Raluca Aurora Stepa and Klaus Kuhl, The Cooperation Centre (Kooperationsstelle), Hamburg
- 1 Introduction
- 2 General description
- 3 Hazards and mechanisms of action
- 4 Occupational exposure
- 5 EU legislation
- 6 Control measures
- 7 Occupational exposure limits
- 8 Voluntary codes of practice
- 9 References
- 10 Links for further reading
Nanomaterials are structures at the nanometre-scale (a nanometre is 10 power of -9 of one metre), a scale, comparable to that of atoms and molecules.
Evidence shows that the same substance behaves differently at nanoscale compared to its coarse version. This allows developing light weight materials with high strength, high conductivity or high chemical reactivity. Nanotechnology is seen as one of the key technologies of the 21st Century. While admitting benefits of nanomaterials, concern about their hazards to health and the environment has grown over the past years.
The term nanoparticles is used for constituent particles of nanomaterials or for nanoscale particles generated by different sources.
Sources of nanoparticles can be natural (like volcano emissions) or anthropogenic: unintentional (like Diesel particles) or engineered (intentionally produced with specific properties). This article focuses on engineered nanoparticles and manufactured nanomaterials.
The European Agency for Safety and Health at Work (EU-OSHA) web site provides detailed information on nanomaterials including reports, factsheets, case studies, legal aspects, risk management and good practice examples. 
Definitions and categorisation
Several international and European organisations have developed or proposed definitions of the term ‘nanomaterial’.
On 18 October 2011, the European Commission adopted a Recommendation on the definition of the term “nanomaterial”, mainly based on considerations on a definition of nanomaterial for regulatory purposes by its Joint Research Centre and on the second opinion adopted by the EU Scientific Committee on Newly and Identified Health Risks. According to this Recommendation:
- 'Nanomaterial' means a natural, incidental or manufactured material containing particles, in an unbound state or as an aggregate or as an agglomerate and where, for 50% or more of the particles in the number size distribution, one or more external dimensions is in the size range 1 nm - 100 nm. The number size distribution is expressed as number of objects within a given size range divided by the number of objects in total.
- In specific cases and where warranted by concerns for the environment, health, safety or competitiveness the number size distribution threshold of 50% may be replaced by a threshold between 1 and 50%.
- By derogation from the above, fullerenes, graphene flakes and single wall carbon nanotubes with one or more external dimensions below 1 nm should be considered as nanomaterials.”
The scope of the Recommendation by the Commission covers nanomaterials when they are substances or mixtures, but not when they are final products. This means that if a nanomaterial is used amongst other ingredients in a formulation the entire product will not become a nanomaterial. This is in line with the definitions proposed by the Organisation for Economic Co-operation and Development (OECD) and the International Organization for Standardization (ISO).
This definition is meant to be used as a reference for determining whether a material should be considered as a ‘nanomaterial’ for legislative and policy purposes in the European Union. Seeing the fast pace of technological development and scientific progress, it was envisaged that the scope of the European recommendation on the definition of a nanomaterial will be reviewed by December 2014, in particular with regard to:
- whether the number size distribution threshold of 50 % should be increased or decreased;
- and whether to include materials with internal structure or surface structure in the nanoscale (such as complex nano-component nanomaterials, including nano-porous and nano-composite materials that are used in some sectors).
The Working Party on Manufactured Nanomaterials (WPMN) under the OECD Joint Chemicals Programme applies the following definitions:
- Nanomaterial: material which is either a nano-object or is nanostructured;
- Nano-object: material confined in one, two or three dimensions at the nanoscale;
- Nanostructure: having an internal or surface structure at the nanoscale.
The European Committee for Standardization (CEN) and the International Organization for Standardization (ISO) co-operate in elaborating standards for terminology and definitions for nanomaterials. The technical specification ISO/TS 80004-2:2015, Nanotechnologies - Vocabulary, Part 2: Nano-objects lists terms and definitions related to particles in the field of nanotechnologies. This standard proposes to refer to natural or unintentionally generated nanoparticles as 'ultrafine particles'. This standard was published with the intention to standardise and facilitate communication on nanoparticles and nanotechnologies.
In ISO TS 80004-1:2010 the term nanomaterial is defined as material with any external dimension in the nanoscale or having internal structure or surface structure in the nanoscale, whereby 'nanoscale' is defined as 'the size range from approximately 1 nm to 100 nm. This generic term is inclusive of nano-object and nanostructured material. ISO/TR 11360:2010 ‘Nanotechnologies – Methodology for the classification and categorization of nanomaterial’ describes a classifying system by which wide ranges of nanomaterials can be categorised.
In the absence of an internationally agreed official terminology, the way the different types of nanomaterials are referred to may differ from one document to another. For example, in the case of fullerenes some authors use this term regardless of their shape: round (spherical like 'buckyballs' or multiple-walled ellipsoids like 'buckyonions') or tubular, while others refer to the latter as carbon nanotubes. Several criteria have been proposed to define different categories of nanomaterials, based for example on material composition (organic/inorganic), the source of nanomaterials (natural/unintended/engineered), their properties (insoluble/soluble), etc.
The special properties of nanomaterials led to their use in many applications in industrial and non-industrial sectors like aerospace, construction, energy, textile, automotive industry, transport and medical technology. A few examples of applications are presented in Table 1 Table 1: Examples of uses of nanomaterials for different types of applications
|Electronics, ICT and photonics||Carbon nanotubes, fullerenes|
|Pharmaceuticals and medicine||Nanomedicines and carriers (nanobiotechnology)|
|Cosmetics and personal care||Titanium dioxide, zinc oxide, fullerenes, gold|
|Catalysts and lubricants||Cerium oxide, platinum, molybdenum trioxide|
|Paints and coatings||Titanium dioxide, gold, quantum dots|
|Environmental and water remediation||Iron, polyurethane, carbon nanotubes|
|Agrochemicals||Silica as carrier|
|Food packaging||Gold, nanoclays, titanium dioxide, silver|
Source: Adapted from Senjen 
The international on-line inventory of nanotechnology-based consumer products contains, as of October 2013 a number of 1628 products or product lines. The inventory has grown 521% in the interval 2006-2010.
Some materials, as shown in Table 2, are well known as nanomaterials (like carbon black), others, like fullerenes or nanotubes, are newer discoveries. Fullerenes are cage-like structures made of pentagonal and hexagonal carbon rings. Fullerenes have been studied for applications in catalysis, pharmaceuticals and molecular sieves. Carbon nanotubes have two dimensions at nanoscale and can be single-walled (SWCNT) or multiple-walled (MWCNT). Carbon nanotubes have a quite large variety of applications in electronics, medical sector, as lightweight composite materials, in textiles etc.
Table 2: Non-exhaustive list of nanomaterials either currently used commercially or being produced in significant quantities for research or development purposes
|Aluminium oxide||Dysprosium oxide||Polystyrene|
|Aluminium hydroxide||Fullerenes||Praseodymium oxide|
|Antimony oxide||Germanium oxide||Rhodium|
|Antimony pentoxide||Indium oxide||Samarium oxide|
|Bismuth oxide||Iron oxides||Silicon dioxide|
|Boron oxide||Lanthanum oxide||Silver|
|Calcium oxide||Lithium titanate|| Single and multi-walled
|Carbon black||Manganese oxide||Tantalum|
|Cerium oxide||Molybdenum oxide||Terbium oxide|
|Cluster diamonds||Nanoclays||Titanium dioxide|
|Cobalt oxide||Nickel||Yttrium oxide|
|Colloidal gold||Niobium||Zinc oxide|
|Copper(II) oxide||Palladium||Zirconium oxide|
Hazards and mechanisms of action
The hazards of a substance at nanoscale may differ from those of the same substance at larger scale.
The available information on adverse effects to health of nanomaterials is generally based on animal and cell laboratory studies (in vivo and in vitro). Epidemiological and toxicological studies on airborne ultrafine particles (for example Diesel exhaust, or unintentional by-product of certain working processes such as metal welding fumes) are also available and, seeing the similar characteristics of such ultrafine particles and engineered nanomaterials, it has been suggested to inform the current debate on nanomaterials using the available knowledge on health effects of ultrafine particles. Diesel exhaust exposures and PM10 concentrations (inhalable particulate matter of less than 10 µm aerodynamic diameter) have been related to higher mortality in the general population at higher pollution rates, and to aggravation of asthma and lung cancer in workers. Metal oxide fumes, for example from welding or abrasive treatment, may lead to an influenza-like disease called metal fume fever. Exposure to ultrafine particles has also been linked to cardiovascular effects, for example of carbon black.
Evidence of pulmonary effects of nanomaterials was found. Such effects may include inflammation, cytotoxicity (cell toxicity), fibrosis (formation of excess connective tissue) and tumour generation.
Dermal toxicity (skin irritation or allergic reactions) has not been observed in vivo. However, a serious case of erythema multiforme-like contact dermatitis (result of allergic response) was described in a worker exposed to dendrimers (repetitively branched molecules).
Cytotoxicity and oxidative stress of cells has been observed in different in vitro studies like those involving zinc oxide and cadmium sulfide in kidney cells or silver nanoparticles in brain cells.
Genotoxicity studies are few and still contradictory. Titanium dioxide and fullerenes (C60) are among the most studied nanoparticles but even in their case results do not allow a final conclusion.
Inhaled nanoparticles can cross the pulmonary epithelium, enter into the bloodstream and spread to other organs. Silver nanoparticles have been found to reach the liver and brain after inhalation exposure in rats. Increased manganese levels were detected in the brain of rats after inhalation of manganese oxide. Migration of inhaled particles to the brain via the olfactory nerve has also been found. Inhaled gold nanoparticles have been shown to accumulate in the olfactory bulb and increased levels were also detected in the lung, oesophagus, tongue, kidney, aorta, spleen, septum, heart and blood in rats.
Nanoparticles of less than 1.5 nm have been found to accumulate in rat placenta and to even cross the placenta barrier to the foetus also found translocation to the brain, as well as in all other secondary organs that were part of the study including foetus, following inhalation, ingestion and intravenous administration in rats of nanoparticles of iridium, carbon, titanium dioxide and gold.
Other routes for particles dispersion into the body have also been observed, like crossing intestinal epithelium after ingestion.
It is generally acknowledged that the activity and toxicity of nanomaterials are influenced by various parameters such as size, chemical composition, surface area, surface charge, coating, reactivity, shape, solubility, etc. The way each of these properties influence the penetration of nanomaterials into the body, their mobility, reactivity, accumulation or elimination is not totally understood, but scientific efforts have been multiplied in this respect.
Size is a distinctive feature of nanoparticles. Studies have shown that, for the same chemical composition, nanoparticles prove a higher toxicity compared to coarse particles. For example after respiratory exposure of mice to titanium dioxide, the lung inflammatory reaction proved to be more important for particles at nanoscale as compared to the micrometric scale.
Size alone is not always determinant of nanoparticles behaviour. For example particles of the same size (20 nm) but different chemical nature (titanium dioxide and carbon black) had different rates of penetrating the alveolar interstitium (network of thin connective tissue fibres within the walls of lung alveoli) in the respiratory zone of the lungs: about 50% for the titanium dioxide and 4% for the carbon black.
Surface composition was shown to influence toxicity in several studies. For example the presence of sodium citrate impurities on the surface of gold nanoparticles ‘might play a pivotal role in inducing cytotoxicity to human alveolar cells, in vitro.
Coatings can change some of the properties of nanoparticles, with possible effects on health. Multi-walled carbon nanotubes coated in polystyrene-based polymer showed decreased toxicity when administrated intratracheally to mice.
The shape of nanoparticles may also influence their toxicokinetics and their effects on health. Carbon nanotubes have a length-to-diameter ratio similar to that of fibres and are insoluble and biopersistent. These characteristics have been encountered in asbestos, another well-known lung toxicant, initially considered to be harmless. Some studies have shown that carbon nanotubes have the same length-dependent pathogenicity as asbestos, concluding that the longer, straighter and more fibre-like is the nanotube, the more pathogenic it is likely to be. Studies investigating toxicity of carbon nanotubes on mice showed that they induced epitheloid granulomas – tumour-like nodules - and in some cases inflammation of the lungs . Surface contaminants are also of concern, because they may contribute to the health effects.
Aggregation of nanoparticles in the air has been studied and some of the results show that they de-agglomerate inside the body while other authors consider there is no, or little de-agglomeration. In the questions and answers on the Commission Recommendation on the definition of nanomaterials, the Commission states that ‘agglomerated or aggregated particles may exhibit the same properties as unbound particles. There can be cases during the life-cycle of a nanomaterial where the particles are released from weakly bound agglomerates or under certain conditions even from more strongly bound aggregates’.
The large specific surface area and reactivity of nanoparticles influence not only their toxicity but also safety hazards, as nanoparticles show a high potential for catalytic reactions, ignition or explosion. Their ability to get and remain airborne for a long time and their low minimal ignition energy raises the risk of explosion, including that induced by electrostatic charges that may occur when powders are manipulated.
Engineers of the German accident insurance company for the chemical industry and raw materials (BG RCI) showed that dusts at micro scale tend to explode more vehemently and the ignition sensitivity tends to increase the finer the particles become. The temperature of self-ignition also decreases when the particles are finer.
Studies have classified the explosion severity of different nanoparticles from weak (carbon black and carbon nanotubes) to very strong (aluminium), depending on particle nature, size and agglomeration. Aluminium powders have a minimum ignition energy that is low enough to be ignited with static energy .The severity of their explosion was classified as strong to very strong, depending on particle size. Tests showed that aluminium nanopowders were less explosive than micropowders, probably due to the oxide layer on nanoparticles. Moreover, the same study concluded that if a nanopowder agglomerates, it shows explosion severity of the same order as micropowder of the same substance. If flammable substances, like solvents, are adsorbed on the surface of the particles, the explosion is even more likely.
Sources of exposure
Occupational exposure to nanomaterials may occur during the production stage if appropriate control measures are not in place. The small size of nanoparticles makes them easily airborne and favours their dispersion. Processes in which dry nanomaterial powders are generated, handled or used are likely to lead to significant occupational exposure. Blending, reloading, drying or vacuum cleaning are operations that may increase the level of exposure to airborne nanomaterials. The same applies for sprayed colloidal suspensions, whereby the hazards of the dispersant should also be considered.
Production phases are generally run under controlled conditions, in principle using closed-systems. It is therefore where worker exposure is the easiest to control. However, possible exposure when maintaining or cleaning the installation, or in the case of leakage or waste handling has to be considered and also properly controlled. Significant exposure may also occur when the nanomaterial is picked out of the installation and further processed. Measurements of airborne nanomaterials have shown higher levels for example where processes such as extrusion and cutting of bags containing nanomaterials, or dry-sawing of nanomaterial-containing composites took place. 
Whether exposure can occur when handling, processing or using nanomaterials embedded into a solid matrix or products containing nanomaterials is currently a subject of debateand needs further investigation (for example machining or abrading coatings containing nanomaterials e.g. in construction work or maintenance of vehicles, or at the waste treatment stage of such products). As long as no clear conclusions can be drawn on this, the Precautionary Principle should apply in terms of the choice of prevention measures.
If information on the presence of nanomaterials is not available down the user chain – which in most cases seems to be the situation as little or no information is provided in the Safety Data Sheets – employers and workers may not be aware that they handle products containing nanoparticles/nanomaterials. Significant exposure is more likely in such situations since employers and workers do not have the necessary information to implement adequate protection and prevention measures.
Nanomaterials may enter the body through inhalation, ingestion and through skin contact.
The small size of nanoparticles allows for deep penetration into lungs, up to the alveoli (ends of the respiratory tree) and from here into the blood stream and to other organs. In some cases, migration via the olfactory nerve was also observed as presented above.
Ingestion may happen accidentally or as a result of breaking hygiene rules (e.g. eating with contaminated hands). Ingestion is also possible as a “secondary” effect of inhalation (deposition on the lips, nose and throat membranes and ingestion of secretions).
Penetration of nanoparticles through the skin has been subject for debates, especially regarding the hazard associated to cosmetics and sunscreen protection. Recent studies reported that titanium dioxide nanoparticles do not penetrate beyond the epidermal level but the discussion is not concluded.  The barrier function of the skin could be limited by skin lesions, small nanoparticles (< 5 to 10 nm) or strong mechanical strain.
Occupational exposure monitoring
For most of the chemical agents, monitoring is performed by measuring their mass concentration in air, in the breathing zone of the worker. For fibres the measured parameter is the number of fibres in a given air volume. When legislation provides occupational exposure limits (OELs), monitoring results are compared to these limits and considered in the risk assessment.
In the case of nanoparticles mass is not as relevant as surface area, size, volume, particle number, solubility, etc.These particularities put in question the relevance of monitoring nanoparticles using the methods employed for chemical agents in general.
At present there are no standardised methods to measure relevant properties of nanomaterials in order to determine occupational exposure. Several types of methods are currently employed to characterise nanomaterials properties like mass concentration, particle number size distribution, surface area, charge, morphology, etc.. OECD has published a nanomaterial emission assessment guidance proposing procedures as well as sampling and measuring devices.
Many of the monitoring methods are not affordable for the average user because of costs and the high level of skills required. In addition, the measuring devices available allow measuring one or two parameters only. Differentiating between background concentration of ultrafine particles and engineered nanomaterials is also challenging. A further challenge is how to ensure that nanomaterials that might be bound to aggregates or agglomerates are taken into account, since the possibility of release of the nanoparticles from these cannot be excluded once inhaled. Efforts are made to develop devices for in situ monitoring, that are easier to use and allow the measurement of relevant characteristics of airborne nanomaterials at the workplace.
Monitoring should be done according to a strategy that will integrate aspects regarding emission sources, working processes and procedures, workplace design and conditions, possible aggregation of particles and measuring objectives. Background concentration of ultrafine particles should be measured and distinguished when reporting occupational exposure results.
Medical surveillance of persons exposed to nanoparticles should at least follow the legal provisions for the type of chemical agent. Whenever potential target organs are identified examination should address them. Since toxicological mechanisms of nanoparticles are not known well enough, in many cases the results of medical investigations may not have the necessary relevance. Keeping records of workers’ exposure and exposed worker medical tests may provide useful information.
There is no specific occupational health and safety legislation for nanomaterials at EU level. The EU legislation that applies to nanomaterials in the workplace is the one that generally applies to worker protection, chemicals, as well as consumer and environment protection that could be in some cases relevant to the workplace (e.g. General Product Safety Directive).
The Framework Directive 89/391/EEC presents general principles of prevention and basic obligations for the employer and workers that apply to practically any occupational risks, therefore addressing also nanomaterials. Council Directive 98/24/EC on the protection of the health and safety of workers from risks related to chemical agents at work presents preventive principles and other measures for eliminating and, if not possible, substituting by less hazardous substances or reducing chemical risks to a minimum and also applies to nanomaterials. This means that the employer has the duty to assess the risks to workers from nanomaterials in the workplace and to protect workers adequately from these risks by implementing the hierarchy of prevention measures, giving priority to elimination of the risk, followed by substitution, collective technical control measures at the source of the risk, organisational measures and, as last resource, provision of personal protective equipment. Directive 2004/37/EC on the protection of workers from the risks related to exposure to carcinogens or mutagens at work applies to substances that meet the criteria for carcinogenic and/or mutagenic substances, regardless of their size and introduces stricter provisions in particular with regards to substitution.
Regulation 1907/2006 on Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH) does not refer specifically to nanomaterials but substances regardless of their size are covered by it. REACH provisions for the registration of chemicals beyond the threshold of 1 tonne produced or imported substance per year, apply to nanomaterials too. When registration is required it shall contain information for the adequate identification of the substance, which may include, beside chemical composition, data on particle size if relevant (nanoscale in the case of nanoparticles).
The on-line registration form was updated to facilitate the identification of a substance as nanomaterial and a manual was published to help registrants. Other gaps in the applicability of the REACH information requirements, including the appropriateness of the relevant endpoints and test methods, have been identified and proposal have been made to better address nanomaterials specificity.
Regulation 1272/2008 on the Classification, Labelling and Packaging of Substances and Mixtures (CLP Regulation) provides criteria for the classification of hazardous substances, as well as indications on labelling and packaging. Nanomaterials that fulfil these criteria for classification as hazardous must be accordingly classified and labelled. The CLP Regulation also provides an obligation to notify to the European Chemicals Agency (ECHA) all substances which meet the criteria for classification as hazardous substances, independently of the tonnage in which they are placed on the market.
The European Parliament resolution of 24 April 2009 called specifically on the European Commission to review legislation such as the workers’ protection legislation and REACH to ensure that the particular features of nanomaterials are adequately addressed by the EU legislative frameworks and that information to consumers and workers is improved, with appropriate labelling indicating the presence of nano-sized ingredients, regardless of their risks. In particular with regard to REACH, it requested the Commission to evaluate the need to review REACH, concerning among others:
- simplified registration for nanomaterials manufactured or imported below one tonne;
- consideration of all nanomaterials as new substances;
- a chemical safety report with exposure assessment for all registered nanomaterials;
- notification requirements for all nanomaterials placed on the market on their own, in preparations or in articles.
The Commission replied in October 2012 that important challenges relate primarily to establishing validated methods and instrumentation for detection, characterization, and analysis, completing information on nanomaterial hazards and developing methods to assess exposure to nanomaterials. They found that:
- current risk assessment methods are applicable, even if work on particular aspects of risk assessment is still required,
- within the REACH framework more specific requirements for nanomaterials have proven necessary. The Commission envisages modifications in some of the REACH Annexes.
In addition the Commission created a web platform with references to all relevant information sources, including registries on a national or sector level.  In parallel, the Commission will launch an impact assessment to identify and develop the best means to increase transparency and ensure regulatory oversight, including an in-depth analysis of consequent data gathering needs. This analysis will include those nanomaterials currently falling outside existing notification, registration or authorisation schemes. 
In 2014 the European Commission issued guidance on safe use of nanomaterials:
- Guidance for workers
- Guidance for employers and health and safety practitioners.
Since hazards of nanomaterials are still being investigated and are not yet totally known, the Precautionary Principle should be applied when it comes to choosing prevention measures; see the Communication from the Commission on the precautionary principle.  Smaller companies should seek external guidance from e.g. accident insurance associations or labour inspections.
Appropriate protection measures should be taken to eliminate exposure or to reduce it to a minimum based on the results of the workplace risk assessment. Some specific tools to support the risk assessment of nanomaterials in the workplace have been developed, e.g. control-banding tools and other guidance/guidelines on risk assessment.. Emergency situations have to be also considered.
Control measures should be applied for all workers that may be exposed to nanomaterials at work, whether during the main technological activities or during maintenance, cleaning, storage, or waste treatment. A current critical issue is that, since little or no information is currently available in the Safety Data Sheets, little information is available to employers and workers at the use stage and it is therefore difficult for them to assess the exposure and to implement adequate prevention measures.
Prevention principles and measures for exposure to fine and ultrafine particulate matter are those currently recommended in the case of nanomaterials, with measures suited for the specificity of their nanoscale. Workplace codes of practice or regulation to limit workplace exposures to ultrafine particles are available and can be used for preventing risks of nanomaterials, for example the German Technical Rules for Hazardous Substances TRGS 528, related to welding work.
Elimination of hazardous substances, including hazardous nanomaterials, from processes and products is the measure that has to be given priority.
If elimination is not feasible, substitution by a non-hazardous or less hazardous substance, or by a different and safe technology should be considered.
Engineering controls by other measures to reduce exposure could be considered if the ones mentioned above cannot be applied, like changing the working process. For example, powder nanomaterials should be avoided as much as possible and embedded into a matrix as it avoids suspension of the nanomaterials into the air. The use of nanomaterials in wet form (suspensions, paste) instead of dry powders therefore reduces the risk of exposure by inhalation. However, attention should be paid to exposure by other routes, mainly skin contact.
Technical measures like processing in closed, automated systems are effective in reducing exposure. Isolating equipments in confined spaces endowed with systems for extraction and filtering of particulate emissions also prevents exposure, not only by inhalation but also by skin contact or ingestion. Exposure during maintenance and cleaning of such closed areas as well as exposure in case of leakage should not be overlooked.
Local and general ventilation helps prevent dispersion of airborne nanomaterials in the working area and to adjacent spaces. For removing nanoparticles from the exhaust air, an appropriate filtration system has to be used. This can be a multi-stage system with high efficiency particulate air filter (HEPA) or ultra low penetration air filters (ULPA) as final filters.
Optimising process design and operational practices so that hazardous by-products and waste generation is mitigated will reduce exposure at the workplace.
- prevention barrier: reduction of accident probability by reinforced maintenance procedures that prevent fugitive emissions, accidental generation of explosive atmosphere, build-up of static electricity, accidental ignition sources;
- mitigation barrier: reduction of process factors, by lowering process temperature and pressures;
- mitigation barrier: reduce nanopowder severity parameters by substitution or dilution;
- protection barrier: increase the degree of protection for workers at risk.
Organisational measures can help keeping to a minimum the number of persons that may be exposed and the time and frequency of potential exposure.
Documenting safe procedures and working instructions for processes involving nanomaterials and making them available at the workplace will provide the basis for appropriate working practices and will be a reference for continual improvement.
Access to areas where exposure may occur should be restricted; safety and hazard signals should be used appropriately. There are no specifications in the legislation on how to label and sign nano-risks, but some guidance is available for labelling and some documents recommend the sign ‘nano-objects’ for areas with such risk.
Measures for proper maintenance, cleaning and personal hygiene should be taken.
Workers have to be trained on the safe handling of nanomaterials and on the control measures implemented. By law, they have to be consulted and to be able to participate in decisions that might affect their health and safety. Workers information should also include information on the specific hazards of nanomaterials and on the particular importance of the precautionary principle, due to the still limited knowledge on the health and safety hazards and exposure assessment of nanomaterials. Measures should be taken to make sure workers understand the risks and apply the control measures correctly
Personal protective equipment should be used whenever other preventive and protective measures are not sufficient or feasible. HEPA filters, respirator cartridges and masks made with fibrous filters, protective clothing, goggles and gloves can be used. Filtering half masks have to fit well to the face because inadequate sealing rises the risk of exposure.
Protective clothing made from air-tight fabrics consisting of non woven textile seem to be more efficient to protect workers against nanoparticles than cotton and polypropylene. Nitrile, Latex, Neoprene gloves proved to be efficient for nanoparticles of around 10 nm diameter, when exposing the glove for few minutes. Workers should be informed on the limits of the protective equipment, its validity and correct use.
Occupational exposure limits
There are no occupational exposure limit values (OELs) specific for nanoparticles in EU legislation. Due to so many influencing factors (size, surface area, charge, composition, etc) with only partially known contribution to the toxicology it is difficult to estimate a No Observable Adverse Effect Level (NOAEL) or a Lowest Observable Adverse Effect Level (LOAEL) and establish a health-based occupational exposure limit.
In any case, the absence of OELs does not undermine the obligation of carrying out a risk assessment and implementing the hierarchy of prevention measures giving priority to elimination, followed by substitution, reduction at source with collective measures, etc.
Some organisations have proposed tentative OELs, such as the US National Institute for Occupational Safety and Health (NIOSH) for titanium dioxide (TiO2). NIOSH recommends an OEL of 0.3 mg/m3 for nanoparticles of TiO2 (versus 2.4 mg/m3 for fine particles > 100 nm).
So called “benchmark levels” have also been proposed. Benchmark levels may be used as a tool in assessing occupational exposure. They are no health-based limit values, but represent a pragmatic guidance level.
The British Standard Institute has suggested benchmark exposure levels for four nanoparticle hazard types:
- For insoluble nanomaterials a general benchmark level of 0.066 × OEL of the corresponding microsized bulk material (expressed as mass concentration) is proposed;
- For fibrous nanomaterials the proposed benchmark level is 0.01 fibres/ml;
- For highly soluble nanomaterials a benchmark of 0.5 × OEL of the corresponding microsized bulk material is proposed;
- For substances classified as carcinogenetic, mutagenic, asthmagenic or reproductive (CMAR) in their coarse form, the same hazards will be considered for the nano form and the suggested benchmark level is 0.1 × OEL (mass concentration) of the corresponding microsized material.
The German Institute for Occupational Safety and Health of the German Social Accident Insurance (IFA) has also developed recommendations for benchmark limits, using size and density of the nanoparticles as classification criteria. IFA proposed the following benchmark limits as increases over the background exposure to ultrafine particles during an 8-hour working shift, based upon its experience in measurement and the detection limits of the measurement methods currently employed:
- For metals, metal oxides and other biopersistent granular nanomaterials with a density of > 6,000 kg/m3, a particle number concentration of 20,000 particles/cm³ in the range of measurement between 1 and 100 nm should not be exceeded.
- For biopersistent granular nanomaterials with a density below 6,000 kg/m3, a particle number concentration of 40,000 particles/cm3 in the measured range between 1 and 100 nm should not be exceeded.
- For carbon nanotubes (CNTs) for which no manufacturer's declaration is available that the CNTs have been tested as safe against asbestos-like effects, a provisional fibre concentration of 10,000 fibres/m3 is proposed for assessment, based upon the exposure risk ratio for asbestos.
Voluntary codes of practice
- Code of conduct for responsible nanotechnology elaborated by the European Commission;
- Responsible nanocode for business, elaborated by the Royal Society (UK);
- Guideline for operation with nanomaterials at workplaces, elaborated by the Association of Chemical Industry (VCI) and the Federal Institute for Occupational Safety and Health (BAuA), in Germany;
- BASF Code of conduct ‘Nanotechnology’;
- Responsible Care Chart (applicable to nanomaterials but not specific) initiated by the International Council of Chemical Association (ICCA).
Voluntary schemes and networks, where organisations are encouraged to share data on nanomaterials, including toxicity or exposure levels, are active in Europe, like the ‘UK voluntary reporting scheme for engineered nanomaterials’ of the Department for Environment Food and Rural Affairs or Nanoinventory in Switzerland. OECD also recommended reporting based on voluntary declaration of manufacturers. France has included mandatory declaration of nanomaterials in the national OSH strategies.
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Links for further reading
BSI – British Standard Institute, Guide to assessing airborne exposure in occupational settings relevant to nanomaterials PD 6699-3:2010, 2010.
CEFIC – European Chemistry Industry Council, Responsible Production and Use of Nanomaterials: Implementing Responsible Care, 2010. Available at: 
DG ENV – Environmental Directorate General of the European Commission, Nanomaterials in REACH, 2008. Retrieved 30 June 2015, from: 
Dick Hoeneveld, D., Kuhn, J., Nijenhuis, J., Kamerling, R., Schmidt-Ott, A., Nanosafety Guidelines. Recommendations for research activities with ‘free nanostructured matter, 2008. Available at: [www.veiligheidskunde.nl/xu/document/cms/streambin.asp?requestid=43531312-6BA0-400D-B916-7562D0EEBDE3]
EFBWW – European Federation of Building and Wood Workers and European Construction Industry Federation (FIEC), Nano-products in the European Construction Industry – State of the art 2009, 2009. Available at: in the European Construction Industry.pdf
ETUC – European Trade Union Confederation, The 2nd resolution on nanotechnologies and nanomaterials, 2010. Available at: 
Groso, A., Petri-Fink, A., Magrez, A., Riediker, M., Meyer, T., ‘Management of nanomaterials safety in research environment’, Particle and fibre Toxicology, Vol. 7:40, 2010. Available at: 
Hakim, L. F., King, D. M., Zhou, Y., Gump, C. J., George, S. M.& Weimer, A. W., ‘Nanoparticle Coating for Advanced Optical, Mechanical and Rheological Properties’, Adv. Funct. Mater, 2007, 17, pp. 3175–3181.
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Health and Safety Executive, Fire and explosion properties of nanopowders, Research Report RR 782, 2010. Available at: 
ISO – International Standard Organisation (2011). ISO/TR 12885:2008 Health and safety practices in occupational settings relevant to nanotechnologies‘ describes procedures applied in manufacturing and processing of nanomaterials. Retrieved 03 March 2011, from: 
Krug, H., Kuhlbusch, T., Nau, K., Steinbach, C., Förster, A., Nano Health-related Aspects of Synthetic Nanomaterials, 2009. Retrieved 03 March 2011, from: 
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Ostiguy, C., Roberge, B., Woods, C. & Soucy, B., Les nanoparticules de synthèse – Connaissances actuelles sur les risques et les mesures de prévention en SST, 2e edition, RAPPORT R-646, l’Institut de recherche Robert-Sauvé en santé et en sécurité du travail (IRSST), Quebeq, 2010. Available at : 
Reijnders, L., ‘Hazard Reduction in Nanotechnology’, Journal of Industrial Ecology, vol 12, issue 3, 2008. Available at: 
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Simko, M., Mattsson, M. O., ‘Risks from accidental exposures to engineered nanoparticles and neurological health effects: A critical review’, Particle and Fibre Toxicology, Vol. 7:42, 2010. Available at: 
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Wikipedia – The Free Encyclopedia (2015). Nanoparticle. Retrieved 24 June 2015, from: