Safety and Industrial Hygiene of working with
Carbon Nanotubes
 Nanotechnology
is the engineering and
manipulation of materials at the
molecular level
 The dimension of nanomaterials are
between 1 and 100 nanometers
• 1nm is 1 billionth of a meter
• A human hair is 50,000 nanometers in diameter
 Particles
created at the nanoscale have
different chemical and physical
properties than larger particles of the
same material
 Carbon
Nanotubes (CNTs) in particular
have unique electrical, mechanical, and
thermal properties with a large potential in
electronics, aerospace, and many other
industries.
• CNTs exist in two forms, single-wall (SWCNTs) and
multi-wall (MWCNTs)
 Due
to the relatively new nature of
nanotechnology, research is still being
conducted on the health hazards
 Two facts must be known to determine if
workers are at risk
• The type and concentration of nanoparticles in
the workplace
• The specific properties of the nanoparticles that
could potentially affect the body
 Workplace
exposure
tasks that increase the risk of
• Handling powders of nanomaterials
• Maintenance on equipment and processes used
to produce or fabricate nanomaterials and the
cleaning-up of spills and waste material
containing nanomaterials
• Cleaning of dust collection systems used to
capture nanoparticles
• Machining, sanding, drilling, grinding, cutting, or
other mechanical disruptions of materials
containing nanoparticles
 In
lab animals, some nanoparticles reach
blood, brain, and other organs when
inhaled
 This causes adverse effects such as
inflammation and fibrosis in the lungs and
other organs
 Recent
studies have shown that size,
surface area, surface chemistry,
solubility, and possibly shape all play a
role in determining the potential to cause
harm
 Studies
in workers exposed to aerosols of
some manufactured or incidental
microscopic and nanoscale particles
have reported adverse lung effects
including lung function decrements
and obstructive and fibrotic lung
disease
 CNTs
may contain metal catalysts as
byproducts of their production, which could
contribute to their toxicity
 Regardless
of the process by which CNTs were
synthesized and the types and amounts of
metals they contained, CNTs were capable of
producing inflammation, epithelioid
granulomas (microscopic nodules), fibrosis,
and biochemical/toxicological changes in the
lungs
 SWCNTs
have been shown to produce
adverse effects at mass doses at which
ultrafine carbon black did not produce
adverse effects. Both are carbon based
but SWCNTs have a unique structure
 SWCNTs were shown to be more toxic
than quartz, which is considered a
serious occupational health hazard if it is
chronically inhaled
 MWCNTs
have been shown to produce
lung lesions similar to those observed in
studies with SWCNTs
 These results indicate that, if CNT
particulates reach the lung in sufficient
quantity, they will produce a toxic
response
 These
studies do not answer the
important health risk question of whether
airborne CNT particles can reach the
lungs, because in all cases the CNTs
were placed inside the lungs of animals,
not inhaled
 The
lungs aren’t the only organ affected
by CNTs
• Studying the effects on mouse hearts, scientists
found damage to the DNA, an increase of plaque
in the aortic area, and an increase of
atherosclerotic lesions in the brachiocephalic
arteries
 The
risk of nanotubes is often compared
to that of asbestos
 Exposure to asbestos is not the same
exposure that could occur with CNT’s.
According to Lance Criscuolo, president
of Zyvex Performance Materials, an Ohiobased company that uses CNTs, “CNTs,
once mixed into a polymer matrix, are
bound up and no longer releasable into
air or water.”
 This
means the workers in most concern
are the ones actually creating the CNTs
and putting them into plastics
 The EPA is most concerned with the
fibrous, dry powder and less concerned
with CNTs that are integrated into
polymer materials, said David Burton,
General Manager, Applied Sciences Inc.
 Criscuolo
said Zyvex has done air
monitoring studies throughout the entire
process. “These studies were performed by
a certified company. They were not able to
detect any significant amount of CNTs in the
airstream. This testing was also included in
the composite cutting and sanding area.
This provides some solid evidence that
once CNTs are encapsulated within a resin
system, that they are not able to become
free from that system.”
 Inhalation
• This is the most common and most dangerous
type of exposure
• It has been determined that the factors that have
a role in pulmonary toxicity include, but are not
limited to:
 particle number and size distribution
 dose of particle to target tissue
 surface treatment on particles
 the degree to which engineered nanoparticles
aggregate/agglomerate
 surface charge on particles
 particle shape and/or electrostatic attraction
potential
 method of particle synthesis – i.e., whether formed by
gas phase or liquid phase synthesis and postsynthetic modifications, which likely influence
aggregation behavior.
 Ingestion
• Nanoparticles may enter the gastrointestinal tract as
they are cleared from the upper respiratory tract and
they appear to pass through relatively quickly
• It is known that some nanoparticles, specifically
nanotubes and nanofibers, can undergo surface
oxidation and length shortening in presence of
strong acid conditions, so it is possible that the
acidic gastric environment will not only be unable to
destroy the nanoparticles, but it may functionalize
and shorten the particles to a point that their
toxicological effect on the surrounding environment
might change drastically
 Dermal
• Some studies show that nanoparticles may
penetrate the skin due to their small size. This
possibility is being investigated
 Traditional
industrial hygiene sampling
methods can be used to measure
airborne nanoparticles
• Scientists are developing more sensitive and
specific sampling techniques
 Workers
need the development of
sensors that simultaneously detect
airborne nanoparticles and determine
their potential to generate reactive
oxygen species- possibly providing early
indications of harm
 These
materials are used in the
production of the CNT’s
 Employers
should use engineering
controls to reduce workers exposure to
nanoparticles
• Source enclosure
 Isolating the generation source from the worker
• Local exhaust ventilation systems
 Exhaust ventilation systems that use HEPA filters are
effective in removing nanoparticles
 (See next slide)
 Prevent
food and beverages in
workplaces where nanomaterials are
handled
 It’s a good idea to systematically evaluate
exposure to ensure that control measures
are working properly and that workers
are being provided the appropriate
personal protective equipment
 Existing
U.S. regulations do not specifically
address nanomaterials
 The EPA apparently intends to designate
CNT releases into US waters as a “significant
new use,” which would likely trigger a major
amount of additional compliance recordkeeping for companies
 For a specific examples of a protocol for
handling of nanotubes see:
• PROTOCOLS FOR HANDLING NANOTUBE
COMPOSITES.doc
• C-nano Material Safety Data Sheet.pdf

EPA is issuing significant new use rules (SNURs)
under section 5(a)(2) of the Toxic Substances Control
Act (TSCA) for two chemical substances which were
the subject of Premanufacture Notices (PMNs). The
two chemical substances are identified generically
as multi-walled carbon nanotubes (MWCNT) (PMN
P–08–177) and single-walled carbon nanotubes
(SWCNT) (PMN P–08–328). This action requires
persons who intend to manufacture, import, or
process either of these two chemical substances for a
use that is designated as a significant new use by this
final rule to notify EPA at least 90 days before
commencing that activity. EPA believes that this
action is necessary because these chemical
substances may be hazardous to human health and
the environment.
 Exclusions
include:
• After they have been completely reacted
(cured);
• Incorporated or embedded into a polymer
matrix that itself has been reacted (cured); or,
• Embedded in a permanent solid polymer form
that is not intended to undergo further
processing except for mechanical processing.
 Personal
Environmental Monitors can
detect the amount of nanomaterials in the
air that a worker is exposed to
• This is crucial in the production of nanomaterials
• Examples of PEMs
 Inhalation
and ingestion protection can
be provided by respirators
• Must be(NIOSH)-approved air-purifying, tight-
fitting full-face respirator equipped with N100
filters)
 Ingestion
protection can be aided by
frequent washing of the hands and
maintaining a clean work environment
 Dermal penetration can be prevented by
the use of nitrile gloves and full-coverage
lab coats
 Accidental
spills of nanotubes are inevitable
during their production, and the massive
use of nanotubes-based materials could
lead to increased environmental pollution
 Research is being conducted to help aid in
this situation
• Scientists have found that CNTs deteriorate when
exposed to the natural enzyme horseradish
peroxidase, also called HRP
• Once fully developed the method could be
administered as easily as chemical cleanups in
today’s labs
 The
use of HEPA filtered vacuums and/or
wet wiping techniques should be use
often to keep the workplace clean
 Workers must wash hands frequently
 Setting up conforming hazardous waste
management practices is a good idea