from 0.04 to over 5 mg.m3, often well above occupational standards. Factors influencing the variation from industry to industry in risks associated with exposure to silica-containing dusts include (a) the presence of other minerals in the dust, particularly when associated with clay minerals; (b) the size of the particles and percentage of quartz; (c) the physicochemical characteristics, such as whether the dust is freshly fractured. Longitudinal studies suggest that loss of lung function occurs with exposure to silica dust at concentrations of between 0.1 and 0.2 mg.m3, and that the effect of cumulative silica dust exposure on airflow obstruction is independent of silicosis. Nevertheless, a disabling loss of lung function in the absence of silicosis would not occur until between 30 and 40 years exposure.