Smartphones, computer monitors, laptops and televisions all typically use thin film transistor liquid crystal display (TFT-LCD) panels to display visual content. In many respects, therefore, TFT-LCD have profoundly shaped our culture to become an essential component of modern human life. The global TFT-LCD market is anticipated to be valued at over £150 billion, by 2024.
For several years, however, it has been speculated that aspects of TFT-LCD factory production processes (array, cell and module assembly) expose workers to dangerous levels of volatile organic compounds (VOC), e.g. benzene and formaldehyde, which are highly reactive and potentially harmful molecules, with known adverse health effects.
In 2009, Chang et al investigated cases of kidney dysfunction among exposed TFT-LCD factory workers, before going on, in 2020, to look into prevalence of hypertension (high blood pressure) among the same.
What about post-manufacture? Does the posited association between VOC and TFT-LCD products dissipate for end-user consumers?
Chemists are concerned that this may not be the case, prompting researchers at the University of Toronto to explore in greater detail.
VOC are commonly emitted in indoor environments by plants, furniture, carpets and wood flooring, kitchen countertops, cleaning products and disinfectants, air fresheners, cosmetics, shower gels, paint, ink, adhesives, varnishes, sealants, etc.
Despite extensive public use, the impact of TFT-LCD-containing technology on indoor air quality is comparatively unknown.
To see whether TFT-LCD panels release airborne constituents, proton-transfer reaction mass spectrometry was employed to identify the chemical signatures of compounds in two types of sample:
- Regular indoor air.
- Indoor air collected near the surface of a TFT-LCD screen (a new computer monitor, a used laptop and a new television).
These signatures were then cross-referenced against a list of 362 liquid crystal monomers (LCM) used in TFT-LCD fabrication methods (so-called ‘building block chemicals’), around 90 of which were labelled as ‘persisting organic pollutants’, a few years ago.
Publishing findings in the PNAS (Proceedings of the National Academy of Sciences) journal, they revealed that TFT-LCD screens do exude ‘significant levels’ of VOC, which are likely derived from LCM used to make liquid crystals.
More specifically, the Canadian team disclosed that over 30 VOC and 10 LCM were ‘heavily emitted into the air exposed to the screen’, including ‘extremely reactive’ isoprene and acetic acid.
According to the study authors, the results indicate that TFT-LCD screens are a ‘previously unrecognised’ and ‘potentially important’ source for indoor VOC. Furthermore, they accentuate the need to better appreciate the ‘environmental fate’ and ‘toxicological properties’ of VOC emissions from TFT-LCD screens.
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