Objective Occupational exposure to indium compounds including indium-tin oxide (ITO) can result in potentially fatal indium lung disease. We compared plasma, serum and whole blood indium concentrations (InP, InS and InB) from workers at a single ITO production facility to assess the comparability of these matrices used for biological monitoring of indium exposure.
Method InP, InS and InB were measured using inductively coupled mass spectrometry from consenting workers at an ITO production facility with specimen collection occurring during June−July 2014. Matched pairs from workers were assessed to determine the matrix relationships using the Pearson correlation, paired t-tests, per cent difference, linear regression and κ statistics.
Results Indium matrices were collected from 80 workers. Mean (SD) InP, InS and InB were 3.48 (3.84), 3.90 (4.15) and 4.66 (5.32) mcg/L, respectively. The InS−InP difference was 14%; InS was higher in all but two workers. InP and InS were highly correlated (r=>0.99). The InB−InS difference was 19%; InB was higher in 85% of workers. The InB−InP difference was 34%; InB was higher in 66% of workers. InB was highly correlated with both InP and InS (r=0.97 and 0.96, respectively). κ Statistics were 0.84, 0.83 and 0.82 for InP, InS and InB, respectively, for individuals with each matrix ≥1 mcg/L (p<0.01).
Conclusions While all matrices were highly correlated, we encourage the use of InP and InS to reliably compare studies across different populations using different matrices. The higher per cent difference and increased variability of InB may limit its utility in comparisons with InP and InS in different populations.
- Indium-tin oxide (ITO)
- Indium lung disease
- Blood matrices
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Funding This work was supported by the intramural National Occupational Research Agenda (NORA) funding from the National Institute for Occupational Safety and Health (NIOSH).
Competing interests None declared.
Patient consent Obtained.
Ethics approval NIOSH HSRB.
Provenance and peer review Not commissioned; externally peer reviewed.