Parameters influencing behaviour differ across the literature when dealing with behaviour and mitigating plastic pollution. Deng et al. (2020) suggest that attitudes and knowledge about microplastics can predict microplastic mitigation behaviours. Felipe-Rodriguez et al. (2022) expanded on this work, suggesting that information campaigns may benefit from combining facts about specific sources of microplastics with practical guidance on pro-environmental behaviour for mitigating microplastic sources. Garcia-Vazquez and Garcia-Ael (2021) found that knowledge of microplastics is central to the psychological framework of (micro)plastic pollution, directly connected with the willingness to adopt more pro-environmental behaviour, with risk perception and perceived control identified as less important. In Indonesia, Arifani and Haryanto (2018) observed that environmental knowledge positively impacted the intention to purchase a reusable shopping bag. However, though knowledge is a key term in past research, multiple predictors should be considered. For example, Hasan et al. (2015) found that among students in Malaysia, perceived behavioural control showed the strongest relationship with behaviour when reducing plastic consumption, compared to other variables.

This research provides a first step toward understanding the past and current behaviour of the Kendari City population in managing their waste, as well as the psychological factors behind this behaviour. Research-informed interventions have been identified as beneficial for governments and municipalities at local, national, or international levels to reduce plastic pollution (Pahl & Grünzner, 2023). Policies can influence people's behaviour, but practical implementation and the removal of barriers are crucial for achieving desired outcomes (Deng et al., 2020; Kollmuss & Agyeman, 2002). In Indonesia, the absence of robust waste management services and infrastructure may be a significant barrier, especially when compounded by further identified barriers, including socio-economic constraints, convenience, and effort.

Prior research on marine pollutants in Indonesia has demonstrated an increased awareness, linked to a decreased willingness to consume seafood among housewives (Fercudani, 2015). Research on the health impacts of microplastics in seafood is still in its infancy. However, there is interest, especially from the governments of countries dependent on fishing sectors, in determining whether a similar health-protective behaviour occurs with microplastics.

Seafood consumption behaviour is potentially crucial for communities that rely on seafood as a primary source of protein and income. Additionally, the fisheries sector is a valuable contributor to the Indonesian economy (Kementerian Kelautan dan Perikanan, 2013). In Southeast Sulawesi, the province where Kendari City sits, fisheries are the primary coastal income source and account for 149,200 tons (~2%) of the national captured fisheries production (Sholeh, 2018). As an essential source of protein and income, any changes in consumption due to emerging information regarding microplastic contamination are of concern and unknown.

Although emerging concerns about health and microplastics, especially associated chemicals, are growing, no established human health effects linked to microplastics have been identified (Naidoo et al., 2020). The emerging concerns are based on the detection of microplastics in seafood (Bakir et al., 2020), particularly in the edible parts, such as meat and muscle (Abbasi et al., 2018), as well as in seafood containing intestinal tracts (Van Cauwenberghe & Janssen, 2014). Additional concerns arise from the negative impacts on biota (Maes et al., 2020), the presence of contaminants within microplastics (Rodrigues et al., 2019), and the known effects of these contaminants on health. An expanded summary of this information is available in Supplementary Information (see SI 3 in Preston-Whyte et al., 2026). Though nanoplastics (1–1,000 nanometers; GESAMP et al., 2019) have been found to enter the bloodstream and traverse tissues (Leslie et al., 2022), for ease of communication in this study, only the term microplastics has been used.

All participants' responses were utilised in the qualitative data analysis.

Regarding the qualitative interviews, the data, including interview records and notes, printed documents, and government statistics data, were organised and broken down into manageable units, categorised and organised by research concept/question (Bogdan & Biklen, 2007; Miles et al., 2014). The interview records were transcribed and translated into English for further analysis (Ochs, 1979). We clustered similar codes to construct fewer categories, then defined pattern codes (Miles et al., 2014). Coding to arrange the various responses by clustering, creating similar topics, and subsequently defining patterns (Miles et al., 2014) was conducted manually. Analysis included both thematic and content analysis. We filtered, clustered, and coded them into themes and sub-subthemes, and presented the results in two columns: frequency/co-occurrence and percentages, which were then interpreted. Coding was reviewed by at least two members of the research team to ensure consistency and theoretical coherence. Where possible, data gained from participants and interpretations derived from the data were shared with key participants to ensure the accurate capture of their comments (Bogdan & Biklen, 2007).

The qualitative results, organised into themes, are presented in Figure 4.

For the combined stakeholders (Figure 4A), the qualitative data reveals a mid (46%) to high (35%) level of self-assessed subjective knowledge, with 58% recognising plastic pollution as lethal to marine species, human health and the environment. The civil society stakeholders (Figure 4B) have a mid (90%) level of self-assessed subjective knowledge, with 100% recognising plastic pollution as lethal to marine species, human health and the environment. The involved stakeholders (Figure 4C) have a range of self-assessed subjective knowledge, with high (44%), mid (29%), and low (27%) levels, and 46% recognise plastic pollution as sublethal to marine species, human health, and the environment.

Regarding pro-environmental waste management behaviour, 97% of combined stakeholders (Figure 4A), 95% of civil society (Figure 4B), and 98% of involved groups (Figure 4C) produce plastic waste every day. Plastic waste reduction efforts are practised by 68% of combined stakeholders (Figure 4A); however, 83% do not practice waste sorting, and 35% still dispose of it indiscriminately. A minor fraction (17%) engages in waste sorting, predominantly at a low level (81%). Regarding civil society (Figure 4B), 90% reported engaging in plastic waste reduction efforts. However, 65% do not practice waste sorting, and only 5% still dispose of it indiscriminately. Waste sorting is predominantly at a low level (95%). Regarding involved groups (Figure 4C), 60% practice plastic waste reduction efforts; however, 90% do not practice waste sorting, and 46% still dispose of it indiscriminately. A minor fraction (10%) engages in waste sorting, predominantly at a low level (75%).

Considering health-protective behaviour, most (90%) combined stakeholders (Figure 4A) do not consider (micro)plastic contamination of seafood to affect their willingness to consume seafood. Most (85%) of civil society (Figure 4B) do not consider (micro)plastic contamination of seafood to affect their willingness to consume seafood. Most (92%) of the involved stakeholders (Figure 4C) do not consider (micro)plastic contamination of seafood to affect their willingness to consume seafood. Seventy-six percent of respondents in the fishing and seafood processing industry perceive their productivity and profits as stable (Figure 4A and Figure 4C).

Regarding policy regulations on plastic pollution, 74% of the combined stakeholders were aware of existing policy regulations related to waste management. However, 57% perceived the current policies or regulations as ineffective. Additionally, 79% of participants identified the most significant challenge in addressing plastic/microplastic pollution as a lack of awareness. The emphasis is placed on reducing plastic usage and waste, with 53% and 26% considering it more crucial than awareness campaigns and programs. Regarding civil society (Figure 4B), 20% of respondents were aware of policy regulations related to waste management. However, 80% perceived the current policies or regulations as ineffective. Additionally, 70% of participants identified the most significant challenge in addressing plastic/microplastic pollution as a lack of awareness. The emphasis is on awareness campaigns (70%) as most participants already practice reducing plastic use and waste. Regarding the involved stakeholder groups (Figure 4C), 94% of respondents were aware of existing waste management policies. However, 48% perceived the current policies or regulations as ineffective. Additionally, 85% of participants identified the most significant challenge in addressing plastic/microplastic pollution as a lack of awareness. The emphasis is on reducing plastic use and waste, with 67% considering it more crucial than awareness campaigns and programs.

Key identified quotes from the qualitative interviews are provided in Table 4, with their importance highlighted in the table’s footnotes. Participants regularly experience plastic pollution in a wide range of environments. For participants, the blocking and related flooding of sewers and storm drains are of notable concern, as is the human health and ecosystem risks. The fishers themselves identify additional risks they face in their industry, such as entanglement with plastic pollution. Participants exhibit varying levels of knowledge regarding waste and plastic waste. Participants demonstrate a discrepancy in their understanding of organic/inorganic waste. Levels of concern about microplastic contamination in seafood varied between participants. However, participants overwhelmingly did not consider microplastic contamination to affect their seafood consumption. Many participants do not consider the deep-sea fish they eat to be contaminated by microplastics. Fishing industry stakeholders see their profits as currently stable but acknowledge the possibility of future impacts.

Our quantitative results suggest that self-assessed pro-environmental behaviour is positively linked to self-assessed subjective knowledge among combined stakeholders, civil society, and involved groups. Additionally, for combined stakeholders and civil society, this behaviour is positively related to their experience of plastic pollution in the environment and of microplastic contamination of seafood. Greater experience of plastic pollution in neighbourhoods is associated with higher self-assessed pro-environmental behaviour when all stakeholders are considered together, but with lower self-assessed pro-environmental behaviour among civil society stakeholders. The qualitative interviews introduce nuances to subjective knowledge and self-assessed pro-environmental behaviour, with mid (46%) to high (35%) subjective knowledge among combined stakeholders, and only behaviour focused on reducing plastic waste production shows as a sufficient pro-environmental behaviour (68%) for combined stakeholder groups. However, this rises to 90% for civil society.

Past research has shown that knowledge or awareness influences individual perceptions of waste management behaviour (Deng et al., 2020) or willingness to adopt pro-environmental behaviour (Garcia-Vazquez & Garcia-Ael, 2021). Our MRA shows that increased subjective knowledge is associated with increased pro-environmental behaviour (p < .001, Table 2 and Table 3).

The results of both the questionnaire and interviews acknowledge that pro-environmental practices are not daily practices. The interviews underscore reasons for this, citing “inconvenience,” “time,” and “complicated”. This finding is consistent with the TPB framework — if these actions were perceived as easier to do or people had higher self-efficacy to do them, engaging in waste management may be easier. The implication is: how can we make it easier for people? Further factors underpinning the above reasons may include service delivery, infrastructure deficiencies, or alternative reduction or disposal costs. Household waste management strategies are contingent on available services. In Kendari City, 32% of waste (by weight) remains uncollected, underscoring the lack of collection and recycling. Participants in the qualitative interviews emphasised the importance of waste pickers, often referred to as “scavengers”, in the absence of adequate waste management services.

Understanding the existing pro-environmental behaviour is essential. In the qualitative interviews, though there is variation between stakeholder groups, most participants reported practising plastic waste reduction (64% of combined stakeholders, 90% of civil society and 60% of involved groups, Figure 4), and both the questionnaire and survey results indicate that when sorting occurs, sorting out organics is the dominant practice (SI 5, Figure S4c, Preston-Whyte et al., 2026; and Table 4;). Reduction of waste production is recognised as important, as expressed by one respondent, “in light of a large amount of unmanaged solid waste, particularly plastic, the only way to handle it was by reducing the waste”. Participants show competence regarding separating organic waste, expressed in different terms. However, it is noteworthy that not all qualitative participants recognised removing organic waste as sorting, indicating a potential underestimation.

The importance of subjective knowledge in promoting more pro-environmental waste management practices suggests an opportunity to extend efforts to assess and implement tangible transformations. Khuc et al. (2023) highlight communication as a robust variable influencing waste-related decisions, focusing on household-level strategies to address plastic waste pollution in Vietnam. Their findings suggest that communication plays a role in reducing plastic waste by raising awareness. Our results suggest a similar case for Indonesia, provided that associated improvements in infrastructure or waste management service delivery support communication campaigns. The qualitative interviews highlight that stakeholders across stakeholder groups consider a lack of awareness as one of the barriers to effective policy and solutions (Figure 4). This finding aligns with Fian et al. (2024), who highlighted challenges in effective public communication as a barrier to effective regulations. There was variation in knowledge and awareness levels among participants, particularly evident in the in-person interviews, where open-ended questions allowed the authors to measure knowledge rather than self-assessed knowledge. Communication strategies would need to consider these differences in knowledge levels.

Our MRA (p < .05, Table 3) showed that plastic experience in the environment was positively associated with self-assessed pro-environmental behaviour for combined and civil society stakeholders. Greater experience of plastic pollution in neighbourhoods is associated with higher self-assessed pro-environmental behaviour when all stakeholders are considered together, but with lower self-assessed pro-environmental behaviour among civil society stakeholders. Plastic experience with microplastics in seafood was positively associated with self-assessed pro-environmental behaviour among both combined and civil society stakeholders. Plastic pollution is prevalent in the participants' environment (as detailed in Figure 3 and Table 4), which was expected given the high leakage of plastic pollution from Indonesia (Jambeck et al., 2015). Previous Indonesian research has shown heightened environmental awareness and concern about plastic pollution (Tyllianakis & Ferrini, 2021); however, the translation of experiencing plastic pollution within their environment or seafood and increased pro-environmental behaviour is an interesting result. The contrasting behavioural effects of neighbourhood pollution are also interesting. The negative response of civil society aligns with the Broken Windows Theory (Kelling & Wilson, 1982; Zimbardo, 1969), the Focus Theory of Normative Conduct (Cialdini et al., 1990) and TPB (Ajzen, 1985). The Broken Windows Theory, though originally utilised to describe the link between visible signs of disorder and rising levels of crime, is also linked to antisocial behaviour such as littering (Cialdini et al., 1991). The Focus Theory of Normative Conduct directly shows that littering increases in the presence of existing litter. TPB explains that when people believe others litter, they themselves feel less social pressure to properly dispose of their own waste.

As in previous research (Dowarah et al., 2022), participants appear to demonstrate a greater awareness of plastic pollution than of microplastic pollution (Figure 3). However, the data’s standard error does not allow for statistical inference. Additionally, participants showed awareness of the risks and concern for both.

Despite concerns about microplastic contamination in seafood, our results suggest a nuanced relationship between self-assessed health-protective behaviour and awareness of plastic and microplastic pollution. The quantitative questionnaire (p < 0.05, Table 3) showed that higher subjective knowledge is associated with a lower willingness to consume seafood among combined stakeholders, civil society, and involved groups. For civil society, those who had experienced microplastic contamination in seafood were less willing to consume it. However, an increase in seafood consumption was associated with increased subjective knowledge among civil society, as well as increased concern about plastic and microplastics among combined stakeholder groups and increased concern about microplastics among the involved groups. The qualitative interviews show no effect on willingness to consume seafood (90% for combined stakeholders, Figure 4), nor any observed by the industry itself (Figure 4).

Previous research on other marine pollutants has demonstrated a negative impact on the willingness to consume seafood with increased knowledge of contamination (Fercudani, 2015). The current study shows more nuanced results, depending on stakeholder group analysis, and on willingness vs actual consumption. The MRA revealed that subjective knowledge affects all stakeholder groups, with increased subjective knowledge linked with reduced willingness to consume, while increased microplastic experience reduced civil society's willingness to consume. Regarding seafood consumption, a significant positive relationship exists between concerns about plastic and microplastics for combined stakeholder groups. There is a significant positive relationship between subjective knowledge and consumption in civil society, as well as between microplastic concern and consumption among involved groups. Thus, high levels of subjective knowledge and microplastic concern are not linked to reduced seafood consumption in the relative stakeholder groups. In line with this, the interviews reveal that 90% of participants do not believe this knowledge affects their seafood consumption (Figure 4, SI 6, Table S4; Preston-Whyte et al., 2026), indicating that a link between increased awareness of plastic pollution and seafood consumption could not be established. This concern, rather than knowledge and more nuanced overall results, raises the question of whether microplastic contamination carries less weight than other pollutants or if Indonesia presents an outlier where the concerns may not outweigh the health, economic, and cultural benefits of eating seafood or the availability of alternative protein sources.

The interviews offered insights into the contrasting results, which could not be captured in the online questionnaire, with one informant expressing, “They still believed the fish was captured in a deep ocean where microplastics might not reach the area” [sic]. Thirteen participants repeated this concept. Such quotations reveal an interesting form of geographical distance with depth. Psychological distance is linked to geographical distance, with close geographic, social, or temporal distances linked to more effective concern and mitigating behaviour (Jones et al., 2017). Here, greater geographical distance (i.e., depth) reduces concern. Individuals do not believe that the fish they consume is contaminated, indicating either a disconnection of knowledge or distrust of information sources. This disconnection highlights a lack of understanding that the seafloor serves as a repository for plastic pollution (Harris et al., 2023).

Although concerned about microplastics, the local fishing industry does not associate awareness of microplastic pollution with decreased productivity or profits. The MRA revealed that concern about microplastics was significantly correlated with consumption among the involved groups. Nevertheless, the highest seafood consumption and willingness to consume seafood responses were from involved groups, potentially due to ease of access and reduced costs from fishers and seafood processing industry stakeholders. According to the interviews, 76% of the industry feels that their productivity and profits are stable but may be impacted in the future (Figure 4, SI 6, Table S4; Preston-Whyte et al., 2026). Various factors, including increased production, stock depletion, rising temperatures, and other forms of marine pollution, contribute to the fishing industry’s profits (Costello et al., 2016). One interviewee said, “The seafood business was not affected by the microplastic issue. It’s reflected by the number of consumers that remain relatively steady” [sic]. However, as our work did not consider these interpretations, any explanation would be conjecture. Future studies should consider the challenge of disentangling the influence of one factor from its cumulative and interconnected effects.

The use of knowledge, awareness and emotional responses, such as concern, to influence behaviour is employed in public health initiatives (Simpson, 2017). However, there is a lack of consensus within the threat and behaviour field (Palosaari et al., 2023), as the impact of behavioural interventions varies across audiences (Vlasceanu et al., 2024), underscoring the importance of baseline localised behaviour data. The graphic health warnings on cigarette packets have reduced, but they have not led to smoking cessation (Cummings, 2020). Within the Covid-19 pandemic, messaging that appealed to fear was polarising, producing a strongly negative emotional response and potentially undermining social cohesion (McClaughlin et al., 2023). When considering seafood consumption, the awareness disparities render microplastics a nuanced subject. It is possible that focusing on seafood consumption is a distraction. A more productive approach might focus on health concerns related to significant plastic pollution (such as nanoplastics in the bloodstream or societal health impacts) and explore ways to leverage such insights to instigate behavioural changes that reduce waste production and enhance waste management practices, thus combating plastic pollution itself.

The research context presented various challenges, including differences in internet access (discussed in the methods section) and literacy among the participants. Literacy differences may account for some participants not counting separating organics as waste separation, an issue identified during qualitative data analysis.

The quantitative questionnaire development contained limitations. The authors note that the online quantitative questionnaire required all questions to be answered, without an option for participants who did not know the answer. Unfortunately, this did not account for participants who may not have understood the question. However, the stakeholders who completed the online quantitative questionnaire had high literacy levels. A question-derived limitation, acknowledged by the authors and identified during the analysis phase, involved one double-barreled question (Lenzner & Menold, 2016) in the quantitative questionnaire, which may also be considered a leading question. Q31 and Q32 refer to the respondent’s knowledge of the risks of plastic and microplastics, respectively (Table 1). However, both questions consider overall risks while referring to both the marine ecosystem and human health. The question does not allow for separating risk knowledge into environmental and human components.

There are limitations in the variables utilised in this study, especially regarding the risk aspect of subjective knowledge. By positioning the risks together, one cannot consider the subjective knowledge related to environmental or human health separately. If future studies wish to consider risk specifically, this should be split into two variables. Additionally, perceived behavioural control, values, and norms should be introduced in future studies.

This study has spatial-temporal limitations. Replication on more extensive and diverse scales is necessary to extrapolate the results to broader contexts.

Future research should prioritise investigating strategies that may facilitate positive outcomes concerning pro-environmental behaviour, with a primary focus on barriers to behaviour change and behavioural shifts over time. Even minor adjustments in waste management behaviour could significantly impact global sustainability. As one interviewee noted, “Many people were aware of plastic waste; they have a willingness, but somewhat they did not take real action”[sic]. Areas for future research include understanding the differences between people's intended, self-assessed and actual behaviour, as well as any long-term changes and identifying factors that prevent positive change.

Our quantitative results indicate that self-assessed pro-environmental behaviour is positively associated with subjective knowledge among combined stakeholders, civil society, and involved groups. For both combined stakeholders and civil society, pro-environmental behaviour is also positively related to experience of plastic pollution in the environment and awareness of microplastic contamination in seafood. In contrast, experience of plastic pollution in neighbourhoods is positively associated with pro-environmental behaviour among combined stakeholders but negatively associated with such behaviour among civil society stakeholders. These findings suggest that pro-environmental behaviour may be enhanced in Indonesia by utilising additional awareness interventions, provided they are supported by enhanced service delivery and policy enforcement that overcome barriers such as socio-economic constraints, convenience, and effort. Keeping neighbourhoods clean is also important for supporting pro-environmental waste management behaviour. Reducing plastic waste production and sorting out organics are widespread pro-environmental behaviours that can be built upon for future mitigation strategies in Indonesia. Currently, policies addressing marine litter in Indonesia are known but deemed ineffective.

A conclusive link between the psychological links of (micro)plastic pollution and health-protective behaviours was not established, suggesting that the fisheries sector in Indonesia is currently unaffected by consumers' awareness of microplastics in seafood.

This study emphasises the importance of a mixed-methods approach in understanding self-assessed behaviour. It also helps close the data gap for non-WEIRD countries such as Indonesia, which, given the plastic pollution in and around Indonesia and the significant economic and cultural role of its fisheries sector, is critical.