Nanoparticles Actual Knowledge about Occupational Health and Safety Risks and Prevention Measures

New materials with unique properties A new industrial revolution based on nanotechnologies is underway. The enthusiasm for these technologies is sweeping the planet, generating several billions of dollars of investment annually in research and development (RandD). Using current technologies, we can handle materials and synthesize products at the atomic level; nanoparticles demonstrate properties that are completely different from products with the same composition but larger dimensions. The era of nanomaterials and nanotechnologies promises to be one of major scientific developments and breakthroughs that in the not too distant future will permanently affect our everyday lives. Several of these products are already being used and many organizations foresee annual world markets, beginning in 2015, of the order of US 1,000 billion dollars. Welcome to the nanoworld, where everything occurs at the level of the nanometre (nm), that is, a billionth of a meter (10-9 m). Nanotechnologies cover a broad, multidisciplinary field in which, globally, research activity and the setting up of industries have grown extremely rapidly over the last decade. Physicists, chemists, biologists, engineers, electronics technicians and various experts specializing in materials, processes and applications are working together on objects of nanometric proportions. Nanoparticles can be produced by a whole series of chemical, physical or biological processes, some of which are totally new and innovative, while others have existed for a very long time. New technologies allow us to build new materials, atom by atom. This often endows the materials with properties that are very different from ordinary materials. Nanoparticles and nanotechnologies do not simply represent another step towards miniaturization. At the “nano” level, the behaviour of particles is dominated by quantal effects. The particles may be confined to a small structure, distributed over large surfaces or demonstrate an entire series of unique phenomena and properties not encountered in larger materials. We need to bring together existing knowledge The main objective of the present assessment is to bring together current scientific knowledge on nanoparticles, while paying special attention to their health risks and to ways of protecting Quebec workers from exposure to nanoparticles produced in new ways. Our review takes into account the new nanoparticles (carbon nanotubes, fullerenes, quantum dots, nanopigments of titanium dioxide and certain metals of nanometric dimensions) but excludes products of nanometric dimensions generated by combustion during various industrial processes (diesel exhaust emissions, soldering fumes and fumes from various industrial processes), and products of nanometric dimensions already manufactured on a large scale, such as silica fumes. Developing new products Research pertaining to the production, marketing and use of the new nanomaterials is extremely important and is a vehicle for the strategic objectives of sustainable economic development, especially in Asia, Europe, the United States, Canada and Quebec. Potential uses for nanoparticles are foreseen in a wide variety of sectors, including the biomedical field, the metallurgical industry, agriculture, textiles, coatings, cosmetics, energy, catalysts and electronics, etc. Chemical-resistant materials, self-cleaning windows, medication transmitted directly to affected sites and graffiti-resistant paintings constitute but a few possible applications. Hundreds of Quebec workers may already have been exposed In Quebec, there are about 200 professor-scholars active in the field and over 1000 students dispersed among almost all the universities, certain CEGEPS and several research centres. Most of these individuals have potentially been exposed to nanoparticles. About forty Quebec firms are either currently active in the production of nanomaterials or are in the introductory phase. This is four times as many as there were barely three years ago. We must also take into account that Quebec imports nanoparticles for use in a variety of sectors, including textiles, where workers and users have already been exposed. The principal health impacts While research on developing new products, setting up industries and marketing has been bubbling over with excitement for more than a decade, research aiming to improve our understanding of the health impacts of occupational exposure, and of the links between nanoparticles and industrial safety, are far less advanced. Nonetheless, there is a body of knowledge clearly demonstrating that nanometric particles are more toxic than larger particles (with micrometric dimensions) of the same substance. Thus, this data supports the recommendation that we should treat nanoparticles of a particular substance as a new product with its own toxicity. The principal way these particles are absorbed in an occupational setting is via the respiratory route, as are other dusts. Toxicological studies clearly demonstrate that the very small size of nanoparticles plays a key role in its toxicity, especially when the particles are non-soluble or only slightly soluble. First, the location in the lungs where they are deposited varies greatly and is a function of the granulometry of the particle. Thus, particles measuring one nm cannot reach the pulmonary alveoli; they are deposited in the upper regions of the lungs. Particles measuring five nm are deposited relatively evenly in the nose and pharynx, the windpipe and bronchial tubes and, lastly, the alveoli. More than 50% of nanoparticles measuring 20 nm are deposited in the alveoli. Second, toxicological studies have shown that the toxicity of a nanoparticle is related to the surface area of the particle, not to its mass. Third, surface properties, the ability to induce free radicals and the ability to release certain ions can also have a considerable influence on toxicity. Several pulmonary effects have been documented, including the ability of certain nanoparticles to induce pulmonary granuloma. Currently available data seems to indicate that absorption through the skin is limited. Translocation, that is, the ability to move to other sites in the body, is another important characteristic of insoluble nanoparticles. The latter are able to traverse the pulmonary epithelium and reach interstitial sites; they then enter the bloodstream, which distributes them throughout the body. These particles can even go directly to the brain, though they take a variety of routes; nanoparticles that are caught in the nose go to the brain via the olfactory nerve. Nanoparticles can even cross intestinal, cellular and placental barriers. The pharmaceutical field is pinning many of its hopes for therapy on the fact that certain nanoparticles are able to cross the bloodbrain barrier and enter the brain directly. Certain nanoparticles modify blood parameters and accumulate in particular organs, including the liver and the spleen. Epidemiological studies reveal a significant correlation between the rate of mortality due to cardiorespiratory disease and the content of particles of nanometric dimensions present during air pollution episodes. Quantitative evaluation of the health risk to workers The significant lack of scientific knowledge obliges us to confront a major uncertainty concerning the risks raised by nanoparticles. Currently, in spite of the fact that numerous toxic effects on animals have been demonstrated, quantitative evaluation of the risks associated with any of the new nanomaterials is almost impossible to carry out. Nonetheless, toxicological research is underway and several of its results have already been published. One IRSST report (Ostiguy et al., 2006) details all listed toxicological knowledge specific to nanoparticles. Synthesizing nanoparticles Four major processes are employed in synthesizing the new nanoparticles: gaseous phase, vapour deposition, wet chemistry and grinding. Several of the processes for producing nanoparticles are similar to existing chemical production processes. Limits to current knowledge In considering the occupational health and safety risks related to nanoparticles, currently available information allows us to conclude that: the four principal production processes can result in occupational exposure by way of the pulmonary, cutaneous and ingestion routes; gaseous phase processes present the greatest potential for exposure during the nanoparticle synthesis stage. On the other hand, all of the processes may result in exposing the worker via the three absorption routes; the exposure occurs during the stages of recovery, bagging and manipulation of powders, which often consist of one or another of the agglomerated nanoparticles; to avoid the aggregation of particles, several processes include a post-synthesis stage designed to modify the particle surface, frequently by covering it with another organic or inorganic substance; this operation has an impact on the toxicity of the nanoparticle; at present, the tools normally used in industrial hygiene to evaluate the exposure of workers are ill suited to the applications of nanoparticles in an occupational setting. Currently, the data found in the literature cannot be used to estimate the exposure of researchers, students and workers. The little data available suggests that exposure during the manipulation of powders may be considerable. current scientific knowledge on nanoparticle toxicity is inadequate for carrying out quantitative risk assessment. due to their large specific surface area, several nanoparticles have significant reactivity potential that can result in fires or explosions; specific preventive measures must be introduced to avoid these kinds of events. Several research organizations working in occupational health and safety or in environment such as the National Institute for Occupational Safety and Health (NIOSH) and the Environmental Protection A

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