Negative Effect of Long-Term Inhalation of Toner on Formation of 8-Hydroxydeoxyguanosine in DNA in the Lungs of Rats In Vivo

Effects of toner-handling work on respiratory function, chest X-ray findings, and biomarkers of inflammation, allergy, and oxidative stress: a 10-year prospective Japanese cohort study

Background

Exposure to toner, a substance used in photocopiers and printers, has been associated with siderosilicosis and other adverse effects. However, these findings are limited, and there is insufficient evidence on the long-term effects of toner exposure. Using longitudinal analysis, this study aimed to examine the effects of work involving toner exposure on the respiratory system over time.

Methods

We conducted a prospective cohort study in a Japanese toner and copier manufacturing enterprise between 2003 and 2013. The cohort included a total of 1468 workers, which comprised 887 toner-handling workers and 581 non-toner-handling workers. We subdivided the toner-handling workers into two groups according to the toner exposure concentration, based on the baseline survey in 2003. We compared the chest X-ray results, respiratory function indicators, and serum and urinary biomarkers of inflammation, allergy, and oxidative stress among the three groups: high-concentration toner exposure group, low-concentration toner exposure group, and non-toner-handling group. To consider the effects of individual differences on the longitudinal data, we used a linear mixed model.

Results

Similar chest X-ray results, the biomarkers, and most of the respiratory function indicators were found in the non-toner-handling and toner-handling groups. There were no significant yearly changes in the percentage of vital capacity (%VC) in the high-concentration toner exposure group, while there was a significant yearly increase in %VC in the low-concentration toner exposure group and non-toner-handling group. The yearly change in each group was as follows: high-concentration toner exposure group, − 0.11% (95% confidence interval [CI], − 0.29 to 0.08; P = 0.250); low-concentration toner exposure group, 0.13% (95% CI, 0.09–0.17; P < 0.001); and non-toner-handling group, 0.15% (95% CI, 0.01–0.20; P < 0.001).

Conclusions

In our 10-year prospective study, toner-handling work was not associated with the deterioration of respiratory function and an increase in biomarker values for inflammation, allergy, and oxidative stress. This finding suggests that toner-handling work is irrelevant to the onset of respiratory disease and has minimal adverse effects on the respiratory system under a well-managed work environment.

Supplementary Information

Supplementary information accompanies this paper at10.1186/s12890-020-01320-6.

Pilot deep RNA sequencing of worker blood samples from Singapore printing industry for occupational risk assessment

Several engineered nanomaterials (ENMs) are used in toner-based printing equipment (TPE) including laser printers and photocopiers to improve toner performance. High concentration of airborne nanoparticles due to TPE emissions has been documented in copy centers and chamber studies. Recent animal inhalation studies by our group suggested exposure to laser printer-emitted nanoparticles (PEPs) increased cardiovascular risk by impairing ventricular performance and inducing hypertension and arrhythmia, consistent with global transcriptomic and metabolomic profiling results. There has been no genome-wide transcriptomic analysis of workers exposed to TPE emissions to systematically assess the occupational exposure health risks. In this pilot study, deep RNA sequencing of blood samples of workers in two printing companies in Singapore was performed. The genome-scale analysis of the blood samples from TPE exposed workers revealed perturbed transcriptional activities related to inflammatory and immune responses, metabolism, cardiovascular impairment, neurological diseases, oxidative stress, physical morphogenesis/deformation, and cancer, when compared with the control peers (office workers). Many of these disease risks associated with particle inhalation exposures in such work environments were consistent with the observation from the PEPs rat inhalation studies. In particular, the cell adhesion molecules (CAMs) was a top significantly perturbed pathway in blood samples from exposed workers compared with the office workers in both companies. The protein expression of sICAM was verified in plasma of exposed workers, showing a positive correlation with daily average nanoparticle concentration in indoor air measured in these two companies. Larger scale genomic and molecular epidemiology studies in copier operators are warranted in order to assess potential risks from such particulate matter exposures.

Integrated Transcriptomics, Metabolomics, and Lipidomics Profiling in Rat Lung, Blood, and Serum for Assessment of Laser Printer-Emitted Nanoparticle Inhalation Exposure-Induced Disease Risks

Laser printer-emitted nanoparticles (PEPs) generated from toners during printing represent one of the most common types of life cycle released particulate matter from nano-enabled products. Toxicological assessment of PEPs is therefore important for occupational and consumer health protection. Our group recently reported exposure to PEPs induces adverse cardiovascular responses including hypertension and arrythmia via monitoring left ventricular pressure and electrocardiogram in rats. This study employed genome-wide mRNA and miRNA profiling in rat lung and blood integrated with metabolomics and lipidomics profiling in rat serum to identify biomarkers for assessing PEPs-induced disease risks. Whole-body inhalation of PEPs perturbed transcriptional activities associated with cardiovascular dysfunction, metabolic syndrome, and neural disorders at every observed time point in both rat lung and blood during the 21 days of exposure. Furthermore, the systematic analysis revealed PEPs-induced transcriptomic changes linking to other disease risks in rats, including diabetes, congenital defects, auto-recessive disorders, physical deformation, and carcinogenesis. The results were also confirmed with global metabolomics profiling in rat serum. Among the validated metabolites and lipids, linoleic acid, arachidonic acid, docosahexanoic acid, and histidine showed significant variation in PEPs-exposed rat serum. Overall, the identified PEPs-induced dysregulated genes, molecular pathways and functions, and miRNA-mediated transcriptional activities provide important insights into the disease mechanisms. The discovered important mRNAs, miRNAs, lipids and metabolites may serve as candidate biomarkers for future occupational and medical surveillance studies. To the best of our knowledge, this is the first study systematically integrating in vivo, transcriptomics, metabolomics, and lipidomics to assess PEPs inhalation exposure-induced disease risks using a rat model.

A Cohort Study on Respiratory Symptoms and Diseases Caused by Toner-Handling Work: Longitudinal Analyses from 2003 to 2013

The purpose of this study was to examine the effects of toner-handling work on respiratory symptoms and diseases. We conducted a prospective cohort study of 1468 workers between 2003 and 2013. The cohort included 887 toner-handling workers and 581 non-toner-handling workers, employed in one toner and copier manufacturing enterprise. Toner-handling workers were subdivided into two groups based on the 8-h time-weighted average toner exposure concentration for each work category in the baseline survey. We compared the incidence of respiratory disease and longitudinal changes in the prevalence of subjective respiratory symptoms among three groups, as follows: High-concentration toner exposure group, the low-concentration toner exposure group, and a control group. The incidence of respiratory disease and changes in the prevalence of subjective respiratory symptoms were not significantly different between the non-toner-handling group and the toner-handling group. In contrast, the odds ratio for yearly changes in the prevalence of wheezing without asthmatic response was significantly lower in the high-concentration toner exposure group than in the control group. At the study site, dust scattering was well controlled and workers used respiratory protection appropriately. These findings suggest that toner-handling work had little adverse effect on respiratory function in a work environment with sufficiently controlled ventilation.

A cohort study of the acute and chronic respiratory effects of toner exposure among handlers: a longitudinal analyses from 2004 to 2013

This study examines the acute and chronic respiratory effects of toner exposure based on markers for interstitial pneumonia, oxidative stress and pulmonary function tests. A total of 112 subjects working in a Japanese toner and photocopier manufacturing company participated in this study in 2004. We annually conducted personal exposure measurements, pulmonary function tests, chest X-ray examinations, biomarkers, and questionnaires on respiratory symptoms to the subjects. We report in this paper the results of the analysis of combined annual survey point data from 2004 to 2008 and data from three annual survey points, 2004, 2008, and 2013. During these survey periods, we observed that none of subjects had a new onset of respiratory disease or died of such a disease. In both the analyses, there were no significant differences in each biomarker and pulmonary function tests within the subjects, nor between a toner-handling group and a non-toner-handling group, except for a few results on pulmonary function tests. The findings of this study suggest that there were no acute and chronic respiratory effects of toner exposure in this cohort group, although the number of subjects was small and the level of toner exposure in this worksite was low.

Development and characterization of an exposure platform suitable for physico-chemical, morphological and toxicological characterization of printer-emitted particles (PEPs)

An association between laser printer use and emissions of particulate matter (PM), ozone and volatile organic compounds has been reported in recent studies. However, the detailed physico-chemical, morphological and toxicological characterization of these printer-emitted particles (PEPs) and possible incorporation of engineered nanomaterials into toner formulations remain largely unknown. In this study, a printer exposure generation system suitable for the physico-chemical, morphological, and toxicological characterization of PEPs was developed and used to assess the properties of PEPs from the use of commercially available laser printers. The system consists of a glovebox type environmental chamber for uninterrupted printer operation, real-time and time-integrated particle sampling instrumentation for the size fractionation and sampling of PEPs and an exposure chamber for inhalation toxicological studies. Eleven commonly used laser printers were evaluated and ranked based on their PM emission profiles. Results show PM peak emissions are brand independent and varied between 3000 to 1 300 000 particles/cm³, with modal diameters ranging from 49 to 208 nm, with the majority of PEPs in the nanoscale (<100 nm) size. Furthermore, it was shown that PEPs can be affected by certain operational parameters and printing conditions. The release of nanoscale particles from a nano-enabled product (printer toner) raises questions about health implications to users. The presented PEGS platform will help in assessing the toxicological profile of PEPs and the link to the physico-chemical and morphological properties of emitted PM and toner formulations.

Small airway epithelial cells exposure to printer-emitted engineered nanoparticles induces cellular effects on human microvascular endothelial cells in an alveolar-capillary co-culture model

The printer is one of the most common office equipment. Recently, it was reported that toner formulations for printing equipment constitute nano-enabled products (NEPs) and contain engineered nanomaterials (ENMs) that become airborne during printing. To date, insufficient research has been performed to understand the potential toxicological properties of printer-emitted particles (PEPs) with several studies using bulk toner particles as test particles. These studies demonstrated the ability of toner particles to cause chronic inflammation and fibrosis in animal models. However, the toxicological implications of inhalation exposures to ENMs emitted from laser printing equipment remain largely unknown. The present study investigates the toxicological effects of PEPs using an in vitro alveolar-capillary co-culture model with Human Small Airway Epithelial Cells (SAEC) and Human Microvascular Endothelial Cells (HMVEC). Our data demonstrate that direct exposure of SAEC to low concentrations of PEPs (0.5 and 1.0 µg/mL) caused morphological changes of actin remodeling and gap formations within the endothelial monolayer. Furthermore, increased production of reactive oxygen species (ROS) and angiogenesis were observed in the HMVEC. Analysis of cytokine and chemokine levels demonstrates that interleukin (IL)-6 and MCP-1 may play a major role in the cellular communication observed between SAEC and HMVEC and the resultant responses in HMVEC. These data indicate that PEPs at low, non-cytotoxic exposure levels are bioactive and affect cellular responses in an alveolar-capillary co-culture model, which raises concerns for potential adverse health effects.

Pulmonary toxicity of printer toner following inhalation and intratracheal instillation

The pulmonary effects of a finished toner were evaluated in intratracheal instillation and inhalation studies, using toners with external additives (titanium dioxide nanoparticles and amorphous silica nanoparticles). Rats received an intratracheal dose of 1 mg or 2 mg of toner and were sacrificed at 3 days, 1 week, 1 month, 3 months and 6 months. The toner induced pulmonary inflammation, as evidenced by a transient neutrophil response in the low-dose groups and persistent neutrophil infiltration in the high-dose groups. There were increased concentrations of heme oxygenase-1 (HO-1) as a marker of oxidative stress in the bronchoalveolar lavage fluid (BALF) and the lung. In a 90-day inhalation study, rats were exposed to well-dispersed toner (mean of MMAD: 3.76 µm). The three mass concentrations of toner were 1, 4 and 16 mg/m(3) for 13 weeks, and the rats were sacrificed at 6 days and 91 days after the end of the exposure period. The low and medium concentrations did not induce neutrophil infiltration in the lung of statistical significance, but the high concentration did, and, in addition, upon histopathological examination not only showed findings of inflammation but also of fibrosis in the lung. Taken together, the results of our studies suggest that toners with external additives lead to pulmonary inflammation and fibrosis at lung burdens suggest beyond the overload. The changes observed in the pulmonary responses in this inhalation study indicate that the high concentration (16 mg/m(3)) is an LOAEL and that the medium concentration (4 mg/m(3)) is an NOAEL.

Effects of copy center particles on the lungs: a toxicological characterization using a Balb/c mouse model

CONTEXT

Printers and photocopiers release respirable particles into the air. Engineered nanomaterials (ENMs) have been recently incorporated into toner formulations but their potential toxicological effects have not been well studied.

OBJECTIVE

To evaluate the biological responses to copier-emitted particles in the lungs using a mouse model.

METHODS

Particulate matter (PM) from a university copy center was sampled and fractionated into three distinct sizes, two of which (PM0.1 and PM0.1-2.5) were evaluated in this study. The particles were extracted and dispersed in deionized water and RPMI/10% FBS. Hydrodynamic diameter and zeta potential were evaluated by dynamic light scattering. The toxicological potential of these particles was studied using 8-week-old male Balb/c mice. Mice were intratracheally instilled with 0.2, 0.6, 2.0 mg/kg bw of either the PM0.1 and PM0.1-2.5 size fractions. Fe2O3 and welding fumes were used as comparative materials, while RPMI/10% FBS was used as the vehicle control. Bronchoalveolar lavage (BAL) was performed 24 hours post-instillation. The BAL fluid was analyzed for total and differential cell counts, and biochemical markers of injury and inflammation.

RESULTS

Particle size- and dose-dependent pulmonary effects were found. Specifically, mice instilled with PM0.1 (2.0 mg/kg bw) had significant increases in neutrophil number, lactate dehydrogenase and albumin compared to vehicle control. Likewise, pro-inflammatory cytokines were elevated in mice exposed to PM0.1 (2.0 mg/kg bw) compared to other groups.

CONCLUSION

Our results indicate that exposure to copier-emitted nanoparticles may induce lung injury and inflammation. Further exposure assessment and toxicological investigations are necessary to address this emerging environmental health pollutant.

Oxidatively damaged DNA in animals exposed to particles

Exposure to combustion-derived particles, quartz and asbestos is associated with increased levels of oxidized and mutagenic DNA lesions. The aim of this survey was to critically assess the measurements of oxidatively damaged DNA as marker of particle-induced genotoxicity in animal tissues. Publications based on non-optimal assays of 8-oxo-7,8-dihydroguanine by antibodies and/or unrealistically high levels of 8-oxo-7,8-dihydroguanine (suggesting experimental problems due to spurious oxidation of DNA) reported more induction of DNA damage after exposure to particles than did the publications based on optimal methods. The majority of studies have used single intracavitary administration or inhalation with dose rates exceeding the pulmonary overload threshold, resulting in cytotoxicity and inflammation. It is unclear whether this is relevant for the much lower human exposure levels. Still, there was linear dose-response relationship for 8-oxo-7,8-dihydroguanine in lung tissue without obvious signs of a threshold. The dose-response function was also dependent on chemical composition and other characteristics of the administered particles, whereas dependence on species and strain could not be equivocally determined. Roles of cytotoxicity or inflammation for oxidatively induced DNA damage could not be documented or refuted. Studies on exposure to particles in the gastrointestinal tract showed consistently increased levels of 8-oxo-7,8-dihydroguanine in the liver. Collectively, there is evidence from animal experimental models that both pulmonary and gastrointestinal tract exposure to particles are associated with elevated levels of oxidatively damaged DNA in the lung and internal organs. However, there is a paucity of studies on pulmonary exposure to low doses of particles that are relevant for hazard/risk assessment.

State of toner exposure of workers who handle toners

OBJECTIVES

The aim of this study was to ascertain the actual state of toner exposure of workers who handle toner.

METHODS

Personal exposure measurements were conducted on workers handling toner in which the respirable dust (RD) concentration by work type was determined. Targeted work types consisted of "machine recycling", "toner manufacturing", "toner research/development", "machine design/development" and "servicing." The implementation period lasted from April 2003 to March 2011, and measurements were conducted annually. The measurement method conformed to the Japanese Working Environment Measurement Standards (new standards adopted starting in 2005).

RESULTS

Comparing the RD concentrations for fiscal year 2003 by work, significant differences were found between machine recycling and the other four work types, as well as in toner manufacturing and the other four work types. Similarly, based on the new legislative standards applied in Japan from fiscal year 2005, significant differences were found between machine recycling and the other four work types, as well as in toner manufacturing and the other four work types.

DISCUSSION

It is clear that workers engaged in machine recycling and toner manufacturing are exposed to toner, and that a certain level of exposure is continuing. Although it cannot be said that workers involved in toner research/development, machine design/development and servicing have no toner exposure, the concentration is of an extremely low level.

CONCLUSIONS

At present, toner exposure levels by work type can be divided into two groups-one consisting of machine recycling and toner manufacturing, and the other consisting of toner research/development, machine design/development and servicing.

Investigation of gene expression of MMP-2 and TIMP-2 mRNA in rat lung in inhaled nickel oxide and titanium dioxide nanoparticles

In order to investigate whether or not dispersed nanoparticles have an effect of inflammation and fibrosis on animals, we developed a nanoparticle generation system and examined the gene expression of matrix metalloproteinase (MMP) and tissue inhibitor matrix proteinase (TIMP) in rat lung containing inhaled nickel oxide (NiO) or titanium dioxide (TiO(2)) nanoparticles. In both experiments, Wistar male rats were exposed to NiO or TiO(2) nanoparticles for 4 wk (6 h/day). The geometric mean diameters of NiO and TiO(2) in the chamber were 139 ± 12 nm and 51 ± 9 nm, respectively. The average concentration of the particle number of NiO and TiO(2) was 1.0E+05 /cm(3) and 2.8E+05 /cm(3), respectively. At 4 d, 1 and 3 months after the end of the inhalation, the rats exposed to these particles were sacrificed and the gene expressions of MMP-2, TIMP-2 and type I collagen were measured using RT-PCR. Pathological finding revealed that there was minimum inflammation with nickel oxide only at 4 d and no change with titanium oxide. However, there were no changes of the gene expression of MMP-2, TIMP-2, and type I collagen in either the NiO or TiO(2) exposure groups. In this study, inhalation of nickel oxide and titanium dioxide nanoparticles did not induce the gene expression of MMP-2 and TIMP-2 mRNA in rat lungs.

[New investigation of the effect of toner and its by-products on human health and occupational health management of toner]

We need a new investigation of the effect of not only toner but also of its by-products on human health, because of the generation of fine particles and the release of volatile organic compounds (VOC) in the process of photocopy. Therefore, we gathered epidemiological and animal data on toner and its by-products, and examined the occupational health management of toner. We examined the effect of carbonblack as the main component of toner, and titanium dioxide and amorphous silica as surface-adhesive nanomaterials, and VOC on human health, and reviewed them. We summarize the results as follows. 1) High sensitive c-reactive protein in serum, 8-hydroxydeoxyguanosine in urine, and heart rate variability (HRV) are useful for biological monitoring of exposure to toner and its by-products. 2) Particle number concentrations have been often measured by scanning mobility particle sizer (SMPS) compared with other apparatus, although this is not measurement gold standard. Taken together, we have examined whole occupational health management of toner and its by-products.