Biomedical Engineering Reference
In-Depth Information
aspect ratio fibers leads to long-term carcinogenic effects (Buzea et al. 2007). Single-walled car-
bon nanotubes (SWCNTs) were found to be toxic in terms of acute inflammation and the onset of
progressive fibrosis as compared to spherical particles (amorphous carbon black) in rat pulmonary
toxicity studies (Buzea et al. 2007).
Surfactant mediums may also contribute to a potential health risk. While deliberate coatings can
help reduce cytotoxicity, it has been found that certain accidental surface reactants can increase
their toxicity. For example, when diesel exhausts interact with ozone, they become more toxic
(Buzea et al. 2007). Properties of NMs can also change when they are subjected to different medi-
ums. In the case of mediums, the medium itself reacts with NPs, which can sometimes lead to
alterations in their physicochemical properties (Colvin 2003). NMs are sometimes easily dispersed
within mediums, increasing their toxicity.
Crystallinity can also affect the toxicity of NMs. Different crystalline forms, even of the same
chemical composition, exhibit different chemical properties. The classic example is that of TiO
2
crystals, in which the rutile form, which has been found to induce toxicity, is more toxic than the
anatase form (Gurr et al. 2005).
1.6
BIOINTERACTIONS OF NANOMATERIALS
1.6.1 I
NteractIoNs
WIth
the
e
NvIroNMeNt
NMs can enter the environment either intentionally or unintentionally through wastes from indus-
tries (Figure 1.9) involved in their production and use, or from natural processes such as volcanic
eruptions. Released particles can consequently deposit on land or on the surfaces of water bodies
Worker exposure
Consumer exposure
Consumer
product
manufacturing
Raw material
production
Consumer use
End of life
Recycle
Landfills
lncinerators
Industrial emissions
Human population and ecological exposure
FIGURE 1.9
Transport of nanomaterials in the environment. (Reprinted with permission from Morris,
J., J. Willis, and K. Gallagher. 2007. Nanotechnology White Paper. US Environmental Protection Agency
.
Washington, DC, www.epa.gov/osa/pdfs/nanotech/epa-nanotechnology-whitepaper-0207.pdf (February 2007).)
