Health and safety issues

health_and_safetyThe widespread use of carbon nanotubes (CNTs), single- (SWCNT) and multi-wall (MWCNT) CNTs, has raised safety concerns about their possible health effects. Short-term and sub-chronic studies in rats and mice have shown qualitatively consistent respiratory adverse effects [1]. Especially CNTs with a high aspect ratio (length / thickness >3:1) are of particular concern, since they might be able to induce lung cancer and mesothelioma, in a manner similar to asbestos fibres [1,2]. The mechanism by which CNTs could cause inflammation and ultimately cancer is, however, largely unknown [3].

Industrial emissions of CNTs and workplace exposures can occur at production, in use, when machining nano-enabled products and composites and from waste, and depends on the working procedures and applied risk control measures. Strategies, techniques (CPCs, ELPI, SMPS, etc) and sampling protocols to characterize and assess releases and exposures to ENMs and CNTs have been developed [4]. However, there is currently no regulated limit values for CNTs. Interim or draft OELs have been suggested by some manufacturers of CNTs (e.g. Baytubes, Nanocyl) and research organizations (NIOSH, e.g. 1 µg/m3) [4].

Measurements of airborne CNTs in industrial processes and workplaces, in research and industrial settings, have shown a likely exposure of workers in some cases. Higher levels of airborne CNTs were found in particular where processes, such as extrusion and cutting of bags containing ENMs or dry-sawing of nanomaterial-containing composites took place [5]. Several authors have studied the potential release of CNTs from polymer nanocomposites. In a recent review of papers addressing the emission of CNTs during mechanical impact, weathering processes and the release due to accidental fire, results from these studies suggest that, in some conditions, free CNTs may be released to the air in these scenarios. However, as pointed out by several authors, there is still a lack of data regarding the measurement of emission and exposure to ENMs and CNTs from the industrial processes [6,7]. In this context, it should be noted that unconventional operation modes in machinery and industrial processes, such as maintenance or adjustment, as well as emergency situations, can produce very relevant releases and exposures to CNTs.

The information about hazards and levels of exposure to ENMs and CNTs is fragmented; most of the parameters of the risk assessment process involve uncertainties, and results in high uncertainties when one tries to estimate the overall outcome of this process. The same issues also apply to environmental risks, where during and after release, transformation reactions are even more important in changing the properties of the pristine ENMs [8].

NIOSH26 recommends that, until results from research studies can fully explain the physical-chemical properties of CNTs that define their inhalation toxicity, all types of CNTs should be considered a respiratory hazard, and exposures should be controlled as low as possible below the OEL. Risk control for CNTs is based on the hierarchy of control measures [9]. Nowadays, basic recommendations for CNTs are to enclose processes and to work in confined environments as much as possible. Specific guidance for safe handling and use of CNTs has been published [10], jointly with recommendations on strategies for engineering controls in nanomaterial production and downstream handling processes [9,11].

nanomaterials_2With regard to risk management, some general guidelines, recommendations, best practices and tools (including Control Banding approaches) to assess and manage EHS topics related to ENMs, applications and processes, have been produced to date, providing in some cases specific advice for CNTs [12,11]. Approaches for integration of nano-risk management into company management system have been also developed. (e.g. CENARIOS-TUV or recently, the risk management model produced by FP7 project SCAFFOLD), based on OHSAS 18001/ISO 31000): Safe-by-design approaches for ENMs, applications and processes have been also lately promoted, e.g. within the FP7 SUN project, for developing sustainable nanotechnology. However, one of the key challenges are that available tools for the assessment & management of the safety of ENMs, applications and processes, are often inappropriate or so laborious that adequate safety assessment remains highly problematic.

Proposed solution; innovations from the PLATFORM project

solutionFor progress beyond the state of the art, the European NanoSafety Cluster (NSC) [1] identified the strategic priorities of nanosafety research for the period 2015-20125. Several priorities of the thematic area 4, are close connected with main EHS research topics covered by PLATFORM, in the areas of risk management and safe-by-design. PLATFORM will focus EHS research in developing and validating a new toolkit of innovative strategies, methods and tools to allow:

  • Customized and integrated EHS risk management of industrial processes involving CNTs, nano-enabled products and composite

 

  • Simple decision-making, on best options for safe-by-design of CNTs based products and processes. Methodologies and approaches such as control banding, multi-criteria decision analysis, integration of risk analysis in decision making and safety management systems will be integrated to construct the toolkit.

In addition, PLATFORM will provide new databases of emissions & exposures to CNTs and effectiveness of strategies and control measures implemented, in relevant project scenarios involving CNTs nano-enabled products and composites (pilot plants, integration scenarios and industrial use cases).

References

[1] COM(2012) 572 final, Communication from the Commission to the European ParliamentSecond Regulatory Review on Nanomaterials.

[2] Linton A, Vardy J, Clarke S, van Zandwijk N (2012). Crit Rev Oncol Hematol 84, 200-212.

[3] Nagai H, Toyokuni S (2010) Arch Biochem Biophys 502, 1-7.

[4] NIOSH (2013) Occupational Exposure to carbon nanotubes and carbon nanofiber. Bulletin 65.

[5] Möhlmann, C. et al. (2011), INRS Occupational Health Research Conference 2011 ” April 2011, Conference proceedings, Session II, p. 64.

[6] Brouwer, D. (2010) Exposure to manufactured nanoparticles in different workplaces. Toxicology. 2010 Mar 10;269(2-3):120-7.

[7] Clark et al (2012). J Nanopart Res (2012)

[8] NSC (2013) Nanosafety in Europe 2015 – 2025: Towards Safe and Sustainable Nanomaterials and Nanotechnology Innovations, 212 pp.

[9] NIOSH (2014) Current strategies for engineering controls in Nanomaterial Production and Downstream Handling Processes, NISOH 2014.

[10] CSIRO (2012) Safe handling and use of carbon nanotubes. Safe Work Australia, 2012.

[11] ISO/TS 12901-2:2014 Nanotechnologies — Occupational risk management applied to engineered nanomaterials — Part 2: Use of the control banding

[12] EU-OSHA (2012) E-Facts, 18 pp. HSE (2011) Risk management of carbon nanotubes.