Dhimiter Bello

Skin Exposure to Isocyanates: Reasons for Concern

Objective Isocyanates (di- and poly-), important chemicals used worldwide to produce polyurethane products, are a leading cause of occupational asthma. Respiratory exposures have been reduced through improved hygiene controls and the use of less-volatile isocyanates. Yet isocyanate asthma continues to occur, not uncommonly in settings with minimal inhalation exposure but opportunity for skin exposure. In this review we evaluate the potential role of skin exposure in the development of isocyanate asthma. Data sources We reviewed the published animal and human literature on isocyanate skin-exposure methods, workplace skin exposure, skin absorption, and the role of skin exposure in isocyanate sensitization and asthma. Data extraction We selected relevant articles from computerized searches on Medline, U.S. Environmental Protection Agency, Occupational Safety and Health Administration, National Institute for Occupational Safety and Health, and Google databases using the keywords “isocyanate,” “asthma,” “skin,” “sensitization,” and other synonymous terms, and our own extensive collection of isocyanate publications. Data synthesis Isocyanate production and use continues to increase as the polyurethane industry expands. There is substantial opportunity for isocyanate skin exposure in many work settings, but such exposure is challenging to quantify and continues to be underappreciated. Isocyanate skin exposure can occur at work, even with the use of personal protective equipment, and may also occur with consumer use of certain isocyanate products. In animals, isocyanate skin exposure is an efficient route to induce sensitization, with subsequent inhalation challenge resulting in asthma-like responses. Several lines of evidence support a similar role for human isocyanate skin exposure, namely, that such exposure occurs and can contribute to the development of isocyanate asthma in certain settings, presumably by inducing systemic sensitization. Conclusions Integrated animal and human research is needed to better understand the role of skin exposure in human isocyanate asthma and to improve diagnosis and prevention. In spite of substantial research needs, sufficient evidence already exists to justify greater emphasis on the potential risks of isocyanate skin exposure and the importance of preventing such exposures at work and during consumer use of certain isocyanate products.

Harmonization of Measurement Strategies for Exposure to Manufactured Nano-Objects; Report of a Workshop

The present paper summarizes the outcome of the discussions at the First International Scientific Workshop on Harmonization of Strategies to Measure and Analyze Exposure to (Manufactured) Nano-objects in Workplace Air that was organized and hosted by the Netherlands Organization for Applied Scientific Research (TNO) and the Institute for Occupational Safety and Health of the German Social Accident Insurance (IFA) (Zeist, The Netherlands, December 2010). It reflects the discussions by 25 international participants in the area of occupational (nano) exposure assessment from Europe, USA, Japan, and Korea on nano-specific issues related to the three identified topics: (i) measurement strategies; (ii) analyzing, evaluating, and reporting of exposure data; and (iii) core information for (exposure) data storage. Preliminary recommendations were achieved with respect to (i) a multimetric approach to exposure assessment, a minimal set of data to be collected, and basic data analysis and reporting as well as (ii) a minimum set of contextual information to be collected and reported. Other issues that have been identified and are of great interest include (i) the need for guidance on statistical approaches to analyze time-series data and on electron microscopy analysis and its reporting and (ii) the need for and possible structure of a (joint) database to store and merge data. To make progress in the process of harmonization, it was concluded that achieving agreement among researchers on the preliminary recommendations of the workshop is urgent.

Characterization of exposures to nanoscale particles and fibers during solid core drilling of hybrid carbon nanotube advanced composites.

Abstract This work investigated exposures to nanoparticles and nanofibers during solid core drilling of two types of advanced carbon nanotube (CNT)-hybrid composites: (1) reinforced plastic hybrid laminates (alumina fibers and CNT); and (2) graphite-epoxy composites (carbon fibers and CNT). Multiple real-time instruments were used to characterize the size distribution (5.6 nm to 20 μm), number and mass concentration, particle-bound polyaromatic hydrocarbons (b-PAHs), and surface area of airborne particles at the source and breathing zone. Time-integrated samples included grids for electron microscopy characterization of particle morphology and size resolved (2 nm to 20 μm) samples for the quantification of metals. Several new important findings herein include generation of airborne clusters of CNTs not seen during saw-cutting of similar composites, fewer nanofibers and respirable fibers released, similarly high exposures to nanoparticles with less dependence on the composite thickness, and ultrafine (< 5 nm) aerosol originating from thermal degradation of the composite material.

Nanoparticles from photocopiers induce oxidative stress and upper respiratory tract inflammation in healthy volunteers

Abstract Photocopiers emit large quantities of nanoparticles (NPs); however, their toxicological properties have not been studied. Here we investigate for the first time early human responses following a days exposure to NPs from photocopiers. Nine healthy subjects spent 6 h at a busy photocopy centre on 2–3 randomly selected days. Matched nasal lavage and urine samples were collected before and at different time points post-exposure. Nasal lavage samples were analysed for 14 cytokines, inflammatory cells and total protein. Urine samples were analysed for 8-hydroxydeoxyguanosine (8-OH-dG). Exposure assessment was conducted using a suite of instruments. The mean total particle number on exposure days was >5 times higher than background, with size distributions in nanoscale range (peak 30–40 nm). Following exposure, 8-OH-dG and several pro-inflammatory cytokines were elevated 2–10 folds compared with pre-exposure levels and remained elevated for up to 36 h. We conclude that NPs from photocopiers induce upper airway inflammation and oxidative stress.

Isocyanate Exposures in Autobody Shop Work: The SPRAY Study

Isocyanates, known to cause respiratory sensitization and asthma, are widely used in automotive refinishing where exposures to aliphatic polyisocyanates occur by both inhalation and skin contact. The work reported here, the characterization of isocyanate exposure in the autobody industry, was part of an epidemiologic study of workers in 37 autobody shops in Connecticut. This article describes workplaces, tasks, and controls, and outlines the frequency, duration, and intensity of isocyanate exposures. Personal air samples taken outside of respirators had median concentrations of 66.5 μg NCO/m3 for primer, 134.4 μg (NCO)/m3 for sealer, and 358.5 μg NCO/m3 for clearcoat. Forty-eight percent of primer, 66% of sealer, and 92% of clearcoat samples exceeded the United Kingdom Health and Safety Executive guideline for isocyanate, though none exceeded the National Institute for Occupational Safety and Health (NIOSH) recommended exposure limit for monomer. Nonisocyanate-containing primers and sealers are used in more than half the shops, but nonisocyanate clearcoats are rare. Eighty-two percent of personal samples taken within a spray booth exceeded the U.K. guideline: 81% of those in downdraft spray booths, 74% in semidowndraft booths, and 92% in crossdraft booths. Only 8% of shops reported that spraying is done exclusively in spray booths. All painters wore some type of respirator. In 30% of shops, painters used supplied air respirators; the rest relied on half face organic vapor cartridge respirators with N95 overspray pads. All shops provided some type of gloves, usually latex, not recommended for isocyanate protection. Despite improvements in autobody shop materials, practices, and controls, there are still opportunities for substantial exposures to isocyanates.

Physicochemical and morphological characterisation of nanoparticles from photocopiers: implications for environmental health

Abstract Several reports link printing and photocopying with genotoxicity, immunologic and respiratory diseases. Photocopiers and printers emit nanoparticles, which may be involved in these diseases. The physicochemical and morphological composition of these emitted nanoparticles, which is poorly understood and is critical for toxicological evaluations, was assessed in this study using both real-time instrumentation and analytical methods. Tests included elemental composition (40 metals), semi-volatile organics (100 compounds) and single particle analysis, using multiple high-sensitivity/resolution techniques. Identical analyses were performed on the toners and dust collected from copiers exhaust filter. Engineered nanoparticles, including titanium dioxide, iron oxide and fumed silica, and several metals were found in toners and airborne nanoscale fraction. Chemical composition of airborne nanoscale fraction was complex and reflected toner chemistry. These findings are important in understanding the origin and toxicology of such nanoparticles. Further investigation of their chemistry, larger scale exposure studies and thorough toxicological characterisation of emitted nanoparticles is needed.

Nanomaterials properties vs. biological oxidative damage: Implications for toxicity screening and exposure assessment

Biological oxidative damage (BOD) has been recognized as a key toxicity mechanism with potential as a novel global metric for nanomaterial (NM) exposure and rapid toxicity screening. A ‘Ferric reducing ability of serum (FRAS)’ assay, recently optimized by our group, was used to quantitate the degree of BOD induced by 19 diverse, commercially important NMs, including carbon blacks, fullerenes, carbon nanotubes, and titanium dioxide. This study investigated the relationship between several physico-chemical parameters of NMs and BOD and their relevance to exposure assessment and toxicity screening. FRAS-measured BOD strongly correlated with specific surface area and total content of select transition metals (especially Fe, Cr, Co, Mo and Mn). These two factors combined explained 93% of the BOD. The FRAS BOD potential of NMs appears to be a valid approach for screening purposes. These findings support the use of BOD as a metric for NM exposures.

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

Abstract 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.

Implications of in vitro dosimetry on toxicological ranking of low aspect ratio engineered nanomaterials

Abstract In vitro high throughput screening platforms based on mechanistic injury pathways are been used for hazard assessment of engineered nanomaterials (ENM). Toxicity screening and other in vitro nanotoxicology assessment efforts in essence compare and rank nanomaterials relative to each other. We hypothesize that this ranking of ENM is susceptible to dispersion and dosimetry protocols, which continue to be poorly standardized. Our objective was to quantitate the impact of dosimetry on toxicity ranking of ENM. A set of eight well-characterized and diverse low aspect ratio ENMs, were utilized. The recently developed in vitro dosimetry platform at Harvard, which includes preparation of fairly monodispersed suspensions, measurement of the effective density of formed agglomerates in culture media and fate and transport modeling was used for calculating the effective dose delivered to cells as a function of time. Changes in the dose–response relationships between the administered and delivered dose were investigated with two representative endpoints, cell viability and IL-8 production, in the human monocytic THP-1 cells. The slopes of administered/delivered dose–response relationships changed 1:4.94 times and were ENM-dependent. The overall relative ranking of ENM intrinsic toxicity also changed considerably, matching notably better the in vivo inflammation data (R2 = 0.97 versus 0.64). This standardized dispersion and dosimetry methodology presented here is generalizable to low aspect ratio ENMs. Our findings further reinforce the need to reanalyze and reinterpret in vitro ENM hazard ranking data published in the nanotoxicology literature in the light of dispersion and dosimetry considerations (or lack thereof) and to adopt these protocols in future in vitro nanotoxicology testing.

Effects of Laser Printer–Emitted Engineered Nanoparticles on Cytotoxicity, Chemokine Expression, Reactive Oxygen Species, DNA Methylation, and DNA Damage: A Comprehensive in Vitro Analysis in Human Small Airway Epithelial Cells, Macrophages, and Lymphoblasts

Background Engineered nanomaterials (ENMs) incorporated into toner formulations of printing equipment become airborne during consumer use. Although information on the complex physicochemical and toxicological properties of both toner powders and printer-emitted particles (PEPs) continues to grow, most toxicological studies have not used the actual PEPs but rather have primarily used raw toner powders, which are not representative of current exposures experienced at the consumer level during printing. Objectives We assessed the biological responses of a panel of human cell lines to PEPs. Methods Three physiologically relevant cell lines—small airway epithelial cells (SAECs), macrophages (THP-1 cells), and lymphoblasts (TK6 cells)—were exposed to PEPs at a wide range of doses (0.5–100 μg/mL) corresponding to human inhalation exposure durations at the consumer level of 8 hr or more. Following treatment, toxicological parameters reflecting distinct mechanisms were evaluated. Results PEPs caused significant membrane integrity damage, an increase in reactive oxygen species (ROS) production, and an increase in pro-inflammatory cytokine release in different cell lines at doses equivalent to exposure durations from 7.8 to 1,500 hr. Furthermore, there were differences in methylation patterns that, although not statistically significant, demonstrate the potential effects of PEPs on the overall epigenome following exposure. Conclusions The in vitro findings obtained in this study suggest that laser printer–emitted engineered nanoparticles may be deleterious to lung cells and provide preliminary evidence of epigenetic modifications that might translate to pulmonary disorders. Citation Pirela SV, Miousse IR, Lu X, Castranova V, Thomas T, Qian Y, Bello D, Kobzik L, Koturbash I, Demokritou P. 2016. Effects of laser printer–emitted engineered nanoparticles on cytotoxicity, chemokine expression, reactive oxygen species, DNA methylation, and DNA damage: a comprehensive in vitro analysis in human small airway epithelial cells, macrophages, and lymphoblasts. Environ Health Perspect 124:210–219; http://dx.doi.org/10.1289/ehp.1409582