Occupational asthma: etiologies and risk factors

Occupational Respiratory Allergy to Flour in the Modern Era

PURPOSE OF THE REVIEW

A comprehensive literature review was conducted in order to identify and summarize recent research on IgE-mediated occupational respiratory allergy to flour, focusing on the impact of modern developments in the baking industry characterized by industrialization of production processes and a growing use of baking "improvers".

RECENT FINDINGS

Although respiratory allergy to flour is a potentially preventable condition through effective workplace control measures, available data indicate that exposure to flour dust has not decreased in the last decade and flour remains the most prevalent cause of occupational respiratory allergy. The development of the baking industry has led to the introduction of new allergen sources, although their contribution to the development of clinical respiratory allergy remains largely uncertain. In recent years, the diagnostic performance of serum-specific IgE antibody determination against wheat/rye flour and α-amylase compared with specific inhalation challenge with flour as the reference standard has been clarified, making these tests a first-line component of diagnostic algorithms. Available information on the prevalence and incidence of respiratory allergy to flour in recent decades indicates that this condition still imposes a substantial health and socioeconomic burden worldwide. Available data highlight the need to reinforce workplace health-related policies and regulations.

Evaluation and Application of the Work-Related Asthma Screening Questionnaire-Long Version (WRASQ[L])

BACKGROUND

The Work-related Asthma (WRA) Screening Questionnaire-Long Version (WRASQ(L)) is a screening questionnaire that could improve the recognition of WRA.

OBJECTIVE

To conduct a definitive evaluation of the WRASQ(L) to justify its implementation in clinical settings.

METHODS

Employed adults aged 18 to 75 years with asthma confirmed by objective measures and the ability to take time off work were eligible. Participants completed the WRASQ(L) and then monitored their peak expiratory flow at and away from work or completed a specific inhalation challenge test. Data were classified as WRA or non-WRA by 2 asthma specialists, blinded to WRASQ(L) answers. Sensitivity (SN), specificity (SP), positive and negative predictive values (PPV and NPV, respectively), and Youden's index were calculated for cutoffs of a positive screen.

RESULTS

Of 106 participants (47.1 ± 7.1 years [mean ± standard deviation]; 60 [57%] female), 14 (17%) were classified as having WRA and were significantly younger in age than non-WRA participants (P = .043). The questionnaire has high SN and NPV (90.9% and 93.1%, respectively) but low PPV and SP (32.1% and 26.0%, respectively).

CONCLUSIONS

The WRASQ(L) has high SN and NPV. High SN is of primary interest to ensure that few false-negative screens are missed and those with potential WRA are identified and continue to specialist care. The SN indicates utility of the questionnaire in clinical settings. Further benefits of the tool include its potential to prompt education on the symptom-workplace relationship, workplace exposures, personal protective equipment use, and collect exposure and occupational history.

Asthma Among Manitoba Workers: Results from the Manitoba Occupational Disease Surveillance System

Background

This study characterized the risk of new-onset asthma among workers in Manitoba, Canada.

Methods

Accepted time loss claims from the Workers' Compensation Board of Manitoba from 2006 to 2019, containing workers' occupations and industries, were linked with administrative health data from 1996 to 2020. After restricting the cohort to the first claim per person in an occupation and applying age and coverage exclusions, the cohort comprised 142,588 person-occupation combinations. Asthma cases were identified if workers had at least two medical records for asthma (International Classification of Diseases, Ninth Revision, 493) within a 12-month period, within the 2 years before 3 years after cohort entry. New-onset asthma was identified using a 3-year washout period. Asthma hazard ratios by occupation and industry were estimated using Cox proportional hazard models, adjusted for age, and stratified by sex.

Results

Increased asthma risk was observed among workers with known asthmagen exposure, including male veterinary and animal health technologists and technicians (hazard ratio 3.97, 95% CI 1.78-8.86), male fish processing workers (3.40, 1.53-7.57), and male machining tool operators (2.91, 1.72-4.92). Increases were also observed for occupations with unknown or suspected allergens, including gas station attendants, drivers, mail/postal and related workers, public works and maintenance laborers, mine laborers and crane operators, and some indoor worker groups. Decreased risks were observed among nurses and residential and commercial installer and servicers.

Conclusion

This database linkage study successfully identified occupations and industries with known sensitizing agents or irritants, and several occupation and industries not typically associated with work-related asthma, warranting further investigation.

Comparison of high- and low-molecular-weight sensitizing agents causing occupational asthma: an evidence-based insight

INTRODUCTION

The many substances used at the workplace that can cause sensitizer-induced occupational asthma are conventionally categorized into high-molecular-weight (HMW) agents and low-molecular-weight (LMW) agents, implying implicitly that these two categories of agents are associated with distinct phenotypic profiles and pathophysiological mechanisms.

AREAS COVERED

The authors conducted an evidence-based review of available data in order to identify the similarities and differences between HMW and LMW sensitizing agents.

EXPERT OPINION

Compared with LMW agents, HMW agents are associated with a few distinct clinical features (i.e. concomitant work-related rhinitis, incidence of immediate asthmatic reactions and increase in fractional exhaled nitric oxide upon exposure) and risk factors (i.e. atopy and smoking). However, some LMW agents may exhibit 'HMW-like' phenotypic characteristics, indicating that LMW agents are a heterogeneous group of agents and that pooling them into a single group may be misleading. Regardless of the presence of detectable specific IgE antibodies, both HMW and LMW agents are associated with a mixed Th1/Th2 immune response and a predominantly eosinophilic pattern of airway inflammation. Large-scale multicenter studies are needed that use objective diagnostic criteria and assessment of airway inflammatory biomarkers to identify the pathobiological pathways involved in OA caused by the various non-protein agents.

[Asthma]

Asthma is a chronic inflammatory disease that affects about 5% of the world's population and generates high health and social costs. Proper management of the disease requires a correct diagnosis, based on objective measures of functional impairment, as well as symptom control and assessment of the future risk of exacerbations.It has been estimated that 18% of asthma patients in Western Europe have severe asthma and approximately 50% of them have poor control. The severity of asthma is established based on the minimum maintenance treatment needs to achieve control. Asthma clinical practice guidelines recommend classifying severe patients into allergic asthma (T2); eosinophilic asthma (T2) and non-T2 asthma in order to establish the most appropriate treatment.In recent decades, new biological therapies have been developed that can be applied according to the phenotype and endotype of asthma, allowing for selective and personalized treatment. These phenotypes and endotypes can change over time and therefore, the identification of biomarkers capable of predicting the severity, the course of the disease and the response to a given treatment seems essential. A large number of biomarkers have been studied in asthma, but so far only a few can be readily used in routine clinical practice. The application of omics technologies (epigenomics, genomics, transcriptomics, proteomics, metabolomics, lipidomics, etc.) for this purpose is still in the research phase.

Hypersensitivity Pneumonitis: Challenges of a Complex Disease

Hypersensitivity pneumonitis (HP) is a complex interstitial lung disease caused by chronic inhalation of a wide variety of antigens in susceptible and sensitized individuals, commonly associated with an occupational exposure. An impressive number of inciting antigens causing hypersensitivity pneumonitis have been found to cover a wide range of occupations. As working practices have changed over time, especially in industrialized countries, new names for occupational HP have emerged. This review emphasizes the main diagnostic issues arising from the high variability of clinical presentation and the broad spectrum of causal antigens. Furthermore, it provides an overview of current methods to unveil possible causes of hypersensitivity pneumonitis, highlights HP's current diagnostic and treatment challenges and the remaining areas of uncertainty, and presents prevention strategies.

Cleaning Tasks and Products and Asthma Among Health Care Professionals

OBJECTIVE

Health care workers are at risk for work-related asthma, which may be affected by changes in cleaning practices. We examined associations of cleaning tasks and products with work-related asthma in health care workers in 2016, comparing them with prior results from 2003.

METHODS

We estimated asthma prevalence by professional group and explored associations of self-reported asthma with job-exposure matrix-based cleaning tasks/products in a representative Texas sample of 9914 physicians, nurses, respiratory/occupational therapists, and nurse aides.

RESULTS

Response rate was 34.8% (n = 2421). The weighted prevalence rates of physician-diagnosed (15.3%), work-exacerbated (4.1%), and new-onset asthma (6.7%) and bronchial hyperresponsiveness symptoms (31.1%) were similar to 2003. New-onset asthma was associated with building surface cleaning (odds ratio [OR], 1.91; 95% confidence interval [CI], 1.10-3.33), use of ortho-phthalaldehyde (OR, 1.77; 95% CI, 1.15-2.72), bleach/quaternary compounds (OR, 1.91; 95% CI, 1.10-3.33), and sprays (OR, 1.97; 95% CI, 1.12-3.47).

CONCLUSION

Prevalence of asthma/bronchial hyperresponsiveness seems unchanged, whereas associations of new-onset asthma with exposures to surface cleaning remained, and decreased for instrument cleaning.

Can COVID-19 infection be considered an occupational disease or injury? Analysis to fill up regulatory gaps

BACKGROUND

Although the pandemic is nearing its end, the question of whether COVID-19 infection will be considered a work-related or occupational disease remains a legal issue. Therefore, this study aims to provide clarification on this matter.

OBJECTIVES

Since the International Labour Organization (ILO) serves as the primary authority on work-related matters, this study is focused on analyzing the ILO's policies regarding the acknowledgment of COVID-19 infections as occupational diseases. It also investigates how States can recognize COVID-19 as such a disease while delving into the connection between the disease or injury and the occupation itself.

METHODOLOGY

This study utilizes a doctrinal methodology, focusing on legal research. This approach employs an applied (expository) research method and discusses the topic from a professional constituency perspective, as proposed by Arthurs in 1983.

RESULT

The findings indicate that the ILO does not explicitly mention the pandemic or COVID-19 infection as an occupational disease in its list. However, it does include "infectious-related diseases" or "work that carries a particular risk of contamination" as occupational or work-related diseases, which can logically be interpreted as encompassing COVID-19 infection as an occupational or work-related disease.

RECOMMENDATION

As the ILO sets guiding principles for its member States, this study recommends that the ILO should establish clear and comprehensive guidelines for member States to recognize COVID-19 infections or any future pandemics as occupational diseases.

CONCLUSION

This study will serve as a valuable resource for policymakers who intend to enact or amend national legislation to align with the ILO. Furthermore, it will assist relevant stakeholders in taking necessary actions based on the study's findings.

Aziz SF, Aizad Za’bah AK, Dapari R, Hassan MR, Che Dom N, Syed Abdul Rahim SS. Factors associated with occupational asthma among food industry workers: A systematic review

INTRODUCTION

Occupational asthma (OA) is a type of Work-Related Asthma characterised by variable airflow limitation and/or inflammation due to causes and conditions attributable to a particular occupational environment, and not to stimuli encountered outside the workplace. There is an increasing need to extend the depth of knowledge of OA to better manage this condition, especially among food industry workers who are affected by it.

OBJECTIVE

This systematic review aimed to determine the factors associated with occupational asthma among food industry workers by electronically collecting articles from two databases (Medline and Scopus).

METHODS

This systematic review was prepared in accordance with the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta Analyses) updated guideline. Two independent reviewers screened the titles and abstracts of the collected data, which were then stored in Endnote20 based on the inclusion and exclusion criteria. The included articles have been critically appraised to assess the quality of the studies using the Mixed Methods Appraisal Tool (MMAT).

RESULT

The search yielded 82 articles from Medline and 85 from SCOPUS, resulting in 167 unique hits. Only 22 articles have been included in the full-text assessment following a rigorous selection screening. Of the 22 articles identified, five were included in the final review. Several factors were found to have contributed to occupational asthma among food industry workers. They were classified into two categories: (1) work environment-related factors; and (2) individual factors.

CONCLUSION

Several work environment and individual-related factors were found to be associated with OA among food industry workers. A better understanding of the development of the disease and its potential risk factors is needed because it can affect worker's quality of life. Pre-employment and periodic medical surveillance should be conducted to assess and detect any possible risk of developing occupational asthma among workers.

Recent Advancements in Polyurethane-based Tissue Engineering

In tissue engineering, polyurethane-based implants have gained significant traction because of their high compatibility and inertness. The implants therefore show fewer side effects and lasts longer. Also, the mechanical properties can be tuned and morphed into a particular shape, owing to which polyurethanes show immense versatility. In the last 3 years, scientists have devised methods to enhance the strength of and induce dynamic properties in polyurethanes, and these developments offer an immense opportunity to use them in tissue engineering. The focus of this review is on applications of polyurethane implants for biomedical application with detailed analysis of hard tissue implants like bone tissues and soft tissues like cartilage, muscles, skeletal tissues, and blood vessels. The synthetic routes for the preparation of scaffolds have been discussed to gain a better understanding of the issues that arise regarding toxicity. The focus here is also on concerns regarding the biocompatibility of the implants, given that the precursors and byproducts are poisonous.

First Steps of Asthma Management with a Personalized Ontology Model

Asthma is a chronic respiratory disease characterized by severe inflammation of the bronchial mucosa. Allergic asthma is the most common form of this health issue. Asthma is classified into allergic and non-allergic asthma, and it can be triggered by several factors such as indoor and outdoor allergens, air pollution, weather conditions, tobacco smoke, and food allergens, as well as other factors. Asthma symptoms differ in their frequency and severity since each patient reacts differently to these triggers. Formal knowledge is selected as one of the most promising solutions to deal with these challenges. This paper presents a new personalized approach to manage asthma. An ontology-driven model supported by Semantic Web Rule Language (SWRL) medical rules is proposed to provide personalized care for an asthma patient by identifying the risk factors and the development of possible exacerbations.

Methyl methacrylate and respiratory sensitisation: a comprehensive review

Methyl methacrylate (MMA) is classified under GHS as a weak skin sensitiser and a skin and respiratory irritant. It has recently been proposed that MMA be classified as a respiratory sensitiser (a designation that in a regulatory context embraces both true respiratory allergens, as well as chemicals that cause asthma through non-immunological mechanisms). This proposal was based primarily upon the interpretation of human data. This review, and a detailed weight of evidence analysis, has led to another interpretation of these data. The conclusion drawn is that persuasive evidence consistent with the designation of MMA as a respiratory sensitiser is lacking. It is suggested that one reason for different interpretations of these data is that occupational asthma poses several challenges with respect to establishing causation. Among these is that it is difficult to distinguish between allergic asthma, non-allergic asthma, and work-related exacerbation of pre-existing asthma. Moreover, there is a lack of methods for the identification of true chemical respiratory allergens. The characterisation and causation of occupational asthma is consequently largely dependent upon interpretation of human data of various types. Recommendations are made that are designed to improve the utility and interpretation of human data for establishing causation in occupational asthma.

The Impact of Ambient Environmental and Occupational Pollution on Respiratory Diseases

Ambient pollutants and occupational pollutants may cause and exacerbate various lung and respiratory diseases. This review describes lung and respiratory diseases in relation to ambient pollutants, particularly particulate matter (PM2.5), and occupational air pollutants, excluding communicable diseases and indoor pollutants, including tobacco smoke exposure. PM2.5 produced by combustion is an important ambient pollutant. PM2.5 can cause asthma attacks and exacerbations of chronic obstructive pulmonary disease in the short term. Further, it not only carries a risk of lung cancer and death, but also hinders the development of lung function in children in the long term. It has recently been suggested that air pollution, such as PM2.5, is a risk factor for severe coronavirus disease (COVID-19). Asbestos, which causes asbestosis, lung cancer, and malignant mesothelioma, and crystalline silica, which cause silicosis, are well-known traditional occupational pollutants leading to pneumoconiosis. While work-related asthma (WRA) is the most common occupational lung disease in recent years, many different agents cause WRA, including natural and synthetic chemicals and irritant gases. Primary preventive interventions that increase awareness of pollutants and reduce the development and exacerbation of diseases caused by air pollutants are paramount to addressing ambient and occupational pollution.

Work-related asthma

Work-related asthma (WRA) is highly prevalent in the adult population. WRA includes occupational asthma (OA), which is asthma caused by workplace exposures, and work-exacerbated asthma (WEA), also known as work-aggravated asthma, which is preexisting or concurrent asthma worsened by workplace conditions. In adults, the estimated prevalence of OA is 16.0%, whereas that of WEA is 21.5%. An increasing number of chemicals used in industrial production, households, and services are associated with the incidence of adult-onset asthma attributable to exposure to chemicals. This review article summarizes the different types of WRA and describes diagnostic procedures, treatment, prevention, and approaches to patient management. It is not always easy to distinguish between OA and WEA. It is important to establish a diagnosis (of sensitizer-/irritant-induced OA or WEA) in order to prevent worsening of symptoms, as well as to prevent other workers from being exposed, by providing early treatment and counseling on social security and work-related issues.

The role of HMGB1 on TDI-induced NLPR3 inflammasome activation via ROS/NF-κB pathway in HBE cells

To explore the potential role of HMGB1 on TDI-induced NLRP3 inflammasome activation, HBE cells were treated with TDI-HSA conjugate to observe the changes of HMGB1, TLR4, NF-κB, Nrf2 and NLRP3 inflammasome related proteins expressions, ROS release and MMP. NAC, TPCA-1 and Resatorvid pre-treatments were applied to explore the effects of ROS, NF-κB and TLR4 on TDI-induced NLRP3 inflammasome activation. The CRISPR/Cas9 system was used to construct HMGB1 gene knockout HBE cell line and then to explore the role of HMGB1 on TDI-HSA induced NLRP3 inflammasome activation. GL pre-treatment was applied to further confirm the role of HMGB1. Results showed that TDI increased HMGB1, TLR4, P-p65, Nrf2 proteins expressions and ROS release, decreased MMP level and activated NLRP3 inflammasome in HBE cells in a dose dependent manner. NAC, TPCA-1 and Resatorvid pre-treatments decreased the expression of P-p65 and inhibited NLRP3 inflammasome activation. Inhibition of HMGB1 decreased Nrf2 expression and ROS release, improved MMP level and reduced NLRP3 inflammasome activation. GL ameliorated NLRP3 inflammasome activation via inhibiting HMGB1 regulated ROS/NF-κB pathway. These results indicated that HMGB1 was involved in TDI-induced NLRP3 inflammasome activation as a positive regulatory mechanism. The study provided a potential target for early prevention and treatment of TDI-OA.

Classification of chemicals as respiratory allergens based on human data: Requirements and practical considerations

Occupational asthma is an important health problem that can include exacerbation of existing asthma, or induce new asthma either through allergic sensitisation, or non-immunological mechanisms. While allergic sensitisation of the respiratory tract can be acquired to proteins, or to low molecular weight chemicals (chemical respiratory allergens) this article is on the latter exclusively. Chemical respiratory allergy resulting in occupational asthma is associated with high levels of morbidity and there is a need, therefore, that chemicals which can cause sensitisation of the respiratory tract are identified accurately. However, there are available no validated, or even widely accepted, predictive test methods (in vivo, in vitro or in silico) that have achieved regulatory acceptance for identifying respiratory sensitising hazards. For this reason there is an important reliance on human data for the identification of chemical respiratory allergens, and for distinguishing these from chemicals that cause occupational asthma through non-immunological mechanisms. In this article the reasons why it is important that care is taken in designating chemicals as respiratory allergens are reviewed. The value and limitations of human data that can aid the accurate identification of chemical respiratory allergens are explored, including exposure conditions, response characteristics in specific inhalation challenge tests, and immunological investigations.

Biobased polyurethanes for biomedical applications

Polyurethanes (PUs) are a major family of polymers displaying a wide spectrum of physico-chemical, mechanical and structural properties for a large range of fields. They have shown suitable for biomedical applications and are used in this domain since decades. The current variety of biomass available has extended the diversity of starting materials for the elaboration of new biobased macromolecular architectures, allowing the development of biobased PUs with advanced properties such as controlled biotic and abiotic degradation. In this frame, new tunable biomedical devices have been successfully designed. PU structures with precise tissue biomimicking can be obtained and are adequate for adhesion, proliferation and differentiation of many cell's types. Moreover, new smart shape-memory PUs with adjustable shape-recovery properties have demonstrated promising results for biomedical applications such as wound healing. The fossil-based starting materials substitution for biomedical implants is slowly improving, nonetheless better renewable contents need to be achieved for most PUs to obtain biobased certifications. After a presentation of some PU generalities and an understanding of a biomaterial structure-biocompatibility relationship, recent developments of biobased PUs for non-implantable devices as well as short- and long-term implants are described in detail in this review and compared to more conventional PU structures.

Innate lymphoid cells in isocyanate-induced asthma: role of microRNA-155

BACKGROUND

Occupational asthma, induced by workplace exposures to low molecular weight agents such as toluene 2,4-diisocyanate (TDI), causes a significant burden to patients and society. Little is known about innate lymphoid cells (ILCs) in TDI-induced asthma. A critical regulator of ILC function is microRNA-155, a microRNA associated with asthma.

OBJECTIVE

To determine whether TDI exposure modifies the number of ILCs in the lung and whether microRNA-155 contributes to TDI-induced airway inflammation and hyperresponsiveness.

METHODS

C57BL/6 wild-type and microRNA-155 knockout mice were sensitised and challenged with TDI or vehicle. Intracellular cytokine expression in ILCs and T-cells was evaluated in bronchoalveolar lavage (BAL) fluid using flow cytometry. Peribronchial eosinophilia and goblet cells were evaluated on lung tissue, and airway hyperresponsiveness was measured using the forced oscillation technique. Putative type 2 ILCs (ILC2) were identified in bronchial biopsies of subjects with TDI-induced occupational asthma using immunohistochemistry. Human bronchial epithelial cells were exposed to TDI or vehicle.

RESULTS

TDI-exposed mice had higher numbers of airway goblet cells, BAL eosinophils, CD4⁺ T-cells and ILCs, with a predominant type 2 response, and tended to have airway hyperresponsiveness. In TDI-exposed microRNA-155 knockout mice, inflammation and airway hyperresponsiveness were attenuated. TDI exposure induced IL-33 expression in human bronchial epithelial cells and in murine lungs, which was microRNA-155 dependent in mice. GATA3⁺CD3^- cells, presumably ILC2, were present in bronchial biopsies.

CONCLUSION

TDI exposure is associated with increased numbers of ILCs. The proinflammatory microRNA-155 is crucial in a murine model of TDI asthma, suggesting its involvement in the pathogenesis of occupational asthma due to low molecular weight agents.

Occupational Rhinitis

There is convincing evidence that tight relationships between the upper and lower airways also apply to the workplace context. Most patients with occupational asthma (OA) also suffer from occupational rhinitis (OR), although OR is 2 to 3 times more common than OA. OR most often precedes the development of OA, especially when high-molecular-weight protein agents are involved, and longitudinal cohort studies have confirmed that OR is associated with an increased risk for the development of OA. The level of exposure to sensitizing agents at the workplace is the most important determinant for the development of IgE-mediated sensitization and OR. Atopy is a risk factor for the development of IgE-mediated sensitization only to high-molecular-weight agents. In workers with work-related rhinitis symptoms, documentation of IgE-mediated sensitization to a workplace agent via skin prick testing or serum specific IgE confirms a diagnosis of probable OR, whereas specific nasal provocation testing in the laboratory remains the reference method to establish a definite diagnosis of OR. Complete avoidance of exposure to the causal agent is the most effective therapeutic option for controlling work-related nasal symptoms and preventing the development of OA. If complete elimination of exposure is expected to induce meaningful adverse socioeconomic consequences, reduction of exposure can be considered as an alternative approach, but it is important to consider the individual risk factors for the development of OA to implement a more personalized management of OR.

Adult Asthma among Workers in Ontario. Results from the Occupational Disease Surveillance System

Rationale: Given that approximately 15% of new-onset adult asthma cases originate because of exposures in the workplace, there is a need for systematic and ongoing monitoring of risk among workers. Objectives: To characterize the risk of new-onset adult asthma among workers in Ontario. Methods: We used 575,379 provincial accepted time-loss workers' compensation claimants data linked to physician billing data. Workers aged 15 to 65 years with a nonasthma compensation claim between January 1, 2002, and December 31, 2013, were eligible for inclusion. Cohort entry corresponded to the date of the claim. The case definition required two or more records for asthma within a 12-month period, within a 3-year time window after cohort entry. A 3-year washout period preceding cohort entry was used to exclude prevalent cases. Workers at risk of new-onset adult asthma were followed from cohort entry date to date of diagnosis, emigration, age 65 years, death, or end of study period. Cox regression models were used to generate birth year- and sex-adjusted hazard ratios (HRs) by occupation, industry, and exposures identified using a job exposure matrix. Sex-stratified risk estimates were also generated. Results: Increased risks were detected among well-recognized groups, including bakers (HR, 1.60; 95% confidence interval [CI], 1.22-2.09) and painters and decorators (HR, 1.67; 95% CI, 1.23-2.28). In the job exposure matrix analysis, flour and isocyanates were associated with increased risk of asthma. Concrete finishers (HR, 1.93; 95% CI, 1.12-3.32) and shipping and receiving clerks (HR, 1.21; 95% CI, 1.03-1.43) also showed elevated risk, whereas results varied across woodworker groups. Decreased risks were detected for nursing and farming groups. Conclusions: This practical data linkage approach was successful for examining associations across hundreds of jobs. Unexpected and previously unrecognized findings deserve further investigation and emphasize the importance of an ongoing system to guide research as well as prevention.

Methodological evaluation of human research on asthmagenicity and occupational cleaning: a case study of quaternary ammonium compounds ("quats")

In this paper, we review methodological approaches used in studies that evaluated the association between occupational exposure to quaternary ammonium compounds (quats) and occupational asthma. This association is of interest because quats are a common active ingredient of disinfectants and have been linked to work-related asthma in some circumstances. However, any evidence-based assessment of an exposure-outcome association needs to consider both strengths and limitations of the literature. We focus on publications cited by various US and international organizations. Eighteen investigations included in the review fall into two broad categories: case reports and challenge studies of individual patients and population studies that examined the association between quats and asthma occurrence in groups of subjects. We evaluated these studies guided by questions that address whether: exposure data on specific quat(s) and other agents that may cause asthma were included, new asthma cases were differentiated from asthma exacerbation, and information on respiratory sensitivity versus irritation was given. We also assessed consistency across studies. Studies of individual patients, particularly those that provided detailed information on challenge test results, document cases of asthma induced by exposure to quats. By contrast, studies of occupational groups with the highest potential for quats exposure (e.g., cleaners and farmers) do not consistently report increased incidence of asthma due specifically to quats. The unresolved methodological issues include: poor understanding of exposure pathways considering that quats are non-volatile, lack of quantitative data allowing for identification of an asthmagenicity threshold, insufficient information on whether quats are sensitizers or act via dose-dependent irritation or some other mechanism, and inability to quantify risk of new-onset asthma attributable to quats. Another important area of uncertainty is the lack of information on the specific quats being used. There is also a lack of data capable of distinguishing the effects of quats from those of other chemical and biological workplace exposures. The current state-of-the-science does not allow a proper assessment of the potential link between quats and occupational asthma.

Health effects of diesel engine exhaust emissions exposure (DEEE) can mimic allergic asthma and rhinitis

BACKGROUND

Patients presenting to Accident and Emergency (A&E) facilities with dyspnoea, coughing, wheezing and nasal blockage are presumed to have allergic asthma and/or rhinitis. Occupational asthma (OA), which has similar symptoms is rarely considered. Triggers of OA include exposure to diesel engine exhaust emissions exposure (DEEEE) that are carcinogenic. We report the case of a patient who presented to an A&E facility with asthma-like symptoms, was treated for allergic asthma. Frequent exacerbations were experienced. Upon investigations it was shown that were symptoms triggered by DEEE exposure.

CASE PRESENTATION

A 36-year-old female bank employee was referred for the evaluation of suspected asthma. She reported a 3-month history of symptoms suggestive of asthma and rhinitis, for which she had previously required A&E treatment. There was no history of atopy. The symptoms only occurred at work or after work. Their onset had coincided with changing offices to one located proximal to a diesel-powered electricity generator. A diagnosis of asthma had been made at the A&E facility and the appropriately used inhaled fluticasone and salbutamol provided limited relief. Skin prick testing was weakly positive for seasonal pollen and house dust mite allergens. Allergen specific IgE tests for 16 regionally relevant aeroallergens were negative. Tests to exclude connective tissue diseases were positive for the anti-Ro-52/TRIM-21 autoantibody. Baseline spirometry values were markedly reduced and bronchodilator administration showed limited reversibility, FEV1 (+ 8%), PEF (+ 5%). Following a 10-day discontinuation of work exposure, the symptoms abated and FEV1 and PEF increased by 10-14% from baseline. The recent onset of asthma, in a non-atopic adult, with workday related symptoms and improvement upon discontinuation of exposure were attributed to passive occupational exposure to DEEE. The diesel generator was relocated, a short course of inhaled fluticasone and oral prednisolone was prescribed and symptoms resolved. This is the first report of the health effects of DEEE mimicking asthma and rhinitis in Zimbabwe.

CONCLUSIONS

Atypical presentations of adult onset asthma in the absence of a history of either atopy or allergen specific IgE antibody sensitization should trigger in-depth evaluation of occupational exposure in all cases including office workers. Serial monitoring of lung function values should be used for diagnostic and monitoring of the patients.

Serum Periostin Levels: A Potential Serologic Marker for Toluene Diisocyanate-Induced Occupational Asthma

PURPOSE

Toluene diisocyanate (TDI) is a leading cause of occupational asthma (OA). Periostin is a matricellular protein implicated in type 2 immunity-driven asthma. Its pathogenic role in TDI-OA has not been completely elucidated. The present study was performed to investigate the role of periostin in TDI-OA.

MATERIALS AND METHODS

Serum periostin levels were measured in subjects with TDI-OA, asymptomatic TDI-exposure controls (AECs), non-occupational asthmatics (NAs), and unexposed normal controls (NCs). To understand the mechanism by which TDI induces periostin production, primary small airway epithelial cells (SAECs) were cultured under stimulation of TDI and neutrophils from asthmatic patients.

RESULTS

Fifty-three subjects with TDI-OA, 71 AECs, 67 NAs, and 83 NCs were enrolled. Serum periostin levels were significantly higher in TDI-OA subjects than in AECs (p=0.001), NAs (p<0.001), and NCs (p<0.001). In TDI-exposed subjects (TDI-OA and AEC), the PC₂₀ methacholine levels were significantly lower in subjects with a higher periostin level than in those with a lower periostin level. TDI exposure did not increase periostin production directly by SAECs; however, periostin production increased significantly after co-culture with TDI and neutrophils, which was suppressed by an antioxidant. In addition, increased release of TGF-β1 was noted from SAECs when exposed to TDI and neutrophils, which was also suppressed by an antioxidant.

CONCLUSION

These results suggest that an increased periostin level may contribute to the progression of airway inflammation to remodeling in TDI-exposed workers. A high serum periostin level is a potential serologic marker of the phenotype of TDI-OA.

The prevalence of exposure to high molecular weight asthmagens derived from plants among workers in Australia

BACKGROUND

Limited information is available on exposure to high molecular weight (HMW) asthmagens derived from plants and on the main occupations and tasks that result in such exposure among workers.

METHODS

Data were collected as part of the Australian Work Exposures Study-Asthma. We estimated adjusted prevalence ratios (aPR) using modified Poisson regression models to determine which factors were associated with exposure.

RESULTS

A 12.8% of 4878 workers were exposed to HMW asthmagens derived from plants. The highest prevalence of exposure was found among farmers/animal workers, education workers, and food processing workers. The main circumstances of exposure were through handling flour, freesias, or through raising livestock. Exposure was more common among female workers (aPR = 1.26, 1.10-1.43) than males, while it was lower among workers born overseas (aPR = 0.70, 0.57-0.86) than those born in Australia.

CONCLUSION

Prevention of exposure to HMW asthmagens derived from plants requires a broad strategy targeting different tasks and occupations.

Medical Monitoring for Occupational Asthma Among Toluene Diisocyanate Production Workers in the United States

OBJECTIVE

The aim of this study was to describe a study of medical monitoring methods and lessons learned in detecting health outcomes in U.S. plants producing toluene diisocyanate (TDI).

METHODS

A multidisciplinary team implemented a medical and environmental monitoring program in three TDI plants.

RESULTS

Of 269 eligible workers, 197 (73%) participated and 42 (21%) met symptom and/or lung function criteria that would trigger evaluation for possible asthma over 5 years of data collection. Subsequent evaluation was delayed for most, and a web-based data collection system improved timeliness.

CONCLUSION

Medical monitoring of TDI workers identified workers triggering further assessment per study protocol. Systems and/or personnel to ensure rapid follow-up are needed to highlight when triggering events represent potential cases of asthma needing further evaluation. Implementation of a research protocol requires resources and oversight beyond an occupational health program.

Toluene Diisocyanate Exposure: Exposure Assessment and Development of Cross-Facility Similar Exposure Groups Among Toluene Diisocyanate Production Plants

OBJECTIVE

The objective of this study was to characterize workplace toluene diisocyanate (TDI) exposures using standardized industrial hygiene exposure assessment procedures for use in a prospective epidemiologic study of occupational asthma.

METHODS

Over 2300 representative routine full shift time-weighted average (TWA) and short-term high potential exposure tasks (HPETs) air samples in groups across three TDI plants were collected over a nearly 7-year period.

RESULTS

Data-derived similar exposure groups (SuperSEGs) were developed across the plants based on TWA sampling using cluster analysis. Individual cumulative exposure estimates were developed on the basis of the SuperSEGs.

CONCLUSION

Workplace TWA exposures to TDI were adequately characterized quantitatively, but HPET exposures were adequately characterized only by qualitative measures. The mean TWA exposure was 0.65 parts per billion for 1594 routine samples. These TWA and HPET exposures can be used to support exposure-response analyses.

Active and passive smoking impacts on asthma with quantitative and temporal relations: A Korean Community Health Survey

This study aimed to evaluate the relations of smoking with asthma and asthma-related symptoms, considering quantitative and temporal influences. The 820,710 Korean adults in the Korean Community Health Survey in 2009, 2010, 2011, and 2013 were included and classified as non-smoker, past smoker or current smoker. Total smoking years, total pack-years, and age at smoking onset were assessed. Information on wheezing, exercise wheezing, and aggravation of asthma in the past 12 months and asthma diagnosis history and current treatment was collected. Multiple logistic regression analysis with complex sampling was used. Current and former smokers showed significant positive relations with wheezing, exercise wheezing, asthma ever, current asthma, and asthma aggravation. Current smokers demonstrated higher adjusted odd ratios (AORs) for wheezing, exercise wheezing, and asthma aggravation than former smokers. Former smokers showed higher AORs than current smokers for current asthma treatment. Longer passive smoking was related to wheezing and exercise wheezing. Greater age at smoking onset and duration since cessation were negatively related to wheezing, exercise wheezing, and current asthma; total pack-years demonstrated proportional associations with these symptoms. Former, current, and passive smoking was positively correlated with wheezing and exercise wheezing. Total pack-years and early initiation were increasingly related to asthma.

Risk factors associated with allergic sensitization and asthma phenotypes among poultry farm workers

BACKGROUND

This study investigated the risk factors for occupational allergic sensitization and various asthma phenotypes in poultry-workers.

METHODS

A cross-sectional study of 230 workers used a modified ECRHS questionnaire, spirometry, FeNO, Phadiatop, and sIgE to poultry farming related allergens.

RESULTS

Worker's mean age was 37 ± 9 years, 68% male, 43% current-smokers, 34% atopic, and 5% casual-workers. The prevalence of non-atopic asthma (NAA = 7%) was higher than atopic-asthma (AA = 5%) and probable allergic occupational-asthma (OA = 3%). Sensitization to at least one poultry farming related allergen was 24%. Workers sensitized to chicken-specific-allergens were more likely to be atopic (OR_unadj  = 20.9, 95%CI: 4.7-93.2) or employed as casual-workers (OR_unadj  = 6.0, 95%CI: 1.1-35.9). Work-related chest symptoms were associated the rearing-department (OR_adj  = 3.2, 95%CI: 1.2-8.4) and exposure to high gas/dust/fumes (OR_adj  = 4.8, 95%CI: 2.4-9.5). Airflow reversibility (OR_adj  = 10.9, 95%CI: 2.0-60.3) was significantly associated with casual-work status.

CONCLUSION

Allergic and non-allergic mechanisms play a role in asthma development among poultry-workers with casual workers demonstrating increased risk.

Role of clusterin/progranulin in toluene diisocyanate-induced occupational asthma

Toluene diisocyanate (TDI) exposure induces oxidative stress and epithelial cell-derived inflammation, which affect the pathogenesis of TDI-induced occupational asthma (TDI-OA). Recent studies suggested a role for clusterin (CLU) and progranulin (PGRN) in oxidative stress-mediated airway inflammation. To evaluate CLU and PGRN involvement in airway inflammation in TDI-OA, we measured their serum levels in patients with TDI-OA, asymptomatic exposed controls (AECs), and unexposed healthy normal controls (NCs). Serum CLU and PGRN levels were significantly lower in the TDI-OA group than in the AEC and NC groups (P < 0.05). The sensitivity and specificity for predicting the TDI-OA phenotype were 72.4% and 53.4% when either CLU or PGRN levels were below the cutoff values (≤125 μg/mL and ≤68.4 ng/mL, respectively). If both parameters were below the cutoff levels, the sensitivity and specificity were 58.6% and 89.8%, respectively. To investigate CLU and PGRN function, we evaluated their production by human airway epithelial cells (HAECs) in response to TDI exposure and co-culturing with neutrophils. TDI-human serum albumin stimulation induced significant CLU/PGRN release from HAECs in a dose-dependent manner, which positively correlated with IL-8 and folliculin levels. Co-culturing with neutrophils significantly decreased CLU/PGRN production by HAECs. Intracellular ROS production in epithelial cells co-cultured with neutrophils tended to increase initially, but the ROS production decreased gradually at a higher ratio of neutrophils. Our results suggest that CLU and PGRN may be involved in TDI-OA pathogenesis by protecting against TDI-induced oxidative stress-mediated inflammation. The combined CLU/PGRN serum level may be used as a potential serological marker for identifying patients with TDI-OA among TDI-exposed workers.

Assessment of work-related Asthma cases: Our three-year experience

Objective

Work-related asthma (WRA) is one of the most common occupational diseases. In this study, we aimed to review diagnosing procedures and the characteristics of patients who were diagnosed with WRA.

Methods

Between November 2013 and June 2016; 214 patients were referred to our clinic with WRA suspicion by an occupational health specialist, personal visit, chest disease specialists [61 (28%), 51 (23%), and 102 (47%) respectively]. Occupational history, functional and radiological assessment, skin prick test, PEF monitoring were done.

Results

Fifty-four patients (25%) were diagnosed with OA, and 24 (11%) with WEA, total 78 workers were diagnosed with WRA. Twenty-five (32.1%) had allergic rhinitis, 13 (16.7%) had allergic dermatitis, and 8 (10%) had both diseases.

Conclusion

WRA can be seen in many areas. Complaints are the basic route for admission to physician, and the diagnosis can be delayed for a long time as one year. Lower rates of referral by occupational health physicians are the signs of limitations on management of cases. Non-specific BPT and skin prick test for selected cases would be sufficient besides occupational history and clinical examination for the diagnosis of WRA. PEF assessment, one of the most important tests for the diagnosis of WRA, must be performed.

Azodicarbonamide (ADCA): A reconsideration of classification as a respiratory sensitiser

Azodicarbonamide (ADCA) is widely used by industry in the manufacture of a variety of products. ADCA has been classified as a respiratory allergen, and the purpose of this article was to consider whether this classification is appropriate based upon the available data. Here both clinical experience and relevant experimental data have been reviewed. Although there have been reports of an association between workplace exposure to ADCA and symptoms of respiratory allergy and occupational asthma, the evidence is less than persuasive, with in many instances a lack of properly controlled and executed diagnostic procedures. In addition, ADCA fails to elicit positive responses in mouse and guinea pig predictive tests for skin sensitisation; a lack of activity that is regarded as being inconsistent with respect to respiratory sensitising potential. Collectively, the data reviewed here do not provide an adequate basis for the classification of ADCA as a respiratory allergen.

Review of Diagnostic Challenges in Occupational Asthma

PURPOSE OF REVIEW

Occupational asthma (OA) is one of the most frequent occupational diseases and its diagnosis is often difficult. This review summarizes its current diagnostic challenges.

RECENT FINDINGS

OA is associated with significant health and socio-economic burden. It is underdiagnosed and physicians need to adopt a stepwise approach to confirm the diagnosis. Although early removal from exposure to the offending agent is associated with a better prognosis, physicians should try to confirm the diagnosis of work-related asthma before taking a worker off work. A proper occupational and medical history is very important but is not enough to make the diagnosis of OA. Objective evidence of work-related asthma is required and this represents a serious challenge to most physicians. Measurement of non-specific bronchial responsiveness (NSBR) and spirometry may confirm the diagnosis of asthma but do not confirm the diagnosis of OA. Serial monitoring of peak expiratory flows (PEF), NSBR, and airway inflammation at and off work may confirm the diagnosis of OA but are often difficult to perform. Confirming sensitization by skin prick tests or specific IgE may help to support the diagnosis of OA. Specific inhalation challenges (SIC) in the lab or at work are considered the reference standard but are of limited access. Medical surveillance programs along with primary prevention (reducing exposure) may help to reduce the burden of OA, but the ideal program has yet to be defined. The diagnostic workup of OA remains a challenge and needs a rigorous stepwise evaluation.

Occupational Respiratory Allergic Diseases in Healthcare Workers

Healthcare workers (HCWs) are exposed to a range of high and low molecular weight agents that are allergic sensitizers or irritants including cleaners and disinfectants, natural rubber latex, and various medications. Studies have shown that exposed HCWs are at risk for work-related rhinitis and asthma (WRA). Work-related rhinitis may precede development of WRA and should be considered as an early marker of WRA. Avoidance of causative exposures through control strategies such as elimination, substitution, engineering controls, and process modification is the preferred primary prevention strategy for preventing development of work-related allergic diseases. There is limited evidence for the effectiveness of respirators in preventing occupational asthma. If sensitizer-induced WRA is diagnosed, it is important to avoid further exposure to the causative agent, preferably by more rigorous application of exposure control strategies to the workplace. This review focuses on allergic occupational respiratory diseases in HCWs.

Occupational Latex Allergy: the Current State of Affairs

PURPOSE OF REVIEW

Allergy to natural rubber latex (NRL) reached epidemic proportions during the nineties and led to intense preventive efforts. The aim of this review was to provide a comprehensive compilation of the current status of occupational NRL allergy.

RECENT FINDINGS

Recent advances led to the characterization of 15 NRL allergens and the development of assays for measuring the allergen content of NRL materials and specific IgE antibodies against NRL allergen components. Preventive measures aimed at reducing workplace exposure to NRL allergens were associated with decreasing incidence rates of NRL allergy. However, a pooled analysis of epidemiological surveys published during the last 10 years provided prevalence estimates of NRL sensitization and allergy similar to those derived from studies conducted before 2003. Substantial progress has been made in the understanding and prevention of NRL allergy, although the disease may still remain a worldwide cause of concern.

Association of MBL With Work-Related Respiratory Symptoms in Bakery Workers

Baker's asthma is the most prevalent occupational asthma, and IgE-mediated response is known as a major pathogenesis. However, recent studies have suggested the involvement of innate immune response because wheat flour contains bacterial endotoxins or lipopolysaccharides. To further understand a role of innate immune response in the development of work-related respiratory symptoms (WRS) in bakery workers, we investigated mannose-binding lectin (MBL), one of the initiating components of the complement cascade in a single cohort of bakery workers. A total of 373 bakery workers completed a questionnaire regarding WRS. The bakery workers were divided into 2 groups according to previous history of allergic rhinitis (AR)/bronchial asthma (BA): those with history of AR/BA (group I) and those without (group II). We measured serum MBL levels by using enzyme-linked immunosorbant assay and genotyped 4 single nucleotide polymorphisms of the MBL2 gene (226G>A in exon 1, -554G>C, -431A>C, and -225G>C in the promoter) by using TaqMan assays. Fifty-nine subjects (15.5%) were previously diagnosed with AR/BA, and 64 subjects (16.8%) complained of WRS. No significant differences were found in serum MBL levels between groups I and II. However, in group II subjects, but not in group I subjects, the serum MBL levels were significantly higher in bakery workers with WRS than in those without. In addition, the serum MBL levels were significantly different according to genetic polymorphisms of the MBL2 gene and its haplotypes. In conclusion, serum MBL, affected by genetic polymorphisms, may be associated with WRS in bakery workers with no previous history of AR/BA.

Development of an Interception Glove Sampler for Skin Exposures to Aromatic Isocyanates

OBJECTIVES

Skin is an important exposure route for isocyanate chemicals and contributes to systemic sensitization. Methods for assessing skin exposure are currently limited and generally rely upon removal (e.g. tape-strip) techniques prone to underestimation. The aim of this study is to (i) develop and field test an interception-based hand exposure sampler to monitor potential skin exposure to isocyanates in the workplace, (ii) to develop an analytical method based on ultra-high-performance liquid chromatography-UV absorbance-tandem mass spectrometry (UHPLC-UV-MS/MS) for analyzing glove samples; and (iii) compare it with tape-stripping skin sampling method.

METHODS

Laboratory investigations assessed different glove materials/fabrics, methods for impregnating with 1-(9-anthracenylmethyl)piperazine (MAP) derivatizing agent, methylene diphenyl diisocyanate (MDI) uptake and recovery, and durability. Following use, gloves were dissected into sections corresponding to different spatial regions (finger, palm) and analyzed using a newly developed UHPLC-UV-MS/MS method capable of differentiating and quantitating different MDI isomers with high sensitivity. Performance of the glove sampler was further assessed in a pilot field study using six workers.

RESULTS

A MAP-impregnated thin cotton glove sampler and UHPLC-UV-MS/MS analytical method for detecting MDI were successfully developed in laboratory studies. In subsequent field studies, a total of 384 samples from 14 glove pairs identified full-shift exposures ranged from 0.01 to 306 µg of 4,4'-MDI/worker for each hand. Surface area adjusted MDI values measured with the glove sampler (0.13-572ng MDI cm^-2) were considerably higher (~400-fold) than values obtained with tape stripping.

CONCLUSION

A glove sampler and a novel UHPLC-UV-MS/MS analytical method were developed to quantitatively measure MDI skin exposure. The novel interception technique overcomes inherent limitations of removal techniques for measuring isocyanate skin exposure and may be useful in exposure surveillance and future research on isocyanate's health risks.

Do Low Molecular Weight Agents Cause More Severe Asthma than High Molecular Weight Agents?

Introduction

The aim of this study was to analyse whether patients with occupational asthma (OA) caused by low molecular weight (LMW) agents differed from patients with OA caused by high molecular weight (HMW) with regard to risk factors, asthma presentation and severity, and response to various diagnostic tests.

Methods

Seventy-eight patients with OA diagnosed by positive specific inhalation challenge (SIC) were included. Anthropometric characteristics, atopic status, occupation, latency periods, asthma severity according to the Global Initiative for Asthma (GINA) control classification, lung function tests and SIC results were analysed.

Results

OA was induced by an HMW agent in 23 patients (29%) and by an LMW agent in 55 (71%). A logistic regression analysis confirmed that patients with OA caused by LMW agents had a significantly higher risk of severity according to the GINA classification after adjusting for potential confounders (OR = 3.579, 95% CI 1.136–11.280; p = 0.029). During the SIC, most patients with OA caused by HMW agents presented an early reaction (82%), while in patients with OA caused by LMW agents the response was mainly late (73%) (p = 0.0001). Similarly, patients with OA caused by LMW agents experienced a greater degree of bronchial hyperresponsiveness, measured as the difference in the methacholine dose-response ratio (DRR) before and after SIC (1.77, range 0–16), compared with patients with OA caused by HMW agents (0.87, range 0–72), (p = 0.024).

Conclusions

OA caused by LMW agents may be more severe than that caused by HMW agents. The severity of the condition may be determined by the different mechanisms of action of these agents.

An official American Thoracic Society Workshop Report: presentations and discussion of the fifth Jack Pepys Workshop on Asthma in the Workplace. Comparisons between asthma in the workplace and non-work-related asthma

The fifth Jack Pepys Workshop on Asthma in the Workplace focused on the similarities and differences of work-related asthma (WRA) and non-work-related asthma (non-WRA). WRA includes occupational asthma (OA) and work-exacerbated asthma (WEA). There are few biological differences in the mechanisms of sensitization to environmental and occupational allergens. Non-WRA and OA, when due to high-molecular-weight agents, are both IgE mediated; it is uncertain whether OA due to low-molecular-weight agents is also IgE mediated. Risk factors for OA include female sex, a history of upper airway symptoms, and a history of bronchial hyperresponsiveness. Atopy is a risk factor for OA due to high-molecular-weight agents, and exposure to cleaning agents is a risk factor for both OA and non-WRA. WEA is important among workers with preexisting asthma and may overlap with irritant-induced asthma, a type of OA. Induced sputum cytology can confirm airway inflammation, but specific inhalation challenge is the reference standard diagnostic test. Inhalation challenges are relatively safe, with the most severe reactions occurring with low-molecular-weight agents. Indirect health care costs account for about 50% of total asthma costs. Workers with poor asthma control (WRA or non-WRA) are less likely to be employed. Income loss is a major contributor to the indirect costs of WRA. Overall, asthma outcomes probably are worse for adult-onset than for childhood-onset asthma but better for OA than adult-onset non-WRA. Important aspects of management of OA are rapid and proper confirmation of the diagnosis and reduction of exposure to sensitizers or irritants at work and home.

Isocyanates and work-related asthma: Findings from California, Massachusetts, Michigan, and New Jersey, 1993-2008

BACKGROUND

Isocyanates remain a leading cause of work-related asthma (WRA).

METHODS

Two independent data systems were analyzed for the period 1993-2008: (1) State-based WRA case surveillance data on persons with isocyanate-induced WRA from four states, and (2) Occupational Safety and Health Administration (OSHA) Integrated Management Information System (IMIS) isocyanate air sampling results.

RESULTS

We identified 368 cases of isocyanate-induced WRA from 32 industries and 678 OSHA isocyanate air samples with detectable levels from 31 industries. Seventeen industries were unique to one or the other dataset.

CONCLUSION

Isocyanate-induced WRA continues to occur in a wide variety of industries. Two data systems uncovered industries with isocyanate exposures and/or illness. Improved control measures and standards, including medical surveillance, are needed. More emphasis is needed on task-specific guidance, spill clean-up procedures, skin and respiratory protection, and targeted medical monitoring to mitigate the hazards of isocyanate use.

Wheezing in tobacco farm workers in southern Brazil

BACKGROUND

Tobacco workers are exposed to several respiratory occupational sensitizers.

METHODS

A representative cross-sectional study was carried out on 2469 tobacco family farming growers. Gender-stratified multivariate analyses evaluated the association between wheezing and socio-demographic, behavioral, and occupational variables.

RESULTS

Wheezing prevalence was 11.0% with no difference between genders. Among men, age, smoking, strenuous work, pesticide use, contact with vegetable dust and dried tobacco dust, lifting sticks with tobacco leaves to the curing barns, and green tobacco sickness (GTS) were risk factors for wheezing. Among women, family history of asthma, tying hands of tobacco, strenuous work, contact with chemical disinfectants, and GTS were positively associated with wheezing. Harvesting lower tobacco leaves was a protective factor for the outcome in both genders.

CONCLUSIONS

Pesticides, dusts exposure, and GTS were risk factors for wheezing. The synergic effect of these factors needs to be better evaluated to improve prevention.

Isocyanates and human health: multistakeholder information needs and research priorities

OBJECTIVES

To outline the knowledge gaps and research priorities identified by a broad base of stakeholders involved in the planning and participation of an international conference and research agenda workshop on isocyanates and human health held in Potomac, Maryland, in April 2013.

METHODS

A multimodal iterative approach was used for data collection including preconference surveys, review of a 2001 consensus conference on isocyanates, oral and poster presentations, focused break-out sessions, panel discussions, and postconference research agenda workshop.

RESULTS

Participants included representatives of consumer and worker health, health professionals, regulatory agencies, academic and industry scientists, labor, and trade associations.

CONCLUSIONS

Recommendations were summarized regarding knowledge gaps and research priorities in the following areas: worker and consumer exposures; toxicology, animal models, and biomarkers; human cancer risk; environmental exposure and monitoring; and respiratory epidemiology and disease, and occupational health surveillance.

Analysis of the interrelationship of the pulmonary irritation and elicitation thresholds in rats sensitized with 1,6-hexamethylene diisocyanate (HDI)

This paper summarizes a range of experimental data central for developing a science-based approach for hazard identification of monomeric and polymeric aliphatic 1,6-hexamethylene diisocyanate (HDI). The dose–response curve of HDI-induced pulmonary responses in naïve or dermally sensitized rats after one or several inhalation priming exposures was examined in the Brown Norway (BN) rat asthma model. Emphasis was directed to demonstrate the need and the difficulty in selecting an appropriate pulmonary dose when much of the inhaled chemically reactive vapor may concentration dependently be retained in the upper airways of obligate nose-breathing rats. The course taken acknowledges the experimental challenges in identifying an elicitation threshold for HDI-monomer near or above the saturated vapor concentration or in the presence of a HDI-polymer aerosol. The inhalation threshold dose on elicitation was determined based on a fixed concentration (C) × variable exposure duration (t) protocol for improving inhalation dosimetry of the lower airways. Neutrophilic granulocytes (PMN) in bronchoalveolar lavage (BAL) fluid in equally inhalation primed naïve and dermally sensitized rats were used to define the inhalation elicitation threshold C × t. Sensitized rats elaborated markedly increased PMN challenged sensitized rats relative to equally challenged naïve rats at 5625 mg HDI/m³ × min (75 mg/m³ for 75 min). PMN were essentially indistinguishable at 900 mg HDI/m³ × min. By applying adjustment factors accounting for both inter-species differences in inhalation dosimetry and intra-species susceptibility, the workplace human-equivalent threshold C × t was estimated to be in the range of the current ACGIH TLV® of HDI. Thus, this rat “asthma” model was suitable to demonstrate elicitation thresholds for HDI-vapor after one or several inhalation priming exposures and seems to be suitable to derive occupational exposure values (OELs) for diisocyanates in general.

Biological and genetic markers in occupational asthma

Occupational asthma (OA) is a complex disease that is often hard to diagnose due to difficulties in detecting relevant exposure, along with inherent differences in disease susceptibility. Numerous studies have attempted to identify relevant biological and genetic markers for OA and to devise tools capable of detecting exposure to the causative agent. Immunological markers, including skin prick test reactivity and specific IgE and IgG antibodies can be used to detect high-molecular-weight allergens in cases of baker's asthma. For OA induced by low-molecular-weight agents, such as isocyanate, potential biomarkers include serum-specific IgE and IgG antibodies to isocyanate-HSA conjugate and IgG to cytokeratin 19 and transglutaminase-2. For protein-based markers, ferritin/transferrin and vitamin D-binding protein levels have been suggested for isocyanate-OA. Genetic markers of susceptibility to isocyanate-OA include human leukocyte antigen and CTNNA3. Further investigations will be needed to identify better biomarkers for OA, which may be used to inform clinical decision.

Is the analysis of histamine and/or interleukin-4 release after isocyanate challenge useful in the identification of patients with IgE-mediated isocyanate asthma?

Isocyanates are a well-known and frequent cause of occupational asthma. The implementation of specific inhalation challenges (SICs) is the gold standard in asthma diagnosis supporting occupational case history, lung function testing, specific skin prick tests and the detection of specific IgE. However, the diagnosis is not always definitive. An interesting new approach, analyses of individual genetic susceptibilities, requires discrimination between a positive SIC reaction arising from IgE-mediated immune responses and one from other pathophysiological mechanisms. Hence, additional refinement tools would be helpful in defining sub-classes of occupational asthma and diagnosis. We used total IgE levels, specific IgE and SIC results for sub-classification of 27 symptomatic isocyanate workers studied. Some mutations in glutathione S-transferases (GSTs) are suspected either to enhance or to decrease the individual risk in the development of isocyanate asthma. Our patient groups were assessed for the point mutations GSTP1*I105V and GSTP1*A114V as well as deletions (null mutations) of GSTM1 and GSTT1. There seems to be a higher risk in developing IgE-mediated reactions when GSTM1 is deleted, while GSTT1 deletions were found more frequently in the SIC positive group. Blood samples taken before SIC, 30-60 min and 24h after SIC, were analyzed for histamine and IL-4, classical markers for the IgE-mediated antigen-specific activation of basophils or mast cells. We suggest that the utility of histamine measurements might provide an additional useful marker reflecting isocyanate-induced cellular reactions (although the sampling times require optimization). The promising measurement of IL-4 is not feasible at present due to the lack of a reliable, validated assay.

Effects of MBL2 polymorphisms in patients with diisocyanate-induced occupational asthma

Diisocyanate (DI) is the most common cause of occupational asthma (OA) in Korea. Mannose-binding lectin (MBL) initiates the lectin complement activation pathway following oxidative stress and plays an important role in the regulation of inflammatory processes. To determine whether there is a genetic association between MBL2 polymorphisms and DI-OA, 99 patients with DI-OA, 99 asymptomatic exposed controls (AECs) and 144 unexposed normal controls were enrolled in this study. Three polymorphisms (-554 G>C, -431A>C and -225 G>C) in the MBL2 promoter were genotyped, and serum MBL levels were determined by enzyme-linked immunosorbent assay. Functional variabilities in the promoter polymorphisms were analyzed by a luciferase reporter assay and electrophoretic mobility shift assay (EMSA). A significantly higher frequency of haplotype (ht) 2 [CAG] was noted in the DI-OA group compared with the AEC group (P=0.044). The patients with DI-OA carrying ht2 [CAG] had significantly lower PC20 methacholine levels (P<0.001) than the non-carriers. The serum MBL levels were significantly higher in the DI-exposed subjects (both the DI-OA patients and AECs) carrying ht1 [GAG] (P=0.028). Luciferase activity was significantly enhanced in ht1 [GAG] compared with ht2 [CAG] in human hepatocarcinoma cells (Hep3B) (P=0.002). The EMSA showed that a -554G probe produced a specific shifted band compared with the -554C probe. These findings suggest that decreased serum MBL levels due to polymorphisms of the MBL2 gene may increase susceptibility to the development of DI-OA in DI-exposed individuals.