A nationwide follow-up study of occupational organic dust exposure and risk of chronic obstructive pulmonary disease (COPD)

Association of low attenuation area scores with pulmonary function and clinical prognosis in patients with chronic obstructive pulmonary disease

The objective of this study was to investigate the relationship between low attenuation area (LAA) scores, pulmonary function parameters, and clinical prognosis in patients with chronic obstructive pulmonary disease (COPD). COPD patients were divided into four LAA-based grades. Various lung function parameters were measured and correlated with LAA scores. Patient symptoms were examined using the St. George's Respiratory Questionnaire (SGRQ) and exercise capacity using the 6-min walk test (6MWT). Statistical analysis determined the significance of differences. Higher levels of LAA were associated with decreased lung function and airflow limitations, suggesting a positive relationship between the two. Clinical symptom scores increased as COPD severity based on LAA stratification worsened. Reduced exercise capacity was shown by a substantial decline in 6MWT scores as COPD severity increased. As LAA scores increased, SGRQ scores increased, indicating a decreased quality of life (QOL). The study demonstrated a relationship between LAA scores and COPD severity. High LAA scores were associated with poor lung function, worse clinical symptoms, limited exercise capacity, and lower QOL. These findings show that LAA scores are clinically relevant for disease severity assessment and COPD management. Further research is required to determine LAA scores' prognostic significance in disease progression and treatment response to enhance COPD therapy.

Respiratory Diseases Associated With Organic Dust Exposure

Organic dusts are complex bioaerosol mixtures comprised of dust and par ticulate matter of organic origin. These include components from bacteria, fungi, pollen, and viruses to fragments of animals and plants commonplace to several environmental/occupational settings encompassing agriculture/farming, grain processing, waste/recycling, textile, cotton, woodworking, bird breeding, and more. Organic dust exposures are linked to development of chronic bronchitis, chronic obstructive pulmonary disease, asthma, asthma-like syndrome, byssinosis, hypersensitivity pneumonitis, and idiopathic pulmonary fibrosis. Risk factors of disease development include cumulative dust exposure, smoking, atopy, timing/duration, and nutritional factors. The immunopathogenesis predominantly involves Toll-like receptor signaling cascade, T-helper 1/T-helper 17 lymphocyte responses, neutrophil influx, and potentiation of manifestations associated with allergy. The true prevalence of airway disease directly attributed to organic dust, especially in a workplace setting, remains challenging. Diagnostic confirmation can be difficult and complicated by hesitancy from workers to seek medical care, driven by fears of potential labor-related consequence. Clinical respiratory and systemic presentations coupled with allergy testing, lung function patterns of obstructive versus restrictive disease, and radiological characteristics are typically utilized to delineate these various organic dust-associated respiratory diseases. Prevention, risk reduction, and management primarily focus on reducing exposure to the offending dust, managing symptoms, and preventing disease progression.

Risk of chronic obstructive pulmonary disease in a large cohort of Ontario, Canada workers

Although several occupational exposures have been linked to the risk of COPD; limited data exists on sex-specific differences. This study aimed to identify at-risk occupations and sex differences for COPD risk. Cases were identified in a large surveillance system established through the linkage of former compensation claimants' data (non-COPD claims) to physician visits, ambulatory care data, and hospital inpatient data (1983-2020). Cox proportional hazard models were used to estimate hazard ratios (HRs) and corresponding 95% confidence intervals (CI) for occupation groups (occupation at time of claim), stratified by sex. HRs were indirectly adjusted for cigarette smoking using another population dataset. A total of 29,445 male and 14,693 female incident cases of COPD were identified. Increased risks were observed in both sexes for construction (HRmale 1.15, 95% CI 1.12-1.19; HRfemale 1.54, 95% CI 1.29-1.83) transport/equipment operating (HRmale 1.32, 95% CI 1.28-1.37; HRfemale 1.53, 95% CI 1.40-1.68) farming (HRmale 1.23, 95% CI 1.15-1.32; HRfemale 1.19, 95% CI 1.04-1.37) and janitors/cleaners (HRmale 1.31, 95% CI 1.24-1.37; HRfemale 1.40, 95% CI 1.31-1.49). Increased risks were observed for females employed as chefs and cooks (HR 1.44, 95% CI 1.31-1.58), bartenders (HR 1.38, 95% CI 1.05-1.81), and those working in food/beverage preparation (HR 1.34, 95% CI 1.24-1.45) among other occupations. This study demonstrates elevated risk of COPD among both male and female workers potentially exposed to vapours, gases, dusts, and fumes, highlighting the need for occupational surveillance of COPD.

The association of forced expiratory volume in one second with occupational exposures in a longitudinal study of adults in a rural community in Iowa

PURPOSE

The Keokuk County Rural Health Study (KCRHS) is a longitudinal population-based study conducted in rural Iowa. A prior analysis of enrollment data identified an association of airflow obstruction with occupational exposures only among cigarette smokers. The current study used spirometry data from all three rounds to investigate whether level of forced expiratory volume in one second (FEV1) and longitudinal change in FEV1 were associated with occupational vapor-gas, dust, and fumes (VGDF) exposures, and whether these associations were modified by smoking.

METHODS

This study sample comprised 1071 adult KCRHS participants with longitudinal data. A job-exposure matrix (JEM) was applied to participants' lifetime work histories to assign exposures to occupational VGDF. Mixed regression models of pre-bronchodilator FEV1 (millimeters, ml) were fit to test for associations with occupational exposures while adjusting for potential confounders.

RESULTS

Mineral dust had the most consistent association with change in FEV1, including ever/never ( - 6.3 ml/year) and nearly every level of duration, intensity, and cumulative exposure. Because 92% of participants with mineral dust also had organic dust exposure, the results for mineral dust may be due to a combination of the two. An association of FEV1 level with fumes was observed for high intensity ( - 91.4 ml) among all participants, and limited to cigarette smokers with results of  - 104.6 ml ever/never exposed,  - 170.3 ml high duration, and  - 172.4 ml high cumulative.

CONCLUSION

The current findings suggest that mineral dust, possibly in combination with organic dust, and fumes exposure, especially among cigarette smokers, were risk factors for adverse FEV1 results.

Farming, pesticide exposure and respiratory health: a cross-sectional study in Thailand

OBJECTIVE

To assess the association of lung function and respiratory symptoms with farming, particularly pesticide use, in an agricultural province in Thailand.

METHODS

We undertook a cross-sectional survey of adults aged 40-65 in Nan province, Thailand, between May and August 2019. We randomly recruited 345 villagers and enriched the sample with 82 government employees. All participants performed post-bronchodilator spirometry and completed a questionnaire covering information on respiratory symptoms, farming activities, pesticide use and known risk factors for respiratory disease. Associations of respiratory outcomes with farming and pesticide exposures were examined by multivariable regression analysis.

RESULTS

The response rate was 94%. The prevalence of chronic airflow obstruction among villagers was 5.5%. Villagers had, on average, a lower percent predicted post-bronchodilator forced expiratory volume in one second/forced vital capacity (FEV₁/FVC) than government employees (98.3% vs 100.3%; p=0.04). There was no evidence of association of lung function with farming activities, the use of specific herbicides (glyphosate and paraquat), insecticides (organophosphates and pyrethroids) or fungicides. The exceptions were poultry farming, associated with chronic cough and an increase of FEV₁/FVC, and atrazine, for which duration (p-trend <0.01), intensity (p-trend <0.01) and cumulative hours (p-trend=0.01) of use were all associated with higher FEV₁/FVC in an exposure-response manner. Cumulative hours (-280 mL/hour), low duration (-270 mL/year) and intensity (-270 mL/hour/year) of atrazine use were associated with lower FVC.

CONCLUSIONS

Chronic airflow obstruction is uncommon among villagers of an agricultural province in Nan, Thailand. Farming and pesticide use are unlikely to be major causes of respiratory problems there.

Organic dust exposure induces stress response and mitochondrial dysfunction in monocytic cells

Exposure to airborne organic dust (OD), rich in microbial pathogen-associated molecular patterns (PAMPs), is shown to induce lung inflammation. A common manifestation in lung inflammation is altered mitochondrial structure and bioenergetics that regulate mitochondrial ROS (mROS) and feed a vicious cycle of mitochondrial dysfunction. The role of mitochondrial dysfunction in other airway diseases is well known. However, whether OD exposure induces mitochondrial dysfunction remains elusive. Therefore, we tested a hypothesis that organic dust extract (ODE) exposure induces mitochondrial stress using a human monocytic cell line (THP1). We examined whether co-exposure to ethyl pyruvate (EP) or mitoapocynin (MA) could rescue ODE exposure induced mitochondrial changes. Transmission electron micrographs showed significant differences in cellular and organelle morphology upon ODE exposure. ODE exposure with and without EP co-treatment increased the mtDNA leakage into the cytosol. Next, ODE exposure increased PINK1, Parkin, cytoplasmic cytochrome c levels, and reduced mitochondrial mass and cell viability, indicating mitophagy. MA treatment was partially protective by decreasing Parkin expression, mtDNA and cytochrome c release and increasing cell viability.

Airborne occupational exposures and the risk of developing respiratory symptoms and airway obstruction in the Lifelines Cohort Study

OBJECTIVES

To date, only a few studies have investigated the associations between occupational exposures and respiratory outcomes longitudinally in the general population. We investigated the associations between occupational exposures and the development of respiratory symptoms and airway obstruction in the Lifelines Cohort Study.

METHODS

We included 35 739 occupationally active subjects with data on chronic cough, chronic phlegm, chronic bronchitis or airway obstruction at baseline and approximately 4.5 years follow-up. Exposures to biological dust, mineral dust, gases/fumes, pesticides, solvents and metals in the current job at baseline were estimated with the ALOHA+job-exposure matrix (JEM). Airway obstruction was defined as FEV1/FVC below the lower limit of normal. Logistic regression analysis adjusted for baseline covariates was used to investigate the associations.

RESULTS

At follow-up, 1888 (6.0%), 1495 (4.7%), 710 (2.5%) and 508 (4.5%) subjects had developed chronic cough, chronic phlegm, chronic bronchitis and airway obstruction, respectively. High exposure to biological dust was associated with a higher odds to develop chronic cough and chronic bronchitis. High exposure to pesticides was associated with a higher odds for the development of all respiratory symptoms and airway obstruction. In the multiple exposures analyses, only the association between pesticides exposure and respiratory symptoms remained.

CONCLUSIONS

Subjects exposed to high pesticides had a higher odds to develop respiratory symptoms on average 4.5 years later. Control measures should be taken to reduce pesticides exposure among the working population to prevent respiratory symptoms and airway obstruction.

Pre-exposure to hydrogen sulfide modulates the innate inflammatory response to organic dust

Animal production units produce and store many contaminants on-site, including organic dust (OD) and hydrogen sulfide (H₂S). Workers in these settings report various respiratory disease symptoms. Both OD and H₂S have shown to induce lung inflammation. However, impact of co-exposure to both H₂S and OD has not been investigated. Therefore, we tested a hypothesis that pre-exposure to H₂S modulates the innate inflammatory response of the lungs to organic dust. In a mouse model of H₂S and organic dust extract (ODE) exposure, we assessed lung inflammation quantitatively. We exposed human airway epithelial and monocytic cells to medium or H₂S alone or H₂S followed by ODE and measured cell viability, oxidative stress, and other markers of inflammation. Exposure to 10 ppm H₂S followed by ODE increased the lavage fluid leukocytes. However, exposure to 10 ppm H₂S alone resulted in changes in tight junction proteins, an increase in mRNA levels of tlr2 and tlr4 as well as ncf1, ncf4, hif1α, and nrf2. H₂S alone or H₂S and ODE exposure decreased cell viability and increased reactive nitrogen species production. ODE exposure increased the transcripts of tlr2 and tlr4 in both in vitro and in vivo models, whereas increased nfkbp65 transcripts following exposure to ODE and H₂S was seen only in in vitro model. H₂S alone and H₂S followed by ODE exposure increased the levels of IL-1β. We conclude that pre-exposure to H₂S modulates lung innate inflammatory response to ODE.

Occupational exposures and exacerbations of asthma and COPD-A general population study

Purpose

Recent studies suggest that occupational inhalant exposures trigger exacerbations of asthma and chronic obstructive pulmonary disease, but findings are conflicting.

Methods

We included 7,768 individuals with self-reported asthma (n = 3,215) and/or spirometric airflow limitation (forced expiratory volume in 1 second (FEV₁)/ forced expiratory volume (FVC) <0.70) (n = 5,275) who participated in The Copenhagen City Heart Study or The Copenhagen General Population Study from 2001–2016. Occupational exposure was assigned by linking job codes with job exposure matrices, and exacerbations were defined by register data on oral corticosteroid treatment, emergency care unit assessment or hospital admission. Associations between occupational inhalant exposure each year of follow-up and exacerbation were assessed by Cox regression with time varying exposure and age as the underlying time scale.

Results

Participants were followed for a median of 4.6 years (interquartile range, IQR 5.4), during which 870 exacerbations occurred. Exacerbations were not associated with any of the selected exposures (high molecular weight sensitizers, low molecular weight sensitizers, irritants or low and high levels of mineral dust, biological dust, gases & fumes or the composite variable vapours, gases, dusts or fumes). Hazards ratios ranged from 0.8 (95% confidence interval: 0.7;1.0) to 1.2 (95% confidence interval: 0.9;1.7).

Conclusion

Exacerbations of obstructive airway disease were not associated with occupational inhalant exposures assigned by a job exposure matrix. Further studies with alternative exposure assessment are warranted.

Dust exposure and the impact on hospital readmission of farming and wood industry workers for asthma and chronic obstructive pulmonary disease (COPD)

Objectives:

It is still not well established how occupational air pollutants affect the prognosis of asthma or chronic obstructive pulmonary disease (COPD). This study uses nationwide Danish registers and quantitative dust industry exposure matrices (IEM) for the farming and wood industries to estimate whether previous year dust exposure level impacts hospital readmissions for workers diagnosed with asthma or COPD.

Methods:

We identified all individuals with a first diagnosis of either asthma (769 individuals) or COPD (342 individuals) between 1997 and 2007 and followed them until the next hospital admission for asthma or COPD, emigration, death or 31 December 2007. We included only individuals who worked in either the wood or farming industries at least one year during follow-up. We used logistic regression analysis to investigate associations between dust exposure level in the previous year and hospital readmission, adjusting for sex, age, time since first diagnosis, socioeconomic status, and labor force participation.

Results:

Asthma readmissions for individuals with low and high dust exposure were increased [adjusted rate ratio (RR_adj) 2.52, 95% confidence interval (CI) 1.45–4.40] and RR_adj 2.64 (95% CI 1.52–4.60), respectively. For COPD readmission, the risk estimates were RR_adj 1.36 (95% CI 0.57–3.23) for low and RR_adj 1.20 (95% CI 0.49–2.95) for high exposure level in the previous year. For asthma readmission, stratified analyses by type of dust exposure during follow-up showed increased risks for both wood dust [RR_adj 2.67 (95% CI 1.35–5.26) high exposure level] and farming dust [RR_adj 3.59 (95% CI 1.11–11.59) high exposure level]. No clear associations were seen for COPD readmissions.

Conclusions:

This study indicates that exposure to wood or farm dust in the previous year increases the risk of hospital readmission for individuals with asthma but not for those with COPD.

Exposure to endotoxins and respiratory health in composting facilities

The impact of bioaerosols in municipal solid waste management is nowadays identified as a growing health concern worldwide. In this study, exposure to endotoxin in composting facilities and its association with lung function and clinical symptoms was investigated in Tehran municipal solid waste management complex (Aradkooh) as one of the largest solid waste management facilities in the Middle East. Airborne endotoxins were collected between June and July 2019 and the concentrations were determined by Limulus Amebocyte Lysate (LAL) method. Healthy workers with no history of respiratory disease were recruited and data on clinical symptoms (cough, phlegm, wheezing, dyspnea, fatigue, headache, eye irritation, runny nose, runny eyes, and sore throat) was obtained by the modified American Thoracic Society questionnaire, and spirometric measurement was performed by an expert. The binary logistic regression test was used and adjusted for confounding variables. The results didn't show any difference in lung function parameters (FEV₁, FVC, FEV₁/FVC, PEF, FEF_25-75%), and most of the respiratory symptoms despite a relatively high difference in the concentration of endotoxin observed in air samples of different locations. Only the increased risk of cough (OR 10.5, 95% CI: 2.4 to 44.8 in the moderately exposed group and 7.8, 95% CI: 1.6 to 39.1 in highly exposed ones), fatigue (OR 3.7, 95% CI: 1.2 to 11.7), and headache (OR 6.02, 95% CI: 1.4 to 24.5) were found in the exposed groups compared to controls after adjusting for age, active and passive smoking. However, findings of the study might be underestimated due to some issues including healthy worker effect, intra and intersubject variability, and self-reporting bias, thereby the results should be interpreted with caution. Although we did not find any relationship, due to the high concentrations of endotoxins observed in some sites, it is recommended to consider some possible prevention measures such as using personal protective equipment to reduce the exposure of workers at an acceptable level.