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3.4 Toxins in Plastics
3.4.1 Introduction
The single largest use of plastics today, taking up a fourth of all plastics
produced or 12 billion pounds of plastics a year, is packaging. Packaging is a
huge industry. The $55.8 billion of packaging in 1985 amounted to 4 percent of
the value of all finished goods sold in the United States. Plastics are the third
largest segment of that industry, exceeded' only by paperboard and metals.
18 Environmental Packaolno Guidelines
Two potential areas of pollution in the plastics processing industry are air pol-
lution during processing, and solid plastic waste generated on-site. In general,
the plastics processing industry does not use large amounts of water, nor does it
generate large amounts of wastewater. Hence, water pollution problems are rel-
atively small.
Air pollution problems presented by the plastics processing industry consist pri-
marily of removing processing chemicals such as solvents, sofleners and
plasticizers from plant exhaust air streams. During molding and forming, most
plastics are relatively inert. But there are threats at this stage as well; from
toxic additives, from hazardous chemicals used in processing, and from heating
up the polymer (which may allow toxic elements to volatilize).
Ingredients in plastic production have dangerous properties for those who work
with them or live near plastic factories. In 1986, EPA ranked the 20 chemicals
whose production generates the most hazardous waste. Five of the top six were
chemicals commonly used by the plastics industry: Propylene (#I), phenol (#3),
ethylene (#4), polystyrene (#5) and benzene (#6). In 1980, 44 percent of
propylene, 73 percent of phenol, 61 percent of ethylene and 72 percent of styrene
produced were consumed by the plastics industry.
The plastics industry is a strong supporter of incineration, arguing that because
plastics are made from petrochemicals, they release much more energy than
other municipal wastes, thereby helping the entire waste stream to burn more
efficiently. Plastic wastes become a potential disposal problem when certain
plastics are incinerated.
Controversy exists regarding the effect of incineration of plastics on the environ-
ment. Although a significant portion of domestic waste contains relatively harm-
less plastics such as polyethylene, the incineration of other components of
garbage may contribute to air pollution and ash disposal problems.
When a high percentage of certain plastics is incinerated, the burning process
may yield potentially toxic gases. For example, the burning of PVC generates
hydrogen chloride gas. The incineration of urethanes produces hydrogen
cyanide. Imperfect burning of plastics produces soot. Specially designed
incinerators have to be used when the plastic content is high to protect the
equipment against corrosive damage from combustion products, such as
hydrogen chloride, ammonia, sulphur oxides and nitrogen oxides.
Of particular concern is the fact that many additives used to process and color
plastics products contain toxic heavy metals such as lead, cadmium and nickel.
Because these heavy metals do not combust, they have been found in both air
emissions and ash from municipal solid waste incinerators.