Abstract:

This study conducts a comprehensive life cycle assessment (LCA) of three prominent sterilization monitoring products using secondary research, employing the OpenLCA software framework to elucidate their environmental footprints. The assessment covers the entire supply chain of the products starting from raw material acquisition to disposal and includes the Steam Chemical Indicator, the Biological Indicator for Steam sterilization detection, and the Bowie-Dick Test Pack. The findings of this study underscore the environmental loadings of each product and suggest interventions for enhancing the ecological profiles of these essential healthcare tools.

INTRODUCTION

Sterlization monitoring is a critical component in ensuring the efficacy and safety of medical procedures. The environmental implications of these indispensable products, however, remain a growing concern as these are single-use products. Life cycle assessment offers a systematic approach to evaluate the environmental burdens associated with product life cycles, providing insights into potential areas for sustainable development. This paper focuses on three products integral to sterilization processes, chosen for their prevalence in healthcare settings. The objective is to apply the ‘cradle to grave’ framework to discern the environmental impacts throughout the products’ life cycles and to offer a basis for comparison among them.

Methodology:

We have used ReCiPe methodology [1] (ReCiPe - PRé Sustainability, 2022) for the analysis. The study delineates the life cycle stages of the products, from raw material extraction through manufacturing, usage, and disposal. Data collection sources include technical datasheets, product descriptions, and the provided image, ensuring comprehensive coverage of inputs and outputs. The functional units are defined by the purpose of each product, and system boundaries are set to encompass all relevant processes, with allocation procedures applied where necessary to address multifunctional processes.

The life cycle impact assessment (LCIA) method is called ReCiPe. In 2008, RIVM, Radboud University Nijmegen, Leiden University, and PRé Sustainability collaborated to create it for the first time. Converting the lengthy list of life cycle inventory data into a small number of indicator scores is the main goal of the ReCiPe approach. The relative severity of an environmental effect category is expressed by these indicator ratings. 

In ReCiPe we determine indicators at two levels:

1. 18 midpoint indicators

2. 3 endpoint indicators

Midpoint: They help us to understand the direct environmental impacts. These are more focused on technical aspects of environmental performance. Examples include:

• Global warming potential (measured in kg CO2 equivalents)

• Acidification potential (measured in kg SO2 equivalents)

• Eutrophication potential (measured in kg phosphate equivalents)

Endpoint: These indicators represent the broader or overall consequences of the midpoint impacts and how they affect human health, ecosystems, and resources. They are further along the cause-effect chain and are more relatable to the actual effects experienced by humans and ecosystems. Examples include:

• Human health damage potential

• Ecosystem quality damage potential

• Resource depletion potential

 2.1 Sample Selection

To perform the LCA of the sterilization monitoring products, a selection of products was made based on their prevalence in healthcare settings and their distinct functions within the sterilization monitoring process:

2.2. Component breakdown and creating Bill of materials

Based on the material listings and dimensional details found in the product sheets, we will next assign specific materials to each component of the product. Subsequently, we will leverage the known density of these materials to calculate the estimated weight of each component.

2.3. LCI analysis

Our next step is life cycle impact analysis by quantifying the emissions from end to end of the life cycle including the energy required to produce the product[Fig 1], and the transportation energy for sourcing raw materials to manufacturing.

Fig 1:  Life cycle assessment process flow diagram

Product Description and Bill of Materials

3.1. Chemical Indicator

The Steam Chemical Indicator with Extender, a widely utilized chemical indicator, was chosen for its integral function in offering immediate visual confirmation that sterilization parameters have been achieved. Each component was segregated and assessed to ascertain the product's environmental footprint.

Chemical indicators (CIs) are devices used in specific equipment tests or to monitor the presence or attainment of one or more of the parameters necessary for a satisfactory sterilization process, according to definitions provided by the International Organization for Standardization (ISO) and the Association for the Advancement of Medical Instrumentation (AAMI). Chemical indicators, for instance, are employed to verify if the sterilant successfully penetrated the objects being sterilized when they are placed into packs. Chemical indicators are utilized in load release and routine performance testing, as well as external and internal indicators. It is crucial to remember that chemical indications do not guarantee sterility on their own. [2] (Chemical indicator for sterilization et al.)

Through meticulous analysis of the product sheet, the following components were identified:

• Adhesive materials employed for securing the structural integrity of the indicator.

• Specialty papers that change colour upon exposure to specific sterilization conditions.

• Chemical substances that are reactive to sterilization processes.

  
  

  

  
  

  Table 1: Bill of Materials for Chemical indicator 

  
  

3.2. Biological Indicator for Steam:

We chose the Biological Indicator for Steam, which is integral to monitoring the efficacy of sterilization. The product's complex makeup requires a detailed analysis to accurately portray its biological indicators (BIs) are test systems that have live microorganisms that offer a particular resistance to a particular sterilizing procedure. To determine the degree of confidence in a sterilization process, a biological indicator tells us whether the conditions were met to kill a given quantity of germs. In BIs, endospores, also known as bacterial spores, are the principal microorganisms employed. They are regarded as some of the hardest to kill. Furthermore, bacterial spores that are known to be resistant to a certain sterilizing procedure are selected for that treatment. For instance, BIs that monitor these sterilizing procedures use Geobacillus stearothermophilus spores because of their mental footprint.

According to ANSI/AAMI and ISO, biological indicators have strong resistance to steam and vaporized hydrogen peroxide. [3] (Biological indicators for sterlization et al.)

Through meticulous analysis of the product sheet, we identified the following components:

• Plastic Vial and Cap: Made of polypropylene, these elements, weighing 3.55 grams, are crucial for housing the biological elements securely.

• Identification Label: A combination of paper and polyethylene, the label weighs 0.16±0.04 grams and provides necessary product information and secure sealing.

• Growth Ampoule: Weighing 1.6 grams and made from borosilicate glass, it contains the growth medium essential for detecting sterilization effectiveness.

• Growth Media: At 2.6 grams, this is a mix of nutrients and indicators that support and reveal the growth of spores, indicating sterilization results.

• Spores Strip: The lightest component at 0.05 grams, this paper strip carries the spores that are the core biological element of the indicator.

Table 2: Bill of Materials for Biological indicator 

3.3. Bowie dick test

By using the Bowie & Dick test, you can make sure that the sterilization chamber is adequately evacuated of air and that porous loads (such as surgical bandanas or gowns) are completely submerged in steam.

The apparatus is operated and the sterilization of porous loads is assessed using the Bowie & Dick test, specifically how well steam fills cavities as a result of the first vacuum phase's effectiveness and the temperature and pressure of saturated steam during the sterilizing phase. [4] (Marcon & Marcon, 2022)

Through meticulous analysis of the product sheet [Table 3], we identified the following components:

• Impermeable Layer: Consists of a polyethylene film weighing 6.75 grams, acting as a barrier to maintain test integrity.

• Reticulated Foam: Made from paper with a weight of 14.8 grams, this component ensures even steam penetration and distribution.

• Porous Substrate: This paper layer, weighing 6.4 grams, allows steam to pass through and react with the test chemicals.

• Primary Test Sheet: Incorporates a combination of chemicals and paper, weighing between 0.128±0.512 to 0.64 grams, changing color to indicate sterilization effectiveness.

• Early Warning Test Sheet: Weighing 0.2056±2 grams, this paper component provides an early indication of the sterilization process success.

• Label with Indicator: Made from paper (80%) and polyethylene, with a total weight of 1.0296±0.1 grams, it displays information and results.

• Disposable Wrap: A paper wrap, the heaviest component at 27 grams, encases the entire test pack to protect it until use.

Table 3: Bill of Materials for Bowie dick test

Life Cycle Inventory for product components 

Chemical Indicator

This granular data collection and material analysis are pivotal to constructing a robust and reliable life cycle inventory, which is the cornerstone of the LCA. The subsequent phases of the LCA will build upon this inventory to model the environmental impacts throughout the product's life cycle stages, from raw material extraction to disposal.

• Chemical Pellet: Minor weight with a focused impact based on chemical production methods estimated to be 0.03g.

• Electricity: Sourced from hydropower, indicating a low impact on the environment quantified to be 0.00154 kWh.

• Graphic Paper: Includes recycled content, reducing the overall environmental footprint compared to using only virgin materials estimated to be 0.72g.

• PMMA Beads: The production impact of these plastics is dependent on the energy and materials used in the manufacturing process estimated to be 0.45g.

• Transport: Represents significant potential for emissions, influenced by the distance and mode of transportation used estimated to be around 21.5 kg*km.

• Waste Incineration: Suggests energy recovery from the incineration process, potentially offsetting impacts from other life cycle stages calculated to be 1.2 g of emission.

Biological Indicator

The product components were estimated using their size and material density. Utilizing the detailed data provided in the tables, we quantified the inputs for the LCI. Biological Indicator has the following processes under LCI:

• Borosilicate glass, essential for the test's visual inspection window, was accounted for at 1.6 grams.

• Electricity consumption, sourced from hydroelectric power, was estimated at 0.00005 kWh, reflecting the energy used during the manufacturing phase.

• Graphic paper, representing the instructional and packaging components, was measured at 0.21 grams.

• Polyethylene low-density foil and polypropylene granulate, forming parts of the packaging and structural elements, weighed 0.04 grams and 3.55 grams, respectively.

• Furthermore, the transportation impact was calculated based on a transport distance of 145 kg*km, which is a critical parameter for understanding the product's environmental impact during the distribution phase.

• For the end-of-life treatment, we estimated a weight of approximately -8 grams for the waste incineration of plastics, assuming that certain components would be directed to energy recovery facilities.

• Water usage was also considered, measured at 2.6 grams, to account for the water embedded in the manufacturing process or required for the product's use phase.

In the case of the borosilicate glass used specifically in the biological indicators, we analyzed additional materials:

• Alumina (aluminum oxide) at 0.048 grams, used in the glass refining process.

• Phosphoric acid weighing 0.208 grams, a chemical reagent in glass manufacturing.

• Micrometer-level components, such as zinc oxide, present in minute quantities at 0.064 grams, contribute to the glass's desired properties.

• For end-of-life treatment, we accounted for the waste incineration of paper components in municipal solid waste, resulting in an estimated 1.2 grams directed toward energy recovery facilities.

Bowie-Dick Plus Test Pack:

In our comprehensive LCA, we have meticulously dissected the Bowie-Dick Plus Test Pack to quantify the inputs from its multifaceted composition. The information provided in the accompanying table has been instrumental in detailing the following components and their environmental considerations:

• Early Warning Test Sheet: Weighing 0.2056 grams, this critical component changes color to indicate exposure to specific conditions within the sterilization process. It is manufactured using precise amounts of materials to ensure accurate results.

• Electricity: The manufacturing of the test pack consumes electricity, here accounted for at 0.006 kWh. Our data specifies that this electricity comes from hydroelectric sources, suggesting a lower carbon footprint compared to fossil fuel-derived electricity.

• Graphic Paper: A significant component of the test pack, the graphic paper is used for instructions and potentially for the packaging. It weighs 52.106 grams and is sourced from a production mix that includes 79% primary fiber and 21% recycled content.

• Polyethylene Low-Density Foil (PE-LD): Used in the packaging of the test pack, the PE-LD foil weighs 7.0074 grams. The use of this plastic material is crucial for maintaining the sterility and integrity of the test pack until use.

• Primary Test Sheet Chemicals: These chemicals, integral to the function of the Bowie-Dick test, weigh in at 0.128 grams. They react to sterilization conditions, enabling the test pack to perform its function.

• Transport: The transport of the test pack is a significant aspect of its life cycle, with an impact calculated at 1075 kg*km. This figure encompasses the journey from the manufacturing site to healthcare facilities and considers the global distribution network.

• Waste Incineration of Paper Fraction in Municipal Solid Waste (MSW): At the end-of-life stage, the waste incineration of paper components is estimated at -59.447 grams. This negative value indicates the potential for energy recovery from the waste paper material, which offsets some of the environmental impacts associated with the product's disposal.

The detailed breakdown of each component allows for a nuanced understanding of the test pack's environmental impact throughout its life cycle. The careful quantification of materials and energy usage forms the basis for the subsequent impact assessment phase of the LCA. In this phase, we will evaluate the potential environmental burdens associated with the Bowie-Dick Plus Test Pack, including resource depletion, waste generation, and emissions to air, water, and soil. This thorough analysis will provide insights into the sustainability of the product and opportunities for improvement in its life cycle management.

Life Cycle Assessment and Data Analysis 

Sustainability is a key issue in contemporary society when it comes to energy use and emissions' effects on the environment and public health. Using Life Cycle Assessment (LCA) approaches, the current study examines the environmental impact of the processes involved in the manufacturing of cylinder heads for both gasoline and diesel vehicle powertrains. [5] (Stavropoulos et al., 2016)

Goal and Scope Definition

The goal of this assessment is to analyze the environmental impacts of three sterilization monitoring products manufactured by the organization over their entire life cycle. This includes the extraction and processing of raw materials, manufacturing, transportation, use, and final disposal. The scope is delimited to the assessment of material usage, energy consumption, waste production, and potential emissions.

Inventory Analysis

a) Steam Chemical Indicator

The Steam Chemical Indicator consists of adhesive, paper, and chemicals and weighs 1.2 grams per unit. It is packaged 500 per bag, with 2 bags per case, and 1000 units per case. The primary materials include a clear plastic display window and a paper/film top cover with steam penetration.

Raw Materials: The extraction and processing of the chemicals and paper used in the product, alongside the production of adhesive materials.

Manufacturing: Based on the information provided, manufacturing takes place in the USA. Energy usage for the machinery and processes, along with waste and emissions, are considered.

Transportation: The products are distributed within the USA and potentially exported. Transportation impacts are calculated based on the weight and distance traveled.

Use: The use phase includes the energy and resources consumed during the sterilization monitoring process in healthcare facilities.

Disposal: The end-of-life phase considers the disposal of the used indicator, whether incinerated, landfilled, or recycled.

Fig. 2 Chemical Indicator life cycle Impact assessment - major contributors to global warming

Fig.3 Biological Indicator life cycle Impact assessment - major contributors to global warming

Fig.3 Bowie dick test pack life cycle Impact assessment - major contributors to global warming

Recommendations for Improvement

The findings from the life cycle assessments and the sensitivity analyses lead to several recommendations:

• Energy Sourcing: For all products, switching to renewable energy sources during the manufacturing process could reduce the carbon footprint significantly. Manufacturing facilities could invest in on-site renewable energy generation or purchase green energy credits.

• Material Efficiency: Redesigning products to minimize material use, especially for those components with higher environmental impacts identified in the LCA, could reduce waste and resource consumption.

• Transport Optimization: Streamlining the transport logistics to reduce distance traveled or switching to less carbon-intensive transport modes could lower the environmental impact.

• Recycling and End-of-Life Management: Improving the recyclability of the products, such as by using materials that are more readily recyclable, or by enhancing the effectiveness of waste separation and collection, could decrease the environmental burden at the disposal stage.

• Biodegradable Alternatives: For the Biological Indicator for Steam, exploring the use of biodegradable materials for components that do not compromise the product's integrity or performance could be a potential improvement.

• Product-as-a-Service Model: Implementing a service model where the products can be returned to the manufacturer for refurbishing or recycling could extend the lifecycle of the materials used and reduce the need for raw material extraction.

These recommendations aim to guide the manufacturer towards more sustainable practices and product designs, contributing to the overall reduction of environmental impacts in the healthcare sector. 

[7] (Matthews, H. S., Hendrickson, C. T., & Weber, C. L. (2008))

[8] (Ashby, M. F. (2012))

Limitations and Further Research

While the study provides valuable insights, it has limitations that must be acknowledged. The LCA results are dependent on the accuracy and completeness of the data available. Further research is recommended to:

• Collect primary data directly from manufacturing facilities for more precise LCA results.

• Extend the scope of the LCA to include more impact categories, such as water footprint and land use.

• Conduct LCAs on alternative products or technologies that could replace the current sterilization monitoring products to compare environmental impacts.

Continued research in these areas will contribute to a more comprehensive understanding of the environmental implications of sterilization monitoring products and will support the development of more sustainable healthcare practices.

[9] (Guinée, J. B., et al. (Editors) (2002))

[10] (Finkbeiner, M., Inaba, A., Tan, R., Christiansen, K., & Klüppel, H. J. (2006))

Conclusions:

This paper culminates by weaving together the environmental impacts revealed by the life cycle assessment. The resulting synthesis offers conclusive reflections on the assessed products' sustainability. The study then delves into the implications of these findings, proposing actionable research directions for further enhancing the environmental responsibility of sterilization monitoring products.

References

1. ReCiPe - PRé Sustainability. (2022, December 22). PRé Sustainability. https://pre-sustainability.com/articles/recipe/

2. What is a Chemical Indicator for Sterilization? | Knowledge Center. (n.d.). https://www.steris.com/healthcare/knowledge-center/sterile-processing/what-is-a-chemical-indicator

3. Biological Indicators for Sterilization | Knowledge Center. (n.d.). https://www.steris.com/healthcare/knowledge-center/sterile-processing/biological-indicators

4. Marcon, M., & Marcon, M. (2022, June 13). Bowie & Dick tests: what is it and why is it important? | Euronda Pro System. Euronda Pro System. https://prosystem.euronda.com/bowie-dick-tests-what-is-it-and-why-important/

5. Stavropoulos, P., Giannoulis, C., Papacharalampopoulos, A., Foteinopoulos, P., & Chryssolouris, G. (2016, January 1). Life Cycle Analysis: Comparison between Different Methods and Optimization Challenges. Procedia CIRP. https://doi.org/10.1016/j.procir.2015.12.048

6. Heijungs, R., & Frischknecht, R. (2020). On the significance of electricity and its sourcing in life cycle assessment: A case study on a chemical plant. International Journal of Life Cycle Assessment, 25(2), 205-217.

7. Matthews, H. S., Hendrickson, C. T., & Weber, C. L. (2008). The importance of carbon footprint estimation boundaries. Environmental Science & Technology, 42(16), 5839-5842.

8. Ashby, M. F. (2012). Materials and the Environment: Eco-informed Material Choice. Elsevier. (Specifically for recommendations on material efficiency and biodegradable alternatives.)

9. Guinée, J. B., et al. (Editors) (2002). Handbook on Life Cycle Assessment: Operational Guide to the ISO Standards. Kluwer Academic Publishers, Dordrecht, the Netherlands. (Particularly for discussing limitations and the scope of LCA.)

10. Finkbeiner, M., Inaba, A., Tan, R., Christiansen, K., & Klüppel, H. J. (2006). The new international standards for life cycle assessment: ISO 14040 and ISO 14044. International Journal of Life Cycle Assessment, 11(2), 80-85. (For further research on impact categories.)