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Shvedova A.A.,NIOSH
American journal of physiology. Lung cellular and molecular physiology | Year: 2014

The hallmark geometric feature of single-walled carbon nanotubes (SWCNT) and carbon nanofibers (CNF), high length to width ratio, makes them similar to a hazardous agent, asbestos. Very limited data are available concerning long-term effects of pulmonary exposure to SWCNT or CNF. Here, we compared inflammatory, fibrogenic, and genotoxic effects of CNF, SWCNT, or asbestos in mice 1 yr after pharyngeal aspiration. In addition, we compared pulmonary responses to SWCNT by bolus dosing through pharyngeal aspiration and inhalation 5 h/day for 4 days, to evaluate the effect of dose rate. The aspiration studies showed that these particles can be visualized in the lung at 1 yr postexposure, whereas some translocate to lymphatics. All these particles induced chronic bronchopneumonia and lymphadenitis, accompanied by pulmonary fibrosis. CNF and asbestos were found to promote the greatest degree of inflammation, followed by SWCNT, whereas SWCNT were the most fibrogenic of these three particles. Furthermore, SWCNT induced cytogenetic alterations seen as micronuclei formation and nuclear protrusions in vivo. Importantly, inhalation exposure to SWCNT showed significantly greater inflammatory, fibrotic, and genotoxic effects than bolus pharyngeal aspiration. Finally, SWCNT and CNF, but not asbestos exposures, increased the incidence of K-ras oncogene mutations in the lung. No increased lung tumor incidence occurred after 1 yr postexposure to SWCNT, CNF, and asbestos. Overall, our data suggest that long-term pulmonary toxicity of SWCNT, CNF, and asbestos is defined, not only by their chemical composition, but also by the specific surface area and type of exposure. Source


Galinsky T.,NIOSH
Rehabilitation nursing : the official journal of the Association of Rehabilitation Nurses | Year: 2010

This study used surveys from 677 home healthcare aides and nurses to explore factors associated with assaults by patients. Among respondents, 4.6% reported one or more patient assaults (being hit, kicked, pinched, shoved, or bitten) during the past year. Logistic regression analysis examined associations between several potential risk factors and assaults. Three factors were significant, including having one or more patients with dementia (OR = 4.31, 95% CI 1.47-12.67), routinely handling patients (OR = 8.48, 95% CI 1.89-37.94), and perceiving threats of violence by others in and around patients' homes (OR = 4.45, 95% CI 1.75-11.32). Assaults were not significantly associated with worker age, gender, race, job title, hours of work, or use of needles during patient care. Assaulted workers and workers who perceived threats of violence by others were significantly more likely to have shortened home care visits. More detailed research is needed to confirm these results and evaluate methods to reduce assault risk. Source


Castranova V.,NIOSH | Schulte P.A.,U.S. National Institute for Occupational Safety and Health | Zumwalde R.D.,U.S. National Institute for Occupational Safety and Health
Accounts of Chemical Research | Year: 2013

Carbon nanotubes (CNTs) are carbon atoms arranged in a crystalline graphene lattice with a tubular morphology. CNTs exhibit high tensile strength, possess unique electrical properties, are durable, and can be functionalized. These properties allow applications as structural materials, in electronics, as heating elements, in batteries, in the production of stain-resistant fabric, for bone grafting and dental implants, and for targeted drug delivery. Carbon nanofibers (CNFs) are strong, flexible fibers that are currently used to produce composite materials.Agitation can lead to aerosolized CNTs and CNFs, and peak airborne particulate concentrations are associated with workplace activities such as weighing, transferring, mixing, blending, or sonication. Most airborne CNTs or CNFs found in workplaces are loose agglomerates of micrometer diameter. However, due to their low density, they linger in workplace air for a considerable time, and a large fraction of these structures are respirable.In rat and mouse models, pulmonary exposure to single-walled carbon nanotubes (SWCNTs), multi-walled carbon nanotubes (MWCNTs), or CNFs causes the following pulmonary reactions: acute pulmonary inflammation and injury, rapid and persistent formation of granulomatous lesions at deposition sites of large CNT agglomerates, and rapid and progressive alveolar interstitial fibrosis at deposition sites of more dispersed CNT or CNF structures.Pulmonary exposure to SWCNTs can induce oxidant stress in aortic tissue and increases plaque formation in an atherosclerotic mouse model. Pulmonary exposure to MWCNTs depresses the ability of coronary arterioles to respond to dilators. These cardiovascular effects may result from neurogenic signals from sensory irritant receptors in the lung. Pulmonary exposure to MWCNTs also upregulates mRNA for inflammatory mediators in selected brain regions, and pulmonary exposure to SWCNTs upregulates the baroreceptor reflex. In addition, pulmonary exposure to MWCNTs may induce levels of inflammatory mediators in the blood, which may affect the cardiovascular system. Intraperitoneal instillation of MWCNTs in mice has been associated with abdominal mesothelioma. MWCNTs deposited in the distal alveoli can migrate to the intrapleural space, and MWCNTs injected in the intrapleural space can cause lesions at the parietal pleura. However, further studies are required to determine whether pulmonary exposure to MWCNTs can induce pleural lesions or mesothelioma.In light of the anticipated growth in the production and use of CNTs and CNFs, worker exposure is possible. Because pulmonary exposure to CNTs and CNFs causes inflammatory and fibrotic reactions in the rodent lung, adverse health effects in workers represent a concern. NIOSH has conducted a risk assessment using available animal exposure-response data and is developing a recommended exposure limit for CNTs and CNFs.Evidence indicates that engineering controls and personal protective equipment can significantly decrease workplace exposure to CNTs and CNFs. Considering the available data on health risks, it appears prudent to develop prevention strategies to minimize workplace exposure. These strategies would include engineering controls (enclosure, exhaust ventilation), worker training, administrative controls, implementation of good handling practices, and the use of personal protective equipment (such as respirators) when necessary. NIOSH has published a document containing recommendations for the safe handling of nanomaterials. © This article not subject to U.S. Copyright. Published 2012 by the American Chemical Society. Source


Wang X.,University of California at Los Angeles | Xia T.,University of California at Los Angeles | Ntim S.A.,New Jersey Institute of Technology | Ji Z.,University of California at Los Angeles | And 6 more authors.
ACS Nano | Year: 2010

In vivo studies have demonstrated that the state of dispersion of carbon nanotubes (CNTs) plays an important role in generating adverse pulmonary effects. However, little has been done to develop reproducible and quantifiable dispersion techniques to conduct mechanistic studies in vitro. This study was to evaluate the dispersion of multiwalled carbon nanotubes (MWCNTs) in tissue culture media, with particular emphasis on understanding the forces that govern agglomeration and how to modify these forces. Quantitative techniques such as hydrophobicity index, suspension stability index, attachment efficiency, and dynamic light scattering were used to assess the effects of agglomeration and dispersion of as-prepared (AP), purified (PD), or carboxylated (COOH) MWCNTs on bronchial epithelial and fibroblast cell lines. We found that hydrophobicity is the major factor determining AP-and PD-MWCNT agglomeration in tissue culture media but that the ionic strength is the main factor determining COOH-MWCNT suspendability. Bovine serum albumin (BSA) was an effective dispersant for MWCNTs, providing steric and electrosteric hindrances that are capable of overcoming hydrophobic attachment and the electrostatic screening of double layer formation in ionic media. Thus, BSA was capable of stabilizing all tube versions. Dipalmitoylphosphatidylcholine (DPPC) provided additional stability for AP-MWCNTs in epithelial growth medium (BEGM). While the dispersion state did not affect cytotoxicity, improved dispersion of AP-and PD-MWCNTs increased TGF-β1 production in epithelial cells and fibroblast proliferation. In summary, we demonstrate how quantitative techniques can be used to assess the agglomeration state of MWCNTs when conducting mechanistic studies on the effects of dispersion on tissue culture cells. © 2010 American Chemical Society. Source


Castranova V.,NIOSH
Journal of Occupational and Environmental Medicine | Year: 2011

Objective: Nanotechnology is the manipulation of matter on a near-atomic scale to produce nanoparticles with unique properties, allowing newcommercial applications. Since nanoparticles exhibit unique physicochemical properties, they are likely to exhibit biological activity significantly different from fine-sized particles of the same chemical composition. Therefore, evaluation of the biological effects of nanoparticles is critical. Methods: The article lists the major objectives of nanotoxicology and briefly reviews the literature concerning biological responses to pulmonary exposure. Results: Interactions of nanoparticles with biological systems depend on particle size, shape, oxidant generation, surface functionalization, and rate of dissolution. Pulmonary, cardiovascular, and central nervous system responses to pulmonary exposure to nanotitanium dioxide and carbon nanotubes are described. Conclusions: Significant biological responses occur in animal models after pulmonary exposure to certain nanoparticles. Control of exposure appears prudent to protect worker health. Clinical Significance: Nanotechnology is synthesizing a wide range of nanoparticles, which exhibit unique physicochemical properties. These unique properties make unique biological activity likely. If certain nanoparticles induce adverse effects in vitro or in animal models, then occupational health surveillance and exposure control may be prudent steps in the protection of worker health. Copyright © 2011 by American College of Occupational and Environmental Medicine. Source

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