Are we asking the right standards questions about advanced materials?
As we consider standards for advanced materials, are we looking at that are based on terms of art, or terms of science?
Opening comments to the ANSI Nanotechnology Standards Panel Advanced Materials workshop, August 20, 2020.
I want to start with an anecdote. Back in the 1980’s when I was in high school in the UK, a select number of students each year sat for the entrance exams for Oxford and Cambridge university. These were well-known for their gnarliness, and ability to trip unsuspecting applicants up.
I never sat the exams. But I do remember the rumors about them, and one in particular about one of the more challenging questions that sometimes came up, where candidates were asked to write an essay on the question “how long is a piece of string?”
Of course, the question — and to be honest l don’t know how true these rumors were — if it existed, was designed to test intellectual and creative aptitude. There are, of course lots of ways it can be answered. But there is no actual quantitative answer to the question.
I mention this because the question is a useful metaphor for thinking about standards and how they apply to advanced materials, as well as their precursor in this particular conversation, nanomaterials.
What the question does rather well is to illuminate the difference between terms of art, and terms of science, when it comes to standards. Both are important, but each has a very different meaning and use. And conflating the two can lead to a whole lot of hurt.
Terms of science are evidence based. They’re derivable They are traceable. And they are insulated from opinion — at least to a certain extent.
In contrast, terms of art encapsulate norms, expectations, opinions and perceptions that are not necessarily grounded in evidence, but that nevertheless grease the wheels that the world runs on.
Both terms of art and terms of science are vital to developing, establishing and applying standards. But using a term of art as if it’s a term of science leads to a process of rationalization that’s akin to asking how long is a piece of string and trying to convince people that you have a definitive answer!
So with that preamble, let me ask another question: As we consider standards for advanced materials — especially building off the standards work done on nanomaterials — are we looking at standards that are based on terms of art, or terms of science? And importantly, are we able to tell the difference?
This is a vital framing question to our discussions here. But there is an even more fundamental question that we need to address in this conversation: Why are we considering developing standards related to advanced materials in the first place?
Of course, there are many reasons why we develop standards, and why they are important. These include, but are certainly not limited to, quality control; scalable innovation; economic growth; competition; establishing a level playing field; and, of course, managing risks to health and the environment.
In approaching standards development in a specific domain, we need to have at least a sense of what the purpose of future standards is, what the most appropriate approach is that we should be taking, together with how we’ll know if the standards are successful, and what the potential consequences of not developing standards are.
These are all important questions as we think about advanced materials. There is an additional question here though, and that is: how can what’s been achieved with nanotechnology and engineered nanomaterials be usefully extended to advanced materials? And of course, this is the focus of this workshop.
At this point, it’s worth asking something that may seem obvious, but is nevertheless helpful I think. And that is: What evidence is there that nanotechnology-related standards have led to measurable positive outcomes?
I have to assume here that there is clear evidence — there certainly should be if we are looking to extend successes in this domain to a broader range of materials. I can’t answer this in a general sense because it lies outside my current work — I’d hope though that participants in this workshop can.
However, what I can provide is some insight into the nanotechnology standards landscape around environmental and health impacts.
Here, despite substantial work over the past decade or so, I fear there is been a muddying of the waters between terms of art, and terms of science. There’s been a tendency to treat terms like “nanotechnology,” “nanomaterial” and “nanoparticle” as if there is a scientific basis for them, whereas these are all ultimately terms of art.
Of course, we can define each of them in terms of size, and length scale, and this is what’s been done. But from a functional perspective, the definitions are arbitrary. 100 nm, no matter how useful it is, is a number of convenience, not of science.
Of course, I’m oversimplifying, and nano standards go way beyond a naïve assumption of a 100 nm cutoff. And I don’t want to downplay the importance of work that has been done here over the past several years But if we don’t recognize the nature of the foundations on which we are thinking about building standards around advanced materials, we run the risk of building a house of cards that will ultimately fail us.
And here I want to be clear that I think there probably are standards that will be needed if we are to fully realize the promise of advanced materials. But the nature and purpose of these standards needs to be well-defined from the get-go.
To illustrate this, consider nanotechnology-focused health and environmental standards for a minute.
A key driver of nanotechnology risk-based standards was research that was carried out in the 1990’s that indicated certain classes of fine particles elicited pulmonary responses that far exceeded those that were expected. And hypotheses began to emerge that the risks they presented were more closely associated with physical parameters such as size, specific surface area, and surface chemistry, rather than the more traditional metrics of bulk chemistry and mass.
These studies didn’t come out of no-where though. They were built on a long tradition of aerosol research going back to the 1950’s that recognized that the inhalation risk associated with occupational airborne particles is related to their physical and chemical form, and the region of the lungs they are capable of penetrating to.
As a result of decades of research, standards were developed that defined potentially harmful materials based on their ability to reach vulnerable parts of the body, and modes of action that were mediated by their physical and chemical form.
In other words, these were standards that directly addressed the implications of complex materials interacting with sensitive biological systems. They were standards that were both evidence-based, and outcomes based. Interestingly, there was even discussion over half a century ago around using exposure metrics such as aerosol surface area and number.
In many ways, more recent health-based standards associated with engineered nanomaterials have been something of a deviation from this evidence-based approach. The term of art here came first — nanotechnology — followed by attempts to treat it as a term of science, with the result that the foundations of some nano-focused standards are probably less useful and more fragile than some of us would like.
With advanced materials, we have an opportunity to get back to basics, and to recognize and respect this term of art for what it is, while developing standards that are both fit for purpose and, where appropriate, evidence-based.
And just to underline this, advanced materials is very clearly a term of art. It has no fundamental scientific basis. It is dependent on context. And it is temporal.
Because of this, we should be asking what the purpose is of standards that relate to what we broadly and indistinctly think of as advanced materials. We should also be asking what the needs and opportunities are here, and how we begin to address what we might consider as relevant functional behavior with actionable standards.
From a health and environment perspective, such relevant functional behavior will depend on exposure or dispersion — that is, the ability of materials to get to places where they can do harm — together with the ways in which these materials interact with biological systems that lead to harm once there.
This, to me, is an essential starting point — and it’s one that focuses on what a material has the potential to do, not what it is called. And here, the stark reality is that nature doesn’t care what we call a material, it just cares about how it behaves.
From this starting point, biological impact becomes the primary driver of standards. This is important, as existing materials that are used in new ways can lead to unexpected risks just as readily as new materials. And likewise, there is no reason to assume that new materials, by default, present new risks.
This challenge of focusing on behavior, rather than being guided by definitions based on terms of art, is one that a couple of colleagues and I set out to explore in our 2010 paper looking at what we termed at the time “sophisticated materials.” Here, I must confess that we chose this term “sophisticated materials” — which is yet another term of art — to try and break away from the conceptual baggage that comes with the terms “nanomaterials” and “advanced materials,” although looking back, this probably didn’t do us any favors citation-wise!
As we worked through what leads to materials raising risk red flags — in other words materials that are likely to slip under the conventional risk radar — we came up with five categories of materials that seemed to warrant particular attention. These included:
Materials that demonstrate abrupt scale-specific changes in biological and environmental behavior, such that by changing the physical structure of the material it is possible to radically alter its risk profile.
Materials that are capable of penetrating to organs and systems that are normally protected against exposure. For instance, materials where their size and structure is such that they are able to cross normally-impermeable biological boundaries.
Active materials, that demonstrate marked changes in biological behavior based on their biological or environmental context.
Self-assembling materials, that have the capacity to alter both form and risk profile in situ.
And materials that otherwise exhibit biological mechanisms of interaction that lead to hazards which are not adequately captured by conventional hazard assessments.
These five categories could all describe “advanced materials.” But they could also equally well describe conventional materials used in new ways, or even existing materials that we haven’t taken seriously in the past, but probably should.
Of course, from a standards perspective, these criteria are not easy to work with. But they, or similar criteria, are amenable to being operationalized within standards that are both evidence based and outcomes based.
And importantly, because they don’t depend so much on terms of art, they help avoid materials slipping the net that don’t confirm to definitions of “advanced materials” and yet still have the potential to cause harm in ways that are not captured through conventional risk assessments.
Of course, environmental and health-based standards are just a small subset of potential advanced material standards. Yet this subset does illustrate the need to be very clear on why standards are being developed, and the potential dangers of building advanced materials standards on nanotechnology standards without fully understanding the limitations of these foundations.
So to wrap up, I want to come back to where I started with that question of how long is a piece of string. And here I wanted to acknowledge that string, of course, is an important product. It needs standards! Standards that define the properties, quality, uses, and a whole host of other aspects of different types of string.
But despite this, “how long is a piece of string” is the wrong question when it comes to developing standards, or at least useful ones.
And this is where I want to leave you — with the question: how do we know we’re asking the right questions with advanced materials?
 e.g. see Maynard, A. D. and E. D. Kuempel (2005). “Airborne nanostructured particles and occupational health.” Journal Of Nanoparticle Research 7(6): 587–614. DOI: https://doi.org/10.1007/s11051-005-6770-9
 Maynard, A. D., D. Warheit and M. A. Philbert (2011). “The New Toxicology of Sophisticated Materials: Nanotoxicology and Beyond.” Tox. Sci. 120(Suppl 1): S109-S129. DOI: https://doi.org/10.1093/toxsci/kfq372