Chemical composition of nanoparticles released from thermal cutting of polystyrene foams and the associated isomerization of hexabromocyclododecane (HBCD) diastereomers

Abstract

Polystyrene foams have various applications, and cutting of them is usually performed with a heated metal wire. However, it has recently been reported that micro- and nanoparticles are released by such thermal cutting at a rate of a few billion particles per second, and these particles have a high likelihood of getting into the respiratory system of the operator. HBCD, as the additive flame retardant, can also be released and is mostly incorporated into the emitted particles. The chemical composition of the emitted particles was investigated in more detail in this study. Samples were collected by a cascade impactor during the thermal cutting of expanded (EPS) and extruded (XPS) polystyrene foam. Samples from three impactor stages were analyzed by GC-MS for their overall chemical compositions. Both particulate and gaseous samples were analyzed by LC-MS/MS for the amount of HBCD diastereomers. It was found that larger particles contain a significantly higher percentage of compounds with high boiling points. The comparison of the HBCD diastereomer patterns in EPS foam and the emitted particles revealed that isomerization occurred among the HBCD diastereomers. The average α-HBCD fractions were 14% and 60% in the EPS foam and emitted particles, respectively. In contrast, the corresponding average γ-HBCD fractions were 83% and 30%. Thermal cutting led to the conversion of a large fraction of γ-HBCD to α- HBCD, which is relatively stable and bio-accumulative. The diastereomer conversion was much more significant in the particles than in the gas emitted from EPS thermal cutting. © Taiwan Association for Aerosol Research.