Current control banding approaches for nanotechnologies
Control banding (CB) is a qualitative risk management approach which can be defined as: “A strategy or process in which a single control technology (such as general ventilation or containment) is applied to a defined range or band of exposure to a chemical (such as 1-10 mg/m3) that falls within a given hazard group (such as harmful by inhalation or irritating to respiratory system)” (
Schulte et al., 2008).
In general CB can simplify the decision making process with regard to selection of control approaches. With the CB approach, it is not necessary for organisations to undertake the steps of worker exposure measurement and make comparisons with occupational exposure standards. This is undertaken by experts in order to inform the development of the CB guidance. CB includes the estimation of a specific hazard band for which a hazardous substance is assigned, based on risk statements (often from a Material Safety Data Sheet; MSDS) in combination with other factors, such as the volatility of the substance (
SWA, 2010).
Underlying the CB approach is the R-phrase (risk phrase) for a substance, which links toxicological data with relative hazard from exposure to a substance via a given route of entry. R-phrases have been referenced and applied as guides in the absence of Threshold Limit Values (TLVs) or occupational exposure limits (OELs) for inhalation of very toxic substances. However it remains doubtful at this point whether specific R-phrases for nanomaterials have been developed to the extent to which they could be used dependably for this purpose.
In relation to nanotechnologies, CB is likely to be a suitable risk control approach for managing nanoparticle exposure in many situations. It is particularly favourable for 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. CB has therefore been presented as a viable approach to aid in the comprehensive evaluation occupational hazards, and there is now an emerging body of literature on the topic. Key literature relevant to the area is summarised below.
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Within this report, which was published in December 2010, a CB method for graduated control of risks associated with nanomaterials is presented. It takes into account the conditions associated with nanomaterial manufacture, use and disposal in order to help to ensure that the resulting control band is relevant to the real-world context of usage.
The full control banding document is available online
here (this document is in French).
Within this
paper, the application of a pilot CB “Nanotool” for risk level assessment and control of nanoparticle exposures is described. The tool provides a structured approach towards determining the severity and probability scores. Severity is calculated based on points assigned for various physico-chemical parameters and toxicity endpoints. Probability is determined from points assigned for estimated amount of nanomaterial used during task, dustiness/mistiness, number of employees with similar exposure, frequency of operation, and duration of operation.
Further information on this CB method may be found
here.
The efficacy of this CB Nanotool was evaluated by
Zalk et al. (2009). The authors considered the CB Nanotool to be consistent with what it was aiming to achieve, i.e. a consistent approach that would generally err on the safe side, in light of the uncertainty associated with the health effects related to nanomaterials. However they did identify that in 10% of the scenarios tested using the tool, control was not as high as would have been recommended by an expert industrial hygienist.
CB for nanomaterials is currently being developed as a Technical Standard within ISO 299 Nanotechnologies. Further information on this control banding schema will be added as it is made available.
A relatively specific type of control banding was proposed in this
BSI document. This suggested specific control approaches appropriate for various activities for 4 categories of nanomaterials. Given the paucity of information available at the time that the BSI document was published, it was intended to provide a conservative approach, and gave strong recommendation that the efficacy of the chosen method should be evaluated.
To support this activity, the guidance also developed Benchmark Exposure Levels (BELs). These guidance values were not health based but again were intended to provide a conservative comparator.
This report was authored by the Monash Centre for Occupational & Environmental Health (MonCOEH) and the Australian Centre for Human Health Risk Assessment (ACHHRA) based at Monash University. It focuses on investigation of the feasibility of:
1. establishing group-based Australian National Exposure Standards for engineered nanomaterials, and;
2. using control banding for engineered nanomaterials in Australia.
The report includes a detailed assessment of the proposed benchmark exposure levels (BELs) and control banding based guidance within the BSI Guidance document PD6699-2 (described above). To access the report in full,
click here.