To define or not to define nanomaterials

There’s been a debate of sorts over whether or not nanomaterials should be defined prior to setting a regulatory framework. It’s a topic I covered most recently in my July 8, 2011 posting,

I have mentioned Andrew’s (Dr. Andrew Maynard [Director of University of Michigan Risk Science Center]) perspective vis à vis bypassing a definition of nanomaterials and getting on with the task of setting a regulatory framework in my June 9, 2011 and my April 15, 2011 postings. I expressed some generalized doubts about this approach in the earlier posting while noting that both Andrew and Dexter Johnson (Nanoclast blog on the IEEE [Institute of Electrical and Electronics Engineers]  Spectrumwebsite) have a point when they express concern that the definition may be based on public relations concerns rather than science.

Andrew’s  ‘comment’, Don’t define nanomaterials, had been published the day before in the journal Nature. An Aug. 30, 2011 news item on Nanowerk alerted me to the latest development. A few days ago, Hermann Stamm of the European Commission Joint Research Centre, Institute for Health and Consumer Protection had a rejoinder published, Risk factors: Nanomaterials should be defined.

So here’s how this part of the debate started in July, Andrew notes his concern that policymakers will give in to expediency and define nanomaterials primarily in relation to size, i. e., 1 to 100 nanometres. From Andrew’s July 7, 2011 Nature comment (Note: This is behind a paywall, you can read a draft version here),

It makes sense to assume that nanomaterials could come with unanticipated risks. A rapidly growing body of research indicates that some nanoscale materials behave differently from their bigger and smaller counterparts1. For instance, normally benign titanium dioxide — widely used as a whitener — becomes increasingly toxic as its particle size shrinks. Nanoscale titanium dioxide has been classified as a potential human carcinogen by the US National Institute for Occupational Safety and Health.

But it is becoming clear that many parameters other than size modulate risk, including particle shape, porosity, surface area and chemistry. Some of these parameters become more relevant at smaller scales — but not always. The transition from ‘conventional’ to ‘unconventional’ behaviour, when it does occur, depends critically on the particular material and the context.

A ‘one size fits all’ definition of nanomaterials will fail to capture what is important for addressing risk.

He then provides a series of arguments supporting his notion that a list of attributes along with values that would precipitate action is preferable to what he described as a ‘one size fits all’ approach.

Herman Stamm’s rejoinder (August 25, 2011 Nature comment [Note: this is behind a paywall]) simplifies Andrew’s arguments for a simple reiteration of his position,

Maynard’s point that such materials are heterogeneous is justified. However, they all have structures on the nanoscale, which modify their other properties. Size is therefore the most appropriate parameter on which to base a broad definition …

My concern with these things has to do with implementation and which approach is going to ensure better safety? Andrew’s approach reminds me of fuzzy logic and computers. I think they’re called ‘if then’ programming scripts: if [xxx happens] then do [yyy]; if [ssss happens] then do [ttt] and so on. Stamm’s approach is a standard one for regulation, i. e., create a hard and fast rule.

Both approaches have their strengths and weaknesses. Andrew’s proposed method allows for great flexibility and agility but as the system becomes more complex (and they always do) then there’s a strong probability of incompatible ‘scripts’ and if there isn’t an overarching principle or rule, then disputes become very difficult if not impossible to resolve.

Stamm’s method, i. e., using size as the key determinant for a rule is likely to lead to an inflexibile attitude and a lack of agility when dealing with situations that are ambiguous or don’t fit the definition. Who hasn’t experienced or heard of a bureaucrat who abides strictly by the rules as written even if they’re not appropriate for the specific situation?

As I’ve noted before I’m slowly coming round to Andrew’s suggestion although I continue to have doubts.

One thought on “To define or not to define nanomaterials

  1. Pingback: Nanomaterials, nanomedicines and nanodefinitions « FrogHeart

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