Nanomaterials: New Emerging Contaminants and Their Potential
Impact to Water Resources
By William E. Motzer
Manufactured nanomaterials (MNMs) are a relatively new class of elemental metals,
chemical compounds, and engineered materials with particle sizes in the nanometer (nm)
range (1 x 10
m to 100 x 10
In comparison, a human hair is 80,000 nm in
diameter, a red blood cell is about 7,000 nm wide, DNA is about 2 to12 nm in width, and
a water molecule is approximately 0.3 nm across. This “nanoworld” now includes several
different substance classes, including:
(1) Carbon-based materials and structures such as C
fullerene, which can be formed into
(2) Metal-based substances such as nanogold, nanosilver, and nanometal oxides such as
These also include quantum dots, which are packed semiconductor
crystals whose optical properties can change with size; they also have the ability to
absorb light and re-emit it in different colors depending on the nanocrystal’s size.
(3) Dendrimers are polymers constructed from branched units.
A dendrimer’s surface
has numerous chain ends that can be designed to perform specific chemical functions.
Also, dendrimers generally are hollow spheres into which other molecules or atoms can
This makes them useful for drug delivery.
(4) Bio-inorganic composites, such as titanium with attached DNA strands.
These can be
used to treat disease (Royal Academy, 2004; Elder, 2006; U.S. EPA, 2007).
Several classes of MNMs are now globally manufactured in hundred to thousands of
metric tons per year.
These include MNMs for structural applications (ceramics,
catalysts, films and coatings, and composite metals), skin care products (metal oxides),
information and communication technologies (nanoelectronic and optoelectronic
materials, organic light emitters, and nanophosphors), biotechnology (drug delivery,
diagnostic markers, and biosensors) and environmental technologies (nanofiltration and
membranes) (Borm and others, 2006).