Documents particle size 20 results

"Dustiness may be defined as the propensity of a powder to form airborne dust by a prescribed mechanical stimulus; dustiness testing is typically intended to replicate mechanisms of dust generation encountered in workplaces. A novel dustiness testing device, developed for pharmaceutical application, was evaluated in the dustiness investigation of 27 fine and nanoscale powders. The device efficiently dispersed small (mg) quantities of a wide variety of fine and nanoscale powders, into a small sampling chamber. Measurements consisted of gravimetrically determined total and respirable dustiness. The following materials were studied: single and multiwalled carbon nanotubes, carbon nanofibers, and carbon blacks; fumed oxides of titanium, aluminum, silicon, and cerium; metallic nanoparticles (nickel, cobalt, manganese, and silver) silicon carbide, Arizona road dust; nanoclays; and lithium titanate. Both the total and respirable dustiness spanned two orders of magnitude (0.3-37.9% and 0.1-31.8% of the predispersed test powders, respectively). For many powders, a significant respirable dustiness was observed. For most powders studied, the respirable dustiness accounted for approximately one-third of the total dustiness. It is believed that this relationship holds for many fine and nanoscale test powders (i.e. those primarily selected for this study), but may not hold for coarse powders. Neither total nor respirable dustiness was found to be correlated with BET surface area, therefore dustiness is not determined by primary particle size. For a subset of test powders, aerodynamic particle size distributions by number were measured (with an electrical low-pressure impactor and an aerodynamic particle sizer). Particle size modes ranged from approximately 300nm to several micrometers, but no modes below 100nm, were observed. It is therefore unlikely that these materials would exhibit a substantial sub-100nm particle contribution in a workplace."

"The nanoparticle and nanotechnology field is a fast-growing research niche. Research has already led to significant breakthroughs, and several products are available commercially. It is currently anticipated that the number of exposed Quebec workers, both in use and processing and in production, will increase over the next few years. The purpose of this literature review is to determine whether nanoparticles represent health risks for workers. The chosen presentation format has the advantage of covering all the aspects that must be considered in toxic risk assessment. For some nanoparticles, the toxicological data are very partial, so this presentation format reveals the scope, and especially the limits, of the information currently available.
Nonetheless, several studies exist on the toxicological properties of nanoparticles. Although the various toxicological aspects and the diversity of the nanomaterials assessed are just beginning, many deleterious effects have been documented, particularly in animals. Insoluble or low solubility nanoparticles are the greatest cause for concern. Several studies have shown that some of them can pass through the various protective barriers of living organisms. The inhaled nanoparticles can end up in the bloodstream after passing through all the respiratory or gastrointestinal protective mechanisms. They are then distributed in the various organs and accumulate at specific sites. They can travel along the olfactory nerves and penetrate directly into the brain, just as they can pass through cell barriers. These properties, extensively studied in pharmacology, could allow organic nanoparticles to be used as vectors to carry medications to targeted body sites. The corollary is that undesirable nanoparticles could be distributed throughout the body of exposed workers. Some of these nanoparticles have shown major toxic effects.
Another special feature of nanoparticles is that their toxicity seems to be linked to their surface. This is a major difference from the usual situations, in which toxicity is normally linked to a product's mass. Nanoparticles are so tiny that small quantities (expressed in terms of mass), could have major toxic effects, because of their large surface. Several studies show much greater toxic effects for the same mass of nanoparticles as compared to the same product with a higher granulometry.
The available studies have shown several effects in animals, depending on the type of nanoparticles. Nephrotoxicity, effects on reproduction and genotoxic effects have been identified so far. Some particles cause granulomas, fibrosis and tumoural reactions in the lungs. Thus, titanium dioxide, a substance recognized as non-toxic, shows high pulmonary toxicity on the nano-scale. Cytotoxic effects have also been reported. …"

"This paper describes the production and characteristics of the nanoparticle test materials prepared for common use in the collaborative research project NanoChOp (Chemical and optical characterization of nanomaterials in biological systems), in casu suspensions of silica nanoparticles and CdSe/CdS/ZnS quantum dots (QDs). This paper is the first to illustrate how to assess whether nanoparticle test materials meet the requirements of a “reference material” (ISO Guide 30, 2015) or rather those of the recently defined category of “representative test material (RTM)” (ISO/TS 16195, 2013). The NanoChOp test materials were investigated with small-angle X-ray scattering (SAXS), dynamic light scattering (DLS), and centrifugal liquid sedimentation (CLS) to establish whether they complied with the required monomodal particle size distribution. The presence of impurities, aggregates, agglomerates, and viable microorganisms in the suspensions was investigated with DLS, CLS, optical and electron microscopy and via plating on nutrient agar. Suitability of surface functionalization was investigated with attenuated total reflection Fourier transform infrared spectrometry (ATR-FTIR) and via the capacity of the nanoparticles to be fluorescently labeled or to bind antibodies. Between-unit homogeneity and stability were investigated in terms of particle size and zeta potential. This paper shows that only based on the outcome of a detailed characterization process one can raise the status of a test material to RTM or reference material, and how this status depends on its intended use."

"Une première revue de la littérature sur les nanoparticules a incité l'IRSST à publier deux rapports à ce propos au début de 2006, soit sur les risques des nanotechnologies pour la santé et sur divers aspects d'hygiène industrielle les concernant. Or, vu l'évolution rapide des connaissances scientifiques, une mise à jour s'impose déjà. Les chercheurs feront une revue exhaustive de la littérature rendue disponible jusqu'à la fin de 2006 relativement aux risques pour la santé, à l'hygiène industrielle et aux moyens de contrôler l'exposition aux nanoparticules en milieu de travail. En plus de consolider le développement de l'expertise québécoise en ce domaine, cette activité permettra d'intégrer de nouvelles données dans le guide de bonnes pratiques en voie d'élaboration ainsi que d'anticiper les risques reliés à des procédés émergents afin de prévenir l'apparition de maladies professionnelles dans les établissements du Québec qui utilisent les nanotechnologies."

"The rapid proliferation of many different engineered nanomaterials (defined as materials designed and produced to have structural features with at least one dimension of 100 nanometers or less) presents a dilemma to regulators regarding hazard identification. The International Life Sciences Institute Research Foundation/Risk Science Institute convened an expert working group to develop a screening strategy for the hazard identification of engineered nanomaterials. The working group report presents the elements of a screening strategy rather than a detailed testing protocol. Based on an evaluation of the limited data currently available, the report presents a broad data gathering strategy applicable to this early stage in the development of a risk assessment process for nanomaterials. Oral, dermal, inhalation, and injection routes of exposure are included recognizing that, depending on use patterns, exposure to nanomaterials may occur by any of these routes. The three key elements of the toxicity screening strategy are: Physicochemical Characteristics, In Vitro Assays (cellular and non-cellular), and In Vivo Assays. There is a strong likelihood that biological activity of nanoparticles will depend on physicochemical parameters not routinely considered in toxicity screening studies. Physicochemical properties that may be important in understanding the toxic effects of test materials include particle size and size distribution, agglomeration state, shape, crystal structure, chemical composition, surface area, surface chemistry, surface charge, and porosity. In vitro techniques allow specific biological and mechanistic pathways to be isolated and tested under controlled conditions, in ways that are not feasible in in vivo tests. Tests are suggested for portal-of-entry toxicity for lungs, skin, and the mucosal membranes, and target organ toxicity for endothelium, blood, spleen, liver, nervous system, heart, and kidney. Non-cellular assessment of nanoparticle durability, protein interactions, complement activation, and pro-oxidant activity is also considered. Tier 1 in vivo assays are proposed for pulmonary, oral, skin and injection exposures, and Tier 2 evaluations for pulmonary exposures are also proposed. Tier 1 evaluations include markers of inflammation, oxidant stress, and cell proliferation in portal-of-entry and selected remote organs and tissues. Tier 2 evaluations for pulmonary exposures could include deposition, translocation, and toxicokinetics and biopersistence studies; effects of multiple exposures; potential effects on the reproductive system, placenta, and fetus; alternative animal models; and mechanistic studies."

Background Several researchers have proposed fiber size ranges representing hypotheses about the biological activity of fibers. Each of these indices has a biologically plausible rationale, yet they propose different fiber dimensions. Methods Four biologically based and one standard fiber analytic method index, the NIOSH 7400 method with B rules, were evaluated in air monitoring data collected in a variety of fiber glass (FG) manufacturing settings to determine their impact on an assessment of fiber exposure for an epidemiologic study of the risk of respiratory cancer among FG production workers. Results All indices varied considerably within and among the range of fiber size distributions sampled in the FG factories. Conclusions The asymptotic relative efficiencies (R2) calculated among the five indices indicate a potentially important loss of power from the use of the standard method index, if one of the biologically based indices is more closely related to the disease outcome in an epidemiologic study.