Indium, a rare heavy metal, extensively used in flat panel display manufacturing, poses potential respiratory health risks to workers. Preserved ratio impaired spirometry (PRISm), a term describing nonobstructive lung function abnormalities, is associated with adverse health outcomes. Despite known risks, the relationship between serum indium levels and PRISm remains underexplored.

A cross-sectional cohort study among non-smoking industry workers potentially exposed to indium in Taiwan was conducted in 2020. Demographic data, and pulmonary function tests were collected comprehensively. Serum indium levels were quantified using inductively coupled plasma mass spectrometry, and respiratory symptoms were obtained via questionnaire. PRISm was defined as FEV₁/FVC ≥0.7 with FEV1 < 80 % predicted. Univariate, and multivariate logistic regression analyses were conducted to identify risk factors associated with PRISm.

Among 2575 eligible participants, those with abnormal serum indium levels (≥3 ng/mL) were older, predominantly male, and had longer total working duration. PRISm prevalence was significantly higher in individuals with abnormal indium levels (22.7 % vs. 7.6 %). PRISm subjects exhibited a higher proportion of abnormal indium levels. Multivariate analysis revealed that serum indium levels ≥3 ng/mL and female sex were significant risk factors for PRISm after adjusting sex, age, body mass index and working duration.

This study demonstrates a significant association between elevated serum indium levels and increased PRISm prevalence among non-smoking workers in Taiwan. Findings highlight the importance of assessing serum indium levels in occupational health surveillance and revising exposure standards to mitigate respiratory health risks associated with indium exposure.