Polyvinyl chloride
Polyvinyl chloride, (
IUPAC Polychloroethene) commonly abbreviated
PVC, is a widely-used
plastic. In terms of
revenue generated, it is one of the most valuable products of the
chemical industry. Globally, over 50% of PVC manufactured is used in construction. As a building material, PVC is cheap and easy to assemble. In recent years, PVC has been replacing traditional
building materials such as
wood,
concrete and
clay in many areas. Despite appearing to be an ideal building material, concerns have been raised about the costs of PVC to the
natural environment and
human health.
There are many uses for PVC. As a hard plastic, it is used as
vinyl siding,
magnetic stripe cards, window profiles,
gramophone records (which is the source of the name for
vinyl records),
pipe,
plumbing and
conduit fixtures. It can be made softer and more flexible by the addition of
plasticizers, the most widely used being
phthalates. In this form, it is used in
clothing and
upholstery, and to make flexible
hoses and tubing,
flooring, roofing membranes, and electrical cable insulation. The material is often used for
pipelines in the
water and
sewer industries because of its inexpensive nature and flexibility.
Polyvinyl chloride is produced by polymerization of the
monomer vinyl chloride, as shown.
|
The polymerisation of vinyl chloride |
Polyvinyl chloride was accidentally discovered on at least two different occasions in the 19th century, first in 1835 by
Henri Victor Regnault and in 1872 by
Eugen Baumann. On both occasions, the polymer appeared as a white solid inside flasks of
vinyl chloride that had been left exposed to sunlight. In the early 20th century, the
Russian chemist Ivan Ostromislensky and
Fritz Klatte of the
German chemical company
Griesheim-Elektron both attempted to use PVC in commercial products, but difficulties in processing the rigid, sometimes brittle polymer blocked their efforts.
In 1926,
Waldo Semon of
B.F. Goodrich developed a method to plasticize PVC by blending it with various additives. The result was a more flexible and more easily processed material that soon achieved widespread commercial use.
Electric wires
PVC is commonly used as for the insulation on electric wires; the plastic used for this purpose needs to be plasticized. In a fire, PVC-coated wires can form
HCl fumes; the
chlorine serves to scavenge
free radicals and is the source of the material's
fire retardance. However, these (intentional) fumes can also pose a health hazard in their own right. Frequently in applications where smoke is a major hazard (notably in tunnels) PVC-free LSOH (low smoke, zero halogen) cable insulation is used.
Pipes
Polyvinylchloride is also widely used for producing pipes. About 90% of all PVC pipes are used for drainage and for protecting/containing cables in buildings.
Unplasticized polyvinyl chloride (uPVC)
|
Modern "Tudorbethan" house with uPVC gutters and downpipes, fascia, decorative imitation "half-timbering", windows and doors. |
uPVC is often used in the building industry as a low maintenance material, particularly in the
UK, and in the
USA where it is known as vinyl.
[uPVC Windows, Doors][Vinyl (Poly Vinyl Chloride) in Construction]. The material comes in a range of colours and finishes, including a photo-effect wood finish, and is used as a substitute for painted wood, most obviously for
window frames and
sills when installing
double glazing in new buildings or to replace older single glazed windows. It has many other uses including
fascia, and
siding or
weatherboarding. The same material has almost entirely replaced the use of
cast iron for
plumbing and
drainage, being used for waste pipes, drainpipes,
gutters and downpipes,
[Fascia, Guttering, Fascias, PVCu Soffits, Roofing, Cladding]Due to
environmental concerns[PVC Products - Greenpeace international] use of PVC is discouraged by some local authorities
[Environmentally conscious buildings] and has been outlawed in
Germany.
Phthalate plasticizers
Many Vinyl products contain additional chemicals to change the chemical consistency of the product. Some of these additional chemicals called
additives and
plasticizers can leach out of vinyl products. Because soft PVC toys have been made for babies for years, there are concerns that these additives leach out of soft toys into the mouths of the children chewing on them. Vinyl
IV bags used in neo-natal
intensive care units have also been shown to leach DEHP (
Bis(2-ethylhexyl) phthalate), a
phthalate additive. In January 2006, the European Union placed a ban on six types of phthalate softeners in toys (See directive
2005/84/EC). In 2003, the US Consumer Product Safety Commission (CPSC) denied a petition for a similar ban in the United States[
1]; however, in the USA most companies have voluntarily stopped manufacturing PVC toys for this age group or haveeliminated the phthalates. In a draft guidance paper published in September 2002, the US FDA recognizes that many medical devices with PVC containing DEHP are not used in ways that result in significant human exposure to the chemical[
2]. However, FDA is suggesting that manufacturers consider eliminating the use of DEHP in certain devices that can result in high aggregate exposures for sensitive patient populations such as neonates. However, alternative softeners have not been properly tested to determine whether they are more or less safe. Other vinyl products, including car interiors, shower curtains, flooring, etc., initially release chemical gases into the
air. Some studies indicate that this
outgassing of additives may contribute to health complications, but this information is preliminary and further study is needed.
According to some medical studies, the plasticizers added to PVC may cause chronic conditions such as
scleroderma,
cholangiocarcinoma,
angiosarcoma,
brain cancer, and
acrosteolysis. PVC has been used in many products for many years and still there is not proof of significant harmful effects from exposure. There have been studies, some cited in this article, that indicate "links" with certain medical problems and exposure to PVC products. These links deserve additional study.
In 2004, a joint Swedish-Danish research team found a very strong link between allergies in children and the phthalates DEHP and BBzP, commonly used in PVC
.
Alternative plasticisers are being developed but in many cases these alternatives remain significantly more expensive and their technical performance varies. It is also worth noting that some, though not all, of the alternatives pose significant health risks.
One hospital network called the Catholic Healthcare West network, the 8th largest hospital network in the country, recently signed a contract with B.Braun for Vinyl free Intravenous(IV) bags and tubing.
Vinyl chloride monomer
In the late
1960s, Dr. John Creech and Dr. Maurice Johnson were the first to clearly link and recognize the carcinogenicity of
vinyl chloride monomer to humans when workers in the polyvinyl chloride polymerization section of a B.F. Goodrich plant near Louisville, Kentucky, were diagnosed with liver angiosarcoma, a rare disease.
Since that time, studies of PVC workers in Australia, Italy, Germany, and the U.K. have all associated certain types of occupational cancers with exposure to vinyl chloride. The link between angiosarcoma of the liver and long-term exposure to vinyl chloride is the only one which has been confirmed by the International Agency for Research on Cancer. All the cases of angiosarcoma developed from exposure to vinyl chloride monomer, were in workers who were exposed to very high VCM levels, routinely, for many years.
According to the EPA, "vinyl chloride emissions from polyvinyl chloride (PVC),
ethylene dichloride (EDC), and vinyl chloride monomer (VCM) plants cause or contribute to air pollution that may reasonably be anticipated to result in an increase in mortality or an increase in serious irreversible, or incapacitating reversible illness. Vinyl chloride is a known human carcinogen which causes a rare cancer of the liver."
[National Emission Standards for Hazardous Air Pollutants (NESHAP) for Vinyl Chloride Subpart F, OMB Control Number 2060-0071, EPA ICR Number 0186.09 (Federal Register: September 25 2001 (Volume 66, Number 186))]A front-page series in the
Houston Chronicle claimed the vinyl industry has manipulated vinyl chloride studies to avoid liability for worker exposure and to hide extensive and severe chemical spills into local communities.
[Jim Morris, "In Strictest Confidence . The chemical industry's secrets," Houston Chronicle. Part One: "Toxic Secrecy," June 28 1998, pgs. 1A, 24A-27A; Part Two: "High-Level Crime," June 29 1998, pgs. 1,A, 8A, 9A; and Part Three: "Bane on the Bayou," July 26 1998, pgs. 1A, 16A.]]Dioxins
The environmentalist group
Greenpeace has advocated the global phase-out of PVC because they claim
dioxin is produced as a byproduct of vinyl chloride manufacture and from incineration of waste PVC in domestic garbage. The European Industry, however, asserts that it has improved production processes to minimize dioxin emissions.
Dioxins are a global health threat because they persist in the environment and can travel long distances. At very low levels, near those to which the general population is exposed, dioxins have been linked to immune system suppression, reproductive disorders, a variety of cancers, and
endometriosis. According to a 1994 report by the British firm, ICI Chemicals & Polymers Ltd., "It has been known since the publication of a paper in 1989 that these oxychlorination reactions [used to make vinyl chloride and some chlorinated solvents] generate polychlorinated dibenzodioxins (PCDDs) and dibenzofurans (PCDFs). The reactions include all of the ingredients and conditions necessary to form PCDD/PCDFs.... It is difficult to see how any of these conditions could be modified so as to prevent PCDD/PCDF formation without seriously impairing the reactionfor which the process is designed." In other words, dioxins are an unavoidable consequence of making PVC. Dioxins created by vinyl chloride production are released by on-site incinerators, flares, boilers, wastewater treatment systems and even in trace quantities in vinyl resins.
[Pat Costner etal, "PVC: A Primary Contributor to the U.S. Dioxin Burden; Comments submitted to the U.S. EPA Dioxin Reassessment," (Washington, D.C. Greenpeace U.S.A., February 1995]The largest well-quantified source of dioxin in the US EPA inventory of dioxin sources is barrel burning of household waste.
[The Inventory of Sources and Environmental Releases of Dioxin-Like Compounds in the United States: The Year 2000 Update, March 2005] Studies of household waste burning indicate consistent increases in dioxin generation with increasing PVC concentrations.
[Costner, Pat, (2005), " Estimating Releases and Prioritizing Sources in the Context of the Stockholm Convention", International POPs Elimination Network, Mexico.] According to the EPA dioxin inventory, landfill fires are likely to represent an even larger source of dioxin to the environment. A survey of international studies consistently identifies high dioxin concentrations in areas affected by open waste burning and a study that looked at the homologue pattern found the sample with the highest dioxin concentration was "typical for the pyrolysis of PVC". Other EU studies indicate that PVClikely "accounts for the overwhelming majority of chlorine that is available for dioxin formation during landfill fires."
[Costner 2005]The next largest sources of dioxin in the EPA inventory are medical and municipal waste incinerators. Studies have shown a clear correlation between dioxin formation and chloride content and indicate that PVC is a significant contributor to the formation of both dioxin and PCB in incinerators.
[ Katami, Takeo, et al (2002) "Formation of PCDDs, PCDFs, and Coplanar PCBs from Polyvinyl Chloride during Combustion in an Incinerator" Environ. Sci. Technol., 36, 1320-1324. and Wagner, J., Green, A. 1993. Correlation of chlorinated organic compound emissions from incineration with chlorinated organic input. Chemosphere 26 (11): 2039-2054. and Thornton, Joe (2002) "Environmental Impacts of polyvinyl Chloride Building Materials, Healthy Building Network, Washington, DC. ]The symbol for polyvinyl chloride developed by the
Society of the Plastics Industry so that items can be labelled for easy recycling is:
The
Unicode character for PVC is U+2675 (HTML ♵).
PVC is not typically recycled due to the prohibitive cost of regrinding and recompounding the resin compared to the cost of virgin (unrecycled) resin.
There is also some contention as to whether PVC is recyclable at all. The Environmental organization greenpeace states that there is no method to recycle vinyl
Blue Vinyl (2002). Directed by Daniel B. Gold and Judith Helfand.
*
List of cancer clusters*
Chlorinated polyvinyl chloride*
Vinyl 2010 is putting into practice the commitment of the European PVC industry to Sustainable Development.*
PVC and Design*
PVC for Pipes*
The European PVC Portal (European Council of Vinyl Manufacturers)*
PVC - the Poison Plastic - Hazards and Safer Alternatives*
Polyvinyl Chloride - Poisonous Plastic*
Health impacts of PVC and guides to alternatives - Healthy Building Network*
PVC Information*
The Vinyl Institute*
Vinyl.org (Vinyl Council of Canada)*
Uni-Bell PVC Pipe Association*
The Association between Asthma and Allergic Symptoms in Children and Phthalates in House Dust: A Nested Case-Control Study*
European Council of Plasticisers and Intermediates*
Blue Vinyl Documentary Homepage link to a site by the first person documentary filmmaker that explores some of the questions about the sustainability of PVC
*
An introduction to vinyl
