Why use a material based on chlorine, which has no equivalent in nature?
Chlorine is one of the most common elements in nature, where it is even more plentiful than carbon. Many people know that common salt contains more than 60% of chlorine, but contrary to what many people believe, organic substances containing chlorine are also very common in nature.
Key natural sources of organic chlorinated substances are the oceans, forest fires and fungal activity. Scientists have identified more than 3,000 naturally-occurring chlorine-based substances. They are made by marine organisms (sponges, corals, sea slugs, jellyfish and seaweeds), plants, seeds, fungi, lichens, bacteria, freshwater algae and insects. Certain phytoplankton and seaweeds produce chlorinated metabolites tentatively identified as trichloroethylene and perchlorethylene, substances well known as chlorinated solvents. The oceans release some three million tonnes of methyl chloride into the atmosphere every year.
The presence of chlorine confers some unique advantages to PVC: Lower use of non-renewable resources like oil, chemical resistance and good fire-resistance properties are among the benefits of chlorine.
Chlorine production creates Hg (mercury) emissions. Isn’t this a reason to stop producing chlorine?
Chlorine and caustic soda are key building blocks that underpin more than half of the Western European chemical industry turnover of EURO 380,000 million. These basic raw materials are made by passing electricity through brine. The majority of Western European plants use mercury as the negative electrode or cathode in this process. The mercury keeps the highly reactive products apart, which is essential for safe and efficient plant operation.
As mercury is a toxic metal, the industry is progressively converting chlorine plants to other technologies when they reach the end of their economic life. This switch is helped by the high cost of power, as membrane technology is more efficient than mercury cells.
Chlor-alkali manufacturing is non-dispersive and depends on the efficient and complete recycling of mercury within the plant. Today, the residual mercury emissions from the chlor-alkali industry are very low. Substantial improvements have been made, with mercury emissions reduced by over 85% in the past decade, to 10 tonnes (1997) and less than that today. This compares with estimated global total man-made and natural emissions of 20,000 tonnes per year.
Isn’t it dangerous to transport and store chlorine?
Most chlorine is used at the site where it is made, and is not stored or transported at all. However, since it is used by industry to make such a diverse range of products, it is inevitable that some must be transported. Railways are the main method of transport, Stringent safety measures are taken during transport. Chlorine is transported in specially-designed steel containers, ranging from cylinders carrying a few kilograms of chlorine to road and rail tank wagons containing several tonnes.
In Europe, the Regulations concerning the International Transport of Dangerous Goods by Rail (RID), were recently upgraded for chlorine rail tankers. Chlorine transport in Europe has been declining. In 1995, 15% of Western European chlorine production was transported in Europe. In 2005, 761,000 tonnes of chlorine (less than 10 % of the amount produced) were transported in Europe, of which more than 75% was shipped by rail.
A Europe-wide chlorine transport emergency system is in place which provides expert technical assistance where needed. Bulk chlorine has been shipped throughout Europe for almost 50 years without a single fatality.
What is done to protect workers from vinyl chloride monomer, which is a known carcinogen?
Most cases of cancer have no known cause but some are related to the exposure to certain chemicals, including Vinyl Chloride Monomer (VCM). From information on cancers in general, it is known that one single exposure does not develop a cancer. Only workers repeatedly exposed during many years to high levels (orders of magnitude higher than those currently permitted) have developed Angiosarcoma of the Liver (ASL). ASL is a very rare form of cancer of the blood vessels of the liver which has been known to pathologists for very many years.
Once it was known that there was a relationship with VCM, the association of Angiosarcoma of the Liver (ASL) with occupational exposure to VCM was established in 1974.
Once this association was established, industry led the way in reducing exposures drastically. We do not believe that any worker who started work after 1975 is currently at risk in plants located in the countries (such as Western Europe) where strict controls were introduced following the discovery of this problem. Some new cases of ASL may however still appear in workers who had high exposures before 1975.
Maximum permitted exposures are now set out in a E.U. Directive. Expert opinion and research has led European governments to be convinced that an exposure of 3 ppm during 8 hours a day through a full career of 40 years poses no significant risk to health. Typical levels in VCM and PVC manufacturing plants are lower and are monitored continuously.
ASL has been definitely linked to vinyl chloride exposure. Possible associations have been reported between exposure to high levels of VCM and other types of cancers. The International Agency for Research on Cancer (IARC) recently reviewed its assessment of the literature. This time, the conclusion of the experts was that there is “sufficient evidence” that vinyl chloride causes also hepatocellular carcinomas (HCC - cancer of liver cells). Proposals to recognise a link between VCM and cancers of other organs were rejected by a majority of the experts. The overall classification of VCM (Class 1) will not change. The main causes of HCC in the general population are hepatitis B and C as well as high alcohol consumption. It is possible that VCM might accelerate the development of a cancer in a liver already damaged by the hepatitis virus or ethanol, but the available information is not sufficient to substantiate this speculation.
Is PVC production dangerous for workers?
Some people believe that work in the chemical industry in general is dangerous, and hence also PVC production. And there were indeed really important negative impacts due to carcinogenic Vinyl Chloride Monomer (VCM) until the seventies, when this carcinogenic property was detected. Not knowing about this hazard, VCM was even used previously as a narcotic gas in hospitals! After this hazard was identified very fast and highly effective measures were taken. Today the management of the potential hazard of working with VCM within the PVC industry is an example cited of how to responsibly, and effectively, solve such a problem.
In general, the levels of hazardous substances in the atmosphere of chemical plants is closely monitored and controlled. Control of emissions, personal protection, training and medical control of plant personnel ensure that exposure remains well within the margins of safety. The frequency and severity of accidents is very low today in the chemical industry, much lower than the average of the total industry And this lowering of accident numbers goes on, many companies in the chemical industry aim for a “zero accident future”
Is VCM emitted into the atmosphere during PVC production?
The European Council of Vinyl Manufacturers (ECVM) which represents all of the European EDC/VCM/PVC producers has issued two industry Charters:
- Industry Charter for the Production of VCM and PVC (suspension process), in 1994
- Industry Charter for the Production of Emulsion PVC, in 1998.
Among other commitments, these Charters set tight limits on VCM emissions from VCM and PVC plants as well as on the maximum amount of residual VCM present in PVC resin.
The inter-governmental Oslo and Paris Commissions for the Protection of the North Sea (OSPAR) later issued two Decisions on emissions from VCM and suspension PVC plants as well as a Recommendation on emissions from emulsion PVC plants. The limits imposed by OSPAR for VCM emissions are broadly in line with the limits specified in the Charters.
In 1999, the companies that signed the 1994 charter underwent a third party verification by an independent consultant (Det Norske Veritas - DNV). A new verification was completed at the end of 2002. A verification of compliance with the emulsion PVC Charter was completed in 2004.
As a result of industry efforts, the total yearly emissions of VCM to atmosphere from all plants of the companies that signed the Charters went down from 7694 tons in 1989 to 1062 tons in 1999. This represented less than 200 g per ton of PVC produced. A recent eco-profile of the PVC industry showed that the emissions of VCM related to the production of suspension PVC (the most common type of PVC) are now around 75 g per ton of PVC produced.
Unless in extremely high concentrations, which pose an ignition hazard, the trace emissions of VCM from production facilities pose no toxic hazard at all to humans or the environment. The VCM dissipates very rapidly in the open atmosphere to a highly diluted form and breaks downs within a few hours once exposed to daylight.
Is transporting quantities of potentially volatile VCM worth the risk?
Transporting VCM presents the same risks as transporting other flammable materials such as propane, butane or natural gas, for which the same safety regulations apply.
For many years now there has been a trend in the industry towards integrated plants where both VCM and PVC are manufactured on the same site. As logistics costs increase further we expect this trend to continue, however VCM transport will still be needed for some smaller PVC plants that do not require sufficient quantities of VCM to make on-site production feasible.
As with petroleum and other volatile gases, when VCM is transported the tankers used are designed and constructed to the highest standards to resist impact and corrosion. The routes for road tankers are controlled and monitored to avoid heavily populated areas and the drivers of tanker trucks are specially trained. Risk assessments are conducted to make sure that the lowest risk transport option is selected and in some cases this has resulted in the industry taking on accepting additional logistics costs to make risks as low as possible.
We are not aware of any fatal accidents in Europe involving the transport of VCM over the last 50 years.
Are there any toxic by-products of VCM production?
First of all, use of Best Available Techniques includes taking measures to suppress by-product formation. This makes both economic and environmental sense.
Techniques for the prevention of emissions to atmosphere include capturing vent gases, which are treated by scrubbing, filtration for removal of particulate matter, and subsequently by thermal oxidation in dedicated units or in a hazardous waste incinerator.
Techniques for the prevention of discharges into water include appropriate recycling of streams back into the process, stripping of volatile pollutants, alkaline treatment of streams containing less volatile chlorinated organics to convert them to inorganic chloride. Biological treatment of the pre-treated wastes reduces residual pollutants to acceptable levels, for example by concentrating them into the activated sludge for subsequent solid waste treatment. Any dioxins produced and not destroyed within the process are segregated into the solid waste stream.
Heavy end tars from distillation are recycled into the process or destroyed by incineration or equivalent technologies. The chlorine is recovered in the form of HCl and usually recycled into the production process.
All solid wastes containing organic by-products, including spent catalyst from oxychlorination, are appropriately treated as hazardous wastes because of their organics content.
Isn’t PVC production a recognised source of dioxin emissions?
The chemicals industry as a whole, and the PVC production chain in particular, are only very minor contributors to dioxins’ emissions throughout the world (much less than 1 %). As an example, a survey carried out in 1993 attributed to the entire chemical industry only 0.5 gram/year of dioxin emissions out of a total of 484 grams emitted per year in the Netherlands.
In 2001 US PVC manufacturers carried out an extensive monitoring programme, to evaluate the extent of dioxins releases to the open environment as well as to secure landfill. The most likely estimate was 32 g I-TEQ/yr with approximately 12 g being released into the open environment and about 19 g disposed of in secure landfill. This compared to a total released to air of several thousands of grams.
A recent eco-profile of the PVC industry showed that the total emissions of dioxins in Western Europe related to the production of PVC are now around 2 g I-TEQ per year
Formation of very small quantities of dioxins can only occur in the ethylene oxychlorination, which is one of the process steps leading to the production of VCM. These dioxin molecules are adsorbed by the solid catalyst and hence are easily contained by filtration and controlled treatment of this catalyst.
The production of PVC itself and of PVC-based products takes place at temperatures far below those required for dioxin formation.
Do products made of PVC contain dioxins?
There are no detectable amounts of dioxins in the PVC resin sold by ECVM member companies. A published study dating from 1998, demonstrated that virgin suspension from 11 major production sites in Europe does not contain any process generated dioxins at concentrations above the limits of quantification (2 parts per trillion).
Doesn’t PVC contain potentially toxic metal additives?
Additives play a vital role in creating the wide range of performance characteristics, which allow the current use and innovative development of PVC applications. Additives include stabiliser systems which contribute to guarantee long term performance and durability of the articles in which they are used and this contributes to an efficient use of the resources. Metals are immobilized in the plastic matrix, in much the same way as they are within traditional glass products made from lead crystal, and will not be released during the service life of the articles.
The use of these materials is subject to a range of existing regulations. The field of regulation is continuously evolving with risk assessments playing an important role. The PVC industry fully supports and is deeply involved in the process of assessing the risks of additives and taking phase-out measures when appropriate.
Isn’t lead, used as a stabiliser in PVC, poisonous?
Lead-based stabilisers used within PVC formulations are immobilized in the plastic matrix in much the same way as they are within traditional glass products made from lead crystal, and lead compounds will not be released during the service life of the articles.
The Risk assessment on lead shows that the use of lead stabilizers is safe to the consumers.
Despite this absence of identified risks, ESPA and EuPC committed in 2000 to replace lead stabilisers by 2015. Based on intensive effort and significant investment, the first interim target of a 15 percent reduction was achieved in 2004 - one year ahead of the original schedule. 2007 industry statistics indicate that the phase out has now reached around 35%. The next target is a reduction of 50 percent in 2010. The commitment to phase out lead stabilisers by 2015 was confirmed and extended to the EU 25 in April 2006.
Is it true that phthalate plasticisers, used in soft PVC, cause cancer?
No. Phthalates are not classified as human carcinogens by the World Health Organisation (WHO) and there is no evidence to suggest that phthalates can cause cancer in human beings. Since 1980 a large number of investigations have shown that feeding high levels (many thousand times greater than foreseeable exposure) of phthalates and other chemicals to rodents over their lifetime causes a large increase in microbodies in the liver called peroxisomes. This 'peroxisome proliferation' leads to the formation of liver tumours. However, when these chemicals are given to non-rodent species such as marmosets and monkeys (primates considered to be metabolically closer to humans), such peroxisome proliferation and liver damage is not seen.
It is now generally accepted that phthalates are one of a number of substances which can cause liver tumours in rodents by a mechanism which does not occur in humans.
On the basis of these differences in species response, it was concluded some years ago that phthalates do not pose a significant health hazard to people. This scientific view was adopted by a European Commission decision of 25 July 1990 which states that DEHP shall not be classified or labelled as a carcinogenic or irritant substance. The correctness of this decision has recently been reaffirmed by two comprehensive reviews
In February 2000, the International Agency for Research on Cancer (IARC) - which is part of the World Health Organisation (WHO) - re-classified the phthalate plasticiser DEHP as "not classifiable as to carcinogenicity to humans." Some years earlier it had been classified as "possibly carcinogenic to humans" based on rodent students.
Further information and references may be found at www.plasticisers.org
It has been said that phthalates could cause human reproduction problems. Is this true?
It has been hypothesised (and at the moment it remains a hypothesis) that some reported cases of reduced sperm count in men may be due to exposure to chemicals in the environment which mimic the natural female hormone oestrogen. There is still no evidence that there is a general problem in humans and no evidence that chemicals in general, or any chemicals specifically, are the cause. However, this hypothesis has sparked interest in the development of screening tests which could be used to identify oestrogenic substances.
The most recent in-vivo (live experimentation) studies specifically intended to look for oestrogenic effects are a series of internationally accepted and validated tests which measure changes in the reproductive organs of female rats which occur via processes under oestrogenic control. They have shown that all the phthalates ranging from dibutyl phthalate (DBP) to diisodecyl phthalate (DIDP) produce no oestrogenic effects.
In addition, numerous multi-generation fertility studies have been carried out on many different phthalates. The most recent of these are 2-generation studies which demonstrate that exposure of rats to diisononyl phthalate (DINP) and DIDP in utero, during lactation, puberty and adulthood does not affect testicular size, sperm count, morphology or motility, or produce any reproductive or fertility effects. No outcome which might be anticipated from hormone modulation was observed. The maximum level dosed was around 600 mg/kg bw/day.
In a 1995 publication Sharpe et al hypothesised that the observed effects on rat testes after administration of a low dose of butylbenzyl phthalate (BBP) were related to an oestrogenic mechanism. In fact there are some inconsistencies in this study and therefore it is being repeated in other laboratories. One of these repeat studies  has been completed and shows no effects on testes at these low doses.
It is true that some laboratories using newly developed in-vitro (test tube) screening assays have shown some phthalates, such as dibutyl phthalate (DBP) and butylbenzyl phthalate (BBP), to exhibit a weak positive result indicating possible oestrogenicity. However, these findings are equivocal in that these phthalates have proved to be non-oestrogenic in some studies.
Most phthalates, including DEHP, diisononyl phthalate (DINP) and diisodecyl phthalate (DIDP), have been tested and found to produce no oestrogenic effects
Recently published data from in-vitro screening tests indicates that, in contrast to other studies DINP may be weakly oestrogenic. However, these authors recognise that when plasticisers are eaten they are broken down to other molecules and that it is these to which humans are actually exposed. They have shown that these breakdown products are not active in the screening tests. They therefore conclude that results from in-vitro tests on whole phthalates may have little significance for human health and that it is the results of the tests on live animals which are important.
The potential reproductive risk posed by some phthalate esters has recently been reviewed by the Commission of the European Communities While it is the case that some phthalates have been shown to cause reproductive effects in rats and mice, these have occurred at levels 10,000 times higher than the estimated exposure to people. It is, therefore, very unlikely that any significant risk to human reproductive health is associated with the use of phthalates.
Further information and references may be found at www.plasticisers.org
Recent evaluations have raised concerns about the use of DEHP in medical devices. Shouldn't we at least limit that application?
DEHP-plasticized medical devices have become vital to modern healthcare. DEHP-plasticized PVC is a popular choice for many medical applications because it is clear, affordable, strong, flexible, easily sterilized and, unlike alternative plastics, won't ‘kink’ restricting the flow within the tube.
In Europe it is the only plasticiser recommended for use in blood bags by the European pharmacopoeia.
The US Food and Drug Administration recently issued a "Consumer Update" stating concern for very young male infants who are critically ill and have prolonged exposure to multiple devices containing DEHP." However, whilst noting that studies have not been conducted which would rule out effects on humans it stated that DEHP-containing devices have been used on newborn babies for many years without apparent ill effect. The FDA expressed little concern for adults receiving medical treatments such as intravenous or dialysis. The concerns about possible risks are based on the effects seen in rodents. However, tests on primates, which are much better predictors of effects of DEHP in humans than rodents, have demonstrated that they are much less susceptible to effects from DEHP than rodents.
Regulatory agencies in many countries that have approved DEHP-plasticized vinyl for use in medical devices make the point that substitutes may expose patients to hazards not present with devices made with DEHP. Any alternative to DEHP in vinyl would have to undergo scientific scrutiny and receive approval from such authorities before it could be used.
The medical device industry is one of the most highly regulated in the world. All such products, including their components, therefore have to conform to rigorous safety standards.
For more information please refer to Plasticisers in Medical Devices and to the DEHP Information Centre
Why use PVC in buildings if fire can result in the emission of toxins, including dioxins?
Out of all plastics, PVC is the most widely used in buildings, such as drinking water and waste water pipes, window frames, flooring and roofing foils, wall coverings, cables etc. Like all other organic materials used in buildings (other plastics, wood, clothing etc.), PVC products will burn when exposed to enough heat. However, unlike these other materials PVC products are naturally self-extinguishing, i.e. if the ignition source is withdrawn they will stop burning. Because of its high chlorine content PVC products have burning characteristics, which are quite favourable, i.e. they are difficult to ignite, the heat production is comparatively low and they tend to char rather than generate flaming droplets.
But if there is a large enough fire in a building PVC products will start to burn and will emit toxic substances like any other organic material.
The most dangerous toxicant emitted during fires is carbon monoxide (CO), which is responsible for 90 to 95% of deaths from fires. CO is a subtle killer, since it has no odour. Most people die in fires while sleeping. And of course CO is emitted by all organic materials, be it wood, textile or plastics.
PVC, as well as some other materials, also emits acids, organic or inorganic ones. These emissions can be smelled and are irritating, rapidly alerting people to the presence of fire. A specific acid, hydrogen chloride, is connected with burning PVC and few other products. To the best of our knowledge, no fire victim has ever scientifically been related to HCl poisoning.
Some years ago no big fire was discussed without dioxins playing a major role both in communication and measuring programmes. Today we know that dioxins emitted in fires do not impact people, since people exposed to fire have been examined in several studies. The dioxin levels measured in these studies were never elevated against background levels. This very important fact has been recognised by official reports. And we know that many other carcinogens are emitted in fires, such as polycyclic aromatic hydrocarbons (PAH) and fine particles, which present a much higher hazard than dioxins.
So there are very good reasons to go on using PVC products in buildings, since they perform well technically, have good environmental and very good economic properties, and do not make any greater contribution than other materials to the toxicological impact of fires.
Don’t harmful vapours build up indoors if you use PVC products like flooring and shower curtains?
Properly installed PVC products have no adverse impact on indoor air quality, and the small amount of volatile organic compounds (VOCs) emitted will dissipate quickly through normal ventilation. Tests have shown that the initial odour of products like shower curtains and vinyl (PVC coated) wallcoverings dissipates much faster than odours from most paints. PVC products are able to meet low VOC requirements in standards such as FloorScore,™ Green Label Plus, and GREENGUARD.
Indoor air quality can be affected by biological factors, as well. In hot and humid climates, vinyl wallcoverings can cause condensation to occur inside the walls. Manufacturers have addressed this issue with innovations such as mildew-resistant or “microvented” products that allow moisture to circulate. By discouraging moisture and resulting microbial growth, PVC flooring products and vinyl-backed carpet are some of the vinyl products that contribute to actually improving indoor air quality
Aren’t harmful dioxins emitted when PVC is incinerated?
Any waste containing chlorine, including wood and food residues has the potential to produce dioxins when incinerated. As soon as the amount of chlorine in the waste exceeds a threshold of a few fractions of %, the actual amount is not a significant factor. The main factor is the operating conditions of the incinerator. The overwhelming importance of combustion conditions on dioxin formation has been established by numerous researchers. The single most important factor in forming dioxin-like compounds is the temperature of the combustion gases. Oxygen concentration also plays a major role on dioxin formation, but not the chlorine content
The design of modern incinerators minimises PCDD/F formation by optimising the stability of the thermal process. To comply with the EU emission limit of 0.1 ng I-TEQ/m3 modern incinerators operate in conditions minimising dioxin formation and are equipped with pollution control devices which catch the low amounts produced. Recent information is showing for example that dioxin levels in populations near incinerators in Lisbon and Madeira have not risen since the plants began operating in 1999 and 2002 respectively.
PVC is not the main source of chlorine in MSW. For instance, a study commissioned by the E.U. authorities showed that the putrescible fraction contributes 35% of the total chlorine whereas the plastics only contribute 25 %.
Several studies have also shown that removing PVC from waste would not significantly reduce the quantity of dioxins emitted. The European Union Commission published in July 2000 a Green Paper on the Environmental Issues of PVC. The Commission states that: “It has been suggested that the reduction of the chlorine content in the waste can contribute to the reduction of dioxin formation, even though the actual mechanism is not fully understood. The influence on the reduction is also expected to be a second or third order relationship. It is most likely that the main incineration parameters, such as the temperature and the oxygen concentration, have a major influence on the dioxin formation”. The Green Paper states further that “at the current levels of chlorine in municipal waste, there does not seem to be a direct quantitative relationship between chlorine content and dioxin formation”.