FAQ: Responsibility and legislation
Q: Are there any general guidelines to follow, since there are no occupational exposure limits specific for nanomaterials?
A: The precautionary principle should always be applied as long as the specific toxicity is not fully evaluated and as long as there are no nanospecific occupational exposure limits. This means that companies/industries that produce or handle nanomaterial should apply a high level of elimination and protection measures in the work environment to limit, control and minimize the airborne exposure of nanoparticles.
Internationally there are several suggestions of occupational exposure limit values that can serve as guideline values until nanospecific occupational exposure limits are available. For carbon nanotubes, the British Standards Institute (BSI) and Institut für Arbeitsschutz der Deutschen Gesetzlichen Unfallversicherung (IFA) have suggested fan occupational exposure limit for fibrous nanomaterials with a high length-to-diameter ratio (>3: 1; length >5µm) based on the occupational exposure limit of asbestos with a safety factor to 0,01 fibers/cm3 [BSI, 2007; IFA, 2009]. In Japan, the Japanese unit for new energy and industrial technology development [Nakanishi, 2011] has suggested a mass-based occupational exposure limit value of 30 µg/m3.
The National Institute for Occupational Safety and Health (NIOSH) have suggested a recommended occupational exposure limit value for carbon nanotubes [NIOSH, 2013] based on elemental carbon (EC) at 0,001 mg/m3, measured as average respirable mass over 8 hours. It is interesting to note that this occupational exposure limit is recommended by NIOSH for all carbon nanofibres and carbon nanotubes, regardless of their length. European Derived No-Effect-Level (DNEL) for multiwalled carbon nanotubes have been suggested for effects in lungs corresponding to 0,2 mg/m3 for short-term exposure, and to 0,034 mg/m3 for long-term exposure [ENRHES, 2010]. Occupational exposure limits are generally based on DNEL-values, and adding a safety factor of 100, the values suggested in Europe approximately corresponds to the values suggested by NIOSH [Vogel et al., 2014]. The internationally suggested occupational exposure limits are very low since several studies have shown that carbon nanotubes are highly toxic. Important to bear in mind is that not all suggested occupational exposure limits are based on health effects, so there is no guarantee even if a suggested occupational exposure limit is followed.
NIOSH  has suggested an American occupational exposure limit for nano titanium dioxide of 0.3 mg/m3 [NIOSH, 2011]. This is one order of magnitude lower (or more) than existing occupational exposure limits for larger sizes of titanium dioxide (eg. 5 mg/m3 in Sweden). In Europe, a DNEL-value for nano titanium dioxide i of 17 mg/m3 has been suggested [ENRHES, 2010]. The lower limits for nano titanium dioxide is, among other things, motivated by the larger surface area per unit mass. With increasing amount of exposure measures (number concentration, surface area, elementary carbon etc.) the possibilities increases for future occupational exposure limits based on the property that causes biological effects. The feasibility of personal exposure measurements is also increasing.
By applying the precautionary principle, and existing regulations containing risk assessments, the possibilities to control and limit occupational exposure are quite good.
Q: Why are there no occupational exposure limits specific for nanomaterials?
A: There is still not enough scientific data to establish occupational exposure limits for any type of nanomaterial, we lack knowledge of both toxicity and exposure levels. Internationally there are institutes and organizations that have suggested occupational exposure limits for some different types of nanomaterials; these can be used as guidelines until we have gained better knowledge. By applying the precautionary principle, and existing regulations containing risk assessments, the possibilities to control and limit occupational exposure are quite good.
BSI. (2007) Nanotechnologies – part 2: guide to safe handling and disposal of manufactured nanomaterials, London: British Standards. PD 6699-2:2007.
ENRHES. Engineered nanoparticles – Review of health and environmental safety (ENREHS). (2010) Available at http://ihcp.jrc.ec.europa.eu/whats-new/enhres-final-report
IFA. (2009) Criteria for assessment of the effectiveness of protective measures. Available at http://www.dguv.de/ifa/fachinfos/nanopartikel-am-arbeitsplatz/beurteilun...
Nakanishi J, editor. (2011) Risk assessment of manufactured nanomaterials: carbon nanotubes (CNT). NEDO project (P06041) Research and development of nanoparticle characterization methods. Final report issued on 17 August 2011.
NIOSH. (2013) Occupational exposure to carbon nanotubes and nanofibers. Current intelligence bulletin 65, publication no. 2013-145. Tillgänglig på http://www.cdc.gov/niosh/docs/2013–145/pdfs/2013-145.pdf.
NIOSH (2011). Current Intelligence Bulletin. Occupational Exposure to Titanium Dioxide. Tillgänglig på https://www.cdc.gov/niosh/docs/2011-160/pdfs/2011-160.pdf
Vogel U. (2014) Handbook of Nanosafety Measurement, Exposure and Toxicology. Academic Press, ISBN 9780124166042
Standard EN1540:2011 (2012) Workplace exposure. Terminology. ISBN 978-0-580-70841-1