Nanotechnology White Paper - US Environmental Protection Agency

42 EPA Nanotechnology White Paper
Figure 19. SEM of a scanning gate probe.
The large tip is the probe for a scanning tunneling
microscope, and the smaller is a gate that allows
sharper imaging of the sample. Instruments such
as these can be used to analyze nanomaterials.
(Image courtesy of Prof. Leo Kouwehnhoven,
Delft University of Technology. Reprinted with
permission from Gurevich, L., et al., 2000)
(Copyright 2000, American Institute of Physics.)
3.5 Human Exposures and Their Measurement and Control
As the use of nanomaterials in society increases, it is reasonable to assume that their
presence in environmental media will increase proportionately, with consequences for human
and environmental exposure. Potential human exposures to nanomaterials, or mixtures of
nanomaterials, include workers exposed during the production, use, recycling and disposal of
nanomaterials, general population exposure from releases to the environment as a result of the
production, use, recycling and disposal in the workplace, and direct general population exposure
during the use of commercially available products containing nanomaterials. This section
identifies potential sources, pathways, and routes of exposure, discusses potential means for
mitigating or minimizing worker exposure, describes potential tools and models that may be used
to estimate exposures, and identifies potential data sources for these models.
3.5.1 Exposure to Nanomaterials
The exposure paradigm accounts for a series of events beginning from when external
mechanisms (e.g., releases or handling of chemicals) make a chemical available for absorption or
other mode of entry at the outer body boundary to when the chemical or its metabolite is
delivered to the target organ. Between outer body contact with the chemical and delivery to the
target organ, a chemical is absorbed and distributed. Depending on the nature of the chemical
and the route of exposure, the chemical may be metabolized. For the purposes of this section, we
will limit the discussion to the types of resources that are needed (and available) to assess
exposure up to the point where it is distributed to the target organ.
3.5.2 Populations and Sources of Exposure
The potential for intentionally produced nanomaterials to be released into the
environment or used in quantities that raise human exposure concerns are numerous given their