Interim Guideline
for Working Safely with Nanotechnology
(Based on the Most Current NIOSH Information at 01-Sep-2005.
This Interim guideline will be revised on completion of the
National Nanotechnology Research Agenda and NIOSH Recommendations)
What is Nanotechnology?
Nanotechnology is somewhat loosely defined, although in general terms it covers
engineered structures, devices and systems that have a length scale of 1 – 100
nanometers1. At these length scales, materials begin to exhibit unique properties that
affect physical, chemical and biological behavior. Researching, developing and utilizing
these properties is at the heart of the new technology.
Nanotechnology is the understanding and control of matter at dimensions of roughly 1
to 100 nanometers, where unique phenomena enable novel applications1. A nanometer is
one-billionth of a meter; a sheet of paper is about 100,000 nanometers thick.
Encompassing nanoscale science, engineering and technology, nanotechnology involves
imaging, measuring, modeling, and manipulating matter at this length scale.
At this level, the physical, chemical, and biological properties of materials differ in
fundamental and valuable ways from the properties of individual atoms and molecules or
bulk matter. Nanotechnology R&D is directed toward understanding and creating
improved materials, devices, and systems that exploit these new properties.
Medical researchers work at the micro- and nano-scales to develop new drug delivery
methods, therapeutics and pharmaceuticals. For instance, DNA, our genetic material, is
in the 2.5 nanometer range, while red blood cells are approximately 2.5 micrometers1.
Nanotechnology involves the creation and/or manipulation of materials at the nanometer
(nm) scale either by scaling up from single groups of atoms or by refining or reducing
bulk materials. A nanometer is 1 x 10-9 m or one millionth of a millimeter. To give a
sense of this scale, a human hair is of the order of 10,000 to 50,000 nm, a single red
blood cell has a diameter of around 5000 nm, viruses typically have a maximum
dimension of 10 to 100 nm and a DNA molecule has a diameter of 2 – 12 nm1.
The use of the term “nanotechnology” can be misleading since it is not a single
technology or scientific discipline. Rather it is a multidisciplinary grouping of physical,
chemical, biological, engineering, and electronic, processes, materials, applications and
concepts in which the defining characteristic is one of size.
Background
The past decade has seen intense interest in developing technologies based on the
unique behavior of nanometer-scale (nanoscale) structures, devices and systems,
leading to the rapidly expanding and highly diverse field of nanotechnology.
Interim Guideline for Working Safely with Nanotechnology
Although many nanotechnologies are still in the pre-competitive stage, nanoscale
materials are increasingly being used in optoelectronic, electronic, magnetic, medical
imaging, drug delivery, cosmetic, catalytic and materials applications. Between 1997 and
2003, worldwide government investment in the field rose from $432 million a year to
just under $3 billion a year, and the global impact of nanotechnology-related products is
predicted to exceed $1 trillion by 20152.
NIOSH is unaware of any comprehensive statistics on the number of people in the U.S.
employed in all occupations or industries in which they might be exposed to engineered,
nano-diameter particles in the production or use of nanomaterials. Perhaps because of
the relative newness of the nanotechnology industry, there appear to be no current,
comprehensive data from official survey sources, such as the U.S. Bureau of Labor
Statistics (BLS).
Occupational
Health
Risks
Existing research shows there is little evidence to suggest that the exposure of workers
arising from the production, handling, and processing of nanoparticles has been
adequately assessed6. Current knowledge is inadequate for risk assessment purposes6.
No information has been identified about worker exposures to nanoparticles in the
university/research sector or in the new nanoparticle companies6.
Occupational health risks associated with manufacturing and using nanomaterials are not
yet clearly understood. The rapid growth of nanotechnology is leading to the
development of new materials, devices and processes that lie far beyond our current
understanding of environmental and human impact. Many nanomaterials and devices are
formed from nanometer-scale particles (nanoparticles) that are initially produced as
aerosols or colloidal suspensions. Exposure to these materials during manufacturing and
use may occur through inhalation, dermal contact and ingestion. Minimal information is
currently available on dominant exposure routes, potential exposure levels and material
toxicity. What information does exist comes primarily from the study of ultrafine
particles (typically defined as particles smaller than 100 nanometers).
Studies have indicated that low solubility ultrafine particles are more toxic than larger
particles on a mass for mass basis. There are strong indications that particle surface
area and surface chemistry are primarily responsible for observed responses in cell
cultures and animals. There are also indications that ultrafine particles can penetrate
through the skin, or translocate from the respiratory system to other organs. Research
is continuing to understand how these unique modes of biological interaction may lead
to specific health effects.
Workers within nanotechnology-related industries have the potential to be exposed to
uniquely engineered materials with novel sizes, shapes and physical and chemical
properties, at levels far exceeding ambient concentrations. To understand the impact of
these exposures on health, and how best to devise appropriate exposure monitoring and
Page 2 of 11
Interim Guideline for Working Safely with Nanotechnology
control strategies, much research is still needed. Until a clearer picture emerges, the
limited evidence available would suggest caution when potential exposures to
nanoparticles may occur.
NIOSH Activities
A number of active research programs within NIOSH are investigating ultrafine and
nanoparticle behavior, and the health risks associated with nanomaterials. A NIOSH
Nanotechnology Research Center is being developed that will coordinate institute-wide
nanotechnology-related activities. The Institute is also working with other agencies to
address health issues associated with nanotechnology, including participation in the
National Nanotechnology Initiative3 and the Nanoscale Science, Engineering and
Technology subcommittee of the National Science and Technology Council committee on
technology (NSET). Building on these initiatives, NIOSH is developing a strategic plan to
address immediate and long-term issues associated with nanotechnology and
occupational health in partnership with other federal agencies, research centers and
industry.
NIOSH, the Environmental Protection Agency, and the National Science Foundation are
seeking applications proposing research about the potential implications of
nanotechnology and manufactured nanomaterials on human health and the environment.
Further information is available at
http://es.epa.gov/ncer/rfa/2004/2004_manufactured_nano.html
NIOSH’s key role in conducting and partnering in research on occupational exposures to
nanomaterials is noted in a new strategic plan under the National Nanotechnology
Initiative. The National Nanotechnology Initiative Strategic Plan: December 2004 charts
the vision, goals, and plans by which NIOSH and partner agencies will work to expedite
the responsible advancement of nanotechnology over the next 5 to 10 years, and to
ensure that the U.S. will remain a world leader in nanotechnology research and
development. The strategic plan is available at
http://www.nano.gov/NNI_Strategic_Plan_2004.pdf
The NIOSH Nanotechnology
and Health
& Safety Research
Program.
NIOSH is conducting a five-year multidisciplinary study into the toxicity and health risks
associated with occupational nanoparticle exposure. Research will cover aerosol
generation and characterization studies in the lab and in the field, toxicity studies
investigating the significance of aerosol surface area as a dose metric, and
cardiopulmonary toxicity and lung disease related to carbon nanotubes, and other
nanoparticles. The Nanotechnology Safety and Health Research Program is coordinated
by Vincent Castranova, Ph.D., who provided information and current recommendations
for this Interim Guideline.
Knowledge
Gaps
1: The nanoparticle
nomenclature
is not sufficiently
Page 3 of 11
well described
or
Interim Guideline for Working Safely with Nanotechnology
agreed
Currently there are no agreed definitions for nanoparticles, nanoparticle aerosols,
or for the various types of nanoparticles which are produced. Definitions
proposed need to define a size interval to take account of the distribution in
sizes likely to be present, to consider whether the definition should be based on
physical dimensions (e.g. length, diameter, surface area) or on some behavioral
property such as diffusivity and take account of agglomerated aerosols. Progress
on nomenclature issues is usually best achieved based on consensus. The
planned conference on nanoparticle health risks (organized by HSE and NIOSH)
will provide an ideal forum to discuss these issues.
2: There are no convenient methods by which exposures to nanoparticles
in the workplace can be measured or assessed
For inhalation, the most appropriate metric for assessment of exposure to most
nanoparticles is particle surface area. Currently there are no effective methods
available by which particle surface area can be assessed in the workplace. There
is a need for more research into the development of new improved methods,
combinations and strategies to provide reliable assessments of exposure to
nanoparticles and nanoparticle aerosols. Development of appropriate methods to
evaluate dermal and ingestion exposure is also necessary. HSE should consider
how best to promote the development of appropriate metrics and exposure
assessment approaches.
3: Insufficient knowledge concerning nanoparticle
exposure is available
Much more information is needed regarding the exposure of workers involved in
the production of all of the various types of nanoparticles via all of the
production processes. In the absences of suitable measurements systems,
coherent approaches as described above should be adopted. At this stage there
is insufficient evidence to judge whether exposure to the various forms of
nanoparticles is occurring at significant levels in nanoparticle production
processes. HSE should consider how to encourage such data to be collected.
4: The effectiveness of control approaches has not been evaluated
Better understanding is required relating to the effectiveness of control of
nanoparticles. This will be better informed given the development of appropriate
methods for assessment of exposure to nanoparticles and a better understanding
on the levels of exposure that may be acceptable. This is true for both inhalation,
dermal and ingestion risks. HSE should consider how to promote the evaluation of
control approaches.
5: Knowledge concerning nanoparticle
risks is inadequate for risk
assessments
Current knowledge is inadequate for risk assessment. Risk assessment
approaches will have to consider how best to use information which is currently
available, and plan to collect new information. An effective strategy for
collecting, storing and disseminating this information is also necessary.
Development of appropriate databases, and other information resources that can
be used to collect and disseminate information on studies to investigate
Page 4 of 11
Interim Guideline for Working Safely with Nanotechnology
exposure or toxicological assessment of nanoparticles is a key element in this.
Researchers must document, collate, maintain and disseminate information
relevant to nanoparticle risk issues.
Carbon Nanotubes
Perhaps the most significant spin-off product of fullerene research, leading to the
discovery of the C60 "buckyball" by the 1996 Nobel Prize laureates Robert F. Curl,
Harold W. Kroto, and Richard E. Smalley, are nanotubes based on carbon or other
elements. These systems consist of graphitic layers seamlessly wrapped to cylinders.
With only a few nanometers in diameter, yet (presently) up to a millimeter long, the
length-to-width aspect ratio is extremely high. A truly molecular nature is unprecedented
for macroscopic devices of this size. Accordingly, the number of both specialized and
large-scale applications is growing constantly.
Carbon nanotubes are fullerene-related structures that consist of graphene cylinders
closed at either end with caps containing pentagonal rings. They were discovered in
1991 by the Japanese electron microscopist Sumio Iijima who was studying the material
deposited on the cathode during the arc-evaporation synthesis of fullerenes. He found
that the central core of the cathodic deposit contained a variety of closed graphitic
structures including nanoparticles and nanotubes, of a type never previously been
observed. A short time later, Thomas Ebbesen and Pulickel Ajayan, from Iijima's lab,
showed how nanotubes could be produced in bulk quantities by varying the arcevaporation conditions. This paved the way to an explosion of research into the physical
and chemical properties of carbon nanotubes in laboratories all over the world.
A major event in the development of carbon nanotubes was the synthesis in 1993 of
single-layer nanotubes. The standard arc-evaporation method produces only multilayered
tubes. It was found that addition of metals such as cobalt to the graphite electrodes
resulted in extremely fine tube with single-layer walls. The availability of these structures
should enable experimentalists to test some of the theoretical predictions that have
been made about nanotube properties.
Smalley’s group described an alternative method of preparing single-walled nanotubes in
1996. Like the original method of preparing C60, this involved the laser-vaporization of
graphite, and resulted in a high yield of single-walled tubes with unusually uniform
diameters. These highly uniform tubes had a greater tendency to form aligned bundles
than those prepared using arc-evaporation, and led Smalley to christen the bundles
nanotube "ropes". Initial experiments indicated that the rope samples contained a very
high proportion of nanotubes with a specific armchair structure. Subsequent work has
suggested that the rope samples may be less homogeneous than originally thought.
Nevertheless, the synthesis of nanotube ropes gave an important boost to nanotube
research, and some of the most impressive work has been carried out on these samples.
Studies into the propensity for carbon nanotubes to form an aerosol, while being
handled, and the toxicity of nanotubes were recently published 4,5.
Page 5 of 11
Interim Guideline for Working Safely with Nanotechnology
Reasonable
Engineering
Control Strategies for Working with Nanoparticles
Research within TEES Facilities
in
Strategies to control exposure to nanoparticles will include:
•
•
•
•
•
•
•
•
•
•
•
•
Total enclosure of the process
Storage of all nano-materials in total enclosure
Local exhaust ventilation, with HEPA filtration
General ventilation
Limitation of numbers of workers and exclusion of others
Reduction in periods of exposure, via SOP’s and personnel training
Regular cleaning of wall and other surfaces; documented cleaning schedule
Use of appropriate personal protective equipment
Prohibition of eating and drinking in laboratories and controlled areas
Transport of nano-materials within secondary containment device
Immediate cleanup of all spills & discharges
Collection of all nanoparticle waste materials for disposal in compliance with the
TAMU Hazardous Waste Management Plan.
CONTROL OF EXPOSURE
BY INHALATION6
Engineering control
For air velocities prevailing in workplaces, airborne nanoparticles can be considered as
having no inertia. They will therefore behave in a similar way to a gas and if not fully
enclosed will diffuse rapidly and will remain airborne for a long time. Because of their
high diffusion velocity, these particles will readily find leakage paths in systems in which
the containment is not complete. Engineering control systems designed for use to
control nanoparticles such as enclosures, local exhaust ventilation (LEV), fume hoods
and general ventilation therefore need to be of similar quality and specification to that
which is normally used for gases rather than for particulate challenges. These systems
do exist and are in common use in the chemical and other industry. Like all such systems
effective performance of these systems will be highly dependent on appropriate use and
maintenance.
Engineering controls are widely used to reduce exposure to welding fume. A variety of
methods are recommended including general ventilation, LEV, fume hoods and on-gun
extraction (HSE, 1990). The level of protection provided by these methods is considered
to be quite variable and dependent on issues previously mentioned such as maintenance
and worker behavior. Engineering controls of this type are also used in the carbon black
industry but as indicated earlier, significant exposure in this industry still occurs.
Filtration
Filtration plays an important role in the control of exposure to airborne particles. High
Efficiency Particulate Arrester (HEPA) filters are used in engineering control systems to
clean the air before returning it to the workplace. These filters are usually referred to as
mechanical filters.
Page 6 of 11
Interim Guideline for Working Safely with Nanotechnology
Filtration theory is well understood and has been extensively described by several
authors (e.g. Brown, 1992). As an aerosol penetrates through a filter, the trajectories of
the particles deviate from the streamline due to various well-understood mechanisms. As
a result, particles may collide with the filter elements (fibers) and become deposited on
them. The mechanisms include diffusion, interception, initial impaction and gravitational
settling. Electrostatic forces can also play a role in some filter types.
For particles less than 100nm, Brownian diffusion is the dominant mechanism (Lee and
Mukund, 2001). Filtration efficiency due to Brownian diffusion increases as particle size
decreases. Brownian diffusion is caused by collisions between particles and the air
molecules to create random paths that the particles follow. The random motion
increases the probability of a particle contacting one of the filter elements. Once the
particle is collected onto a surface it will adhere to it due to the Van der Waals forces.
Therefore filters are likely to be good collectors of nanoparticles.
Current methods for certification of HEPA filters and for respirator filters do not
routinely require testing at particle sizes in the nanometer size range. Internationally
recognized standards for HEPA filters (DOE, 1998) require that the filter is challenged
with an aerosol with a mass median diameter of 300nm and that the particle collection
efficiency is greater than 99.97%. Three hundred nanometers is considered to be a
much more penetrating aerosol for these filters than nanometer size particles due to the
decrease of Brownian diffusion at this particle size. Similarly European Standards for
respirator filter cartridges (CEN, 2001a) and for filtering face pieces (CEN, 2001b)
require that these systems are tested against sodium chloride aerosols with a mass
median diameter of 300nm. Again this is based on an expectation that this would be the
most penetrating size.
Little work has been done to quantify the performance of filters against particles in the
nanometer size range. It is still widely accepted, that with diffusion the dominant
mechanism and the efficiency of filters will be high.
Use of Personal Protective Equipment (PPE)
Use of PPE such as respirators and air fed devices may be used (as a final option) as a
method of control for any airborne hazard. All of these devices depend on filtration as a
means of cleaning the air prior to it being breathed by the worker. The discussion
relating to filtration applies equally here. It is probable, for all but the smallest
nanoparticles (<2nm) that the filtration efficiency will be high. It was not possible to
identify any relevant research that has demonstrated this.
Air-purifying respirators are widely used in diverse workplaces, and thanks to
decades of research and experience, occupational health professionals have confidence
that a NIOSH-certified device with the correct filter, and properly fit-tested, will provide
appropriate protection against silica dust and other traditional airborne contaminants.
But what about particles in the nanoscale range, which are significantly tinier than
traditional particles? Will the same filter be equally efficient in capturing them? To
answer that question, NIOSH recently issued a contract for a laboratory study by
Page 7 of 11
Interim Guideline for Working Safely with Nanotechnology
scientists at the University of Minnesota. NIOSH is funding the contract for one year,
ending March 2006.
Conventional knowledge, based on a substantial body of evidence, holds that airborne
particles 0.3 micrometers in size are more likely to penetrate a filter than particles of
other sizes. Particles larger than 0.3 um will be blocked by filter fibers. Those smaller
than 0.3 um will be stuck on and among the fibers through a process called
“diffusional capture.” Consequently, if a filter captures particles 0.3 um in size,
scientists could be confident that the filter would capture particles of any size.
However, little experimental work has been done to quantify the performance of filters
against particles in the nanometer size range. The NIOSH-funded study aims to
determine if the accepted theory of filtration remains valid for particles on the borders
of nanosize and below. If the study finds that the effectiveness of filters begins to
decrease for nanosize particles, it will attempt to identify at what size this decrease is
likely to occur. Preliminary findings from the study are to be presented at the second
International Symposium on Nanotechnology and Occupational Health, at Minneapolis,
Minn., Oct. 3-6, 2005.
“NIOSH’s support for this study is part of our commitment with many partners to
address current questions about nanotechnology and occupational health, and to design
exemplary research to help answer those questions,” said NIOSH Director John Howard,
M.D. “In so doing, we will help to ensure that the U.S. remains strong and competitive in
the dynamic global nanotechnology market.”
It is well recognized in the science of Industrial Hygiene, however, that the determining
factor governing the effectiveness of respiratory protection equipment (RPE) against
particulate challenges is not absolute penetration through the filter, but rather face-seal
leakage that bypasses the device. Face seal leakage is dependent on many factors
including the fit of the mask to the face, duration of wearing, work activity etc. Since it
is expected that nanoparticle aerosols will have high mobility, it is possible that
enhanced leakage will occur although no more than might be expected for a gas. No
relevant research to quantify this has been identified.
CONTROLS FOR DERMAL EXPOSURE
Issues relating to dermal exposure have only relatively recently come to prominence in
occupational hygiene. Based on our understanding of the various processes by which
nanoparticles can be synthesized there seems to be a strong possibility of dermal
exposure occurring, most likely in the later stages of the process i.e. recovery or
resulting from surface contamination. There is some evidence that dermal exposure to
nanoparticles may lead to direct penetration of nanoparticles into the epidermis and
possibly beyond into the blood stream. Therefore, it may be necessary to introduce
control to exclude or limit the level of dermal exposure likely to occur.
As for inhalation exposure, COSHH provides a framework by which a strategy to prevent
or control dermal exposure can be developed. However, it is acknowledged that
prevention of dermal exposure is not covered so well in the guidance associated with
COSHH.
Page 8 of 11
Interim Guideline for Working Safely with Nanotechnology
As with control of exposure by inhalation, the first approach is enclosure of the process.
This should certainly be achievable as powder-handling processes can be enclosed
successfully. However in practice, particularly with products or processes that are in
development, the main emphasis is on investment and expenditure at the synthesis end
of the process. This is likely to limit the expenditure on sophisticated control and
automation processes to deal with what will be perceived as relatively mundane tasks
such as harvesting and packing of nanomaterials.
In any case even where such processes are in place, the requirements for attention to
breakdowns, maintenance etc means that the possibility of dermal exposure cannot be
excluded at all times. In these and other instances protection against dermal exposure
typically consists of the use of Skin Protective Equipment (SPE) i.e. suits, gloves and
other items of protective clothing.
Even for powders in the macro scale, it is recognized that SPE is very limited in its
effectiveness to reduce or control dermal exposure. Based on current understanding
(Schnieder et al; 2000) multiple processes contribute to dermal exposure, and the
relative ineffectiveness of SPE. In addition to the classical view that the failure of SPE
results from direct penetration or permeation of an agent through the material from
which the equipment is constructed, other process include transfer of substances by
direct contact between surface, skin and outer respectively inner clothing or gloves, and
redistribution of substances between compartments of the same type, e.g.
redistribution of contaminants from one part of the skin contaminant layer to another as
a result of touching the face with contaminated fingers.
Current European testing for certification of PPE against dermal exposure only takes
account of permeation or penetration. Although recently, new tests have been proposed
which take account of the other human factors based on simulations (Brouwer et al;
2004). Since it is likely that nanoparticles which escape into the workplace will become
widely dispersed and will have high surface area, it is likely that the human factor
element will be even more critical than for macrosize particles. In this case, it is quite
likely that SPE will be less effective against nanoparticles than against macro size
particles. It is also quite likely that direct penetration of nanoparticles through the
material from which the protective clothing is made will be higher than for macro-sized
particles.
CONTROLS FOR INGESTION EXPOSURE
Understanding about exposure by ingestion in the workplace is not currently well
developed. It is considered that ingestion exposure in the workplace results primarily
from hand-to-mouth contact. It follows that strategies that tend to reduce dermal
exposure in the workplace will also tend to reduce exposure by ingestion. The converse
of this is also true. At this point in time we have identified no relevant research that has
successfully quantified exposure to nanoparticles by ingestion in the workplace or the
effectiveness of strategies to reduce this exposure.
Page 9 of 11
Interim Guideline for Working Safely with Nanotechnology
References
1. NNI, What is Nanotechnology? www.nano.gov/html/facts/whatIsNano.html.
2. Roco, M. C., Broader societal issues of nanotechnology, J. Nanoparticle Res. 5,
181-189, 2003.
3. NNI, The National Nanotechnology Initiative www.nano.gov.
4. Maynard, A. D., Baron, P. A., Foley, M., Shvedova, A. A., Kisin, E. R., and
Castranova, V., Exposure to Carbon Nanotube Material: Aerosol Release During
the Handling of Unrefined Single Walled Carbon Nanotube Material, J. Toxicol.
Environ. Health 67 (1), 87-107, 2004.
5. Shvedova, A. A., Kisin, E. R., Murray, A. R., Gandelsman, V. Z., Maynard, A. D.,
Baron, P. A., and Castranova, V., Exposure to carbon nanotube material:
Assessment of the biological effects of nanotube materials using human
keratinocyte cells., J. Toxicol. Environ. Health 66 (20), 1909-1926, 2003.
6. Aitken, R.J., K.S. Creely, and C.L. Tran, Nonoparticles: An Occupational Hygiene
Review. Institute of Occupational Medicine. HSE Books, Riccarton, Edinburugh.
2004. ISBN 0 7176 2908 2.
7. An evaluation of a university lab producing single walled carbon nanotubes
reported: “Estimates of the airborne concentration of nanotube material
generated during handling suggest that concentrations were lower than 53
µg/m3 in all cases.” However, “laboratory studies indicated that with sufficient
agitation unrefined SWCNT material can release fine particles into the air.” J.
Toxicol. Environ. Health Part A, 67:87-107, 2004.
8. Unrefined SWCNT are contaminated by up to 30% iron by weight. This iron is
redox reactive and can generate hydroxyl radicals which cause oxidant injury to
human cells in culture. J. Toxicol. Environ. Health Part A, 66:1901-1918, 2003.
9. Pharyngeal aspiration of 10 – 40 ug of purified SWCNT (containing 0.2% iron) in
a mouse model resulted in an interstitial fibrotic reaction that progressed
through 60 days post-exposure. Am. J. Physiol.: Lung Cell Mol. Physiol. (in
press, doi:10.1152/ajplung,00084.2005).
Page 10 of 11
Interim Guideline for Working Safely with Nanotechnology
Appendix
Subject: Draft response for comment
Date: Thu, 1 Sep 2005 11:48:34 -0400
Thread-Topic: Draft response for comment
Thread-Index: AcWvDJxG19srdPPtQ4q1nx6QSZT5BA==
From: "Fominko, Irene" <iaf3@CDC.GOV>
To: <bree@tamu.edu>
Cc: "Castranova, Vincent" <VIC1@CDC.GOV>
Dear Mr. Breeding,
Concerning your question about precautionary guidelines in the handling and storing of carbon nanotubes,
NIOSH is looking into this issue, and best practices for handling nanomaterials is an active topic of the strategic
NIOSH Nanotechnology Research Agenda. NIOSH is currently reviewing available information and intends to
publish soon, on the NIOSH web site, interim discussion and recommendations for best practices. The interim
web document will be subject to stakeholder comment and change as needed, as more information becomes
available through continuing research. In the meantime, if you are not familiar with them, the following are published, peer-reviewed results of NIOSH
studies on single walled carbon nanotubes:
1.
An evaluation of a university lab producing single walled carbon nanotubes reported: “Estimates of
the airborne concentration of nanotube material generated during handling suggest that
concentrations were lower than 53 µg/m3 in all cases.” However, “laboratory studies indicated that
with sufficient agitation unrefined SWCNT material can release fine particles into the air.” J. Toxicol.
Environ. Health Part A, 67:87-107, 2004.
2.
Unrefined SWCNT are contaminated by up to 30% iron by weight. This iron is redox reactive and can
generate hydroxyl radicals which cause oxidant injury to human cells in culture. J. Toxicol. Environ.
Health Part A, 66:1901-1918, 2003.
3.
Pharyngeal aspiration of 10 – 40 ug of purified SWCNT (containing 0.2% iron) in a mouse model
resulted in an interstitial fibrotic reaction which progressed through 60 days post-exposure. Am. J.
Physiol.: Lung Cell Mol. Physiol. (in press, doi:10.1152/ajplung,00084.2005).
These and other NIOSH studies will help lead to a better understanding of nanotechnology’s implications and
applications for occupational health. I hope this information is useful.
Vince Castranova, Ph.D.
Coordinator
Nanotechnology Safety and Health Research Program
National Institute of Occupational Safety & Health (NIOSH)
Page 11 of 11