LEAD Action News vol 4 no 4 Spring 1996
Incorporating Lead Aware Times ( ISSN 1440-4966) and Lead Advisory Service News ( ISSN 1440-0561)
The journal of The LEAD (Lead Education and Abatement Design) Group Inc.
Building a PVC-free Future
by Iza Kruszewska, Greenpeace
Environmental Problems of Additives to PVC
The manufacture of raw PVC is itself a highly polluting process. More environmental problems are created by the toxic chemicals that are added to PVC to give it different qualities such as flexibility fire-resistance, etc.
PVC cannot be used without a range of additives. In many cases, the final PVC product will contain relatively little raw PVC. Additive chemicals acting as stabilisers, plasticisers, pigments, optical brighteners, flame retardants, biocides, foaming agents and lubricants can make up over 50% of the final product.
PVC, on its own, is unstable and must always be used with additives called stabilisers based on heavy metals: lead, cadmium, tin, barium and zinc. Stabilisers prevent the decomposition of PVC during processing and make PVC resistant to light and weathering. The main stabilisers or stabiliser systems used for PVC are lead compounds, organic compounds, barium/zinc and cadmium/zinc systems.
Pigments, also made of heavy metals, are used to add colour to the PVC and halogenated flame retardants make it fire-resistant. PVC is inherently fire-resistant as a result of its high chlorine content. However, softening agents and other additives may be highly flammable requiring the addition of fire retardants. The use of fire retardants, in turn, leads to more smoke formation requiring yet another group of additives - smoke diminishers.
Pollution Problems from Disposing of PVC Products
PVC not only creates environmental problems during its production and use, but also during its disposal. A large amount of PVC cables or flooring, end up in municipal and hospital waste incinerators.
PVC is usually the main source of chlorine in the municipal waste stream and is, therefore, the primary contributor to dioxin formation in incinerators. Several reports have found a direct relationship between the amount of PVC in waste fed into an incinerator and the amount of dioxin emitted. Reducing PVC feed has been found to result in significant drops in dioxin emissions.
During disposal, the vast number of additives in PVC also become dispersed into the environment. Barium/zinc and cadmium/zinc (Cd/Zn) stabilisers are mainly used in flexible PVC Building products and Cd/Zn and lead for rigid PVC products. Heavy metals, especially cadmium, can be released from PVC during incineration.
If they are successfully trapped by incineration plant filters, the filter residues must be disposed of as hazardous waste - a costly process. In Germany, almost 50% of cadmium use is in the plastics sector. In 1987, Denmark banned the use of cadmium in PVC. However, lead - another toxic heavy metal - is often substituted for cadmium, which does nothing to alleviate the problem of heavy metals from incinerators, nor the potential problem of landfilling.
Incineration also produces toxic ash which must be disposed of to landfill.
Where PVC is burnt in incinerators, the dioxin content of the ash will be increased. Burying the ash in landfills does not solve the pollution problem as dioxin and other by-products, such as heavy metals in the ash, can be released either by the activities of micro-organisms or by the direct action of corrosive liquids in the landfill.
PVC IN LANDFILLS
In Australia, many used PVC products in municipal, hospital and industrial wastes are disposed of in landfills. PVC’s durability and non-biodegradability is claimed by industry to ensure its stability in landfills. For this reason, landfill sites are often sealed within PVC membranes, in the belief that this prevents the leaking of hazardous substances from the waste.
There is scarce research information available on the processes occurring in landfills. However, it is known that when PVC is land filled, the various additives, such as DEHP and heavy metals, are liable to leach. These chemicals can migrate through soil to contaminate groundwater.
Recycling of PVC plastic is not the answer to the environmental problems that PVC creates during its life-cycle. Although it is theoretically possible, the potential for post-consumer recycling of PVC is extremely limited. This is because the wide range of chemical additives added to PVC make it difficult to create a consistent end product from the PVC plastics that have been collected. The sorting of PVC plastic for recycling is also complicated and expensive. New PVC also has to be added to most recycled PVC products.
Some industry sources are promoting the idea of incinerating PVC to produce hydrochloric acid and salt. However, the viability of this technique breaks down due to contamination of the salt with chemical additives.
In the recycling of post-consumer plastics, PVC can obstruct or damage the recycling potential of other plastics. Traces of PVC adhering to steel and copper can also create pollution problems during the recycling of these metals.
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Updated 27 November 2012