Nanotechnology is a multidisciplinary grouping of physical, chemical, biological, engineering, and electronic processes, materials, applications in which size is the defining characteristic. Nanotechnology is clearly a diverse concept, not a specific technology. The use of ”nanotechnologies” is in fact more appropiate.
Whereas the potential health and environmental benefits of nanotechnologies have been welcomed, concerns regarding their possible adverse effects have been rightly expressed. It is however particulary difficult to discuss potential risks in general terms. There will be no one-solution-fits-all approach for working safely.
Risk management framework
Hazard is defined as the potential to cause harm; typically assessed, by toxicology, on cultured cells (in vitro) or on laboratory animals or humans (in vivo).
Dose is the amount of the substance that reaches a specific biological system. It is a function of the exposure and of the elimination by the body’s natural defences -> dose-response.
Exposure is the concentration of the substance multiplied by the duration of contact.
Risk is a quantification of the likelihood of harm occuring.
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Hazard potential – Toxicity
We have in the past already gathered a lot of information due to e.g. particles associated with air pollution, quartz and asbestos, and various industrial chemicals and pharmaceuticals.
The most significant finding from research is that cells and organs may demonstrate toxic responses even to apparently non-toxic substances, when they are exposed to a sufficient dose in the nanometre size range.
The effects are mostly related to the larger total surface area and the chemical reaction of that surface, particularly the ability to take part in reactions that release free radicals. This may lead to inflammation and secondary blood-effects.
The size plays an important role. There is suggestion for translocation; nanoparticles may penetrate into cells and cross natural barriers (lung-blood, blood brain). Given previous experience with asbestos, we know that the physical dimension can prevent its removal. That is why nanotubes deserve special attention.
Like for particles of bulk size, the durability and solubility are important toxicological characteristics.
Risk
The relevance of toxicity data obtained in vitro or from experimental animals is difficult to assess in humans. Moreover there are still uncertainties about the relevance of the tested exposures for the real life situation. In other words, it is still unknown how hazard relates to human risk.
The greatest potential for exposure over the next few years will be in the workplace, in industry and in universities. Inhalation is the dominant pathway for humans exposed to manufactured nanoparticles released in the workplace.
Conventional exposure monitoring methods typically rely on characterizing the mass and bulk chemistry of airborne particles, two measures that are propably not appropiate to nanostructured particles. New techniques need to be developed and validated. Such measurements should be performed at all stages of the life cycle of nanomaterials: in research and development, in small scale and mass production, during their normal use and finally when they are disposed as waste.
Precaution principle
Safe workplaces will depend on controlling exposures. Here there are two challenges: evaluate the efficacy of conventional control approaches for airborne nanomaterials, and define appropiate levels of control without a quantitative risk assessment.
Given the absence of adequate toxicity information and extensive history of manufactured nanomaterials use, control guidance is now based on experience of ultrafine particles and gases. Most authorities believe that the risk management should be precautionary: the less certain you are the more you have to tend to reducing exposures.
It is certainly important that toxicological research keeps pace with technological research, because the most promising discoveries may never reach the development stage if the risks to health or the environment prove unacceptable.
Some references and interesting links
Maynard A.D., Ann.Occup.Hyg., 51(1):1-12, 2007
Schulte P. A., Environ Health Perspect, 115:5-12, 2007
Tsuji J. S., Tox Sciences, 89(1): 42-50, 2006
The Royal Society: Nanoscience and nanotechnology, July 2004
Nanosafe1, Final report, 2005
environmental health perspective: a journal
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