By Roberta Baxter
AIDAN TOOK APART AND ROLLED up the wires from his family’s old computer. When his father came home, they set up a new desktop. Aidan thought the new desktop
wasn’t much better than the old one. He was
able to do anything he wanted with a smartphone. But his parents still wanted a desktop.
“Dad, what are you going to do with the old
computer?” Aidan asked, as they set up the
“Put it out for trash pickup,” his dad said.
“But they’ll throw it in the landfill,” Aidan
said. “I think they can charge you a fine for
doing that. Think of all the space this stuff
would take,” he said, pointing at the monitor,
tower, and keyboard.
“OK, let’s see what else we can do with it,
then,” Aidan’s father said.
Aidan went online and found out that each
year, U.S. residents dispose of 40
to 50 million computers. Aidan
picked up a tape measure from his dad’s
workbench and measured the parts of the
computer. The components took up about 2
cubic feet. That didn’t sound like much, but he
kept thinking about the size of the computer
and the amount of space it would take in a
landfill. He estimated that all of those old computers, stacked up, would be the size of the
Great Pyramid of Giza in Egypt!
Recycling computers would prevent all of
this extra trash. Now, Aidan was eager to learn
more about recycling old computers.
Aidan found out that most electronics contain heavy metals, such as lead, mercury, and
cadmium. Chemists do not have a specific
definition for heavy metals, but in general,
heavy metals are those metals with higher
atomic numbers and greater density.
Lead is used in older cathode-ray-
tube monitor screens, where it makes
the glass show a clearer picture and it blocks
radiation, keeping it inside the monitor (Fig. 1).
Mercury is also present in flat-
screen displays, including those on cell
phones. When mercury atoms are electrically
energized, the atoms move to a higher energy
level. When they fall back to lower levels, they
release visible light.
Cadmium is used in rechargeable
batteries that power most electronics.
Aidan also found that lead and cadmium
could cause severe health effects. Exposure to
lead can cause learning disabilities, behavioral
problems, and damage to the heart, kidneys,
and bones. Cadmium exposure can cause
respiratory problems, kidney failure, and softened bones.
Exposure to mercury can cause nerve
damage that leads to shaking hands and
personality and behavioral changes, such as
withdrawing from people, irritability, and even
confusion and hallucinations.
In addition to heavy metals, Aidan learned
that electronics also contain precious metals,
such as gold and silver, which have excellent conductive properties.
Gold, in particular, does not corrode
or break down. It is found in motherboards and in pins in the central processing
unit (CPU) of a computer. A motherboard
Figure 1. Toxic chemical elements present in a typical personal computer A D
16 ChemMatters | OC TOBER/NOVEMBER 2016 www.acs.org/chemmatters
Why Recycling Electronics Matters
1. Lead in cathode ray tubes and solder.
2. Arsenic in older cathode ray tubes.
3. Selenium in circuit boards as power supply.
4. Polybrominated flame retardants in plastic
casings, cables, and circuit boards.
5. Antimony trioxide as flame retardant.
6. Cadmium in circuit boards and semiconductors.
7. Chromium in steel as corrosion protection.
8. Cobalt in steel for structure and magnetism.
9. Mercury in switches and housing.
Hazardous Waste in Your Old Computer