My thoughts on the Health Canada nanomaterial definition

In my Oct. 11, 2011 posting, I noted that Health Canada had released both its nanomaterial definition and its response to the public consultation that took place in 2010. Unfortunately, it’ s not possible to attempt the same sort of  analysis (mentioned in my Oct. 21, 2011 posting) that Dr. Andrew Maynard applied to the US government (National Nanotechnology Initiative) public consultation on EHS (environmental, health and safety) research strategy as Health Canada did not make the submissions available for viewing.

In my first posting, I focused largely on the public consultation aspects, now I’d like to look more closely at the definition itself (especially in the wake of the European Commission’s Oct. 19, 2011 announcement of its nanomaterials definition). Note: Health Canada says nanomaterial; European Commission says nanomaterials.

Here’s the definition (from the Policy Statement on Health Canada’s Working Definition for Nanomaterial webpage),

4.1 Health Canada’s Working Definition of Nanomaterial

Health Canada considers any manufactured substance or product and any component material, ingredient, device, or structure to be nanomaterial if:

  1. It is at or within the nanoscale in at least one external dimension, or has internal or surface structure at the nanoscale, or;
  2. It is smaller or larger than the nanoscale in all dimensions and exhibits one or more nanoscale properties/phenomena.

For the purposes of this definition:

  1. The term “nanoscale” means 1 to 100 nanometres, inclusive;
  2. The term “nanoscale properties/phenomena” means properties which are attributable to size and their effects; these properties are distinguishable from the chemical or physical properties of individual atoms, individual molecules and bulk material; and,
  3. The term “manufactured” includes engineering processes and the control of matter.

4.2 Elaboration

The Working Definition is not an additional source of authority, but works within the existing regulatory frameworks that allow for obtaining information.

Information is submitted to Health Canada regulatory programs as required by legislation and their associated regulations. Within these legislative and regulatory frameworks, Health Canada may request specific information (see Section 6) for a regulated substance or product that is, or contains, a nanomaterial as described in the Working Definition.

The term “manufactured” includes engineering processes and control of matter that lead to the synthesis, generation, fabrication or isolation of nanomaterials. Health Canada may request information regarding a deliberately or incidentally manufactured nanomaterial for risk assessment purposes. This term also includes natural components that have been deliberately used or engineered to have nanoscale properties/phenomena, used in nanoscale encapsulation of bioactive compounds, or used in tissue engineering.

“Part a” of the Working Definition relates to current evidence suggesting that nanoscale properties/phenomena are more likely observable at the scale of 1-100 nanometres (more often at the lower end) and “Part b” reflects that it is possible for nanoscale properties/ phenomena to be exhibited outside this size range, such as select quantum devices.

A variety of lexicons and interpretations of “nano-terminology” currently exist, underlining the importance of understanding the context in which these terms are used. In the risk assessment context supporting hazard and exposure assessment for risk characterization and management, the term “nanoscale properties/phenomena” refers to size-related properties which have qualities or characteristics that do not readily extrapolate from those observed in individual atoms, molecules or bulk materials. For example, “bulk” gold is not very reactive, but nanoscale gold can act as a chemical catalyst. For risk assessment purposes, this term includes observable biological or environmental effects resulting from size-related properties as described above. Examples of such biological or environmental effects could be increased permeability through cell membranes or increased reactivity of iron/iron oxides for the purposes of groundwater remediation, respectively.

Internal or surface structures at the nanoscale include nanomaterials that are aggregated or agglomerated to form a larger group. While the break-up of aggregates is less likely, a larger group could be broken down into component nanomaterials in the human body or the environment. Some regulatory programs may request information above the 100 nm size range to an upper limit of 1000 nm in order maintain flexibility to assess potential nanomaterials, including suspected nanoscale properties/phenomena. The 1000 nm cut-off attempts to separate characteristics attributable to macro-scaled materials from those of nanomaterials. However, a product or substance that contains nanomaterial could measure beyond 1 micron in size (for example (e.g.) bundles of carbon nanotubes that are very long). In these cases, regardless of the size, information may be requested for risk assessment purposes.

In addition to requesting information about nanomaterials, information regarding particles above the 100 nm size range may also be requested by some regulatory programs to assess possible biological effects that could be attributable to their dimension or size. These approaches may be applied on a case-by-case basis or to a whole product class.

While not expressly stated in the Working Definition, information regarding nanomaterial size distribution, especially number size distribution, is also relevant for risk assessment purposes.

Currently, there is insufficient evidence to establish common threshold values for size distributions of relevance across all substances and product lines that Health Canada regulates.

I find the fact that this is called a ‘working’ definition immediately establishes a very different frame of reference as the term ‘working’ in this context suggests flexibility. like a ‘working’ hypothesis which can by redefined as more information becomes available. You can find a longer definition for working hypothesis in this Wikipedia essay.

The first two items in the definition are very generalized (in fact, downright vague) but this changes when the meaning of the terms are described where everything becomes more specific. It’s only when reading the elaboration that one realizes how very carefully this definition has been constructed. They have given themselves a lot of ‘wiggle room’. For example,  “”Part a” of the Working Definition relates to current evidence suggesting that nanoscale properties/phenomena are more likely observable at the scale of 1-100 nanometres (more often at the lower end) and “Part b” reflects that it is possible for nanoscale properties/ phenomena to be exhibited outside this size range, such as select quantum devices.”  [emphasis mine]

I’m still waffling as to whether or not a definition is necessary although I’m inclined to say yes to a definition when I see something like this. I think a good balance has been struck between caution and unnecessary (at this time) regulation. E.g., ” Currently, there is insufficient evidence to establish common threshold values for size distributions of relevance across all substances and product lines that Health Canada regulates.” [emphasis mine]

2 thoughts on “My thoughts on the Health Canada nanomaterial definition

  1. Pingback: Dr. Andrew Maynard discusses the Health Canada nanomaterial definition « FrogHeart

  2. Pingback: Nanoparticle size doesn’t matter « FrogHeart

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