Life Cycle Assessment of Swimming Goggles: Evaluating Environmental Impact and Consumer Awareness

Abstract

This study evaluates the environmental impact of swimming goggles through a Life Cycle Assessment (LCA), comparing virgin and recycled polycarbonate models. It identifies key hotspots, assesses circular economy benefits, and examines barriers to sustainable disposal, aligning with European Union’s (EU) 2050 sustainability objectives. The LCA was modeled using SimaPro, with the Environmental Footprint (EF) 3.1 method to analyze 16 impact categories (e.g., climate change, human toxicity, resource depletion). Two scenarios were assessed: (1) virgin polycarbonate production and (2) a closed-loop system (80% recycled content, 30% reintegration). Primary data from a survey of 150 competitive swimmers quantified disposal behaviors. The lens production phase (bisphenol A processing) dominated impacts, contributing to 62% of climate change and 75% of human toxicity. The recycling scenario reduced total impact by 23.1% (119 → 91.5 mPt), with significant declines in freshwater ecotoxicity (−28.6%) and marine eutrophication (−25.1%). Survey data highlighted critical gaps: low consumer participation in recycling due to lack of awareness and inadequate disposal infrastructure. Recycled polycarbonate can substantially mitigate environmental impacts, but systemic barriers (consumer behavior, collection gaps) limit progress. Future work should explore bio-based polymers and policy incentives to accelerate circularity.

1. Introduction

The growing environmental concerns regarding plastic waste and resource consumption have led to increasing interest in sustainable manufacturing and recycling practices. In this context, Life Cycle Assessment (LCA) has emerged as a valuable tool for evaluating the environmental impacts of products throughout their entire life cycle, from raw material extraction to end-of-life disposal or recycling. LCA provides a quantitative approach to assessing sustainability, guiding industries and policymakers in the adoption of eco-friendly practices [1,2].

Swimming goggles, commonly used in both recreational and competitive swimming, are primarily composed of polycarbonate and silicone. These materials, while durable and functional, pose environmental challenges due to their energy-intensive production and limited recyclability [3]. Polycarbonate, in particular, is associated with high carbon emissions and reliance on non-renewable resources, making it a key area of concern in sustainability discussions [4]. Meanwhile, silicone production, although contributing less to waste accumulation, remains energy-intensive and generates environmental burdens [5].

LCA studies on consumer plastic products, particularly those made from recycled polymers, highlight the environmental benefits of material recovery and circular economy strategies. For instance, research on polyethylene terephthalate (PET) bottles demonstrates that due to the largest contribution (nearly 84%) to the environmental profile of the bottles life cycle, a substantial improvement could be achieved by replacing 50% of the total amount of virgin PET used with recycled PET [6]. It has been reported that various products made from recycled plastics produce significantly low carbon emissions with respect to various products made from virgin plastics [7].

This study focuses on recycled polycarbonate as a transitional solution toward sustainable sports equipment. Bio-based materials, including lignin-derived polycarbonates and upcycled polymer composites, show promise for further reducing environmental impacts. These polymers offer sustainable, high-performance alternatives to petroleum-based versions, maintaining excellent mechanical strength, thermal stability, and optical clarity [8,9]. While they demonstrate strong potential for circular design, their technical suitability for swimming goggles requires thorough testing of material performance. Comprehensive LCA is also needed to evaluate their full sustainability profile in comparison to both conventional and recycled polycarbonate, quantifying environmental trade-offs and identifying optimal application scenarios. Such comparative studies would provide the critical data required for material selection in next-generation sustainable sports equipment.

The central part of the study is the assessment of the environmental impact of swimming goggles using LCA methodologies. The primary objective is to compare the life cycle of goggles produced from virgin polycarbonate with those made from recycled materials. This analysis aims to determine if using recycled polycarbonate significantly reduces the environmental impact of products, in accordance with the sustainability goals established by the European Union’s 2050 Agenda (EU 2050) [10,11].

The results of this research provide valuable insights into the feasibility and benefits of incorporating recycled materials into swimming goggle manufacturing. Additionally, the study highlights the role of consumer behavior, disposal practices, and industry innovation in fostering a more sustainable future. The widespread lack of knowledge regarding proper disposal emphasizes the need for better education and clearer recycling guidelines for end-users. By addressing the environmental challenges associated with polymer-based sporting goods, this work contributes to the broader discourse on circular economy principles and sustainable product design within the sports industry [12].

2. Materials and Methods

The production of swimming goggles begins with the selection of raw materials. Lenses are typically made of polycarbonate, a lightweight and impact-resistant thermoplastic known for its optical clarity [13]. Frames and straps are typically made of flexible, durable materials such as silicone, thermoplastic rubber (TPR), or polyvinyl chloride (PVC), which provide a comfortable fit and durability [14]. Soft silicone or rubber is used as a sealant to prevent water leakage. The manufacturing process involves molding the lenses and frames, which are then assembled. Polycarbonate pellets are heated until molten, and then injected into molds to form the lenses, ensuring homogeneity and clarity. Frames are created in a similar manner, with silicone or TPR injected into molds, creating flexible but strong structures that hold the lenses securely [15]. Once molded, the components are cured and cooled to harden their shape and improve the material properties.

After the blown products are formed, they must be assembled to form a final product. The lenses are inserted into frames, providing a secure and airtight seal. Soft pads are attached to the frame around each lens to create a watertight seal on the face. Adjustable straps, often with buckles or other mechanisms, are then attached to this system to allow swimmers to customize the fit to their liking.

LCA is a standardized methodology used to evaluate the environmental impacts associated with a product, process, or service throughout its entire life cycle. By systematically analyzing resource consumption, emissions, and potential environmental effects, LCA provides a comprehensive assessment of sustainability performance. This approach follows the principles outlined in International Organization for Standardization (ISO) 14040 and ISO 14044, ensuring consistency and reliability in environmental evaluations [1,16].

The assessment was conducted using SimaPro 9.6.0.1 with the Environmental Footprint (EF) 3.1 method, ensuring a consistent and scientifically robust impact evaluation. The EF 3.1 method was selected for its comprehensive coverage of impact categories, including climate change, resource depletion, and ecotoxicity, aligning with the study’s goal of identifying key environmental hotspots.

In accordance with ISO 14040 and ISO 14044 standards, SimaPro 9.6.0.1 implements the conventional Life Cycle Assessment calculation framework. At the Life Cycle Inventory stage, emissions and resource uses are quantified by multiplying activity data with the corresponding emission factors from the Ecoinvent 3.10 database, as expressed in the general form:

$${LCI}_j=\sum \left(A_i\times {EF}_{i,j}\right)$$

where $A_i$ is the activity data of process i and ${EF}_{i,j}$ is the emission factor of elementary flow j.

At the Life Cycle Impact Assessment stage, inventory flows are linked to environmental impact categories through characterization factors:

$${LCIA}_c=\sum ({LCI}_j\times {CF}_{c,j})$$

where ${LCIA}_c$ is the result for impact category c, and ${CF}_{c,j}$ is the characterization factor that converts the inventory flow j into an equivalent indicator within category c.

The LCA study presented in this work, assessing the cradle-to-grave environmental impact of swimming goggles, is structured according to the four key phases defined by the methodology: goal and scope definition, life cycle inventory (LCI), life cycle impact assessment (LCIA), and interpretation. The following sections provide a detailed description of each phase.

2.1. Goal and Scope Definition

The main goal of this study is to evaluate the environmental impact of swimming goggles by comparing the production of goggles made with virgin materials versus those made partially with recycled materials. The analysis will focus on how these choices could contribute to the sustainability goals set by the European Union’s 2050 Agenda, which promotes the circular economy, the reduction in greenhouse gas emissions, and optimal management of natural resources [10].

Specifically, the goals that this work intends to achieve are as follows:

• Assess the environmental impact of swimming goggles across their production and disposal phases, comparing virgin and recycled polycarbonate, to evaluate whether recycling significantly reduces their ecological footprint.
• Evaluate the potential of recycled polycarbonate to reduce the environmental burden, with a focus on key impact categories such as climate change, human toxicity, and resource depletion.
• Examine the alignment of recycled polycarbonate adoption with the European Union’s 2050 sustainability agenda, specifically assessing its contribution to greenhouse gas reduction, efficient resource utilization, and circular economy implementation in the sporting goods sector.

2.2. Functional Unit and System Boundaries

Based on the survey conducted for this study, the functional unit is defined as 1.5 pairs of goggles per competitive athlete per season, considering a total of 150 athletes over a time horizon extending to 2050, amounting to 5625 pairs of swimming goggles. Each goggle weighs 23 g, leading to a total assessed material weight of 129.37 kg.

Participants were recruited through convenience sampling via social networks, facilitated by a lifeguard at the swimming pool. The questionnaire was distributed within two age-stratified swimming groups (16–25 and 25–50 years old), yielding a gender distribution of 65% men and 35% women. Respondents were informed that their responses would be used for academic research, though formal ethical approval was not obtained due to the anonymized and non-invasive nature of the survey (common for such observational studies in this context). The survey, originally administered in Italian, collected data on goggle usage patterns. Key limitations include the following:

• Representativeness: The sample was drawn from a single sporting center, potentially limiting generalizability to broader consumer behavior.
• Gender Imbalance: Female swimmers were underrepresented (35%) due to the male-dominated composition of the surveyed swimming groups.
• Convenience Sampling: Recruitment via social networks may introduce self-selection bias.

These limitations are partially mitigated by the study’s focus on establishing a baseline functional unit rather than broader behavioral trends. Further details, including the questionnaire, are provided in the Supplementary Materials.

Two scenarios are analyzed:

• No Recycling Scenario: 100% virgin polycarbonate production with landfill/incineration disposal.
• Recycling Scenario: 80% of used polycarbonate is mechanically recycled and 30% reintegrated into the production process.

In this approach, 80% of used goggles are collected and recycled. This value is based on survey results, illustrated in Figure 1, indicating that 89% of respondents would prefer to purchase goggles made from recycled materials rather than virgin ones, reflecting a strong consumer inclination toward circular solutions. Despite this, only 5% of respondents reported recycling their old goggles, while 70% typically dispose of them in general waste (Figure 2). The low actual recycling rate is primarily attributed to the lack of accessible collection systems, particularly at swimming facilities. A study on waste management at sport events showed that proper recycling points increased plastic collection by 120.5% and boosted recycling rates by 157%, demonstrating how small changes can have a major impact [17]. The 80% recycling rate is therefore used to represent a realistic future scenario in which appropriate infrastructure (such as dedicated collection containers in sports centers) is implemented to match the high consumer willingness.

Figure 3 illustrates the process of substituting virgin polymer (new, unused plastic material) with recyclate (recycled plastic material) in manufacturing. There are two main recycling methods: advanced recycling, which can completely substitute virgin plastic but is too costly for widespread use, and mechanical recycling, which is more common but has drawbacks. Mechanical recycling lowers plastic quality over time, requires blending with virgin material to maintain performance, and still leads to some waste going to landfills/incineration. It serves as a reference for industries aiming to adopt circular economy principles by reducing reliance on virgin materials.

In total, 30% of the resulting polycarbonate is blended with 70% virgin polycarbonate (PC) to produce new goggles. This ratio is selected because higher shares of recycled material may compromise optical clarity and mechanical performance [18].

Figure 3. Substituting virgin polymer with recyclate [19].

Figure 3. Substituting virgin polymer with recyclate [19].

Using at least 30% recycled polycarbonate results in a notable reduction in overall environmental impacts while maintaining properties comparable to those of virgin PC. In this study, we conducted experimental tests to evaluate the impact of incorporating recycled material on the technical properties of the polycarbonate [18]. The results demonstrated that a 30% recycled content does not significantly affect the material’s key technical characteristics, which was a crucial aspect for this study. Consequently, adopting a 30% blend offers a balanced solution between environmental benefits and functional performance, indicating that this formulation remains essentially on the same performance level as virgin PC under the conditions tested. Recycled polycarbonate can also be repurposed for other manufacturing applications, such as solar photovoltaic devices, where it serves as a sustainable alternative to traditional aluminum frame. Thanks to its exceptional strength-to-weight ratio and superior corrosion resistance, recycled polycarbonate presents a compelling option for photovoltaic module frames, offering durability while reducing environmental impact [20].

The system boundaries, which are illustrated in Figure 4 and Figure 5, include material production, assembly, and disposal. The use phase is not directly assessed in the LCA but is analyzed through consumer surveys regarding replacement frequency and disposal behaviors.

Figure 4 illustrates the cradle-to-grave life cycle of swimming goggles, representing a linear production and disposal model. The process begins with the production of raw materials. Polycarbonate and other plastics are synthesized to form the main components of the goggles, including the lenses, straps, and frames. These materials are then transported to assembly facilities where the individual parts are molded and assembled into the final product. Once assembled, the goggles are packaged and transported to distribution centers, retail outlets, or directly to consumers.

During the usage phase, goggles are employed by users over a certain lifespan, which may vary depending on frequency and conditions of use. At the end of their useful life, the goggles are discarded. In this scenario, no material separation occurs at disposal, and the entire product is sent to landfill or incinerated. This results in the permanent loss of potentially valuable materials, contributing to environmental burden through both waste generation and the need for continuous input of virgin materials.

Figure 5 presents an alternative scenario that integrates a recycling loop for the lenses, partially closing the material cycle. As in the previous model, the life cycle starts with the production of raw materials, followed by the assembly of lenses, frames, and straps into complete goggles. The finished products are then transported to consumers and used as intended.

Upon reaching the end of their functional life, the goggles undergo a separation process in which the lenses are selectively recovered for recycling, while the straps and frames are disposed of as in the linear model. The recovered lenses are sent back to material production facilities, where they are reprocessed and reintegrated into the manufacturing cycle, thereby reducing the demand for virgin polycarbonate and minimizing the overall environmental impact. This circular approach aims to enhance resource efficiency by diverting a portion of waste from landfill and supporting the use of secondary raw materials.

In both cases, 90% of PC is considered to be produced using phosgene, while 10% is produced from a polyaddition process [21].

The life cycle stages under analysis are as follows:

• Material Production: This phase includes the manufacturing of polycarbonate (both virgin and recycled) and silicone.
• Assembly: The process of assembling the components (frame, lenses, straps) is analyzed.
• Use: The present study excludes impacts associated with transporting goggles from the manufacturing site to end users, as well as the operational impacts during actual use. However, some insights regarding the frequency and reasons for replacement as well as the purchase and disposal habits of various athletes have been obtained through the survey.
• Final Disposal: The management of the goggles’ end-of-life is analyzed, with a particular focus on the potential for recycling and the effectiveness of disposal in landfills or incineration, highlighting how poor end-of-life management affects the overall ecological footprint.

2.3. Life Cycle Inventory

The data collection process is a key step in Life Cycle Assessment, as the quality of the information collected determines the reliability of the results. In this study, secondary data were collected from various sources, including scientific publications. The focus was on quantitative indicators, such as the number of raw materials used, the amount and type of energy used and outputs such as emissions and waste. According to the background data, the information was obtained from the Ecoinvent database (V3.10). Given the lack of detailed data on transportation in this study, the selected data fell under the market category. This classification is used to describe material flows and processes related to the European market and material availability, ensuring that the analysis reflects real-world supply chains. The complete LCI table is provided in the Supplementary Materials.

Since the survey was conducted in Italy, the data used in this simulation are related to the Italian polycarbonate production and recycling process. Due to the unavailability of data from the Italian manufacturer, data from Chinese polycarbonate production were used with adaptations to align with the Italian context [22]. This adaptation primarily focused on the electricity supply, replacing the original background data with the Italian medium-voltage grid mix to reflect the national energy profile and its higher share of renewables. In addition, for other background processes such as raw material production, transport, and waste treatment, datasets were selected following a geographic hierarchy: Italian datasets were used when available, followed by European datasets, and finally global datasets when no regional alternatives were present in the database. However, this modification inherently introduces uncertainties, as technological differences, plant efficiencies, and energy sources can significantly vary. A sensitivity analysis was carried out to compare the Italian-adapted polycarbonate production data with the European dataset from the Ecoinvent database. The aim was to determine whether the applied adaptations produce results aligned with those derived from a European context, thereby supporting the reliability of the chosen approach.

2.4. Life Cycle Impact Assessment

In this study, SimaPro 9.6.0.1 was utilized to model the life cycle of goggles. This software is a widely recognized tool for LCA that allows the analysis of the life cycle of products and systems, integrating a variety of environmental impact categories [23]. It also supports the creation of detailed inventories enabling the identification of key environmental hotspots, as well as helping guide decisions aimed at reducing the overall ecological footprint of a certain product or process.

The impact categories and indicators used are based on the Environmental Footprint 3.1 method (EF 3.1). This method, introduced by the European Commission under Recommendation 2013/179/EC, provides a standardized approach for assessing and communicating the life cycle environmental performance of products, ensuring compatibility with key European policy directives (e.g., circular economy initiatives) [24]. It is an intermediate-level approach as it incorporates specific characterization factors producing sixteen different impact categories, ranging from climate change and acidification to toxicity and resource depletion.

The EF 3.1 method was chosen over other methods (such as ReCiPe or ILCD) due to its strong policy relevance and alignment with the European Commission’s environmental objectives. EF 3.1 is particularly suitable when aiming to support eco-design and product policy within a European context. It focuses on harmonization and comparability across products within the EU market. While ReCiPe or TRACI might offer additional perspectives, such as damage-oriented analysis or region-specific impacts (e.g., for North America), EF 3.1 provides more granular and updated characterization factors for Europe market.

By integrating EF 3.1, the present work not only remains aligned with current EU guidelines but also provides a comprehensive view of possible impacts, thereby enabling a more robust identification of environmental hotspots throughout the product’s life cycle. Specifically, the impact categories determined are presented in

Table 1. Sixteen EF 3.1 impact categories (impact category name, description and unit used).

Impact Category	Description	Unit
Acidification	Measures the potential soil and water acidification caused by emissions of gases like nitrogen oxides and sulfur oxides	kg mol H+
Climate Change	Global Warming Potential (100 years) assesses the climate impact of greenhouse gas emissions	kg CO2-eq
Ecotoxicity Freshwater	Impact on freshwater organisms of toxic substances emitted to the environment	CTUe
Particulate Matter	Indicator of the potential incidence of disease due to particulate matter emissions	Disease incidence
Eutrophication Marine	Measures nutrient enrichment in marine ecosystems caused by nitrogen emissions	Kg N-eq
Eutrophication Freshwater	Measures the ecosystem’s nutrient enrichment caused by nitrogen or phosphorus emissions	kg PO4-eq
Eutrophication Terrestrial	Measures nutrient enrichment in terrestrial ecosystems caused by nitrogen emissions	mol N-eq
Human Toxicity (Cancer)	Impact on humans of toxic substances emitted to the environment. Divided into non-cancer and cancer-related toxic substances.	CTUh
Human Toxicity (Non-Cancer)
Ionizing Radiation	Impact of ionizing radiation on the population, in comparison to Uranium 235	kBq U-235
Land Use	Soil quality index	Dimensionless
Ozone Depletion	Destructive effects on the stratospheric ozone layer over a time horizon of 100 years	kg CFC-11-eq
Photochemical Ozone Formation	Indicators of emissions of gases that affect the creation of photochemical ozone in the lower atmosphere (smog) catalyzed by sunlight	kg NMVOC-eq
Resource Use (Fossils)	Abiotic resource depletion fossil fuels (ADP-fossil); based on lower heating value	MJ, net calorific value
Resource Use (Minerals and Metals)	Abiotic resource depletion of natural fossil fuel resources (ADP ultimate reserve)	kg Sb-eq
Water Use	Relative amount of water used, based on regionalized water scarcity factors	m3 water eq. deprived

.

This study highlights key environmental impacts of goggles throughout their life cycle, from production to disposal, providing insights for sustainability improvements. This approach was chosen to provide a more comprehensive analysis, avoiding an exclusive focus on Global Warming Potential and considering also other impact categories that could have significant environmental implications.

2.5. Sensitivity Analyses

Sensitivity analyses were conducted to evaluate how assumptions, data sources, and uncertainties might influence the reliability of the study’s results and conclusions. Two critical factors were specifically explored:

(1)

The sensitivity of the LCA results was assessed by changing the polycarbonate production data from manufacturer-specific data adapted to the Italian market and to polycarbonate production data related to European production available in the Ecoinvent database.

(2)

Impact assessment method: While the primary results were obtained using the Environmental Footprint 3.1 method, the alternative LCIA method IMPACT World+ was applied [25]. This comparison at the midpoint level allowed validation and cross-checking of the primary results and an understanding how sensitive results are linked to method selection.

3. Results and Discussions

3.1. Life Cycle Impact Assessment Results—Comparison of Processes

This section presents a comparative analysis of the environmental impacts of swimming goggle production in two scenarios: production using only virgin materials versus a recycling-based approach. The results are evaluated using the Environmental Footprint 3.1 method. Figure 6 presents the environmental damage assessment results for both scenarios (virgin materials vs. recycling) across the 16 impact categories of the EF 3.1 method.

Figure 6 shows that the recycling scenario leads to a reduction in impact across most categories, with the highest reductions observed in freshwater ecotoxicity (−28.6%), marine eutrophication (−25.1%), and resource use of minerals and metals (−25.1%). These improvements are primarily driven by the reduced demand for virgin raw materials, which significantly lowers resource extraction impacts, emissions from material processing, and waste generation. Although recycling processes introduce additional environmental impacts due to energy consumption, extra transportation to recycling facilities and the requirement of Supplementary Materials for reprocessing polycarbonate, all these factors have been explicitly accounted for within the defined LCA system boundaries. Despite these additional burdens, incorporating recycled material substantially reduces the demand for virgin polycarbonate production, leading to a clear net environmental benefit across nearly all evaluated categories. While the results presented in the previous section highlight improvements across all 16 impact categories, interpreting multiple indicators separately can be complex. To provide a more comprehensive assessment, weighting factors have been applied to aggregate the impact categories into a single score, reflecting their relative importance based on predefined normalization and weighting methodologies.

The weighting analysis on Figure 7 reveals that the most influential impact categories in determining the overall environmental performance are climate change, resource use (fossils), and human toxicity (cancer). These three categories contribute the most to the total weighted score, indicating that they are the primary drivers of environmental impact in both scenarios. This is primarily due to polycarbonate production, particularly the use of bisphenol A and the electricity required for its synthesis, which contribute significantly to both the climate change and fossil resource use categories. For human toxicity (cancer), approximately 72% of the impact arises from bisphenol A.

3.2. Life Cycle Impact Assessment Results—Swimming Goggles Without Recycling

As shown in Figure 8, the production phase of swimming goggles has the greatest impact in the Life Cycle Assessment compared to the disposal phase.

Specifically, within the production stage, lens manufacturing contributes the most to each impact category, except for ozone depletion, where strap production plays a more significant role, as shown in

Table 2. Damage assessment results of swimming goggle production phase.

Impact Category	Unit	Lens Production	Strap Production
Acidification	kg mol H+	3.81	0.52
Climate Change	kg CO2-eq	993	115
Ecotoxicity Freshwater	CTUe	21,663	1276
Particulate Matter	Disease Inc.	3.29 × 10−5	5.52 × 10−6
Eutrophication Marine	Kg N eq	0.71	0.10
Eutrophication Freshwater	kg P eq	0.25	0.03
Eutrophication Terrestrial	mol N eq	7.25	1.04
Human Toxicity (Cancer)	CTUh	9.62 × 10−6	1.54 × 10−6
Human Toxicity (Non-Cancer)	CTUh	7.16 × 10−6	9.86 × 10−7
Ionizing Radiation	kBq U-235 eq	96.43	12.59
Land Use	Pt	3428	595
Ozone Depletion	kg CFC11-eq	2.37 × 10−5	3.57 × 10−5
Photochemical Ozone Formation	kg NMVOC-eq	3.58	0.40
Resource Use (Fossils)	MJ	18,610	1920
Resource Use (Minerals and Metals)	kg Sb-eq	5.58 × 10−3	5.50 × 10−4
Water Use	m3 depriv.	427	126

.

Within lens production, the primary contributor is bisphenol A, which is essential for polycarbonate production.

Bisphenol A stands out in almost all categories, except for ionizing radiation, water use, and ozone depletion, as shown in Figure 9. In ionizing radiation, electricity accounts for 37.4% of the impact, followed by injection moulding (22.1%), which has a significant impact due to its electricity consumption. In terms of water use, electricity has the highest impact (43.7%), followed by silicone production (20.9%). Ozone depletion is mainly driven by silicone production (59%) for strap production, with the impact primarily resulting from the production of methyl chloride used in its synthesis, which can release chlorine and contribute to ozone depletion.

Bisphenol A (BPA) production has a particularly significant impact in categories such as ecotoxicity (freshwater), where it accounts for 86.2%, mainly due to the production of benzene used in BPA synthesis. In human toxicity (cancer), BPA production contributes 71.9%, also driven largely by benzene production. Additionally, in resource use (minerals and metals), BPA production accounts for 61.7%, primarily due to the construction of chemical plants necessary for producing the chemicals involved in its synthesis.

The pronounced influence of BPA production on these impact categories is closely tied to its upstream supply chain, particularly the synthesis of benzene and phenol, which are key precursors in BPA manufacturing. Benzene production emits polycyclic aromatic hydrocarbons and other hazardous substances that accumulate in aquatic systems, where limited dilution capacity intensifies freshwater ecotoxicity [26,27]. Furthermore, BPA synthesis itself is energy-intensive and relies on chlorinated intermediates, amplifying its adverse toxicological and environmental effects [28].

3.3. Life Cycle Impact Assessment Results—Swimming Goggles with 30% Recycling Materials

Given the significant environmental impact of the production phase of swimming goggles, polycarbonate recycling and reuse have been introduced to reduce the demand for virgin material. As shown in the comparison results section, introducing the reuse of 30% of polycarbonate reduced the impact of swimming goggles from 119 mPt to 91.5 mPt, a decrease of 23.1%. In this case, the disposal phase of the swimming goggles reduces the overall impact, as illustrated in

Table 3. Damage assessment of the swimming goggle production scenario with recycling of polycarbonate.

Impact Category	Unit	Production	Disposal (Recycling)
Acidification	kg mol H+	4.58	−1.14
Climate Change	kg CO2-eq	1166	−265
Ecotoxicity Freshwater	CTUe	23,118	−6172
Particulate Matter	Disease inc.	4.08 × 10−5	−9.70 × 10−6
Eutrophication Marine	Kg N eq	0.860	−0.175
Eutrophication Freshwater	kg P eq	0.303	−0.0747
Eutrophication Terrestrial	mol N eq	8.8	−2.14
Human Toxicity (Cancer)	CTUh	1.13 × 10−5	−2.81 × 10−6
Human Toxicity (Non-Cancer)	CTUh	8.47 × 10−6	−1.85 × 10−6
Ionizing Radiation	kBq U-235 eq	117	−29.3
Land Use	Pt	4418	−1032
Ozone Depletion	kg CFC11-eq	6.06 × 10−5	−6.92 × 10−6
Photochemical Ozone Formation	kg NMVOC-eq	4.16	−1.04
Resource Use (Fossils)	MJ	21448	−5476
Resource Use (Minerals and Metals)	kg Sb-eq	0.00623	−0.00164
Water Use	m3 depriv.	570	−122

with the following damage assessment results:

In particular, the weighting results of Figure 10 show that climate change, human toxicity (cancer), and resource use (fossil) are the categories that benefit the most from the reuse of polycarbonate.

Climate change decreases significantly, primarily due to the reduced need for bisphenol A and lower electricity consumption in polycarbonate production, which were the main contributors in the production phase. A similar trend is observed in fossil resource use. The benefits in human toxicity are mainly due to the reduced need for virgin bisphenol A.

The results underscore the environmental advantage of integrating recycled polycarbonate into the production chain. Notably, several commercial initiatives have already demonstrated the feasibility of using recycled PC in products requiring high transparency and durability. For example, companies in the eyewear and optical accessory sectors have adopted mechanically recycled PC for lenses and frames, provided that strict quality controls are in place to ensure optical clarity [29]. Similarly, some sports equipment manufacturers have successfully incorporated post-consumer recycled PC in protective visors, helmet shells, and performance gear, suggesting that material reintegration is technically viable in use cases with demanding mechanical and aesthetic requirements [30].

3.4. Sensitivity Analysis

Sensitivity analyses were conducted to assess the reliability of the study. The sensitivity of the LCA model was evaluated by examining the impact of changes in the polycarbonate production data and characterization method.

3.4.1. Change of Polycarbonate Production to Ecoinvent Data

Two scenarios were analyzed (Figure 11): Scenario 1, where PC production data for lens manufacturing are based on data adapted to the Italian context, and Scenario 2, using the European polycarbonate dataset available in the Ecoinvent database.

Overall, the trend remains consistent across all impact categories, indicating that data source selection does not drastically alter the conclusions. Differences are observed in three categories: manufacturer data show slightly higher impacts for climate change and resource use (fossil), while ecotoxicity (freshwater) is lower.

Differences in climate change and resource use (fossil) impacts for manufacturer data are likely due to a more detailed representation of energy consumption, which may reflect a higher reliance on fossil-based energy sources compared to the industry-averaged data in the database. In contrast, ecotoxicity (freshwater) is lower with manufacturer data, possibly because the database includes conservative or generic emission factors, while the manufacturer’s data reflect more efficient wastewater treatment or lower emissions of toxic substances.

3.4.2. Alternative Impact Assessment Method

To evaluate the sensitivity of the obtained LCA results from different methods, a comparative analysis was conducted by recalculating the environmental impacts using two distinct methods: Environmental Footprint 3.1 and IMPACT World+ midpoint. The comparison in

Table 4. Comparison of the environmental impacts calculated by EF 3.1 and Impact World+ midpoint.

	Life Cycle Swimming Goggles with Recycled Content		Life Cycle Swimming Goggles
Impact Category	EF 3.1	Impact World+	EF 3.1	Impact World+
Climate change (kg CO2-eq)	901	929	1177	1218
Photochemical Ozone Formation (kg NMVOC-eq)	3.12	3.18	4.02	4.09
Ozone layer Depletion (kg CFC11-eq)	5.36 × 10−5	8.14 × 10−5	5.95 × 10−5	8.76 × 10−5
Freshwater Ecotoxicity (CTUe)	1.69 × 10−4	1.47 × 10−7	2.37 × 10−4	2.30 × 10−7
Human Toxicity, Cancer (CTUh)	8.48 × 10−6	1.78 × 10−4	1.12 × 10−5	2.33 × 10−4
Human Toxicity, Non-Cancer (CTUh)	6.62 × 10−6	1.32 × 10−4	8.83 × 10−6	1.77 × 10−4
Marine Eutrophication (kg N eq)	6.86 × 10−1	9.36 × 10−2	9.16 × 10−1	1.61 × 10−1
Water Use (m3 depriv.-eq)	448	436	544	530

highlighted both similarities and significant discrepancies across impact categories.

Climate change, photochemical ozone formation and ozone depletion exhibit relatively small differences between the two methods, reflecting similar underlying characterization models. Specifically, climate change results show differences within 2–4%, confirming consistency for global warming potential assessment.

However, substantial variations emerge in freshwater ecotoxicity, human toxicity (cancer and non-cancer), and marine eutrophication categories. Freshwater ecotoxicity presents higher values when assessed with IMPACT World+, exceeding those calculated with EF 3.1 by a factor of three. This considerable variation is due to the different implementations and parameterizations of the USEtox model (EF 3.1 employs an adapted version of USEtox 2.1, whereas IMPACT World+ uses USEtox 2.0 parameterized at continental scale). Similar differences are observed for human toxicity categories, highlighting a methodological divergence in assessing toxicological effects.

The marine eutrophication impact also presents notable differences likely to distinct fate models: EF 3.1 uses the EUTREND model focusing on nutrient emissions reaching marine compartments with nitrogen as a limiting factor, whereas IMPACT World+ employs an atmospheric deposition model specifically accounting for nitrogen compounds emitted to coastal areas.

Lastly, water scarcity results show limited differences (<3%), as both methods rely on the AWARE model, demonstrating integrity in this impact category.

Given these findings, EF 3.1 was selected for the primary assessment in this study, as it offers standardized characterization factors, comprehensive impact categories, and is recommended by the European Commission. These features ensure greater methodological transparency and facilitate comparability and reproducibility within the context of European environmental impact evaluations.

4. Conclusions

This study identifies the production phase, especially lenses, as the main contributor to environmental impact. Main reason is bisphenol A production, which is driving the highest burdens in climate change, human toxicity (cancer), and resource use (fossils). The high environmental footprint of virgin polycarbonate highlights the need for more sustainable production strategies.

The recycling scenario significantly reduces environmental impact, particularly in freshwater ecotoxicity (−28.6%), marine eutrophication (−25.1%), and resource use (minerals and metals) (−25.1%). Total environmental impact reduced by 23.1%. These findings demonstrate that shifting toward closed-loop recycling processes can effectively reduce resource consumption, emissions, and waste generation. The sensitivity analysis demonstrated that the choice of polycarbonate production data had a limited impact on overall trends, though differences were noted in climate change, resource use, and ecotoxicity categories. Similarly, comparing impact assessment methods revealed consistency in climate change results but significant discrepancies in toxicity-related impacts and marine eutrophication due to methodological differences.

To maximize these benefits, increasing consumer participation in proper goggle disposal is essential. Setting up collection points in pools, sports stores, and recycling stations can help reduce waste and ensure more materials are recovered. From an industrial perspective, implementing such collection systems at scale represents a feasible and cost-effective strategy to improve end-of-life management. These locations already serve as points of contact with frequent users and could function as efficient hubs for take-back programs. While some logistical challenges remain (e.g., sorting mixed materials, managing hygiene standards), early-stage pilot programs could provide valuable insights into operational models, economic viability, and consumer participation rates. Addressing these aspects will be crucial to ensure that recycling-based circular systems are not only environmentally beneficial but also scalable and sustainable in real-world settings.

However, several limitations should be acknowledged. First, the study relies on secondary data from existing LCA databases, which may not fully represent the latest manufacturing technologies or regional variations. Second, assumptions made regarding the recycling scenario (e.g., collection efficiency, material recovery rates) are based on optimistic but unverified estimates and may not reflect current real-world practices. Third, the assessment does not include social or economic aspects, which could provide a more holistic understanding of sustainability. Lastly, the study focuses on a single product type (polycarbonate goggles), limiting the generalizability of results to other goggle designs or materials. Future research should incorporate more primary data, explore hybrid LCA approaches, and expand the scope to better capture these dimensions.

Future efforts should expand the LCA scope to assess alternative materials, such as bio-based or non-toxic polymers, and further optimize recycling processes. Strengthening circular economy strategies will allow manufacturers to lower environmental impact while improving resource efficiency and sustainability.