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#217 - Plastics -- Part 2: Why Plastic Landfill Liners Always Fail, 22-Jan-1991

In the landfill business, government and industry say plastic liners
are going to save the day. For example, U.S. Environmental Protection
Agency (EPA) and industry both argue that incinerator ash can be safely
"disposed of" in a double-lined ash "monofill." A "monofill" is a
landfill that contains only ash, no raw garbage. Like any other
landfill, the basic design is a bathtub in the ground. The bottom of
the bathtub is formed by a huge sheet of plastic. In an expensive
landfill, you have two sheets of plastic separated by about two feet of
sand and gravel--thus creating one bathtub inside another bathtub.
Therefore, a doublelined ash monofill is a landfill (which is really
just a polite word for a dump) in the form of a bathtub created by two
plastic liners, containing incinerator ash and nothing else.

The theory behind the monofill is that ash contains only small amounts
of aggressive organic chemicals that might eat a hole in the plastic
liner, so the plastic liner will remain intact and protect us against
the lead and cadmium and other toxic metals contained in the ash. (See
RHWN #92.) As always, the key question is: what is the duration of the
hazard and what is the duration of the protection provided by the
plastic liner? (The "cap" or umbrella covering a landfill will also be
made of the same plastic, so a landfill is really a "baggie" in the
ground, containing toxins. What is the lifetime of this baggie? How
long will it protect us?)

What is the duration and nature of the hazard from metals in
incinerator ash? As we saw earlier (in RHWN #92) incinerator ash is
rich in toxic metals. For example, it typically contains anywhere from
3000 parts per million (ppm) to 30,000 ppm of lead. U.S. Environmental
Protection Agency Region (Boston), and the Harvard University School of
Public Health have recommended a cleanup action level of 1000 ppm for
lead in soil--in other words, they recommended that remedial action, as
would be needed at a Superfund site, should be undertaken wherever lead
in soils exceeds 1000 ppm.[1] In recommending the 1000 ppm action
level, EPA and Harvard wrote, "While we believe a greater margin of
safety would be achieved with an action level of 500 ppm, we think it
necessary to set priorities for remedial activity." (What they meant
was that there are so many places in urban America where there is 500
ppm lead in soil that EPA would be overwhelmed with work if 500 ppm
were set as the threshold for remedial action--so 1000 ppm is a more
"realistic" cleanup action level even though it's not as safe as the
nation's children really need it to be.)

Given that EPA Region I and the Harvard School of Public Health have
recommended that Superfund-type cleanup be initiated whenever soils
contain more than 1000 parts per million (ppm) of lead, we know
immediately that every ash monofill will have to be cleaned up at some
time in the future because all incinerator ash contains more than 1000
ppm lead. (Ash also contains dangerous amounts of other toxic metals--
cadmium, arsenic, chromium, and perhaps others, so lead is not the only
reason why a cleanup might be needed.) Therefore, when we create ash
monofills we know we are creating Superfund sites that our children
will pay for--either in damage to their brains and nervous systems, or
in enormous outlays of money--or both.

Because lead and cadmium and other metals never degrade into anything
else, but remain toxic forever, the duration of the hazard is
perpetual, everlasting, eternal. The danger will never go away.

The incineration industry, and its acolytes in government, argue that
the plastic liners will protect us and our children forever.
Unfortunately, this idea is based on a misunderstanding (or more likely
an intentional misrepresentation) of what happens to plastics as they
get older. Plastics are not inert; they do not stay the same as time
passes. They change. They come apart spontaneously.

A recent book by Deborah Wallace, Ph.D., describes this process well.
[2] The book is about the dangers of plastics in fires, but in telling
the story of "Why today's fires are so dangerous," (the answer is
because burning plastics give off toxic gases that kill people who
breathe them), Dr. Wallace included a section on the makeup of plastics
at the molecular level, which helps us understand why all plastics
eventually fall apart.

The building blocks of plastics are found in natural gas, coal, and
wood, but the major source is oil. Oil (like coal and natural gas) is a
mixture of molecules of different sizes and structures. To separate out
the different molecules, crude oil is distilled in an oil refinery. The
oil is boiled and smaller, lighter molecules are separated from the
larger, heavier molecules. The heavier molecules are then "cracked" to
break up the large, heavy molecules into smaller, lighter molecules.

The result of this distillation and cracking is organic chemicals,
which is the name for chemicals containing carbon and other elements
(chiefly hydrogen, oxygen, and nitrogen). These organic chemicals form
the building blocks of pesticides, glues, and plastics. Other chemicals
(such as chlorine and lead) are added to give the raw materials new
characteristics (strength, stiffness, color, and so forth).

After the building blocks are manufactured, they are turned into
plastic resin by a process called polymerization. A polymer is a large,
organic, chain-like molecule made of repeated units of smaller
molecules. Polymerization usually requires heating the raw materials in
the presence of helper chemicals called catalysts, until the building
blocks form long chains. Even with the catalysts, a great deal of heat
is used in the polymerization process. "Because of this heat, the long
chains, even during manufacture, may decompose slightly and have defect
points along them," Dr. Wallace explains. The defect points are in the
chemical bonds, which absorb the energy used in the manufacturing
process. The law of conservation of energy states that the amount of
energy in a system after the reaction is the same as the amount of
energy before the reaction. The large amounts of energy (heat) thus
must go somewhere; they go into the bonds between the atoms of the
plastic and are stored there. But nature does not favor this gain of
energy--nature favors low energy chemical bonds, and high energy bonds
tend to release their energy by breaking spontaneously. These are
defect points. Although polymer scientists have striven to reduce the
number of defect points, they have not been able to completely
eliminate them from synthetic polymers.

Dr. Wallace continues, "The physical and chemical defects that are
produced by ordinary processes in the manufacture and use of plastics
demonstrate the fragile and unstable character of these long chains of
molecules that are joined by high energy chemical bonds. When the resin
is further processed to become the finished marketable product,
additional defect points are created because the product is again
heated and handled."

As time passes, plastics decompose--their molecules come apart
spontaneously--beginning at the defect points. Polymer scientists refer
to this decomposition as "aging." All plastics "age" and there is
nothing that can be done about it. Within a few years (at most a few
decades), all plastics degrade, come apart, and fail. They become
brittle, lose their strength, crack, break into fragments. At that
point, any protection the plastic may have afforded against the toxic
dangers lurking in an ash monofill is gone. By that time, the people
who created the ash monofill will have taken their profits and left
town, but the deadly residues they leave behind--the ash--will remain
to plague the community forever, poisoning the community's children
with toxic lead and other metals.

The only affordable solution to this problem is a simple one: prevent
the creation of incinerator ash.

--Peter Montague


[1] P.L. Ciriello and T. Goldberg, "Lead-contaminated Soil Cleanup
Draft Report" which appears as Appendix E in: Agency for Toxic
Substances and Disease Registry, THE NATURE AND EXTENT OF LEAD
(Atlanta, Ga: Agency for Toxic Substances and Disease Registry, Public
Health Service, U.S. Department of Health and Human Services [1600
Clifton Rd. -Mail Stop E-33, Atlanta, Ga 30333; phone (404) 639-0730],
July, 1988). Free while supplies last."

[2] Deborah Wallace, IN THE MOUTH OF THE DRAGON (Garden City Park, NY:
Avery Publishing Group [120 Old Broadway, Garden City Park, NY 11040;
phone (516) 741-2155], 1990). $17.95.

Descriptor terms: epa; landfilling; plastic liners; harvard university
school of public health; studies; remedial action; ash monofills; heavy
metals; deborah wallace; polymerization; leaks;