410 CHAPTER 16 Solid and Hazardous Waste
© Joel W. Rogers/CORBISRebecca Hale/NG Image CollectionEnviroDiscovery
Handling Nanotechnology Safely
Nanotechnology is in the news a lot these days. Nanomaterials,
which are unique materials and devices designed on the
ultrasmall scale of atoms or molecules, have numerous possible
applications. For example, nanoparticles of cadmium selenide
might be injected into cancerous tissue, where they would
accumulate inside cancer cells; when exposed to ultraviolet
radiation, these nanoparticles glow, and surgeons could more
easily excise the cancerous tissues and leave the healthy
tissues intact. Nanocrystals have the potential to be used in
thin-film solar panels to convert solar energy to electricity.
Silica nanoparticles embedded in glass make a heat-resistant
glass capable of withstanding temperatures of up to 1800°C for
several hours (see photograph).
Despite the potential of nanotechnology, particles on the
nanometer scale (a nanometer is one-billionth of a meter) might
pose health, safety, or environmental risks. No one knows for
sure. The EPA has adopted a precautionary approach (see the
section on the precautionary principle in Chapter 4) and decided
to regulate nanomaterials that might adversely affect the
environment. This means that the burden of proof about product
safety will fall on companies that sell nanotechnology. Similarly,
the Food and Drug Administration will have to oversee regulation
of nanotechnology that has potential health and safety risks.
Here we discuss dioxins and PCBs because they are some
of the most persistent hazardous compounds that con-
taminate our environment.
Dioxins Dioxins are a group of related organic chemi-
cal compounds. They become toxic when chemically
combined with chlorine or (less commonly) bromine.
Incineration of medical and municipal wastes accounts
for 70 to 95 percent of known human emissions of diox-
ins. Some other known sources of dioxins are iron ore
mills, copper smelters, cement kilns, metal recycling, coal
combustion, and chemical accidents. Pulp and paper
plants that use chlorine for bleaching release dioxin
in sludge and wastewater. Newer bleaching techniques
avoid chlorine, thereby reducing or eliminating dioxins
(Figure 16.12). Motor vehicles, outdoor grills, and ciga-
rette smoke emit minor amounts of dioxins. Forest fires
and volcanic eruptions are natural sources of dioxins. Diox-
ins also form during the production of some pesticides.
Dioxins emitted to the air settle on plants, soil, and
bodies of water; from there they are incorporated into
the food web. When humans and other animals ingest
Air pollution from a paper mill
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Simpson paper pulp mill near Tacoma, Washington. This plant
was an early adopter of a chlorine free bleaching process.
Consequently, it no longer produces measurable amounts of
chlorinated dioxins.Nanotechnology
The glass between the man and the fire has fire-resistant
properties because of the addition of silica nanoparticles.