C hapTer 11 nanomaterials and nanotechnologies
474
A third frequently observed theme is that many of the specific
claims that unequivocally state that there are, or are not, harmful
effects—claims that seemingly often appear to directly contradict
one another—are often made on the basis of studies that had relatively limited scopes and small sample sets, and that resulting conclusions may or may not have the general applicability claimed. A
fourth theme is that there are research gaps that badly need to be
filled in many areas—from types of general exposure risks through
the effects of specific compositions and particle sizes and shapes.
Recommendations are invariably made that the plethora of scientific and application advancement studies in relation to nanomaterials should be simultaneously balanced by rigorous studies about
potential impacts on human health and the environment. A fifth
theme that is often present is simply that caution is suggested in
any kind of statement suggesting that there are or are not harmful
effects.
Related subthemes address the issue that the toxicological effects
of nanomaterials are particularly difficult to address for several
main reasons. One is that “nanomaterials” are not a particular
type or form of material, as is common in many toxicological
studies; the term is simply a descriptor for a surprisingly large
array of quite different compositions, sizes, embedments, and the
like. A second reason is that though prior understandings are available for a limited number of well-studied ultrafine particles, the
larger distributions of sizes, relative surface areas, possible types
of coatings, and surface reactivities that are associated with many
nanomaterials should lead to cautiousness in statements of findings—for example, there are contentions that even well-studied
materials of one composition and size can exhibit surprisingly different characteristics at different sizes due to small-size and scale
effects (some studies have contended that new chemical behaviors
could exist). It has also been generally observed that a primary difference between ultrafine particles (which have been the subject of
so many studies) and nanoparticles is that the former are largely
“unwanted” results of various activities and processes, whereas
nanomaterials are “wanted” and are quite literally engineered for
specific purposes; hence there can be greater distributions of sizes,
compositions, types of coatings, etc., than commonly encountered
with ultrafine particles. This same fact, however, also suggests
the possibility of engineering specific nanomaterials for uses in
defined circumstances so that any potential harmful effects can be
mitigated or eliminated, such as through the use of coatings that
change surface reactivities.
474
A third frequently observed theme is that many of the specific
claims that unequivocally state that there are, or are not, harmful
effects—claims that seemingly often appear to directly contradict
one another—are often made on the basis of studies that had relatively limited scopes and small sample sets, and that resulting conclusions may or may not have the general applicability claimed. A
fourth theme is that there are research gaps that badly need to be
filled in many areas—from types of general exposure risks through
the effects of specific compositions and particle sizes and shapes.
Recommendations are invariably made that the plethora of scientific and application advancement studies in relation to nanomaterials should be simultaneously balanced by rigorous studies about
potential impacts on human health and the environment. A fifth
theme that is often present is simply that caution is suggested in
any kind of statement suggesting that there are or are not harmful
effects.
Related subthemes address the issue that the toxicological effects
of nanomaterials are particularly difficult to address for several
main reasons. One is that “nanomaterials” are not a particular
type or form of material, as is common in many toxicological
studies; the term is simply a descriptor for a surprisingly large
array of quite different compositions, sizes, embedments, and the
like. A second reason is that though prior understandings are available for a limited number of well-studied ultrafine particles, the
larger distributions of sizes, relative surface areas, possible types
of coatings, and surface reactivities that are associated with many
nanomaterials should lead to cautiousness in statements of findings—for example, there are contentions that even well-studied
materials of one composition and size can exhibit surprisingly different characteristics at different sizes due to small-size and scale
effects (some studies have contended that new chemical behaviors
could exist). It has also been generally observed that a primary difference between ultrafine particles (which have been the subject of
so many studies) and nanoparticles is that the former are largely
“unwanted” results of various activities and processes, whereas
nanomaterials are “wanted” and are quite literally engineered for
specific purposes; hence there can be greater distributions of sizes,
compositions, types of coatings, etc., than commonly encountered
with ultrafine particles. This same fact, however, also suggests
the possibility of engineering specific nanomaterials for uses in
defined circumstances so that any potential harmful effects can be
mitigated or eliminated, such as through the use of coatings that
change surface reactivities.