From 2020science:
Nanotechnology—like
other emerging technologies—presents a dilemma: If you're making new
substances with uncertain health risks, how low is low enough when it
comes to managing exposure?
The issue is raised in the current edition of Nature Nanotechnology by Vladimir Murashov of the National Institute for Occupational Safety and Health (NIOSH), and former NIOSH-director John Howard. But the question has been bubbling along for some time.
And it’s an important one. Uncertainty over safe workplace
practices is bad news for nanotech businesses trying to do the right
thing—especially small start-ups that don’t have the resources to work
out their own bespoke solutions. It’s not much better for
regulators—as the gap between emerging technologies and solid
information on their safe use widens, how do you craft new approaches
to protecting people’s health and the environment?
Back in 2007, the Environmental Defense Fund and DuPont released their Nano Risk Framework... The Framework
places a heavy emphasis on pragmatic exposure-based decision-making.
In a nutshell, the message was: Use the best information available. And
when that runs out, use every trick in the book to come up with the
best possible benchmarks for qualitatively managing risk—until better
information is available. And do all this under “reasonable
worst-case” assumptions.
But the Nano Risk Framework stops short of providing practical guidelines on developing benchmarks for exposure assessment.
This gap was neatly filled by a guidance document from BSI Inc—the British Standards Organization—in January 2008. The “Guide to safe handling and disposal of manufactured nanomaterials” (BSI PD 6699-2:2007)
takes the bold step of recommending starting exposure values for four
different classes of nanomaterials—benchmarks for establishing exposure
decision-points in the absence of anything else. PD 6699-2 refers to them as Benchmark Exposure Levels, and couches them in enough caveats to make the most hardened lawyer proud. A better moniker might have been Lifeline Exposure Levels—because
they quite literally throw a lifeline to anyone completely at sea when
it comes to making practical decisions on making sense of airborne
nanomaterial exposure measurements.
But the Benchmark Exposure Levels are based on assumptions and
speculation, not hard science. And while they are firmly grounded in
recommendations within the Nano Risk Framework—using available
information and reasonable worst-case solutions—they are, in the
long-run, no substitute for quantitative risk assessment.
This is one of the main concerns that Murashov and Howard have about the BSI guidelines in their Nature Nanotechnology commentary.
They argue that exposure limits should be based on generally accepted
principles of risk assessment—and I agree with them. But something is
needed in the interim while these limits are established, otherwise the
whole emerging technology enterprise is on dodgy ground!
This is exactly what the Nano Risk Framework and PD 6699-2
address, and hopefully what additional guidance from organizations like
the International Standards Organization, and even government agencies,
will grapple with.
But this brings us back to the original question—how low is low
enough? Because recommendations like “keep exposures as low as
reasonably practicable” simply don’t cut the mustard without some sense
of how to evaluate exposure, and what the numbers mean.
PD 6699-2 makes a good stab at helping industries develop
internal pragmatic guidelines on how to use airborne exposure
measurements when working with new nanomaterials. Earlier this year, I
took a stab at assessing the validity and utility of the Benchmark
Exposure Limits for BSI—the full assessment is available here (PDF, 168 KB). My conclusions: the benchmark levels are far from perfect, but they are a great starting point.
Assuming that most readers will have better things to do than read through the 12-page assessment, here are the conclusions:
If effective health and safety plans are to be
implemented in research laboratories and workplaces generating and
using nanomaterials, guideline exposure limits are essential. In the
absence of further information, the benchmark exposure levels presented
in BSI PD 6699-2:2007 appear reasonable. Furthermore, the context
surrounding the levels—which is clearly stated in the document—allows
people following the recommendations to adapt the levels to their
specific circumstances, depending on the best available information.
In other words, they are not binding, but rather present a clear
starting point for an informed process of setting relevant exposure
levels. And thus, where evidence exists to suggest that the benchmark
exposure levels are overly stringent or not measurable for a given
material, it is left to the discretion of the person setting the levels
to adjust the accordingly.
These suggested levels are not a substitute for workplace exposure
limits, and do not remove the need for targeted research leading to the
development of evidence-based limits. But until such levels are
developed, they fulfil a role that is essential to underpinning the
development of safe and successful nanotechnologies. As such, BSI
should be applauded for publishing them.
The bottom line here is that industry needs practical guidelines on
safe workplace practices where hard information on risks is lacking,
and at some point this will mean grasping the bull by the horns and
providing advice on how to measure exposures, and what the numbers mean.
Giving meaning to the numbers might simply require establishing
rules of thumb for developing bespoke exposure levels. Or it might
require clear benchmark exposure levels to be suggested for different
classes of materials (with suitable caveats of course). Either way,
there will be exposure data, and people will want to know what they mean, and what action to take as a result.
In the long run however, hard data are still needed to underpin
quantitative and authoritative risk assessment that will supersede
interim qualitative measures. And this of course means there needs to
be a research plan, plenty of funding, and a willingness to translate
new information into informed oversight.
But that is a story for another day...
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Note: See also Rob Aitken's blog on the Murashov/Howard Nature Nanotechnology Commentary