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PVC plays a valuable role in protecting health and improving standards of hygiene. It has helped to provide low cost, high technology health care.
It is found in many areas of hospitals and health care systems, such as:
- Hospital floors and walls, because vinyl can be joined without seams, reducing the risk of cross infection.
- Blood bags, because PVC allows blood to be stored for longer than would be possible in glass containers.(PVC is the only material defined for use for flexible blood collection containers by the European Pharmacopoeia.)
- Pharmaceutical products, because clear rigid PVC foil protects them from deterioration and allows easy visual control of dosage.
- Blister packs for tablets
- Transfusion and intravenous tubing.
- Surgical gloves
The key advantages of PVC over other materials for medical devices are:
Sterilisation: plasticised PVC maintains its product integrity under hot and cold temperatures.
Transparency: Plasticised PVC has good clarity so that tubes and other products retain their transparency.
Flexibility: resistance to kinking in tubing reduces the risk of fluid flow being interrupted.
Strength: and resistance to tearing, eg of vinyl gloves, protect both doctors and patients and help prevent the spread of infection and germs.
PVC is the material of choice in many medical applications not only because of its performance characteristics, but because it is also inexpensive and allows hospitals to use quality disposable items that help reduce infection rates.
Plasticised PVC in Medical Products & Devices
Flexibility is vital in some medical devices. For example, tubing delivering blood, drugs and intravenous solutions to patients must have sufficient flexibility that it doesn't kink and restrict fluid flow. PVC tubing performs extremely well and is the preferred material for most tubing.
Plasticisers are added to PVC to make it flexible. Since the 1940s, the most commonly used plasticisers have been from the family of phthalate compounds and of these, by far the most widely used is DEHP (di-2-ethylhexyl phthalate), sometimes known as DOP (di-octyl phthalate).
The potential exposure route to a plasticiser occurs when a patient receives fluids intravenously. How much plasticiser is released depends on the fluid properties, storage time, temperature and the type of plasticiser used. The amount that might migrate is very small and phthalates are quickly metabolised and eliminated from the human body.
Plasticiser not carcinogenic
In the early 1980s, the US EPA classified DEHP as a possible human carcinogen based on tumour findings in rodent studies. However, after extensive scientific review, the European Commission in 1990 and the World Health Organisation in 1992, found insufficient grounds for such a classification in humans. In 2000, the International Agency for Research of Cancer confirmed this when it downgraded its classification of DEHP to signify no evidence of cancer-causing potential in humans. It took into account the evidence that the mechanism by which DEHP induces liver tumours in rats and mice - a process called peroxisome proliferation - is not relevant to humans.
Reproductive and Developmental Health
As a consequence of their extensive use, the toxicology and ecotoxicology of phthalates have been carefully investigated. This has included testing for endocrine modulating effects using in-vitro (test-tube) and in-vivo (live animal) methods.
In 2000, the US Federal Government's expert scientific authority on reproductive and developmental toxicity, the CERHR, published a set of major risk assessments on phthalate plasticisers. For DEHP, the CERHR found there were no major exposure concerns for the general population; however, it identified a lack of information to assess effects of higher exposure which may be experienced with certain medical procedures, especially by premature infants undergoing intensive treatment such as replacement blood transfusion or extra corporeal membrane oxygenation (ECMO). The assessments are available at http://cerhr.niehs.nih.gov
This report was followed, in September 2001, by the US Food and Drug Administration's (FDA) report on the safety of DEHP in medical devices. The findings were similar to those of the CERHR. For the vast majority of medical uses of DEHP plasticised PVC (e.g., storage containers for IV solutions and drugs), the FDA determined that there is "little to no risk" to patients.
The FDA reported that the greatest concern is for very young, critically ill male infants with prolonged exposure to high levels of DEHP through multiple devices. The FDA echoed the CERHR's concern that, in such situations, the level of exposure may adversely affect male reproductive tract development although it added that "the risk posed by patient exposure to the amount of DEHP released during ECMO is uncertain." The FDA added that, in considering such potential risks, the availability and safety of alternatives must also be assessed.
The FDA report is available at http://www.fda.gov/cdrh/ost/dehp-pvc.pdf.
Should we use alternatives to PVC medical devices?
Medical device manufacturers want to use the best available material for the job, and because of the nature of their use, medical devices and products are rigorously tested by health authorities to provide confidence in the safety and efficacy of the product. PVC has been a proven performer in healthcare for decades. DEHP-plasticised PVC is currently one of the best materials for collection and storage of some blood components.
According to Baxter International, a major medical device manufacturer with operations in Australia, PVC bags provide good flexibility at the cold temperatures needed to store red blood cells and are able to withstand the extreme forces that are placed on the bags in the process of separating blood components.
Alternatives to PVC are used for the collection and storage of other blood components, not because of a concern about patient safety, but rather because these alternatives are thought to perform better, for example, by providing superior oxygen permeability which improves platelet survival.
Medical device manufacturers are continually striving to improve the performance of their products and for this reason, constantly research new materials. For many applications however, PVC continues to be the preferred material for delivery high quality, affordable healthcare.
Baxter believes that:
"Five to seven billion patient-days of acute exposure and one to two billion days of chronic exposure to DEHP-plasticized medical products over the last 40 years without report of significant adverse effects attest to the safety of this chemical."
Australian phthalates review
In 2004, Australia's National Industrial Chemicals Notification and Assessment Scheme (NICNAS) called for information on phthalate use and supply in Australia and in 2005, commenced conducting hazard screenings on 25 of those most commonly used in Australia. In December 2005, NICNAS announced that 9 phthalates, including DEHP, were to be declared as Priority Existing Chemicals (PEC) to undergo a rapid risk assessment. Click here for an update on the NICNAS review.
At the same time the Therapeutic Goods Administration, with responsibility for medical devices and medicines, will conduct a risk assessment of phthalates in medical devices.
Phthalates are not manufactured in Australia and there is very little PVC toy manufacturing here. Nevertheless, the outcome of the assessment is of interest to all users of phthalates in the PVC and other sectors and we are currently sharing information with NICNAS as it completes the review.
Medical waste disposal
It is sometimes claimed that PVC is not a suitable material for medical products because the manufacturing of PVC and incineration of PVC products releases dioxin.
PVC manufacturing is not a significant source of dioxin emissions. Dioxin is a by-product of burning and is not specific to vinyl. For example, a report to Environment Australia estimates that 60-80% of dioxin emissions to air in Australia arise from agricultural burning off, residential wood combustion and bushfires. Medical incinerators, municipal waste incinerators and halogen chemical manufacture (such as PVC production) together contribute less than 1% in total.
It has been reported that the key determinants of incinerator dioxin generation are combustion temperature and efficiency of cool-down, rather than the chlorine content of the feed.
Further information:
Phthalate Plasticisers
Endocrine modulation
Dioxins
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