A field evaluation of a single sampler for respirable and inhalable indium and dust measurements at an indium-tin oxide manufacturing facility

Abstract

Indium-tin oxide production has increased greatly in the last 20 years subsequent to increased global demand for touch screens and photovoltaics. Previous studies used measurements of indium in blood as an indicator of indium exposure and observed associations with adverse respiratory outcomes. However, correlations between measurements of blood indium and airborne respirable indium are inconsistent, in part because of the long half-life of indium in blood, but also because respirable indium measurements do not incorporate inhalable indium that can contribute to the observed biological burden. Information is lacking on relationships between respirable and inhalable indium exposure, which have implications for biological indicators like blood indium. The dual IOM sampler includes the foam disc insert and can simultaneously collect respirable and inhalable aerosol. Here, the field performance of the dual IOM sampler was evaluated by comparing performance with the respirable cyclone and traditional IOM for respirable and inhalable indium and dust exposure, respectively. Side-by-side area air samples were collected throughout an indium-tin oxide manufacturing facility. Cascade impactors were used to determine particle size distribution. Several statistical methods were used to evaluate the agreement between the pairs of samplers including calculating the concordance correlation coefficient and its accuracy and precision components. One-way ANOVA was used to evaluate the effect of dust concentration on sampler differences. Respirable indium measurements showed better agreement (concordance correlation coefficient: 0.932) compared to respirable dust measurements (concordance correlation coefficient: 0.777) with significant differences observed in respirable dust measurements. The dual IOM measurements had high agreement with the traditional IOM for inhalable indium (concordance correlation coefficient: 0.997) but lower agreement for inhalable dust (concordance correlation coefficient: 0.886 and accuracy: 0.896) with a significantly large mean bias (−146.9 mg/m3). Dust concentration significantly affected sampler measurements of inhalable dust and inhalable indium. Results from this study suggest that the dual IOM is a useful single sampler for simultaneous measurements of occupational exposure to respirable and inhalable indium.

Assessment of Occupational Exposure to Indium Dust for Indium-Tin-Oxide Manufacturing Workers

“…A large-scale study in Korea previously estimated the fraction of respirable indium dust ( n = 13) from the total dust ( n = 16) at 39% [ 14 ]. A comparable Japanese study revealed the mean respirable fraction in the indium manufacturing process ( n = 17) to be 38% (Total In/Respirable In 2.64) [ 15 ], and a similar study in the US revealed a mean respirable indium fraction of 30% (respirable In: 10.9 µg/m 3 ; inhalable In: 36.5 µg/m 3 ) [ 16 ], consistent with the results of this study. In contrast, in the indium-recycling plant, the proportion of respiratory indium dust was low [ 17 ].…”

Review of Workplace Based Aerosol Sampler Comparison Studies, 2004–2020

“…The Button (inhalable) sampler was studied on five occasions (5 studies; 23%) followed by the Respicon sampler (4 studies; 18%), which is capable of measuring multiple aerosol fractions. In some studies, the samplers have been referred to as different sample names, for example the IOM head with the PU foam [ 28 ] is also referred to as the IOM dual sampler [ 29 ]. In this instance this is referred to as the IOM dual sampler hereafter.…”

“…Under half of the retrieved studies assessed the respirable fraction (32%). This includes the Higgins-Dewell cyclone [ 37 , 38 ], the Aluminium SKC cyclone [ 39 , 40 ], and the GK2.69 cyclone [ 29 ]. The thoracic fraction has only been assessed in two of the retrieved studies (>9%), with the GK2.69 cyclone being used in both [ 38 , 40 ].…”

“…In 27% of the publications, multifraction samplers have also been used and compared with differing samplers. The IOM dual sampler, which measures both the inhalable and respirable fractions has been used in three publications [ 28 , 29 , 37 ]. In addition, two publications [ 40 , 41 ] have used the Respicon sampler to analyse the inhalable, respirable and thoracic fractions and one publication has used the Respicon sampler to analyse the inhalable and thoracic fractions [ 42 ].…”

“…The IOM dual sampler and the GK2.69 respirable cyclone have been compared for measuring exposure to indium and dust in an indium tin oxide manufacturing facility for the respirable fraction and the IOM dual sampler has been compared with the IOM sampler for the inhalable fraction [ 29 ]. The sampler flow rate for the IOM sampler was 2.0 L min −1 and 4.2 L min −1 for the cyclone.…”