Development and environmental improvements of plastics for hydrophilic catheters in medical care:
an environmental evaluation
Håkan Stripplea,
a
,
, Robert Westmanb and Daniel Holmb
IVL Swedish Environmental Research Institute, Aschebergsgatan 44, P.O. Box 5302, SE-40014
Gothenburg, Sweden
b
Astra Tech AB, P.O. Box 14, SE-43121 Mölndal, Sweden
Received 28 June 2007; revised 22 November 2007; accepted 3 December 2007. Available online
28 January 2008.
Abstract
Single-use medical devices have been under close scrutiny for several years, especially the choice
of plastic materials. Many different requirements such as medical safety, treatment functionality and
efficiency, environmental performance, etc. have to be fulfilled. Today, the most commonly used
materials for hydrophilic urinary catheters are polyvinylchloride (PVC) and thermoplastic
polyurethane (TPU). In this research study, these two materials' environmental performance was
evaluated. In light of the knowledge gained in that study a new plastic material for use in urinary
catheters was developed. The aim of the development of this new material was to design a high
performance material with superior environmental performance. The newly developed plastic
material is a polyolefin-based elastomer. The ecological environmental performance of the new
material was evaluated and compared to the existing plastic materials. The study focused
exclusively on the choice of plastic materials and their ecological environmental performance.
The analysis has been performed using a system perspective and a life cycle assessment (LCA)
methodology. The functional unit has been set to the treatment of one patient during one year. The
results from the LCA models have been presented both in terms of direct inventory data, such as
energy use and formed emissions, and in terms of the results from four different impact assessment
methods. Analysis of the results based on direct inventory data, i.e. common inventory results such
as energy resource uses and emissions of CO2, NOx and SO2 show an overall better environmental
performance for the new polyolefin-based elastomer compared to the existing PVC and TPU plastic
materials. The normalization and weighting steps in the analyzes have indicated the importance of
energy resource uses and global warming as indicator for the environmental performance even if
other impact categories also can play a role. In the environmental impact assessment, the
polyolefin-based elastomer showed a clearly better environmental performance than the TPU
material. Compared to PVC plastic material the new polyolefin-based elastomer showed an almost
equivalent environmental performance. This can be mainly explained by the different materials'
energy use. The new material has thus also shown to be an environmentally good alternative to
PVC if a PVC-free material is requested. Basing the plastic formula, on simple bulk plastics with
low energy use in the production of single-use medical devices, has been shown to be a successful
method of producing high quality products with superior environmental performance.
Keywords: Environment; Disposable articles; Medical care; Medical device; Plastics; Hydrophilic
urinary catheter; Single-use catheter; Astra Tech; Lofric; Intermittent catheterisation; PVC; TPU;
Polyolefin; LCA
Article Outline
1. Introduction
2. Description of the product group
3. Methodological aspects
4. Description of the materials and the development background
5. Description of the analyzes
6. Results from the LCA models and evaluation of the results
6.1. Impact assessment – EPD
6.2. Impact assessment – Eco-indicator 99
6.3. Impact assessment – CML 2
6.4. Impact assessment – EPS 2000 and final score values
7. Discussion
8. Conclusions
Acknowledgements
References
1. Introduction
The endeavour towards a more sustainable society with low environmental impact affects most of
industrial production processes and products. Single-use disposable products have been under close
scrutiny for their environmental impact and different studies investigating the possibilities to
replace single-use products have been initiated. However, single-use products have many
advantages compared to other products, especially for medical devices. They are often easy to
handle and offer an easy solution to a common problem.
For medical devices, single-use disposable devices offer additional and essential advantages. Risk
of infection and sterilization requirements often make the use of recycled products in medical care
impossible. Disposable products are therefore used very frequently in medical care and offer safe
medical treatment. However, medical materials are also subject to environmental requirements and
ambitions to improve their environmental impact. Medical devices have many different
requirements to fulfill, such as medical treatment performance and technical functionality, handling
and operational performance, medical/patient safety, environmental impact and cost efficiency. All
of these aspects have to be weighed against each other and optimized.
Astra Tech is a large producer of medical devices with a world-wide market. The environmental
aspect is of major concern for Astra Tech and an important factor in the development of new
products. The aim of the present research work was to establish a base for the internal choice of
material in the production and to show the environmental performance for the different alternatives.
However, ecological aspects are complex and require advanced handling methods. In order to be
able to analyze the present product situation and to design new products with high environmental
performance, it is important to establish a method for evaluating the environmental impact. For this
purpose, IVL Swedish Environmental Research Institute carried out the present study.
In this study, we analyzed the environmental performance of three different plastic materials for
urinary catheters. These three plastic materials represent a bulk plastic material (polyvinylchloride,
PVC), a high quality performance plastic (thermoplastic polyurethane, TPU) and a newly developed
plastic material based on the experiences from the present environmental evaluations (a polyolefinbased elastomer). In this article we show how the material selection for a product and the
development of a new, environmentally improved, material can be based on LCA results.
2. Description of the product group
A urinary catheter is used as a standardized treatment method for intermittent emptying of the
bladder, e.g. for patients suffering from urine retention. The surface structure of the catheter is of
special importance and designed to avoid damage to the urethra. Historically, uncoated catheter
tubes in combination with low friction gels have been used. Later, catheters with a hydrophilic
coating were developed. However, these hydrophilic catheters carry with them a significant risk of
osmotic dehydration of the surface coating. To counteract dehydration of the surface coating and
thus secure low friction throughout the entire procedure, a hydrophilic surface coating with salt was
developed. This was first achieved with LoFric™ catheters equipped with Urotonic™ Surface
Technology. The surface structure and coating varies for different materials in the catheter tube. A
modern coating process, however, reduces friction between the urethra and the catheter by 90–95%.
This considerably reduces the discomfort for the patient and minimizes the risk of trauma and
complications.
The physical and chemical properties of the plastic material used in the catheter tube are other
important design aspects. Some essential properties for plastic materials used in hydrophilic
catheters are listed below:
1. The catheter must be flexible but without a tendency to kink when bent.
2. The material must not break, i.e. have acceptable mechanical strength.
3. The material must tolerate the sterilization process.
4. The material must be compatible with the chemical coating process.
These constraints considerably limit the choice of materials. The choice of plastic material is thus of
great importance for the product's functionality and overall behaviour.
The product in this study is a single-use hydrophilic catheter used in hospital medical care and for
home treatment of patients. The main function of the product, besides the medical treatment, is to
offer patients a comfortable therapy, efficient treatment and a safe product. The urinary catheter
consists of a catheter tube and a connector that can be connected to a urine collection bag. The tube
and the connector are welded together. Fig. 1 shows a picture of a typical urinary catheter.
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Fig. 1. The picture shows a typical design for a urinary catheter.
The physical geometry of the product and the surface structure are of great importance for the
product's functionality. The catheters are produced with different diameters (charrière 06-24) and
different lengths (15, 20, 30 and 40 cm) to fit varying patient requirements. The charrière number is
three times the outer diameter of the catheter tube, measured in millimetres. The two most common
catheter tips are Nelaton and Tiemann.
3. Methodological aspects
Obviously, there is no single methodology that covers all of the different design aspects at the same
time. The different requirements can also show conflicting effects and the balancing of these effects
is not obvious. However, for each of the above listed requirements, there are methods to analyze a
medical device's performance, even if each analysis can be comprehensive. This study has focused
on the environmental impact of the different plastic materials used in the uncoated catheter.
In order to analyze the entire effect of a material, a system analysis is required. A system analysis is
a tool that allows a product to be analyzed through its entire life cycle, from raw material extraction
and production, via the material's use to waste handling and recycling. The most common tool for
system analysis is the life cycle assessment (LCA) methodology. The LCA methodology is
described in, for example, the standard EN ISO 14044:2006 [1]. In a life cycle assessment, a
mathematical model of the system is designed. This model is of course a representation of the real
system, including various approximations and assumptions. The LCA methodology allows us to
study complex systems, where interactions between different parts of the system exist, to provide as
complete a picture as possible of the environmental impacts of, for example, a product.
An LCA is usually made in three steps with an additional interpretation step, see ISO standard. In
the goal and scope definition, the model and process layout are defined. The functional unit is also
specified. The functional unit is the measure of performance that the system delivers. In the life
cycle inventory analysis (LCI), the material and energy flows are quantified. Each sub-process has
its own performance unit and several in- and out-flows. The processes are then linked together to
form the mathematical system being analyzed. The final result of the model is the sum of all in- and
out-flows calculated per functional unit for the entire system. The life cycle impact assessment
(LCIA) is defined as the phase of life cycle assessment aimed at understanding and evaluating the
magnitude and significance of the potential environmental impacts for a product system throughout
the life cycle of the product. The impact assessment is performed in consecutive steps including
classification, characterization, normalization and weighting. The LCIA phase also provides
information for the life cycle interpretation phase, where the final environmental interpretation is
made.
Evaluation and valuation of the results in this study have been performed both with a direct
inventory data comparison, such as a comparison of energy use and formed emissions, and by using
the following four impact assessment methods.
1. A comparison after classification and characterization in line with the environmental product
declaration (EPD) system [2].
2. An impact assessment according to the Eco-indicator 99 system [3].
3. An impact assessment according to the CML 2 system [4].
4. An impact assessment according to the EPS 2000 system [5].
The EPD system is not a complete impact assessment system but includes classification and
characterization. Both Eco-indicator 99 and CML 2 are complete LCA tools that include
classification, characterization, normalization and weighting. EPS is a monetary-based LCIA
method. In the EPS method, a ‘willingness to pay’ (WTP) to restore damage in the society (in this
case in the OECD countries) caused by environmental impact is applied. The first two impact
assessment methods will result in different data sets for different environmental effects that have to
be interpreted, while the last three methods can also be used to calculate a final total score from the
assessment.
4. Description of the materials and the development background
Today, two different plastic materials dominate the market for plastic material used in hydrophilic
urinary catheters: polyvinylchloride (PVC) and thermoplastic polyurethane (TPU). The PVC plastic
used is of a plasticized type and the PVC polymer is produced with suspension polymerization.
Different plasticizers can be used, but di(2-ethylhexyl) phthalate (DEHP) is the most common and
best evaluated plasticizer for PVC and thus assumed in this study. TPU is chemically less
homogenous and can be considered more as a group of plastics. Thus, many different types of TPU
exist and it can sometimes be difficult to know exactly which polyurethane is used for a certain
application. In this study, the production of TPU is based on known inventory data. The assumed
composition of the TPU elastomer in this study is: polytetramethylene ether glycol (PTMEG),
hydrogenated methylene diisocyanate (HMDI) and 1,4-butanediol. HMDI is used instead of MDI to
avoid formation of methylene dianiline (MDA), which has been shown to be hepatotoxic. MDA is
not formed if an aliphatic polyurethane is used instead of an aromatic one. 1,4-Butanediol is
produced from methanol (formaldehyde), acetylene and hydrogen through 1,4-butynediol.
Inventory data for the production of the materials are taken from the large LCA study performed by
the plastics manufacturers [6], [7], [8] and [9].
In the first phase of this study, the TPU showed a poorer environmental profile than PVC. PVC, on
the other hand, contains chlorine and plasticizers which can, under certain circumstances, be a
potential risk factor. However, no scientific consensus exists concerning the environmental and
health risks of PVC plastics. In spite of this, there remain opportunities to improve the materials
used in urinary catheters. From an environmental point of view, simple polyolefin materials such as
polyethene and polypropene show good results. However, due to their physical and mechanical
properties, these materials cannot be used directly without some chemical modifications. The
preferred modification should be of a bulk polymer type in order to keep energy use at a low level.
Today, many different tailor-made plastics exist. A plastic material is no longer a simple polymer
molecule of one type, but a complex, highly developed structure involving co-polymerization,
chemical modifications and mixtures. The challenge is thereby to develop a new polymer material
that fulfills all of the technical and medical constraints, while at the same time fulfilling the high
demands of an environmentally superior material.
With this challenge in mind, a development project was launched with the aim of developing a new,
environmentally high-performing material. A new polymer material was developed, analyzed and
implemented in the urinary catheter production process. This new plastic material is principally
based on different bulk polyolefins and styrene block copolymer. This indicates a basis for good
environmental performance. The new material is termed polyolefin-based elastomer in this article.
5. Description of the analyzes
This study will only focus on the selection of plastic materials for the uncoated catheters that are
later coated to become hydrophilic. The catheter tube and the connector are assumed to be of the
same type of material. The study focuses on the environmental effects of different plastic materials
used for a raw catheter (the uncoated catheter). An LCA methodology has been used for the
environmental evaluation. The methodology thus covers ecological environmental issues. The LCA
system includes the extraction of raw materials, production of the plastic material, production of the
raw catheter, transports, waste handling and energy recycling of the plastic materials. Other
processes, i.e. packaging, hydrophilic coating and sterilization are considered equal for the different
materials and have thus not been considered.
In this study, the most common catheter size was selected for the analysis. The chosen catheter is a
40 cm long, Nelaton tip, charrière 12. The actual function of a hydrophilic urinary catheter is to be
part of a urological treatment and to be the tool in catheterisations. With single-use catheters, one
catheter is used for each catheterisation. One catheter is thus identical to one catheterisation, and the
amount of catheters can thereby be used as a measure of the functional unit. In this case, the
functional unit for the entire model has been chosen as the treatment of a patient with catheters
during one year. Typical catheter use during treatment is five catheters per day, which amounts to
1825 catheters in one year. Accordingly, the model covers the life cycle of 1825 catheters.
LCA models for the raw catheters of the three different plastic materials were developed. An
internal independent expert review has been performed by Lars-Gunnar Lindfors (IVL) of the LCA
models. In the review report it was concluded that the LCA models were developed according to
good practice and that the results were balanced and supported by the models [10]. The results from
the models were analyzed and the three materials were compared and evaluated. The study has been
carried out as a comparative study of the three different plastic materials.
The different plastic materials also have different densities, which give the catheters different
weights. The densities and the total weights of the different catheters are listed below.
Material
Weight of catheter (tube and connector) in g
Density in g/cm3
PVC
5.11
1.22
TPU
4.82
1.15
Polyolefin-based elastomer
3.77
0.93
Two different waste handling methods have been considered; incineration (40% of the plastics) and
landfill (60% of the plastics). This can reflect an average of the present situation in the OECD
countries. For the landfill process calculations [11], an infinite time period has been used, i.e. the
material in the landfill is broken down completely and all the emissions have been released. Note
that this can take several 100 years. Recycling of plastic materials from medical devices is not
possible, due to the risk of infection. For destruction of medical devices, incineration is preferred.
However, several different factors influence waste treatment after use. Important factors here are
the type of use (hospital use or home use) and the design of the local waste treatment system where
the product is used. In home use, the products are usually mixed with municipal household waste. It
is assumed that approximately 50% of the landfill gas formed is collected and recovered as fuel.
The rest will migrate through the soil cover, where some of the methane will be oxidized to CO2 by
microorganisms. At a typical landfill, about 10–20% will be oxidized (15% has been assumed in the
calculations). Collection of landfill gas is assumed to occur during the first 100 years of the landfill.
The data module for incineration [11] covers incineration in a municipal solid waste (MSW)
incinerator. The data are based on modern OECD standard equipment with well-controlled exhaust
gas cleaning equipment. Controlled HCl emissions have been assumed with an emission level
equivalent to 3% of total formed HCl. The incinerator is also assumed to be connected to a district
heating system for energy recovery.
The energy released during waste incineration or the production and combustion of methane from
landfills is, as an example, treated as the corresponding gain in energy resource use and emissions
when the same amount of energy is supplied by a fuel oil boiler. For electric power production, an
OECD power production mix has been used. Transport distances related to the application have
been assumed to be equal for the different materials and carried out by heavy diesel trucks.
However, for specific inventory data such as production of different plastic materials, specific data
for electric power production and transports have been used.
6. Results from the LCA models and evaluation of the results
The inventory data describing the system in terms of resource use, emissions, etc. are relatively
comprehensive and includes many different parameters with different environmental impacts. In
this case, the environmental evaluation begins with a presentation of some central inventory
parameters, such as energy use, and some emissions to show the main trends in the data. The impact
assessment is then carried out using the four methods presented in Section 3.
The overall energy resource use for PVC, TPU and polyolefin-based elastomer catheters is shown
in Fig. 2. As shown in the figure, the energy resources are mainly fossil-based and only a small
amount comes from renewable energy resources. Natural gas and crude oil are the main energy
resources for all catheters. The crude oil gain is relatively equal for all catheters. The crude oil gain
parameter shows, as an example, how much crude oil can be saved if the waste energy from
incineration and landfill gas is used to replace fuel oil in a district heating network. To facilitate a
comparison of overall energy use, the different materials' total net energy use is summarized and
presented in Fig. 3. The results are shown with and without the potential crude oil energy gains
from the waste processes. The summarized figure shows that the newly developed material has a
lower energy use than the existing materials, regardless of the gain in crude oil use. This is probably
due to a high use of low complex, bulk plastics, even if the new plastic material is a highly
advanced and developed material. The new material also has a low density, which reduces the
amount of material used in the product and thereby also contributes to better environmental
performance. Fossil CO2 emissions show the same trend as energy use, with TPU having the
highest CO2 emissions and the new polyolefin-based elastomer having the lowest emissions, Fig. 4.
Also, NOx and SO2 emissions follow the same emissions pattern, Fig. 5. However, many more
parameters have been investigated and analyzed in the impact assessment methods below.
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Fig. 2. Energy resources used by PVC, TPU and polyolefin-based elastomer catheters, calculated
from inventory data using the LCA model.
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Fig. 3. Total net energy resources used by PVC, TPU and polyolefin-based elastomer catheters.
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Fig. 4. Total CO2 emissions for PVC, TPU and polyolefin-based elastomer catheters.
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Fig. 5. Total NOx and SO2 emissions for PVC, TPU and polyolefin-based elastomer catheters.
6.1. Impact assessment – EPD
The first impact assessment method to be applied is a pure classification and characterization in line
with the EPD system. The results of the classification and characterization are presented in Fig. 6.
In this figure, the results have been scaled so that the sum of each impact category is 100%. The
figure shows the relative contribution to an impact category for the plastic materials compared to
the total impact of the PVC, TPU and polyolefin-based elastomer catheters. As we can see in the
figure, the new material has a low general environmental impact compared to the older materials. It
has a lower impact than TPU in all impact categories and a lower impact than PVC in all categories
except global warming, eutrophication and photochemical ozone. The increased acidifying potential
for PVC can be explained by HCl emissions to water caused by landfilling of PVC and the higher
ODP level is caused by the use of CFC/HCFC in PVC polymer production. TPU's high
eutrophication potential is caused by the polyurethane material's nitrogen content. The potential
environmental gain from waste energy has been included in the figure, but is relatively low, see
Fig. 2, Fig. 3, Fig. 4, Fig. 5, Fig. 13, Fig. 14 and Fig. 15.
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Fig. 6. Impact assessment results showing the plastic materials' relative contribution to an impact
category, compared to the total impact of PVC, TPU and polyolefin-based elastomer catheters,
using the EPD methodology. Gains from using waste heat energy are included in the results.
6.2. Impact assessment – Eco-indicator 99
In Fig. 7, an equivalent figure to Fig. 6 is shown for the Eco-indicator 99 hierarchist impact
assessment method. The figure shows the result after characterization but without normalization and
weighting. Compared to TPU, the new polyolefin-based elastomer shows a lower environmental
impact in all categories except ecotoxic emissions and extraction of minerals. Compared to PVC,
the polyolefin-based elastomer shows a lower impact in six of nine categories.
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Fig. 7. Impact assessment results showing the plastic materials' relative contribution to an impact
category, compared to the total impact of PVC, TPU and polyolefin-based elastomer catheters,
using the Eco-indicator 99 hierarchist version without normalization and weighting. Gains from
using waste heat energy are included in the results.
Figures showing only data after characterization are mainly used for comparison of each individual
impact category. However, the different impact categories cannot be considered to be equally
important. This can be illustrated using normalization and weighting methods. EN ISO 14044:2006
defines normalization as the “calculation of the magnitude of the category indicator results relative
to some reference information”. For example, this reference information can be the total impact of a
category for a country, for Europe or the world. Weighting methods are used to rate the importance
of the different impact categories and can thereby include a large portion of subjective valuation.
No scientifically objective weighting method exists. Therefore, weighting methods should be used
carefully and are only included in the ISO standard as an option and not recommended for
comparative studies. However, in this research study we want to show the entire potential of the
modern impact assessment methods. Thus, here we do not follow the ISO standard.
If the standard normalization and weighting factors are applied to Eco-indicator 99, the category
“Extraction of fossil fuels” will dominate the environmental impact as shown in Fig. 8 and Fig. 9,
even if the climate change category plays a significant role. This will favour materials with low
energy use, such as the new polyolefin-based elastomer and PVC plastics. The waste energy gain
potential, however, is small. The normalization and weighting methods used are described in
Ref. [3]. The weighting method used is based on the panel procedure with the following weighting
factors: human health 40%, ecosystem quality 40% and resource use 20%.
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Fig. 8. Impact assessment figure showing the results after characterization and normalization using
the Eco-indicator 99 hierarchist version. Gains from using waste heat energy are included in the
results.
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Fig. 9. Impact assessment figure showing the results after characterization, normalization and
weighting using the Eco-indicator 99 hierarchist version (see text). Gains from using waste heat
energy are included in the results.
6.3. Impact assessment – CML 2
If we also produce the same type of figure (results after characterization) for the CML 2 impact
assessment method, the same impact pattern can be found here as well, Fig. 10. Here as well, the
new material shows an overall low environmental impact. Compared to TPU, the polyolefin-based
elastomer has a lower or equivalent environmental impact in all impact categories. Compared to
PVC, its impact is lower in five out of 10 impact categories. The results of the normalization and
weighting step in the CML 2 method are shown in Fig. 11 and Fig. 12. In this study, normalization
has been carried out from a Western European perspective [4]. No standard weighting method has
been developed for the CML 2 method. However, Huppes G et al. [12] have developed a weighting
method that can be used with the CML 2 method. This weighting method is based on a panel
procedure developed in the Netherlands. Unfortunately, this weighting method does not include
resource use. For this method to be applicable, it has been modified to include resource use. A
similar weighting approach as in Eco-indicator 99 has been used. In this case, the weighting factors
have been scaled so the resource use has a weighting of 20% and the remaining, existing weighting
stands for 80%. The weighting factors used in the calculation are shown in Fig. 12. As shown in
Fig. 11 and Fig. 12, “Ozone layer depletion” and “Freshwater aquatic ecotoxicity” show low levels,
while “Abiotic depletion” (resource use) and “Global warming” and, to some extent, also Marine
aquatic ecotoxicity, show high levels in both the normalization and the weighting methods.
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Fig. 10. Impact assessment results showing the plastic materials' relative contribution to an impact
category, compared to the total impact of PVC, TPU and polyolefin-based elastomer catheters after
characterization using the CML 2, baseline 2004 method, problem-oriented approach. Gains from
using waste heat energy are included in the results.
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Fig. 11. Impact assessment figure showing the results after characterization and normalization using
the CML 2, baseline 2004 method, problem-oriented approach with Western European
normalization. Gains from using waste heat energy are included in the results.
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Fig. 12. Impact assessment figure showing the results after characterization, normalization and
weighting using the CML 2, baseline 2004 method, problem-oriented approach with Western
European normalization and a panel-based weighting (see text). Gains from using waste heat energy
are included in the results. The weighting factors used in the calculation are also shown in the
figure.
6.4. Impact assessment – EPS 2000 and final score values
The valuation results using the EPS 2000 method are shown in Fig. 13. In the EPS method, all
impacts are calculated in ELU units. ELU stands for environmental load unit and is an economic
unit describing society's willingness to pay for prevention or restoration of a negative environmental
impact. In this impact assessment method, the new material shows a significantly lower impact than
TPU, but a slightly higher impact than PVC plastic. CH4 and CO2 emissions, together with natural
gas, crude oil and copper use play an important role in the environmental impact according to this
method.
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Fig. 13. Results of impact assessment using the EPS 2000 method. ELU stands for environmental
load unit. Gains from using waste heat energy are shown separately.
As shown in Fig. 13, the EPS 2000 method presents the impact assessment result in a final score
value. For the EPS method, based on an economic calculation, this is a normal presentation. The
other impact assessment methods, based on natural science, are more difficult. However, it is
possible to summarize the weighting results into a final score for the Eco-indicator 99 and the CML
2 methods as well. This has been done in Fig. 14 and Fig. 15. Even in these cases, the results show
the highest environmental impact for the TPU catheter, while the polyolefin-based elastomer and
the PVC catheters show almost equivalent environmental impact, with a small favour towards the
PVC catheter. However, it is important to keep in mind that these final scores are based on
weighted values. If we, for example, consider total energy use or CO2, NOx or SO2 emissions, as in
Fig. 3, Fig. 4 and Fig. 5, the polyolefin-based elastomer catheter shows the lowest environmental
impact, followed by the PVC catheter and the TPU catheter having the highest environmental
impact.
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Fig. 14. Summary figure showing total weighted scores after impact assessment using the Ecoindicator 99 method. Gains from using waste heat energy are shown separately.
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Fig. 15. Summary figure showing total weighted scores after impact assessment using the CML 2
method and the special weighting factors. Gains from using waste heat energy are shown separately.
7. Discussion
As we can see in the evaluation of the results, the newly developed polyolefin-based elastomer
catheter material in general has a low environmental impact. The impact is significantly lower than
the TPU catheter materials and in the same level as the existing PVC bulk plastic material. In the
analyzes, we can see that the different plastic materials' overall energy use plays an important role.
One reason for the new material's improved environmental behaviour can be found in the strategic
choice of low energy bulk materials. TPU is normally a more complex plastic material with high
performance, which is difficult to combine with a low energy profile. When this type of material is
used for less demanding applications, for example where a bulk plastic material can be used, the
results of an environmental analysis can favour the bulk plastic material. This is why the PVC
plastic also showed favourable environmental behaviour. The environmental performance of PVC
plastic has also improved significantly during the last 15 years and many previous environmental
issues have been resolved or reduced. The mercury process for chlorine production has been
replaced by the membrane process, thereby eliminating mercury emissions from production. Strict
pollution control has also significantly reduced emissions of chlorinated compounds such as
vinylchloride monomers and dioxins from production. Increased awareness in the waste handling
process for PVC has also improved its environmental performance, e.g. in the incineration process.
All these actions have contributed to an overall improvement in environmental performance.
Modern industry data from the years 2002 to 2005 have been used for the production of the
different plastic compounds.
The use of di(2-ethylhexyl) phthalate (DEHP) as a plasticizer in PVC plastic has also been
accounted for in the CML 2 analysis as a general environmental pollutant. The environmental and
health effects of DEHP have been in focus for several years and various studies have analyzed
different aspects of this. Large national or EU summaries and analyzes of the present research status
have been conducted both in the USA [13] and [14] and in Europe [15]. The population has been
exposed to DEHP for many years and DEHP is widely used in many products in society, such as
plastic carpets. According to the above studies, little data concerning the direct human effects of
DEHP exists. Most of the data comes from studies on rats and mice. No clear consensus concerning
the health effects of DEHP can be found and evaluated. It has therefore not been possible to include
an evaluation of the health effects of DEHP in this study. These effects have to be evaluated
separately. An overview of the situation can be found in, e.g. Section 2.2 in [13] and in [16].
Also, polyurethanes can form harmful compounds in different situations, e.g. in production
processes like sterilization, radiolysis, etc. Several organic compounds containing nitrogen are
biologically active and can thereby also be harmful for humans and the ecological environment.
Nitrogen compounds can thus be toxic, but are in many cases relatively easily degradable in nature.
Information from polyurethane suppliers indicates that methylene dianiline (MDA) can be formed
from aromatic polyurethanes in steam sterilization or extrusion at high moisture content. MDA is
known to be hepatotoxic. MDA is not formed if an aliphatic polyurethane is used. Knowledge about
the behaviour of the TPU material can be good to keep in mind as background information on a
potential risk factor, rather than as an immediate danger posed by the material.
8. Conclusions
Three different urinary catheter materials (a newly developed polyolefin-based elastomer plastic, a
PVC plastic and a TPU plastic) were investigated in order to analyze their ecological environmental
performance. The analysis was carried out using a system perspective and an LCA methodology.
Three different LCA models have been designed; one for each material. The functional unit has
been set to the treatment of one patient during one year. The results from the models have been
presented both in terms of direct inventory data, such as energy use and formed emissions, and in
terms of the results of four different impact assessment methods.
Analyzes of the results based on direct inventory data, i.e. common inventory results such as energy
resource uses and emissions of CO2, NOx and SO2 show an overall better environmental
performance for the new polyolefin-based elastomer compared to the existing PVC and TPU plastic
materials. The normalization and weighting steps in the analyzes have indicated the importance of
energy resource uses and global warming as an indicator for the environmental performance even if
other impact categories also can play a role. In the impact analyzes, the polyolefin-based elastomer
showed a clearly better environmental performance than the TPU material. Compared to PVC
plastic material the new polyolefin-based elastomer showed an almost equivalent environmental
performance. This can be mainly explained by the different materials' energy use. The new material
has thus also shown to be an environmentally good alternative to PVC if a PVC-free material is
requested. Basing the plastic formula, on simple bulk plastics with low energy use in the production
of single-use medical devices, has been shown to be a successful method of producing high quality
products with superior environmental performance.
Acknowledgements
Financial support for the study described in this paper was provided by IVL Swedish
Environmental Research Institute through the Swedish Environmental Protection Agency
(Naturvårdsverket) and by Astra Tech AB. The latter has also provided valuable technical
background information.
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Corresponding author. Tel.: +46 31 725 62 00; fax: +46 31 725 62 90.
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