Posted: August 5, 2010

New Safe Work Australia report investigates feasibility of exposure standards for nanomaterials

(Nanowerk News) The focus of the new report "Engineered Nanomaterials: Feasibility of establishing exposure standards and using control banding in Australia" is to investigate the feasibility of:
– establishing group-based Australian National Exposure Standards for engineered nanomaterials
– using control banding for engineered nanomaterials in Australia.
In December 2007, the British Standards Institution (BSI) published: "Nanotechnologies – Part 2: Guide to safe handling and disposal of manufactured nanomaterials" (the BSI Guide). The BSI Guide defines four hazard type groups for engineered nanomaterials, includes information on benchmark exposure levels (BELs) which are guidance on control levels for nanomaterials in those groups, and provides control guidance for those groups based on control banding. Investigating the feasibility of establishing group-based Australian National Exposure Standards and using control banding for engineered nanomaterials involved a detailed assessment of the groups, the BELs and the guidance based on control banding.
While there are some issues associated with the hazard type groups suggested in the BSI Guide, they appear to be practical groupings of nanomaterials. In relation to each of the BELs proposed in the BSI Guide for each of the hazard type groups, this report finds:
– The BEL for insoluble fibrous nanomaterials should be modified to 0.1 fibre/ml, rather than the 0.01 fibre/ml recommended in the BSI Guide, as there is no evidence that these nanomaterials are more toxic on a fibre-by-fibre basis than asbestos, and also, a higher number of fibres will be counted by electron microscopy which is needed to resolve fine fibres, e.g. carbon nanotubes. This BEL may also be applied to poorly soluble fibrous nanomaterials.
– There is currently limited scientific evidence to support a quantitative BEL for nanomaterials which are already classified in their larger form as carcinogenic, a reproductive toxin, asthmagenic or mutagenic (CMAR) of 0.1xWEL, as proposed in the BSI Guide. This was a recommendation based on prudence and a rule of thumb, and should be supported by following a precautionary approach until knowledge is enhanced.
– In regard to insoluble nanomaterials, there is toxicological evidence to support the BSI Guide recommendation of a quantitative BEL of 0.066xWEL for nanomaterials similar to TiO2, but there is a lack of quantitative evidence for most insoluble nanomaterials. Combining the use of mass-based BELs and the particle number concentration BEL of 20 000 particles/ml may be the optimum approach. The particle size range over which a particle number concentration BEL should be measured needs to be defined.
– Although there is currently insufficient evidence to support the BSI recommendation of a quantitative BEL of 0.5xWEL for soluble nanomaterials, this may be prudent due to the possibility that the size, shape and surface chemistry of soluble nanoparticles may lead to increased dose rates, or doses to parts of the body not usually exposed to such materials. However, a number of soluble nanomaterials do not have bulk forms for which exposure limits are set.
If quantitative exposure limits or benchmark exposure levels are adopted, then one approach is to adopt them as BELs (guidance) initially, and convert to National Exposure Standards as further hazard, risk and measurement data become available.
There are a number of initiatives internationally to consider the control banding methodology as a means to effectively control nanomaterials in the workplace. Two control banding approaches examined in this report look promising:
– the Control Banding Nanotool, which has been specifically designed for control of nanomaterials
– use of the control banding guidance in the BSI Guide should enable organisations to reduce exposures below the BELs. Exposures below the BELs should be achievable using conventional engineering controls.
Control banding for the nanomaterial industry is likely to be a suitable risk control approach for managing nanoparticle exposure in many situations. Control banding is particularly favourable to the control of chemical hazards where there is limited toxicological information and workplace exposure limits are absent as is currently the case with engineered nanomaterials.
However, in general, Australian workplaces do not have wide experience of using the control banding approach for other hazards and this situation is likely to remain so until there is impetus nationally to accept the control banding approach in support of State, Territory and Commonwealth regulations. Therefore, if control banding is to be used, it should be used in combination with the conventional approach towards the assessment and control undertaken in the current jurisdictional regulations, including those existing for human carcinogens. The use of both benchmark exposure levels and control banding, as proposed in the BSI Guide, are consistent with a precautionary approach to handling nanomaterials, as recommended by Safe Work Australia where limited information about hazards and risks is available.
There is a need to develop further capability of measuring nanomaterial exposures, which will also enable assessment of control against Benchmark Exposure Levels. The OECD Working Party for Manufactured Nanomaterials (WPMN) guidance for emissions measurement of nanomaterials appears to be a practical way to measure nanomaterial exposures in workplace settings. This is currently being validated by Queensland University of Technology and Workplace Health and Safety Queensland in a project commissioned by Safe Work Australia. Following completion of the validation, focus should be placed on dissemination of the methodology to occupational hygienists in Australia. The methodology can be used to assess performance against BELs.
Recent literature reviews and industry surveys (overseas) suggest that there is a need for guidance on the safe handling, control and disposal of nanomaterials in the industry. Currently, there are no Australian guides for safe handling and control of specific engineered nanoparticles that can be incorporated into the current legislation framework used within Australia. CSIRO is currently developing guidance for safe handling and disposal of carbon nanotubes for Safe Work Australia.
Source: Safe Work Australia