A Survey of Beachgoers to Estimate Sunscreen Coastal Water Input and Potential Eco-Label Consumption: Contributions to Sustainable Tourism

Abstract

The rise of sun and beach tourism has led to concerns about the environmental impact of sunscreens on marine ecosystems. Although the contaminants included in sunscreens are being studied from various perspectives, there are still gaps in the understanding of beachgoers’ habits and sunscreen use, and their awareness of the problems these products can cause. But do we even know how much sunscreen ends up in the ocean when beachgoers apply it? To estimate the amount of sunscreen entering coastal waters during a summer season, a survey (n = 429) was conducted at two urban beaches in southern Spain (La Caleta and La Bajadilla). It was estimated that 76.3 to 109.3 mL of sunscreen per beachgoer enters the water during the season. For this estimation, it was crucial that we the analyze beachgoers’ behavior statistically. Additionally, our study calculated their willingness to pay (WTP) for eco-labeled sunscreen alternatives. The results showed significant differences between the two sites, with La Bajadilla reporting higher sunscreen usage (11.9 mL vs. 7.9 mL per application) and a greater WTP for eco-labeled sunscreen (€14.2 vs. €11.5). These findings highlight the need for more field studies to better understand the input of sunscreen into coastal waters, which is closely linked to beach use and its social factors. This approach, which considers specific sunscreen input and characterizes beachgoers’ habits, behaviors, and preferences for alternatives, provides valuable insights for decision-makers and may guide future research on the potential impact of sunscreens on marine ecosystems using behavioral data as well as alternative approaches to solving the problem.

1. Introduction

Sun and beach tourism contributes significantly to creating economic and social opportunities [1,2,3]. However, its growing trend has not been accompanied by a proportional increase in research on its impacts and pressures on marine and coastal ecosystems [4,5]. Excessive anthropogenic pressure can lead to the degradation of the natural environment, endangering its preservation and ability to provide ecosystem services [5,6,7,8,9,10,11,12,13].

Changes in ecosystem services due to tourism-driven changes have become the focus for research on tourism and concern the impacts on ecosystems caused by different modes of tourism, including coastal tourism and ecotourism [14,15]. The scientific approaches used to assess the balance between tourism growth and environmental outcomes have become the focus of research related to sustainable tourism. However, further steps are required to ensure significance and accuracy for decision-making processes when measuring sustainable tourism growth [16]. This implies a need to better define the pressures and social dynamics related to beach use that may impact coastal–marine ecosystems (the destruction of habitats, the modification of sedimentary patterns, and physical or chemical pollution). One of the pressures related to beach tourism is derived from the use of sunscreens that enter the sea through the dilution of what is applied on the skin of beachgoers before they carry out aquatic activities in the sea. Showers on the beach (often without special treatment) and outfalls that contain wastewater discharges could be other pathways for these products. Sunscreen input from beach showers and wastewater treatment (sewage treatment plants (STP)) has not been analyzed this time.

We hypothesize that the estimation of beachgoers habits and potential impacts remains highly theoretical, specific, and partial, involving under- or overestimated generalities. We have analyzed the input of sunscreen related to the habits and behavior of beachgoers. Therefore, another of the goals of our work is to analyze how beachgoers perceive the emerging threat of sunscreen pollution and their willingness to pay (WTP) for eco-labeled options. Our findings can inform destination managers about the state of the art, as well as guide more in-depth research to drive concrete action. For this purpose, we conducted a survey at two urban beaches in the Andalusia region (southern Spain) as distinguished sun and beach tourist destinations in this paper. Our results provide basic behavioral and socio-demographic information to properly address the problem in conjunction with other specific disciplinary research.

2. Literature Review and State of the Art

2.1. Sunscreen Uses at Coastal Destinations

Tourism at beach destinations typically involves multiple activities in which many beachgoers apply sunscreen to protect their skin from sunburn and damage resulting from exposure to ultraviolet (UV) radiation [17,18,19]. There are multiple references in the last two decades where we can contextualize the evolution of the statistics on sunscreen usage and which show the need to continue updating these statistics. For example, Autier et al. [20] and Bimczok et al. [21] estimated that the application of sunscreens was between 4 to 5 times below the recommended dosage of 2 mg/cm² of skin, corresponding roughly to 36 g of product for each application [22]. Heerfordt et al. [23] conducted a study on sunscreen use among beachgoers in Denmark from 1992 to 2016, observing a significant increase in the consumption of sunscreen in both quantity and type from 45% to 78% for women and from 39% to 49% for men during that period. The authors suggest that the intensification of campaigns by international health organizations may have contributed to the evolution of habits relating to sunscreens. However, more recently, Carrao et al. [24] demonstrate that sunscreen users in the US are still applying less than the recommended amount, on average 1.27 and 1.67 mg/cm² to their face and body, respectively, when they plan to go to the beach on a warm and sunny day.

Casas-Beltrán et al. [25] used the statistics from Rodríguez-Fuentes et al. [26] on beach use and tourism, which estimated that 83.7% of beachgoers in Cancún used sunscreen, to calculate the usage of sunscreen products on its beaches. Labille et al. [27] estimated the amount of sunscreen that beachgoers introduce into coastal waters at French beaches, finding that 68% of beachgoers that use sunscreen release the product into the water directly. The variability of usage descriptors found, as well as the methods or sample of the population analyzed, highlight the need for more fieldwork to better define habits related to sunscreen use. The variability of the descriptors of use found and the methodologies or sample of the population analyzed highlight the need for more fieldwork to better understand the socio-demographic characteristics of beachgoers and typologies of beach destinations to advance in the definition of more general patterns of sunscreen use.

2.2. From Skin, to Water and Marine Ecosystems

Analyzing how sunscreens are transferred to water, Poiger et al. [28] assessed the impact of tourists and the resident population on two Swiss lakes. They highlight the significant contribution of swimming activities to water pollution. Although the estimation was based on the applications stated and sampling of the lakes studied, it overlooked any intermediate mechanisms between application to the skin and product input into the water. In the same line of research, Danovaro et al. [18] suggested that approximately 25% of the sunscreen applied washes directly into the water. Both studies demonstrate the need to specifically interpret the connection between the amount of sunscreen effectively applied and the amount that actually passes into the aquatic environment. Although these studies constitute a conservative approach that should be the object of specific methodological development and updated with new evidence, they can provide an approximate context for the scenario assumed in this study.

Once in the water, some of the components contained in sunscreens can negatively impact the species and mesocosms of marine ecosystems. The main concerns related to marine contamination from sunscreens are their toxic effects and the bioaccumulation of some of their ingredients, such as UV filters, which can lead to the persistence of these contaminants of concern throughout the food chain [29,30]. Several authors have studied the still uncertain effects of sunscreens, addressing the great complexity and diversity of their constituent components [8,9,29,30,31]. Documented effects include coral bleaching [18,32,33,34], habitat avoidance by the shrimp Palaemon varians [35], malformations in the early developmental stages of the sea urchin Paracentrotus lividus [36], and growth inhibition of the growth of the marine diatom Chaetoceros gracilis [37]. In addition, the bioaccumulation of toxic ingredients released by sunscreens has been observed at both the laboratory scale (e.g., bivalves) [38,39,40,41] and in marine biota collected in the field, such as in the endemic Mediterranean seagrass, Posidonia oceanica [42].

2.3. Management Responses for a More Sustainable Tourism

In response to the increasing concern on the potential environmental impacts of sunscreens, some tourist destinations have already taken steps to protect and conserve their marine and aquatic resources [43]. For example, Hawaii and the Republic of Palau have banned or regulated the use of sunscreens containing certain ingredients (e.g., oxybenzone and octinoxate) to protect their coral reefs, [44,45]. Measures to control and preserve ecosystems, such as banning certain products in specific locations [33], could benefit from any input derived from field studies that take into consideration the specific characteristics of beachgoers and locations.

Furthermore, some researchers have analyzed potential consumer responses to help mitigate the environmental threat associated with the use of sunscreen. For instance, the majority of individuals visiting water parks, cenotes, and beaches in the Mexican Caribbean expressed a willingness to adopt more environmentally healthy practices when applying sunscreens [46].

We face a challenge when attempting to standardize the effects of sunscreens in research studies due to their complex formulations that combine UV filters and many other ingredients. This is compounded by consumer demand for different product additions, such as the inclusion of complementary ingredients in different forms such as: body-milk (moisturizing), oils, lotions, gels, sticks, or sprays [44]. As an alternative to conventional products and in response to an increasing demand for environment-friendly options, manufacturers have developed eco-labeled sunscreen products that claim to meet eco-friendly requirements. Although some authors are conducting studies on these products from the ecotoxicological point of view [19,33], this issue remains still uncertain. The terminology “eco-friendly”, used on sunscreen labels, is often based on the removal of a specific UV filter that has been shown to be ecotoxic. However, this designation typically does not consider the effects of the other ingredients in the sunscreen formula or the impact of the new UV filters that have replaced the ones removed. A more comprehensive assessment of UV filter compositions could be achieved taking into consideration the intrinsic properties of both organic and inorganic UV filters (e.g., [47,48]) or by evaluating the sunscreen as a complex matrix with the potential to release harmful substances into the marine ecosystem (e.g., [8,18,28,33,35]). Our study does not address the effectiveness of genuinely environmentally safe alternatives or the marketing strategies behind eco-labeled products.

Finally, we should mention that we contribute to the literature by emphasizing the importance of obtaining field-based data specific to each case on the actual use of sunscreens (e.g., [27,28,49]). Our study allows us to quantify the amount of these products that enter the marine environment, which serves as a proxy indicator of the environmental pollution associated with beach tourism [46]. This will contribute to and address the direct input of sunscreen ingredients from beachgoers into seawater from the behavioral perspective. Furthermore, we adjusted the product input calculation formula based on the uses and frequencies obtained from the survey data.

3. Methodology

Our study is based on a field survey at two representative urban tourist beaches in two seemingly similar locations to analyze any potential differences between habits, perception, and consumers’ intention. The survey provided primary information on the following: socio-demographic characteristics of beachgoers, stated sunscreen use behavior, and perception of the sunscreen problem. This allows the estimation of sunscreen input into coastal waters, and the WTP for eco-labeled sunscreen alternatives (intention).

3.1. Study Area

Sun and beach tourism is a major industry in Spain and has been growing in the recent decades [50,51]. Spanish institutions are increasingly focusing on sustainable sun and beach tourism to promote responsible tourism practices and preserve coastal ecosystems [52]. In a global context of growing coastal tourism, Andalusia stands out by distinguishing itself among Spanish beach destinations. In 2021, Andalusia welcomed over 20 million tourists, both domestic and foreign, that were concentrated mostly in the provinces of Málaga (26.5%) and Cádiz (19.2%), both with a strong association with beach tourism [53,54].

For our field study, we selected two cases of urban beaches in these two most visited provinces of Andalusia: (i) La Caleta Beach in Cádiz on the Atlantic coast; and (ii) La Bajadilla beach in Málaga on the Mediterranean coast (Figure 1). Both beaches have some similarities in terms of general characteristics. In addition, they offer similar scenic views and facilities, including toilets, restaurants, and accommodation with reduced mobility access.

3.2. Field Survey for Socio-Demographic Characterization and Stated Habits

We conducted the field survey in situ with a team of interviewers during July and August 2022 (high summer season in Spain). The survey was created and implemented using the Tickstat© online platform (www.tickstat.com). The platform automatically downloads the responses, generating a real-time database of the survey’s results. We obtained 429 valid questionnaires, from which 26 corresponded to a prior pre-test used to validate the survey. The remaining 403 valid questionnaires constitute the final sample (n = 205 in La Caleta and n = 198 in La Bajadilla). The design of the final questionnaire was informed by the pre-test and consultations with experts.

We present the results of the 2022 summer season and we differentiate between La Caleta and La Bajadilla. The survey targeted national beachgoers at both beaches, thus avoiding any potential language barriers concerning foreign visitors. Although this is a limitation of our study, the questionnaire still collected information from a sample of more than two-thirds (only nationals) of the Andalusian beachgoers [50].

The survey had four sections: (i) the beachgoer’s profile and characteristics; (ii) the typology of the beach visited, beachgoer’s perception of the beach’s characteristics (rated on a 1–5 Likert scale), and knowledge regarding the impact of sunscreens on coastal waters; (iii) the beachgoer’s habits and behaviors related to sunscreen use; (iv) a contingent valuation exercise to evaluate WTP for eco-labeled sunscreen products; and (v) socio-demographic characteristics. Supplementary Materials S2 shows an English version of the questionnaire in Spanish used.

We performed a descriptive analysis (mean, standard deviation, and Student’s t-test for mean comparison between beaches) for all the survey’s questions using basic statistical software packages such as Microsoft Excel© 16 and SPSS© 29.0. Our results focus on two blocks of questions: (i) sunscreen use by beachgoers and associated inputs into coastal waters; and (ii) the contingent valuation exercise.

3.3. Estimations of Sunscreen Use and Input from Beachgoers

We calculated the Total Input of Sunscreen per beachgoer (TIS_beachgoer) in milliliters that enters the coastal water during the summer season based on the proposal of Casas-Beltrán et al. [46], adjusting the formula by reflecting the beachgoers’ stated habits regarding aquatic activities, the frequency of sunscreen application, and the transfer rate from skin to water.

The input coefficient into the coastal water (I_c) is one of the key aspects that correlates with the behavior stated in the in situ questionnaire. The I_c considers the frequency of product discharge occurrences into the coastal water, which depends on the number of sunscreen applications per day (AP_d) and immersions into the sea per day (SB_d) covered by questions 30 and 38, respectively. The word “immersion” includes activities such as swimming, snorkeling, just getting into the water to cool down, etc. The I_c value for an individual will be equivalent to the lowest value of the two variables:

⁃

If the number of immersions is lower than the number of daily applications, the I_c will be decided as the number of immersions into the water. Each immersion is associated with at least one application of sunscreen (and, therefore, a sunscreen wash-off each time beachgoers go into the water);

⁃

If the number of sunscreen applications is lower than the number of immersions, the I_c will be equal to the number of applications. We assume, for this first approximation, that the successive immersions into the sea without applications do not introduce sunscreen into the aquatic environment. Therefore, the following equation applies:

I_c = SB_d if SB_d < AP_d; and I_c = AP_d if SB_d > AP_d

(1)

Finally, we calculated the Total Input of Sunscreen per beachgoer (TIS_beachgoer) in Equation (2). To estimate the quantity of sunscreen utilized per beachgoer and application (SQ_ap), we relied on the specific responses stated by beachgoers in the questionnaire to estimate the quantity of sunscreen utilized per beachgoer and application (SQ_ap). These responses included the following: (i) the number of daily applications while at the beach (q. 38); (ii) the number of bottles of sunscreen used during the summer season per beachgoer (q. 39); and (iii) the amount (ml) of product contained in each bottle (q. 35). In addition, we calculated the average number of days spent at the beach during the summer season (q. 2 and q. 3). T_d is the total number of days on the beach in the summer season. The coefficient of 0.25 is the transfer rate of the sunscreen from the skin to the water [18,19,27]. While transfer rates are contingent on the lipophilic or hydrophilic attributes of UV filters, the wash-off fractions of UV filters from the skin typically vary between 50 and 100% [56]. Additionally, other factors, including the sunscreen’s properties and application format, influence these rates [57]. In our current investigation, we adopted a conservative estimate for the total sunscreen matrix transfer rate, specifically 0.25, in alignment with the findings of the aforementioned authors. In this work, only direct point sources of sunscreen contamination (i.e., recreational activities) such as swimming have been considered. Potential indirect point sources, such as beach showers [58] or municipal wastewater treated effluents ([59,60]), have not been included:

TIS_beachgoer = SQ_ap × I_c × T_d × 0.25

(2)

We adjusted the total number of visitors according to official tourism statistics to estimate the total input of sunscreen into the coastal waters of a specific system (e.g., beach or region). Of all beachgoers, we consider the percentage of beachgoers who use sunscreen and engage in aquatic activities based on the information declared in the field study as an approximation of the real behavior of beachgoers. Both criteria are essential for estimating the input of sunscreen into the coastal waters directly from beachgoers of a particular system.

3.4. Contingent Valuation and Willingness to Pay for Alternative Options

Contingent valuation is a survey-based stated preference method that simulates a market for non-commercial goods or services to estimate their potential demand [61]. Its main goal is to elicit an estimate of the respondents’ WTP for products and services that are not always easily available. In our research, we selected this method to estimate the potential demand for eco-labeled sunscreens among beachgoers in our two beach case studies.

Previous to the contingent valuation question, and as part of the hypothetical setting designed for this valuation exercise, we assessed the respondent’s degree of knowledge regarding the problem of polluting sunscreens in coastal waters, using a 1–5 Likert scale, where 1 was “non-existent” and 5 “very high” (see Supplementary Materials S2, q. 43).

In the contingent valuation scenario, respondents were presented with the possibility that the next sunscreen they would buy included an “Ocean Respect” or “EU Eco-label” brand as an example of an alternative sunscreen. It should be recalled that the survey did not specify the differentiating features of these eco-labels, nor the environmental implications (not the objective of this study). We appealed to the generalized perception of the population about alternative theoretically “green options” to analyze WTP and intentionality. For the question, we used the single-bounded format [61] in which respondents were presented with an amount to pay, in addition to what they were currently paying for a sunscreen bottle, to buy this type of eco-labeled sunscreen (q. 40).

The amounts to be paid presented in each questionnaire were randomly selected from the following vector of bid values (€3, €6, €9, and €12). We compared the quintiles of a normal and a log-normal distribution [62,63] of values obtained from the results of both a single-bounded and an open-ended question included in the pre-test to obtain this vector of bid values. The single-bounded question was followed-up by an open-ended question on maximum WTP (q. 41) and a follow-up question for those who answered “no” to the single-bounded question and zero euros to the open-ended question (q. 42). The follow-up question was aimed at identifying the reasons why respondents would not pay for the purchase of eco-labeled sunscreens.

For the analysis of the single-bounded question, we follow Cameron [64] who proposes modeling a WTP function using a flexible specification of the explanatory variables that allows for a more direct interpretation of the associated coefficients (see Section 5 in Supplementary Materials S1). We estimated the logit models presented and their associated censored logistic regressions using the LIMDEP© NLOGIT v9.0 software.

4. Results

The most relevant results, both in terms of the descriptive nature of the variables analyzed and the significant differences, are described below. However, the complete results of all the variables analyzed, as well as the statistics, can be found in Supplementary Materials S1, where the tables of each of the following sections can be consulted.

4.1. Socio-Demographic Characteristics, Typology of Beachgoers, and Site Perceptions

Most of the socio-demographic variables considered showed statistically significant differences between beachgoers for each case study (Table S1 in Supplementary Materials S1). This socio-demographic information shows the similar characteristics of both beaches do not lead to a similar beachgoer profile (Figure 2). In both cases, the majority of the beachgoers are locals (residents in the beach city analyzed): 45.4% are in La Caleta and 52.5% in La Bajadilla. In terms of place of birth, native beachgoers (born in the city) are predominant in La Caleta (47.7%), while, in La Bajadilla, the beachgoers born in the region are in the majority (39.4%).

Other variables analyzed indicate that the typical La Caleta beachgoer is older (47.7 vs. 45.2 years old), has a higher level of education (57.3% vs. 43.9%), and belongs to a household group with a higher mean income per person (€1655.2 vs. €1532.1).

If we examine the data concerning the visits and perceptions of beachgoers (Table S2 in Supplementary Materials S1), we can see that La Caleta beachgoers are more dispersed as they also visit other beaches (40.3% of total beach days spent in La Caleta) as opposed to the beachgoers of La Bajadilla, who are more specific (78.4% of total beach days spent in La Bajadilla). Additionally, we may observe that beachgoers stay longer at La Caleta (4.5 h vs. 3.6 mean h). These aspects show the level of specificity and intensity of the use of a given beach.

In terms of the importance of the beach visited (sampled) (q. 15 or q. 29), compared to other alternatives for that visit, La Caleta was rated 6.9 on a scale of 1 to 10 by the beachgoers, while La Bajadilla was rated 8.4. These results suggest that La Bajadilla beachgoers attach greater importance to that particular beach when compared to other alternatives.

The beachgoers’ perception (q. 4) of the overall features of the beaches evaluated demonstrated a high level of acceptance. Using a scale of 1 “totally disagree” and 5 “totally agree”, beachgoers gave their opinion on statements regarding the state of conservation (“the state of conservation of this beach is good”), the quality of the water (“the quality of the water was an important factor in deciding to visit this beach”), the perceived number of people (“there are too many people on this beach”), and the facilities and services offered (“the facilities: parking, walkways, showers, toilets, first aid kits, fountains, footbaths…. of this beach are adequate”) (Figure 3).

There is no significant difference in the perception about preservation status or the water quality, which could mean that beachgoers do not perceive an ecological degradation or exceptional condition of preservation at either beach. However, significant differences were found in the perceived level of crowding and the quality of facilities and services between the two beaches. While the mean score for perceived crowding was above 3, indicating no overcrowding at either beach, beachgoers at la Bajadilla gave more favorable overall ratings. Both beaches received positive ratings for equipment and services, with average scores of around 4, although the beachgoers of La Caleta reported slightly greater satisfaction.

4.2. Sunscreen Use and Beachgoers Input into Coastal Water

While nearly all the beachgoers at La Caleta use sunscreen (97.1%), the percentage drops to 89.4% at La Bajadilla (Table S3 in Supplementary Materials S1). The daily application rate per beachgoer is slightly higher in La Caleta (2.5 versus 2); however, this difference lacks statistical significance. These findings align with those reported by Labille et al. [27], where beachgoers applied sunscreen to their skin an average of 2.6 times per visit to the beach. Based on data concerning the number of sunscreen bottles used per beachgoer in the summer season from our survey and the average contents of said bottles, we estimate that the amount used per application is 7.9 milliliters in La Caleta and 11.9 milliliters in La Bajadilla (Table S3 in Supplementary Materials S1).

As a first general approximation to compare with the main references in the literature, we assumed a standard type of sunscreen with a density of 1.26 g cm⁻³ for sunscreens containing 25% zinc oxide [65]; however, if the compound was TiO instead of ZnO, the density would be different. The average beachgoer at La Caleta uses 9.9 g of sunscreen, while the average beachgoer at La Bajadilla uses 14.99 g per application. Our results show that product application is 3.6 and 2.4 times lower than the recommendation of 36 g per application from the European Commission [22] at La Caleta and La Bajadilla, respectively, while, below these recommendations, these results are still higher than the most commonly cited estimates in the literature (e.g., [20,21,24]).

The next relevant aspect is to calculate the input related to the frequency of getting into the sea. The number of immersions per day is consistent at both locations (4.2 times per day), although the La Bajadilla beachgoers spend substantially longer average times in the water. In aggregated terms for the summer season, significant differences are observed in the time spent in the water carrying out various aquatic activities (56.8 h at La Caleta, contrasted with 80.8 h at La Bajadilla).

Calculating the potential input of sunscreen into coastal waters depends on two essential conditions: the percentage of beachgoers engaging in aquatic activities such as swimming and diving, among others, and the percentage of beachgoers reporting sunscreen use. The results of our survey indicate that 95.6% of La Caleta and 89.4% of La Bajadilla beachgoers meet both of these requirements (Figure 4). Using the formula described in Section 2.2, the mean total input of sunscreen into the coastal waters of La Caleta and La Bajadilla was calculated to be 76.3 milliliters and 109.3 milliliters per beachgoer and season, respectively (considering the average days that a user spends on the beach; see Table S2 in Supplementary Materials S1).

We estimated the volume of sunscreen used during the 2022 summer season on Andalusia’s beaches to illustrate the potential application of our proposal. The calculation used data obtained from a survey, with the mean product usage (92.81 mL per beachgoer, per season) and an assumed percentage of beachgoers (92.5%) who apply sunscreen before entering the water from both of the beaches surveyed. Based on the DATAESTUR 2023 report [66], approximately 1.8 million Spanish tourists specifically chose to visit Andalusia for sun and beach tourism during the May–September 2022 summer period. This would have contributed an estimated 157,372 L of sunscreen released into the Andalusian beach waters from domestic tourism.

4.3. Typology of Sunscreens and Willigness to Pay for Alternative Products

Firstly, in terms of top brands, beachgoers mentioned more than 33 different brands in a similar distribution pattern between the two beaches. At the two beaches analyzed, most beachgoers used moisturizing-lotion sunscreen with an SPF of 50, followed in both cases by the SPF 30 sunscreen and the spray format (independent attributes). Only 5.6% of La Caleta beachgoers reported using an eco-labeled sunscreen compared to 9.6% of La Bajadilla (Figure 5). In addition, the questionnaire did not specify the different categories of eco-labels or brands, but simplified the question to whether or not it was labeled. We should remember that sunscreens are complex formulations with UV filters as key components. The ban on certain filters has led to new compositions, often labeled as eco-friendly, which replace organic filters with inorganic ones like zinc oxide (ZnO) [67]. However, ZnO is highly toxic to aquatic life, making these new formulations potentially as harmful as their predecessors. This has led the EU Commission to consider regulating eco-labels on sunscreens [33]. It is important to note that assessing the environmental impact of each label is not the focus of this study.

The participants were also asked to rate their knowledge concerning the “problem” of sunscreens in coastal waters on a scale of 1–5, where 1 corresponds to “non-existent” and 5 to “very high” (q. 43). The results revealed that both La Caleta and La Bajadilla had a mean score of 2.0 and 1.9, respectively, indicating a low level of awareness about this issue. This information is important because the depth of knowledge about the problem is critical to how beachgoers might respond to the problem.

Before displaying the contingent valuation scenario and WTP, we calculate the current average price stated as the basis. The cost was €135.3 per liter of product in La Caleta and €79.0 per liter in La Bajadilla. This difference was explained by the higher volumes and differing characteristics of the sun protector (different SPF distribution and application format; see Figure 5 above and Table S4 in Supplementary Materials S1). Most notably, the fact that the container format in La Bajadilla is significantly larger (223.6 mL) than in La Caleta (162.3 mL). The distribution in La Bajadilla indicates that most individuals consume larger volumes of sunscreen at lower prices.

The model of additional WTP for the purchase of a bottle of eco-labeled sunscreen without explanatory variables shows that the additional mean WTP is €7.5 per bottle (162.3 mL) in La Caleta and €12.7 per bottle (223.6 mL) in La Bajadilla. These prices would be paid by 50% of the beachgoers at each beach, with confidence intervals of (€6.7–€8.2) and (€9.0–€16.4), respectively. Assuming a constant relationship of WTP with the increase in product volume (same marginal WTP regardless of subsequent increases in the ml of a bottle), we present a comparative result of €11.5 (La Caleta) and €14.2 (La Bajadilla) for a standard 250 mL container.

The model incorporating explanatory variables shows that the respondent monthly family income positively affects WTP with an increase of between 1.5 and 1.7 euros of additional WTP for every 1000 euros of monthly family income stated. Being born in the city where the beach is located affects WTP differently regarding each beach. While the additional WTP decreases 1.9 euros at La Caleta for respondents born in the city, with respect to those born elsewhere, the additional WTP increases by 3.9 euros at La Bajadilla for the respondents born in the city. The other variables in these models are site-specific. At La Caleta, the size of the family group negatively affects WTP, with a reduction of €0.8 in the additional WTP for each additional member in the family group. At La Bajadilla, the number of applications per day increases the additional WTP by €3 for each additional application per day.

5. Discussion

Knowing the socio-demographic characteristics of beach users is important in order to correlate subsequent analyses of habits and intentionality. In this way, we describe the typical population of two sample beaches, in order to justify future comparisons by contextualizing the results. With a sufficient number of case studies, it would be possible to profile places with specific behaviors or, quite the opposite, to find patterns between cases (types of beaches classified based on user habits and profiles).

The information on the specificity of the typical visitor to the two beaches studied, as well as the “importance” of the beach in the decision to travel, provides information on the intensity of use at certain places, as well as the initial perceptual assessment of the environment attributes. The questions and results related to the perception of different general aspects of the beaches (Figure 3) serve to anticipate the relative weight of environmental vs. social issues (number of people or facilities) in the choice of destination. With the information subsequently provided in relation to the beachgoers’ knowledge of the problem (see Section 4.3 on the analysis of knowledge of the problems associated with sunscreen in coastal waters), we can see that knowledge of the potential problem is at an early stage and, at the same time, does not highlight (either positively or negatively) the state of preservation in general or the quality of the water in particular. These two issues would be interesting to contrast in future field studies, where different results are obtained concerning knowledge about the problem with the perception of environmental attributes and the predisposition to adopt potentially more environmentally sustainable habits.

Regarding the stated habit of sunscreen use and beach behavior, there is a need to update this analysis, given the contrast of results with similar studies (e.g., Labille et al. [27]). Our results about percentages (97.1% and 89.4% use sunscreen in La Caleta and La Bajadilla, respectively) are higher than the percentage reported by Labille et al. [27] in a survey conducted at three Mediterranean beaches located in Marseille, France, where only 68.4% of the interviewees used sunscreen products. In our study, we show similar results in terms of the number of applications. However, our research provides insights into the actual amounts of sunscreen applied and how much enters aquatic systems, considering that not all the sunscreen applied reaches coastal waters through aquatic activities. Therefore, there are differences in the percentage of users that should be further analyzed through empirical studies.

Our estimate of sunscreen use provides relevant interesting information that complements other analyses focused on secondary inputs, such as beach showers or discharges from wastewater treatment plants. This study demonstrates the magnitude of the problem, although our approximation needs further detail to analyze releases into seawater. Updating the stated habits of beachgoers is essential in order to model the impact of sunscreen pollutants in specific environmental units. Our research fills a crucial gap in analytical methods by providing direct input related to user behavior.

Knowing the general characteristics of sunscreens (Table S4 in Supplementary Materials and Figure 5 above) is fundamental to establishing a baseline to evaluate the potential consumption of eco-labeled alternatives. Additionally, characterizing the typology of sunscreens used might be useful for future research on the components present in each type of cream (by format, SPF, or the presence of substances with specific attributes). Section 4.3 discusses the impact of eco-labels on sunscreen typology and WTP. This study focuses on the consumption declared on the “type” labels. Subsequent studies should break down labeling types and their ecological implications.

The WTP analysis using models (see Section 5 of Supplementary Materials S1) to analyze possible explanatory variables, as well as the contextualization of the reported habit and consumption, provide useful information since the socio-demographic variables are correlated with specific response scenarios. In our analysis, we have obtained results that indicate the WTP increases by €1.5 in La Caleta and €1.7 in La Bajadilla for each increase of €1000/income. On the other hand, the effect of the place of birth is striking, with an increase of €1.9 for those born in La Caleta and €3.9 more for those born in La Bajadilla. This highlights the importance of socio-demographic characteristics when analyzing the stated and potential behaviors. In our study, an analysis of alternative eco-label sunscreen is considered as a complementary factor for management response.

We should mention that a limitation of our study is the biased consideration of domestic users only. We did not consider international beachgoers, who are also an important factor in Andalusia’s status as a tourist destination. This limitation was driven by logistical and budgetary limitations but could provide an interesting focus for future analysis.

6. Conclusions

This study shows that the literature has generally underestimated the importance of direct sunscreen input into coastal waters resulting from beachgoers’ habits. Our main contribution is the characterization of beachgoers’ behavior and the related estimation of sunscreen input during the summer season at two beaches on the Andalusian coast (76.3 and 109.3 mL/user in La Caleta and Bajadilla, respectively). Our estimate of 157,372 L of sunscreen entering the sea from local and domestic beachgoers is not a negligible quantity. Although aquatic activities are not the sole pathway for sunscreen to enter the ocean, this study serves as a baseline contribution to future research on other sources such as hotel runoff, beach showers, and wastewater treatment.

Our results also highlight that generic assumptions about behavior across different locations can lead to significant errors. While our case studies demonstrate the potential of on-site surveys, further testing and support for future analytical studies are needed to comprehensively assess sunscreen-related environmental impacts. Our results can advance the drive for a comprehensive assessment of sunscreen-related issues and highlight the need for targeted management responses. Beachgoer impact varies by profile, even at similar beaches, underscoring the need for more field studies to obtain reliable, generalizable data on different types of beaches and beachgoers’ behavior and habits.

Regarding beachgoers’ perceptions, our findings indicate that this topic is still in its early stages. Despite the limited awareness, the high WTP for eco-labeled sunscreens suggests a general predisposition toward environmentally friendly behaviors. The contingent valuation analysis reveals that, while there is potential for eco-labeled products, the minimal information provided in the survey may not fully capture the specific WTP. The analysis of explanatory variables shows how family income influences the willingness to buy eco-label sunscreens at both beaches positively, while being a local has the opposite effect in each case. Thus, the industry and policy makers should target the local population differently depending on the case study analyzed. These insights are valuable for the sunscreen manufacturers who wish to obtain an eco-label and decision-makers to understand consumer intentionality, especially in regulated environments. Raising awareness among beachgoers, tourists, and industry stakeholders about the environmental impact of sunscreens is crucial for promoting sustainable tourism practices.