Emissions of Liquid Crystal Monomers from Obsolete Smartphone Screens in Indoor Settings: Characteristics and Human Exposure Risk

Abstract

Liquid crystal monomers (LCMs) have been found to accumulate in indoor environments, but the emission kinetics of LCMs from electronic devices are not well understood. Leakage from damaged liquid crystal displays may be an important mechanism for LCMs to enter the environment and become potential health hazards to humans. To address this issue, we conducted chamber experiments to characterize the emissions of LCMs from obsolete smartphone screens and estimated the doses of residential and occupational exposures to LCMs. The emission rates of the detected LCMs were in the ranges of 0.1–7 μg m–2 h–1 at 80 °C, 0.05–7 μg m–2 h–1 at 60 °C, and 0.002–0.2 μg m–2 h–1 at 25 °C. Liquid crystal monomers with large molecular weights and low volatilities tended to accumulate at screen surfaces and were re-emitted at elevated temperatures, leading to high emission rates of heavy LCMs upon thermal treatment. The estimated doses of residential and occupational exposures to individual LCMs were 0.0001–0.009 and 0.007–2 ng kg–1 d–1, respectively. As LCMs are potentially carcinogenic based on in silico assessments, LCMs emitted from obsolete smartphones in indoor settings may become human health hazards.

Health Risks Posed by Dermal and Inhalation Exposure to High Concentrations of Chlorinated Paraffins Found in Soft Poly(vinyl chloride) Curtains

“…Models for evaluating the behaviors of semivolatile organic compounds (SVOCs) using mass balance theories have been developed dramatically recently, − and many are simple to use and effectively predict the behaviors of SVOCs in the environment. , Models were therefore used here to investigate the risks posed by CPs in soft PVC curtains used in indoor environments. Few studies have been conducted on the behaviors of CPs in the environment because of the complexities of CP mixtures, so statistical models and simulation experiments were used in this study to comprehensively assess the behaviors of CPs in soft PVC curtains in the indoor environment and the health risks posed.…”

Release Behavior of Liquid Crystal Monomers from Waste Smartphone Screens: Occurrence, Distribution, and Mechanistic Modeling

“…These results also explained the previous laboratory study for underestimation of released LCMs compositions escaping from obsolete smartphone screens in all examined temperature ranges due to this similar overestimation of the corresponding used K m‑a. Different from the SVOCs encapsulated in building materials and furniture, LCM mixtures were physically embedded in the thin film layer between two glass sheets of the LL component. Therefore, the release of LCMs from LL could not be fully controlled by internal diffusion .…”

“…These findings suggested that the migration pattern for individual LCM from LL to LGP and SP could potentially follow different diffusion-partitioning behaviors, which were possibly influenced by different structures of LGP and SP, as well as different physiochemical properties of LCMs, such as molecular weights, vapor pressure, P L and K oa . 11,21 In addition, 2O3cHdFP and 3VbcH were the highest compositions of F-LCMs and NF-LCMs in all three disassembled parts. Correlation analyses showed that the AP of detected LCMs were significantly correlated between LL and LGP (Pearson's r = 0.976; p < 0.05), as well as LL and SP (Pearson's r = 0.957; p < 0.05) (Figure 2b), indicating that AP might also play an important role for the diffusion and release of LCMs.…”

“…The environmental emission test conducted in the sealed chamber could not differentiate between the involved processes, such as internal diffusion, interfacial diffusion, and/or surface sorption . Therefore, the test data cannot be directly used to determine the model parameters of diffusion-partitioning models. , To evaluate the diffusion-partitioning behaviors of LCM release from various components of dismantled waste screens in realistic environments, the occurrence of LCMs in both disassembled parts of SP and light guide plate (LGP) can be used to verify the LCM release. In detail, the LCD panel is the main part of waste smartphone screens after primary dismantling, , which is a complex multilayer assembly, typically consisting of a glass substrate, backlight modules, and a metal frame .…”

“…In a previous study, Shen et al suggested that air could serve as an important temporary storage and transmission medium for released LCMs, as these compounds predominantly partition to the gas phase. 11 Since LCM mixtures were physically sandwiched in the LL component and their release was not constrained by solidphase diffusion within screens, 21 it could be reasonable to assume a gas-like structure for the liquid-crystal layer. (3) The assumption of the gas/particle approach could be utilized to incorporate the parameter of AP into the developed diffusionpartitioning model that was developed to explain the release of LCMs from waste smartphone screens, providing a robust theoretical basis for these developed equations (eqs 1−14).…”