477
titanium, zirconium, and alumina, are used in the manufacturing
of various products, such as pigments for paints, that utilize thixotropic agents (see Chapter 10). Other sources of ultrafine particles
include diesel emissions. Particles from these emissions are obviously not found in workplaces only but more generally in the air
around us. Several epidemiological studies suggest relationships
between exposures to airborne ultrafine particles and adverse respiratory and even cardiovascular effects, particularly in susceptible
or vulnerable population segments. Combustion-derived particles,
for example, show a range of demonstrated pathologies of different
consequence in humans or animals. Particles from diesel exhausts,
for example, have been related to inflammation in human lungs
after short-term high exposures. Dust containing silica that has
been inhaled can result in silicosis, a common occupational lung
disease. Exposure types, concentrations, and other factors are all
important. Actual sizes are important. Particulate matter at the
100 nm scale is an important reference measure (the so-called
PM 10 level).
Completed studies directed specifically toward engineered nanomaterials remain few but are currently the subject of many research
efforts. The high surface-to-mass ratio of nanoparticles is often generally noted as particularly important (as it can be in many ultrafine
particles as well). In general, surface effects might ultimately prove
more important than mass effects.
Additionally, many nanoparticles with diameters less than 10 nm
or so have surface properties that are dominated by quantum
effects, which potentially can give them quite different properties from their counterparts at the submicron or micron level.
Large percentages of atoms in a nanoparticle are at their surfaces,
which can then be extremely reactive. For some compositions,
oxygen radicals can be generated. The surface chemistry and
interparticle forces of nanomaterials depend on whether particles
are individually dispersed or form aggregates or agglomerates.
For inhaled circumstances, many may be deposited as aggregates,
whereas agglomerates might disassociate. One of the positive
attributes of many nanomaterials in the medical sphere—that
small sizes (say, less than 50 nm) can translocate into cells
easily and can interact with enzymes—is a relevant concern if it’s
happening without control (larger particles do not translocate
quite as easily). There are suggestions that nanoparticle sizes
might change in interactions with biological settings and change
properties.
Health Concerns
titanium, zirconium, and alumina, are used in the manufacturing
of various products, such as pigments for paints, that utilize thixotropic agents (see Chapter 10). Other sources of ultrafine particles
include diesel emissions. Particles from these emissions are obviously not found in workplaces only but more generally in the air
around us. Several epidemiological studies suggest relationships
between exposures to airborne ultrafine particles and adverse respiratory and even cardiovascular effects, particularly in susceptible
or vulnerable population segments. Combustion-derived particles,
for example, show a range of demonstrated pathologies of different
consequence in humans or animals. Particles from diesel exhausts,
for example, have been related to inflammation in human lungs
after short-term high exposures. Dust containing silica that has
been inhaled can result in silicosis, a common occupational lung
disease. Exposure types, concentrations, and other factors are all
important. Actual sizes are important. Particulate matter at the
100 nm scale is an important reference measure (the so-called
PM 10 level).
Completed studies directed specifically toward engineered nanomaterials remain few but are currently the subject of many research
efforts. The high surface-to-mass ratio of nanoparticles is often generally noted as particularly important (as it can be in many ultrafine
particles as well). In general, surface effects might ultimately prove
more important than mass effects.
Additionally, many nanoparticles with diameters less than 10 nm
or so have surface properties that are dominated by quantum
effects, which potentially can give them quite different properties from their counterparts at the submicron or micron level.
Large percentages of atoms in a nanoparticle are at their surfaces,
which can then be extremely reactive. For some compositions,
oxygen radicals can be generated. The surface chemistry and
interparticle forces of nanomaterials depend on whether particles
are individually dispersed or form aggregates or agglomerates.
For inhaled circumstances, many may be deposited as aggregates,
whereas agglomerates might disassociate. One of the positive
attributes of many nanomaterials in the medical sphere—that
small sizes (say, less than 50 nm) can translocate into cells
easily and can interact with enzymes—is a relevant concern if it’s
happening without control (larger particles do not translocate
quite as easily). There are suggestions that nanoparticle sizes
might change in interactions with biological settings and change
properties.
Health Concerns