Abstract
ABSTRACT
Background
Tens of millions of workers in South Asian informal industries are exposed daily to hazardous dusts and fumes without regulatory protection. Despite the scale of this workforce, no quantitative synthesis of spirometric and symptomatic evidence from this population has previously been conducted.
Methods
A pre‐registered systematic review and meta‐analysis (OSF: 10.17605/OSF.IO/ZARDP) was conducted by searching MEDLINE, Embase, Scopus, Web of Science, and CINAHL. Cross‐sectional studies comparing spirometry or respiratory symptom prevalence between informal sector workers and healthy controls in South Asia were eligible. Screening was conducted independently by two reviewers using Rayyan. Risk of bias was assessed with the AXIS tool and the JBI cross‐sectional checklist. Pooled mean differences (MD) and odds ratios (OR) were estimated using random‐effects models with restricted maximum likelihood (REML) estimation and the Knapp–Hartung (HKSJ) correction. Heterogeneity was quantified by I
2
and prediction intervals (PIs); meta‐regression examined smoking prevalence, mean age, occupational sector, geographic region, and exposure measurement method as moderators. Certainty of evidence was graded using GRADE.
Results
Thirty‐eight studies (33 poolable; ~7880 participants) were included, spanning occupational sectors. There was significant between‐study heterogeneity, with I
2
values of 97%–99% for the main spirometry variables and wide PIs reflecting large interstudy variation in effect sizes by occupation. Brick kiln workers and sawmill workers had the highest and most consistent FEV
1
deficits. Overall pooled analyses showed lower FEV
1
(MD: −0.59 L, 95% CI: −0.84 to −0.33), lower FVC (MD: −0.53 L, 95% CI: −0.71 to −0.35), and lower FEV
1
/FVC ratio (MD: −5.5%, 95% CI: −9.21 to −1.78), although PIs crossed the null for some outcomes. Exposed workers were more likely to have respiratory symptoms, such as chronic cough or breathlessness, across all analyses.
Conclusions
Occupational particulate exposure in South Asian informal sector workers is consistently associated with substantial meaningful reductions in lung function and substantially elevated respiratory symptom burden. Very low evidence certainty underscores the need for high‐quality prospective research and targeted respiratory surveillance programmes for this underprotected workforce.