What are the environmental issues for PVC?
PVC is arguably one of the most scrutinised materials in the world. In a study done by the CSIRO in 2001(1) which discussed some of the scientific issues surrounding the use of PVC the following quote largely sums up the history of this situation:
"As with many controversial subjects, there exist conflicting results and differing interpretations of the same data with regard to the issues relating to PVC. Dean (1995) summarises the situation precisely when he states a large number of the perceived risks from e.g. PVC, dioxins, incineration, furnace ash, waste fuel oil, etc are derived from assumptions that have been unsupported or refuted by later studies, but which remain strongly in the public mind".
Some green groups have questioned the environmental performance of PVC with reference to a range of issues relating to:
- chlorine and vinyl chloride monomer (VCM)
- dioxin - created during manufacture and incineration
- use of hazardous chemicals such as heavy metals and plasticisers.
(Note: each of these issues is dealt with individually and in detail later in this section on frequently asked questions.)
"The focus of this debate was initially concerned with the manufacture of PVC but has now shifted to the use and disposal of the material" (1). This shift is likely due to the resolution of the manufacturing issues that were largely OH&S in nature.
In 1998 and 2001, the CSIRO extensively reviewed recent scientific literature on PVC and concluded: "the balance of available evidence indicates that PVC in its building and construction applications has no more effect on the environment than its alternatives".
In 2004 the US Green Building Council PVC Task Group issued a draft report on PVC related materials. This draft report was based on an analysis of over 2400 scientific papers, submissions from green groups, the building industry and PVC industries. The report concludes "the available evidence does not support a conclusion that PVC is consistently worse than alternative materials on a life cycle environmental and health basis".
Furthermore in 2004 the European Parliament commissioned a Life Cycle Analysis (LCA) study on PVC - "Life Cycle Assessment of PVC & of Competing Materials". This report found no evidence to support a bias against PVC and as a result has placed no restrictions on its use.
(1) "A discussion of some of the scientific issues concerning the use of PVC", Dr P Coghlan, CSIRO, 2001
How is Chlorine and Vinyl Chloride Monomer (VCM) manufactured?
PVC production is a major user of chlorine, consuming around 35% of the manufactured chlorine in the world. Chlorine is used in many products we rely on - medicines, water disinfection, paper and paints to name a few. Chlorine plays a key role in many chemical processes. Whilst there are many naturally occurring compounds containing chlorine it does not naturally exist in its pure state. The manufacture of chlorine involves the breaking down of common salt by electrolysis into chlorine and caustic soda (used in other industrial processes such as aluminium refining).
Chlorine is reacted with Ethylene to form VCM which is then polymerised to form PVC.
Should I be concerned about VCM?
Consumers are not at risk from exposure to VCM. VCM is only present in the polymer raw material stage.
VCM is known to cause a rare form of liver cancer after prolonged high level exposure. The only known deaths as a consequence of contact with VCM have occurred to people involved in the manufacture of PVC. As a result appropriate OH&S procedures have been in place since the mid 1970’s dictating the methods of safe handling of this material. In addition appropriate safe working exposures are in place and manufacturing sites are constantly monitored to ensure a safe working environment is maintained. VCM is very well controlled in the workplace. Confirming the success of this control there have been no known cases of this rare cancer found in workers who have entered the industry since the mid 1970’s.
Is PVC a significant source of dioxin?
PVC pipe contains no dioxin.
The principal sources of dioxin in the western world are municipal and medical waste incinerators - particularly older facilities. In Australia the incinerators are few in number and relatively new and have been engineered to produce very little dioxin. An investigation for Environment Australia in 1998 found that 60-80% of dioxin emissions to air in Australia arise from agricultural burning off, residential wood combustion and bushfires. Waste incinerators and halogen chemical manufacture (including chlorine and PVC production), together contribute less than 1% to the total. This report is available on-line at http://www.ea.gov.au/industry/chemicals/dioxins/pubs/dioxins.pdf. Other more significant dioxin sources include the combustion of coal, ferrous and non ferrous metal manufacture and internal combustion engines.
The level of dioxins in the global environment peaked in the late 1960s and early 1970s. Japanese Government data shows that daily human intake of dioxins fell by 75 per cent between 1977 and 1998 (2). The US EPA has reported that dioxin emissions in the US fell by 80 per cent between 1987 and 1995 (3).
This significant reduction in dioxin emissions is in stark contrast to PVC production that has trebled over the past 20 years - highlighting that the production, use and disposal of PVC has no direct link to dioxin production.
The Swedish EPA found that "a reduction in the PVC content of waste will not change the amount of dioxin emissions in flue gases, or significantly reduce the dioxin content in residual products from flue-gas treatment plants."(4).
(2) Ministerial Council on Dioxin Policy, (1999) Dioxins, Japan.
(3) US EPA, (September 2000) Draft Exposure and Human Health Reassessment of 2, 3, 7, 8-Tetrachlorodibenzo-p-Dioxin ... (etc).
(4) Swedish EPA (June 1996) Report on Disposal PVC Waste.
Is PVC pipe recycled?
PVC pipe is recyclable, contrary to some reports. Both post industrial waste and post consumer waste is recycled.
PVC is a thermoplastic material and as such is readily recycled. Being thermoplastic any waste generated in the manufacturing process is recycled - usually like for like.
PVC pipe is such a durable material that the opportunities for large volumes of material to recycle simply do not exist. When they are available they can be recycled. PIPA, in association with Collex, has successfully established a process to recover plastics pipes from construction and demolition waste across Sydney. Details of this event are found under Plastics Pipe Recycling Trial - End of Trial Report. The process removes practically all plastics pipes from the waste and produces granulated materials suitable for new pipe feedstock. However, it must be recognised that the overall volumes are low for the reasons previously stated.
PVC pipe waste, both factory rework and externally sourced e.g. building site off cuts or demolition waste, is converted into solid wall stormwater pipe, or as a foam or solid core in the middle of multilayer pipe, used for sewer pipe and under ground conduits.
Does PVC pipe contain hazardous chemicals?
The concerns about hazardous chemicals in PVC centre on the use of heavy metal stabilisers (typically Cadmium and Lead) and plasticisers in flexible PVC products (such as phthalates). There are many reports that question the level of concern with respect to these chemicals in PVC. Organisations such as the Vinyl Council have extensive reviews of the scientific papers relating to these chemicals (www.vinyl.org.au).
In the case of PVC pipe the issues can be simplified:
- PVC pipe produced in Australia contains no plasticisers.
- PVC pipe produced in Australia contains no cadmium.
- Lead stabilisers are not used in the manufacture of pressure water pipe in Australia and they are being phased out in other piping applications under the PVC industry's Product Stewardship Program. In any case the impact of lead stabilisers is regarded as insignificant. Small quantities of lead based compounds are used as a thermal stabiliser in some pipe products. The lead stabilisers are held within the PVC matrix and to quote the CSIRO Report from 2001 "the concerns relating to extraction are overstated". In terms of release of lead from PVC pipe there have been extensive studies both in Australia and Europe on leachate from waste water pipes and landfill situations. In both cases the conclusion is that the amount of lead released is insignificant.
How does the Embodied Energy of PVC pipes compare to metal pipes?
Embodied energy analysis quantifies the amount of energy used to manufacture a product. This involves the assessment of the overall expenditure of energy required to extract the raw material and manufacture it into a product. In terms of Embodied Energy PVC pipe products perform significantly better than competitive metallic pipe systems (based on independent CSIRO research (5)). This advantage is often more than a factor of 2 in favour of PVC products - particularly the PVC-O pipe products.
Read a summary of the report at Plastics Pipe Systems Good for the Environment or study the full report by downloading it in PDF format (227 Kb) Piping Systems Embodied Energy Analysis.
(5) M.D Ambrose, D.D Salomonsson, S. Burn, "Piping Systems Embodied Energy Analysis" CSIRO 2002.
What is meant by series 1 and series 2 sizes for PVC pipe?
PVC pipe manufactured to AS 1477 is available in 2 size ranges referred to as Series 1 and Series 2. Series 1sizes are compatible with the ISO 161-1 and 161-2 standard size ranges. The Series 2 pipe is compatible with Australian cast iron sizes (AS2280) - this size range is unique to Australia.
For the same nominal diameter (DN) the Series 2 pipes are slightly larger in diameter. Examples of Series 1 and Series 2 outside diameters are given in the following table:
||Series 1 OD mm
||Series 2 OD mm
It is important to appreciate that the larger OD of Series 2 translates to a larger ID and hence will influence the hydraulic performance of the pipeline for the same DN value.
What is Oriented PVC?
Oriented PVC or PVC-O is the latest advance in PVC pipe manufacture. By orienting the randomly arranged long chain polymer molecules significant improvements can be achieved in the mechanical properties of PVC. Orientation is achieved by controlled stretching and expansion of the PVC pipe. The result is a pipe with around twice the tensile strength as PVC-U with significantly better fatigue resistance, impact resistance and resistance to crack propagation.
These improvements in mechanical properties allow the pipe wall to be thinner producing a larger bore for the same nominal diameter and pressure class. Therefore for the same DN over 10% improvement in hydraulic performance will be achieved compared to PVC-M pipe and even more so compared to PVC-U pipe.
What is modified PVC?
Modified PVC or PVC-M is a PVC alloy. The addition of modifying agents increases the ductility while virtually retaining the same material strength.
The modifying agents significantly improve toughness and impact properties with resistance to crack growth a key performance requirement. The change in material matrix results in more ductile behaviour and thus enables the factor of safety to be lower than PVC-U. The result is a pipe with a thinner wall and larger bore for the same DN and PN rating offering improved hydraulic efficiency over PVC-U.