Abstract
Inhalation exposures to nanoparticles (NPs) from printers and photocopiers have been associated with upper airway and systemic inflammation, increased blood pressure, and cases of autoimmune and respiratory disorders. In this study we investigate oxidative stress induced by exposures to copier-emitted nanoparticles using a panel of urinary oxidative stress (OS) biomarkers representing DNA damage (8-hydroxydeoxyguanosine, 8-OHdG; 8-hydroxyguanosine, 8-OHG; 5-hydroxymethyl uracil 5-OHMeU), lipid peroxidation (8-isoprostane; 4-hydroxynonenal, HNE), and protein oxidation biomarkers (o-tyrosine, 3-chlorotyrosine, and 3-nitrotyrosine) under conditions of acute (single 6 h exposure, 9 volunteers, 110 urine samples) and chronic exposures (6 workers, 11 controls, 81 urine samples). Urinary biomarkers were quantified with liquid chromatography–tandem mass spectrometry after solid phase extraction sample cleanup. 8-OHdG, 8-OHG, 8-isoprostane, and HNE were significantly elevated in both the acute and chronic exposure study participants relative to the controls. In the acute exposure study, the geometric mean ratios post-/pre-exposure were 1.42, 1.10, 2.0, and 2.25, respectively. Urinary 8-OHG and HNE increased with time to at least 36 h post-exposure (post-/pre-exposure GM ratios increased to 3.94 and 2.33, respectively), suggesting slower generation and/or urinary excretion kinetics for these biomarkers. In chronically exposed operators, the GM ratios of urinary biomarkers relative to controls ranged from 1.52 to 2.94, depending on the biomarker. O-Tyrosine and 5-OHMeU biomarkers were not significantly different from the controls. 3-chlorotyrosine and 3-nitrotyrosine were not detected in the urine samples. We conclude that NPs from photocopiers induce systemic oxidative stress by damaging DNA, RNA, and lipids. Urinary levels of 8-OHdG, 8-OHG, HNE, and 8-isoprostane were orders of magnitude higher than in nanocomposite processing workers, comparable to nano titanium dioxide and fiberglass manufacturing workers, but much lower than in shipyard welding and carbon nanotube synthesis workers. Biomarkers 8-OHdG, 8-OHG, 8-isoprostane, and HNE appear to be more sensitive and robust urinary biomarkers for monitoring oxidative stress to NPs from photocopiers.
Highlights
Toner-based laser printing and photocopying is a multi-billion-dollar industry that is growing at an annual rate of 5.8% [1]
We investigated the kinetics of upper airway inflammation in a group of nine healthy volunteers following a single 6 h acute exposure over 36 h, as well as chronic inflammation following repeated exposures in six copier operators [18,19]
We investigated a panel of urinary biomarkers of oxidative stress (OS) in two groups of individuals—health volunteers exposed once to copier emitted nanoparticles [18]
Summary
Toner-based laser printing and photocopying is a multi-billion-dollar industry that is growing at an annual rate of 5.8% [1]. Nanomaterials 2022, 12, 715 to improve printing quality [2,3,4]. It is well-established that printing and photocopying results in the emission of high numbers of nanoparticles [5,6] that seem to be formed primarily from the condensation of semi-volatile organic compounds (SVOCs) evaporated from the toner during the printing process [7,8,9]. The composition of the nanoscale fraction (PM0.1 or particulate matter less than 0.1 μm aerodynamic diameter) generated from the photocopiers has been documented in three comprehensive studies [4,11,12]
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