Hazardous effects of plastics (Prt 1)

Polluting substances
In terms of environmental and health effects it is important to differentiate between
the various types of plastics. Most polymers (macromolecules) are considered nontoxic
(PVC is an important exception). Polyethylene (PE) and polypropylene (PP), for
example, are inert materials,29 but it should be realized that polymers are not
completely stable. Under the influence of light, heat or mechanical pressure they can
decompose and release hazardous substances. For example, the monomers from
which polymers are made may be released and may affect human health. Both
styrene (which is used to make polystyrene, PS) and vinyl chloride (used to make
PVC) are known to be toxic, and ethylene and propylene may also cause problems.7
The environmental effects of plastics also differ according to the type and quantity of
additives that have been used:
• Some flame retardants may pollute the environment (e.g. bromine
emissions).32
• Pigments or colorants may contain heavy metals that are highly toxic to
humans, such as chromium (Cr), copper (Cu), cobalt (Co), selenium (Se),
lead (Pb) and cadmium (Cd) are often used to produce brightly coloured
plastics. Cadmium is used in red, yellow and orange pigments. In most
industrialized countries these pigments have been banned by law.
• The additives used as heat stabilizers (i.e. chemical compounds that raise
the temperature at which decomposition occurs), frequently contain heavy
metals such as barium (Ba), tin (Sn), lead and cadmium, sometimes in
combination.32
From the heavy metals mentioned, lead and cadmium are the most serious
environmental pollutants, and have different effects on human health, depending on
their concentrations. When present at or above specific concentrations, they interfere
with processes in plant and animal tissues, and in the soil.
Polymers such as PVC may also have serious impacts on the environment because
they contain a number of hazardous substances. For example, PVC contains chlorine
which can be released during heating as hydrochloric acid (HCl). As is the case with
many other hazardous materials, HCl in itself is not an unfamiliar nor a necessarily
harmful substance (it is produced by the stomach to digest food), but at high
concentrations in the air it affects the human respiratory system. Pure PVC contains
85
58% chlorine; when plasticizers are added, it contains about 49% chlorine. From a
survey of the composition of waste carried out in the Netherlands, it was found that
the chlorine present in PVC contributes about 50% of the total chlorine content of
municipal waste.32
Other potentially hazardous substances in PVC include the relatively large quantities
of additives such as plasticizers (up to 60%) and heat stabilizers (sometimes up to
3%).32 In the opinion of some environmental and consumer organizations in Western
Europe, the use of PVC and other plastics containing chlorine (or bromine),
especially for packaging, should be halted entirely.