{
  "abstract": "Work-related asthma remains one of the most complex and underappreciated dimensions of adult-onset respiratory disease. Estimated to account for 25% of adult-onset cases,1 it encompasses a heterogeneous set of phenotypes, including immunologic occupational asthma, irritant-induced asthma and work-exacerbated asthma, each with distinct pathophysiological mechanisms and diagnostic challenges.2 This diversity complicates not only diagnosis and management but also surveillance efforts and preventive strategies across different occupations and settings. Nevertheless, surveillance systems remain fragmented and many cases go unrecognised in clinical practice, especially in non-specialist settings.3 Despite increasing awareness of occupational exposures as contributors to airway inflammation and sensitisation, definitive longitudinal evidence linking workplace conditions to asthma incidence remains limited. In this context, the study by Alif and colleagues,4 published in this issue of Thorax, offers a significant advancement. Using data from the European Community Respiratory Health Survey (ECRHS), the authors provide 20-year longitudinal evidence of persistent occupational risk for asthma across Europe. Initiated in the early 1990s, ECRHS has helped define the role of environmental and occupational exposures in adult asthma. ECRHS I included over 15 000 adults in 12 countries, assessing asthma through questionnaires and methacholine challenge. It identified increased risks in occupations like farming, painting and cleaning, with 5–10% of cases attributable to occupational exposures.5 ECRHS II followed symptom-free participants, confirming significant roles for high and low-molecular-weight agents, biocides and cleaning products, with attributable risks up to 25%.6 These studies laid the foundation for ECRHS III among the longest running investigations. This study is distinguished by its methodological rigour, unprecedented duration and longitudinal exposure assessment. The authors analysed data from 5591 adults in 13 countries, initially recruited in 1991–1993 and followed through two subsequent waves. Participants with pre-existing asthma at baseline were excluded to isolate incident cases. Occupational exposures were assessed using the updated Occupational Asthma-specific Job Exposure Matrix, a validated tool improving specificity across jobs.7 Complete work histories were reconstructed using job calendars, enabling cumulative exposure assessment over 20 years, a key strength compared with prior cross-sectional studies. Poisson regression with generalised estimating equations was used to estimate incidence rates, accounting for repeated measures and clustering. Adjustment for key confounders, including age, sex, smoking history, socioeconomic status, weight change and atopy, further reinforces the robustness of findings. Sensitivity analyses comparing included and excluded participants found stable estimates and no major incidence differences, supporting generalisability. The results strongly support the role of occupational exposures in asthma development. The overall incidence of asthma in the cohort was 15 per 1000 person-years, higher than previous studies, which reported incidence rates ranging from 1.4 to 5 per 1000 person-years.8–10 However, the authors adopt a broader definition of asthma based on symptoms and medication use, without functional data such as non-specific bronchial hyper-responsiveness, which were unavailable at the final follow-up. This, together with differences in design, population and duration across studies, may help explain the variability in reported incidence. Nonetheless, while some degree of variability or misclassification cannot be excluded, the observed incidence appears higher than in previous decades. This pattern, echoed by generational increases reported in other cohorts, may indicate a genuine upward trend in asthma incidence that deserves closer epidemiological scrutiny. The estimated population attributable fraction of 18% for work-related asthma, derived from standardised cohort-level analyses, adds novel quantitative weight to the argument that occupational exposures continue to account for a substantial burden of incident adult asthma. Notably, many of the implicated agents are still prevalent in modern occupational settings, underscoring the urgency of updated preventive strategies. High-molecular-weight sensitisers, irritants and biocides were significantly associated with increased asthma incidence, with rate ratios (RRs) of 1.27, 1.21 and 1.28, respectively. Statistically significant associations also emerged for low-molecular-weight agents (RR 1.26), mites (RR 1.38) and reactive chemicals (RR 1.24). Among specific substances, wood dust (RR 1.59), indoor cleaning products (RR 1.30) and bleach (RR 1.40) were particularly relevant. These findings are largely consistent with earlier studies,3 but the current analysis extends this knowledge by demonstrating these associations within a prospective design, leveraging harmonised, time-resolved exposure data over two decades. Some agents were linked to asthma only at low exposure levels, challenging the expected dose–response pattern, particularly for low-molecular-weight chemicals and some biological agents. In contrast, clear gradients emerged for high-molecular-weight sensitisers and irritants. Such discrepancies may reflect exposure misclassification, healthy worker survivor bias, or unmeasured confounding, and highlight the need for further investigation into threshold effects and individual susceptibility. From a clinical standpoint, the findings underscore the need for heightened awareness of occupational exposures in patients presenting with new-onset asthma. Despite excluding participants with known asthma at baseline, diagnostic confirmation was limited, particularly in the absence of bronchial hyper-responsiveness data. Classification between immunologic occupational asthma, irritant-induced asthma and work-exacerbated asthma remains complex. In the absence of gold-standard diagnostic tools, such as specific bronchial provocation testing, these labels should be interpreted with caution.11 Moreover, this study highlights the need for clinicians to consider occupational history as a routine component of asthma diagnosis, particularly in adults presenting with late-onset or treatment-refractory symptoms. A systematic approach to identifying occupational triggers can significantly alter disease management and improve outcomes.12 From a public health perspective, the implications are profound. Regulatory frameworks may need to be revised or strengthened to address not only traditional asthmagens, such as isocyanates and flour, but also agents whose relevance has emerged more recently, including cleaning products and microbial exposures.3 Cleaning products, long known to trigger asthma through irritant and sensitising mechanisms, remain widely used in occupational settings.13 Notably, some cases occur in the absence of bronchial hyper-responsiveness, raising concerns about overlooked phenotypes and diagnostic uncertainty in exposed populations. The identification of storage mites and plant mites as risk factors, even at low exposure levels, further suggests that occupational risk is more pervasive than typically acknowledged. In conclusion, this study provides valuable insight into the occupational determinants of asthma. Its strengths in the scale, duration and analytical rigour of the ECRHS cohort support the need for integrated clinical, epidemiological and regulatory responses. Occupational exposures remain a significant and often underestimated contributor to adult-onset asthma, even at low levels. The heterogeneity of work-related asthma highlights the need for improved diagnostic precision, while the reliance on symptom-based definitions underscores the gap between surveillance and clinical care. Effective prevention requires both stricter exposure control and better integration of occupational health into respiratory practice. As work evolves, so must our strategies to mitigate its respiratory risks.",
  "authors": [
    {
      "affiliations": [
        "Department of Cardiac, Thoracic, Vascular Sciences and Public Health, Università degli Studi di Padova, Padova, Italy"
      ],
      "name": "Filippo Liviero"
    }
  ],
  "title": "Occupational asthma: still an underestimated burden?",
  "uid": "a718a944-9068-52dd-862b-74dc4fe930ac"
}