C hapTer 11 nanomaterials and nanotechnologies
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ingestion, inhalation, and intake dermally, although other paths
exist as well. Ingestion could possibly come from nanomaterial
uses in agriculture. Inhalation is a particular danger in workplace
environments, especially where nanomaterials are manufactured.
Dermal exposures could possibly occur through the use of cosmetics containing nanoparticles. These issues are explored in more
depth in the following discussion.
The issue of exposure and possible migration of nanomaterials
into human bodies is also tied closely to the way in which nanomaterials are found or used in products, especially in the degree
to which they might or might not become unbound. In many
nanopolymeric composites, for example, constituent nanoparticles are covalently bound and not easily susceptible to becoming
unbound. In a nanometallic composite, nanoparticles embedded
in a metal matrix are again less likely to become free than in other
situations.
All these factors must be considered in assessing actual risk levels to
exposed populations. A block of aluminum with embedded nanoparticles that is part of an automobile chassis poses quite a different
risk to a human than does direct ingestion of carbon nanotubes
by sipping—or rather inhaling, which is more likely—from a full
wineglass of them. The risk never really disappears, however, even
when nanomaterials are bound into a matrix. Abrasion or other
actions such as the wearing or even washing of nano-based textiles
could cause particles to become unbound, as could downstream
recycling activities. Full product use conditions and life cycles need
to be considered.
effects
Assuming that exposures occur, the scientific community has long
studied the toxicity of ultrafine particles that are commonly found
in our workplaces and other environments. Ultrafine particles
are usually defined as having diameters in the range 100 nm to 1
micron. Most studied particles, however, are not from engineered
nanomaterials but from sources that have long been with us: fly
ash, carbon black, and welding fumes. These are normally products
of some type of hot processing activity or of a combustion process,
and hence they are often associated with workplaces. Carbon
black, for example, is used in producing rubber-based products.
Other tiny particles, such as fumed silica and other oxides such as
476
ingestion, inhalation, and intake dermally, although other paths
exist as well. Ingestion could possibly come from nanomaterial
uses in agriculture. Inhalation is a particular danger in workplace
environments, especially where nanomaterials are manufactured.
Dermal exposures could possibly occur through the use of cosmetics containing nanoparticles. These issues are explored in more
depth in the following discussion.
The issue of exposure and possible migration of nanomaterials
into human bodies is also tied closely to the way in which nanomaterials are found or used in products, especially in the degree
to which they might or might not become unbound. In many
nanopolymeric composites, for example, constituent nanoparticles are covalently bound and not easily susceptible to becoming
unbound. In a nanometallic composite, nanoparticles embedded
in a metal matrix are again less likely to become free than in other
situations.
All these factors must be considered in assessing actual risk levels to
exposed populations. A block of aluminum with embedded nanoparticles that is part of an automobile chassis poses quite a different
risk to a human than does direct ingestion of carbon nanotubes
by sipping—or rather inhaling, which is more likely—from a full
wineglass of them. The risk never really disappears, however, even
when nanomaterials are bound into a matrix. Abrasion or other
actions such as the wearing or even washing of nano-based textiles
could cause particles to become unbound, as could downstream
recycling activities. Full product use conditions and life cycles need
to be considered.
effects
Assuming that exposures occur, the scientific community has long
studied the toxicity of ultrafine particles that are commonly found
in our workplaces and other environments. Ultrafine particles
are usually defined as having diameters in the range 100 nm to 1
micron. Most studied particles, however, are not from engineered
nanomaterials but from sources that have long been with us: fly
ash, carbon black, and welding fumes. These are normally products
of some type of hot processing activity or of a combustion process,
and hence they are often associated with workplaces. Carbon
black, for example, is used in producing rubber-based products.
Other tiny particles, such as fumed silica and other oxides such as