Geoscience Reference
In-Depth Information
At this point, there is very limited knowledge about the transport and fluxes of
nanoparticles in the natural environment. Colvin ( 2003 ) suggested that if engi-
neered nanomaterial applications develop as projected, increasing concentrations
of nanomaterials in groundwater and soil may present the most significant expo-
sure avenues for environmental risk. Release to the environment, either by acci-
dent or by approved and regulated discharge of effluents and waste water, may
result in direct exposure of humans to nanoparticles via ingestion or inhalation of
airborne (Brigger et al. 2002 ; Dowling 2004 ; Moore 2002 , 2006 ; Warheit 2004 )or
water aerosols, skin contact, and direct ingestion of contaminated drinking water
or particles adsorbed on vegetables or other foodstuffs (Daughton 2004 ; Howard
2004 ; Moore 2006 ).
In addition, direct passage across fish gills and other external surface epithelia
may constitute a route of toxic nanoparticle contamination. A limited investigation
of fish (Oberdörster 2004 ) has indicated that C 60 -fullerenes may be internalized by
these routes. At the cellular level, uptake of nanoparticles into biological systems
may be facilitated by the caveolar and endocytotic systems in cells, but knowledge
of the pathological consequences, if any, is currently very limited (Panyam and
Labhasetwar 2003 ; Pelkmans and Helenius 2002 ; Reiman et al. 2004 ). Also,
indirect exposure could arise from ingestion of organisms such as fish and shellfish
(i.e., mollusks and crustaceans) as part of the human diet. Surface sediment- and
filter-feeding mollusks are prime candidates for uptake of manufactured nano-
particles from environmental releases, if it transpires that some of these nanom-
aterials associate with natural particulates, because these mollusks already are
known to accumulate suspended particle and sediment-associated conventional
pollutants (Galloway et al. 2002 ; Livingstone 2001 ).
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