Authors: Moslem Savari, Mohammad Shokati Amghani, Ashraf Malekian
Categories: Research Paper, Treated wastewater, Production of healthy products, Farmers' decisions, Limited water resources, Health belief model
Source: One Health
Authors: Moslem Savari, Mohammad Shokati Amghani, Ashraf Malekian
Water scarcity has led to the growing use of untreated wastewater for irrigation in Iran, posing serious risks to human health and the environment. Treated Wastewater (TWW) offers a safer and more sustainable alternative, with economic, environmental, and social benefits. However, its adoption by farmers remains limited. This study aligns with the One Health approach by examining how irrigation practices affect interconnected domains—human health, environmental safety, and agricultural productivity—and by identifying behavioral factors that influence farmers' decisions regarding safe water use. This study applies the Health Belief Model (HBM) to explore the determinants of farmers' intentions to use TWW for irrigation. Using a survey-based approach and structural equation modeling (SEM), the study analyzes responses from farmers in Tehran Province, Iran. The findings reveal that the HBM accounts for 72.1 % of the variance in farmers' intentions to adopt TWW, with perceived benefits emerging as the strongest predictor. These results suggest that targeted policy interventions emphasizing the economic, environmental, and social benefits of TWW, along with addressing the negative effects of untreated wastewater (UTWW) on agricultural productivity, could encourage wider adoption among farmers.
The accelerating impacts of climate change, coupled with intensifying droughts, present significant challenges to global food security [[1], [2], [3]]. Population growth, urbanization, and shifting human consumption patterns are driving an increased demand for freshwater resources, especially in arid and semi-arid areas [4,5]. Water scarcity has become a critical issue worldwide, with projections indicating that global freshwater availability will decline to just 65 % of current levels by 2025 [6,7]. It is anticipated that water consumption in many regions will outpace population growth [8]. By 2050, it is predicted that 3.3 billion people will be affected by water scarcity, with the agricultural sector in arid regions being particularly vulnerable due to limited freshwater resources [7]. Agriculture already accounts for 92 % of global water use, with approximately 70 % of this water coming from freshwater sources like rivers and groundwater [[9], [10], [11]].
In response to water stress, many developing regions have turned to the utilization of UTWW for irrigation, a practice that has raised considerable public health and environmental concerns [12]. Treatment of wastewater can mitigate many of these negative impacts, positioning Treated Wastewater (TWW) as a viable alternative with substantial economic, environmental, and social benefits for agriculture [[13], [14], [15]]. Despite these benefits, global adoption of TWW remains limited, with only 50 % of wastewater worldwide currently undergoing treatment [16,17]. Annually, 41 billion m^3^y^−1^ of treated wastewater are used globally in agriculture, compared to 360 billion m^3^y^−1^ of wastewater generated each year, with 188 billion m^3^y^−1^ treated [16].
In the Middle East, where agriculture is the largest consumer of water, the return on this water use remains low, prompting increasing competition between urban and agricultural water demands [18]. As the demand for urban water rises, prioritization of freshwater allocation to urban areas over agricultural needs is becoming more common [19]. This trend is widening the gap between water supply and demand, presenting significant challenges for agricultural water conservation [20]. In response, there has been a global shift toward the use of non-conventional water resources in agriculture, including the recycling and adoption of TWW [21]. Governments worldwide are increasingly focusing on TWW as a sustainable solution to mitigate the irrigation water gap and enhance agricultural productivity [20]. Additionally, TWW offers an important source of nutrients for crops and vegetables, further supporting its use in agricultural irrigation [22].
In various regions around the world, particularly in developed countries such as the United States and Australia, TWW is widely used in agriculture to enhance food production [23], and its global application is expanding rapidly [24]. From an environmental perspective, TWW is recognized as one of the most beneficial resources for agricultural use, as it helps alleviate pressure on freshwater supplies [25]. Furthermore, TWW is advantageous due to its rich nutrient content, which is readily available for plants [26]. Urban TWW has the potential to significantly reduce reliance on freshwater for irrigation, thus helping to conserve these limited resources [27]. The European Union has emphasized that proper wastewater treatment is essential before it is used for irrigation to prevent potential hazards to human health, animals, and the natural resources [28].
It is increasingly apparent that allocating primary freshwater resources for human consumption while utilizing TWW for agricultural irrigation is becoming inevitable. For instance, the wastewater generated by a city with a population of one million can irrigate between 1500 and 3500 ha of agricultural land [8]. In Iran, water scarcity has led to the cultivation of only 18.5 million hectares of the country's 32 million hectares of arable land, with just 3.5 million hectares receiving adequate irrigation [29]. In Tehran Province alone, more than 50,000 ha of agricultural land are watered with untreated sewage [30]. Additionally, 70 % of the sewage discharged in Tehran is domestic, entering alongside clean river waters. Notably, the lead (Pb) content in surface and wastewater entering Tehran is up to 400 times the normal standards [8]. The consumption of UTWW for watering crops not only risks soil degradation and shallow groundwater contamination but also exposes crops to toxic elements. The accumulation of these toxins can lead to soil contamination and pose significant risks to food safety [31]. In response, Iran has made considerable efforts to establish wastewater treatment plants. The first plant, with a daily capacity of 1700 m^3^, was launched in Tehran in 2005, and the network has since expanded, with 69 % of factories in Iran now connected to treatment facilities [30]. Despite government regulations prohibiting the use of UTWW for irrigation, many farmland owners pursue to use it directly, driven by factors such as water scarcity and the belief that wastewater contains valuable nutrients [6]. Another major barrier to the successful implementation of wastewater treatment strategies is the resistance from stakeholders, particularly farmers. If they remain unwilling to utilize TWW for irrigation, sewage reclamation efforts are likely to fail [32]. Therefore, it is crucial to address the behavioral factors influencing farmers' adoption of TWW in Tehran Province. This study aims to explore these psychosocial factors in order to understand the key drivers behind farmers' decisions to adopt TWW for irrigation in Iran's capital.
Psychological research has significantly contributed to identifying the underlying factors that influence human behavior [33]. Among the various models used to understand these factors, the Health Belief Model (HBM) stands out due to its applicability and versatility. This model explains why individuals may not engage in behaviors like conservation programs despite knowing their benefits [34]. For the present study, HBM was selected for several key (1) its ability to investigate complex, multi-dimensional human behaviors [35], ((2) its flexibility in predicting a wide scope of people behaviors [36,37], and (3) the fact that the study's subject—the adoption of TWW for agricultural irrigation—aligns closely with health-related behaviors. These attributes make the HBM a particularly appropriate theoretical framework for this research.
The HBM has been widely employed for over four decades to understand beliefs, values, and attitudes related to a variety of health behaviors. It has proven effective in explaining both behavioral change and the maintenance of health behaviors, providing a guiding framework for health behavior interventions [38]. Essentially, the model suggests that belief changes lead to behavioral changes [39,40]. It operates on the premise that persons are more likely to get involved in activates they perceive will protect them from illness or adverse outcomes. In the context of this model, individuals hold a positive expectation that adopting certain behaviors, such as those recommended for disease prevention, will ultimately safeguard their health. By internalizing these beliefs, people are more likely to participate in behaviors they believe will lead to desirable results [41]. The efficacy of the HBM in predicting human behavior has been well-documented in a range of studies, particularly in the agricultural sector. It has been used to analyze behaviors related to water conservation [35,38], drought adaptation [42], pesticide usage [43], organic farming [44], and crop pattern changes [45]. However, there remains a significant gap in the literature, as no study—either in Iran or internationally—has specifically applied the HBM to understand farmers' attitudes toward the adoption of TWW for watering crops. This gap underscores the novel contribution of the current research.
The HBM is one of the most extensively utilized models in the study of health-related behaviors [46]. Developed in the 1950s, this model focuses on individuals' beliefs regarding their behaviors and decision-making processes [47]. It is an expectancy-value model, where “expectancy” refers to an individual's belief in their ability to carry out a given task or activity, and “value” reflects the motivation or reasons behind performing that task [48]. The HBM consists of four main components, which are organized into two broad categories (Fig. 1).Fig. 1HBM framework.Fig. 1
Perceived Susceptibility refers to a person's understanding of the likelihood that they will experience a particular health issue due to certain behaviors [49]. Previous research has shown that a higher perceived susceptibility correlates with an increased likelihood of adopting protective behaviors [44,45,50]. In the context of this study, perceived susceptibility is understood as farmers' subjective evaluation of the hazards associated with using UTWW for irrigation. If farmers perceive that using TWW can help mitigate the risks associated with water scarcity, their motivation to adopt this practice will increase. Therefore, it is hypothesized that perceived susceptibility can significantly impact farmers' willingness to utilize TWW (Hypothesis 1).
Perceived Severity refers to an individual's belief in the seriousness of a given health risk and its potential consequences [50]. This component is positively correlated with the likelihood of adopting protective behaviors [51]. In the HBM, perceived severity represents the individual's belief in the potential harm or risks associated with a particular health issue [36]. It reflects the understanding that a certain condition or risk could lead to severe outcomes, such as death or long-term health complications [50]. For this study, perceived severity is framed as the belief among farmers that water scarcity and the use of UTWW could have negative, far-reaching consequences, which would increase their willingness to use TWW for irrigation. Thus, it is hypothesized that perceived severity positively influences farmers' intention to adopt TWW for irrigation (Hypothesis 2).
Perceived Benefits refer to a person's assessment of the advantages or rewards linked to engaging in a specific behavior or action [52]. This concept encapsulates the belief that taking preventive or protective action will lead to positive outcomes [53]. It signifies the perception that adopting a particular behavior—such as using TWW for irrigation—will help mitigate health risks or improve other relevant factors, such as crop health, environmental quality, or soil fertility [44]. Previous studies suggest that perceived benefits typically exert a stronger influence on behavior than perceived risks, playing a central role in motivating safety and preventive behaviors [54]. In the current study, it is expected that farmers who perceive the benefits of using TWW—such as improved crop yield, better environmental outcomes, and enhanced soil quality—will be more likely to adopt this irrigation practice. Consequently, the hypothesis for this section is that perceived benefits have a positive and significant impact on farmland owners' willingness to utilize TWW for irrigation (Hypothesis 3).
Perceived Barriers refer to a person's understanding of the costs, difficulties, or obstacles associated with performing a specific behavior. This construct reflects the belief that a particular behavior may involve risks, challenges, or inconveniences [34]. Previous research has indicated that as perceived barriers increase, the likelihood of adopting protective behaviors decreases [55]. Common barriers to behavior adoption include factors such as lack of knowledge, limited time, discomfort, or perceived difficulty in taking action [54]. In the context of this study, if farmers perceive significant barriers to adopting TWW, they are less likely to consider it as a viable option. Thus, it is hypothesized that perceived barriers negatively influence farmland owners' willingness to utilize TWW for irrigation (Hypothesis 4).
Furthermore, the HBM incorporates other cognitive and motivational factors that shape behavior change or prediction, such as cues to action and self-efficacy. These elements serve as additional cognitive triggers that stimulate health-related behaviors and prepare individuals to take action [34,35,38,55,56].
Cues to Action refer to stimuli that prompt individuals to make decisions when they perceive the need to engage in a certain behavior. These cues can come from various sources, such as media, friends, or neighbors, and act as reminders or motivators to encourage behavior change [42]. According to Hochbaum [57], readiness to act can be bolstered by external causes like media campaigns. In this study, it is expected that the presence of consistent promotional messages or signals advocating the use of TWW will increase farmers' willingness to adopt the practice. Hence, it is hypothesized that cues to action positively influence farmers' willingness to consume TWW for irrigation (Hypothesis 5).
The concept of Self-Efficacy was added to the HBM by Rosenstock [47] as a factor related to perceived behavioral control. It refers to a person's belief in his capability to successfully carry out a particular behavior and obtain the positive outcomes [34,42,58]. Research suggests that higher self-efficacy increases the predictive power of the HBM in understanding behavior [59]. In this study, self-efficacy is conceptualized as the farmers' perception of their confidence and capability to utilize TWW effectively for irrigation. Consequently, it is hypothesized that self-efficacy positively and significantly affect farmers' willingness to consume TWW for irrigation (Hypothesis 6).
Tehran, located at 51°06′ E longitude and 35°34′ N latitude, spans an elevation range from 1800 m in the northern part to 1050 m in the south (Fig. 2). As the capital of Iran, it is the second-largest city in the Middle East, with approximately 16 % of the country's population, translating to nearly nine million residents [34]. The per capita water consumption in Tehran, one of the world's major metropolitan areas, fluctuates between 200 and 400 L/day, which is about several times higher than the mean consumption in Western European nations [60]. In recent years, reduced rainfall combined with Tehran's increasing population [61] has intensified concerns over water scarcity, exacerbated by diminishing water resources, declining groundwater levels, and rising contamination risks [34]. Consequently, Tehran is grappling with critical challenges related to water management [61]. Estimates indicate that the per capita wastewater generation is between 186 and 215 L/day. Given Tehran's population of approximately 9 million, this translates into a substantial amount of wastewater, which, if properly treated, could significantly contribute to meeting the region's agricultural and water needs.Fig. 2Study area.Fig. 2
A cross-sectional survey was conducted within Tehran Province. The target population included all farmers engaged in irrigation activities within the province. A sample size of 420 respondents was determined based on Krejcie and Morgan's [62] table. Given the large and dispersed nature of the population across the province, stratified sampling was employed in multiple stages to ensure adequate representation of the various groups. This table was chosen for its utility in cases of unknown population variance and its simplicity and adaptability.
The research questionnaire was developed following an extensive review of relevant literature on treated wastewater, water conservation, ecologically sustainable practices, water scarcity, and drought adaptation. This review aimed to identify items used in previous studies to measure the constructs of the HBM. Based on this analysis, appropriate items were selected and adapted for the current study's focus on wastewater reuse in agricultural irrigation. The willingness to consume TWW was assessed using four items. Additionally, the perceived severity of using TWW was measured with four items, while perceived susceptibility and perceived benefits were each evaluated using four items. Perceived barriers to using TWW were assessed with three items, and self-efficacy related to using TWW for irrigation was measured with four items. Lastly, cues to action for using TWW in irrigation were evaluated using three items (Table 1). A 5-point Likert scale was utilized (1 = very low, 5 = very high) to capture farmers' opinions. This scale is known to mitigate common statistical issues and is widely used in social science research [63].Table 1Measurement items in research.Table 1DimensionsItemsReferenceIntentionIf there is a plan for using TWW for irrigation, I would like to participateShahangian et al. [70]; Bakhtiyari et al. [71]; Delfiyan et al. [72]Given the choice between TWW and fresh water for irrigation, I would prefer to use TWW.My goal for the future is to use TWW in irrigation.I aim to use TWW to protect fresh water resources.Perceived severityUsing raw sewage for irrigation can cause serious damage to farm soil.Karami et al. [50]; Wang et al. [73]Using raw sewage for irrigation will result in unhealthy and poor-quality products.Using raw wastewater for irrigation will cause irreparable harm to my health and that of consumers.If I don't use TWW for irrigation, agriculture will suffer from water stress.Perceived benefitsUsing TWW in irrigation contributes to the health of the community and the crop.Shahangian et al. [34]; Nasiri et al. [38]Using TWW in irrigation can reduce pressure on freshwater resources.Using TWW in irrigation can help reduce the discharge of polluted water into the environment.Using TWW in irrigation can help improve the structure of farm soil.Perceived barriersThere are no facilities or infrastructure required to treat and distribute TWW.Yazdanpanah et al. [56]The process of TWW may be costly and not economical for some farmers.There are strict rules and regulations regarding the use of TWW.Cue to actionI get the necessary information about using TWW in irrigation from local associations.I receive information about the use of TWW in irrigation from local television and radio.I receive information about the use of TWW in irrigation from experts and specialists.Self-efficacyI am confident that I could use TWW for irrigation if I wanted to.Nasiri et al. [38]When I encounter problems using TWW, I can seek help from others.I have sufficient resources to use TWW.I have sufficient knowledge to use TWW.
The validity of the research instrument (questionnaire) was assessed in two 1) Face validity: This is a subjective, non-numeric method that indicates whether the data collection tool is suitable for measuring the studied phenomenon [64]. This approach refers to the extent to which the questionnaire items align with the construct being measured [65]. In face validity, the questionnaire is presented to a panel of experts, who are asked to provide feedback on the quality of the questions. Positive feedback implies that the questionnaire possesses face validity. In this study, face validity was confirmed by a panel of experts in agriculture, water resources, environmental science, and psychology. 2) Construct validity: This indicator, introduced by Fornell and Larcker [63], is assessed through convergent validity using the Average Variance Extracted (AVE) in the measurement model. AVE measures the average variance shared between each construct and its indicators [66]. In other words, AVE shows the correlation between a construct and its indicators, where a higher correlation indicates a better fit [66]. Fornell and Larcker [63] proposed that convergent validity is present if AVE is greater than 0.5. The AVE results are presented in Table 2, indicating that the AVE values for all research constructs exceeded the standard threshold, confirming the construct validity of the questionnaire.Table 2Assessment of the research measurement model fit.Table 2ConstructsMeasurement itemƛtReliability and ValidityVIFPerceived susceptibilityPS10.86134.936AVE: 0.676CR: 0.893a: 0.8411.452PS20.81218.0111.632PS30.78820.0691.563PS40.82724.0471.258Perceived severityPSV10.6067.162AVE: 0.524CR: 0.809a: 0.7041.361PSV10.88137.8621.682PSV10.5345.6771.458PSV10.81622.4281.936Perceived benefitsPB10.85233.808AVE: 0.666CR: 0.888a: 0.8311.485PB20.87932.7781.635PB30.68111.6991.745PB40.83927.8921.625Perceived barriersPBR10.84219.941AVE: 0.704CR: 0.877a: 0.7901.257PBR20.86324.5141.634PBR30.81019.4411.425Cue to actionCA10.84218.435AVE: 0.704CR: 0.907a: 0.8161.335CA20.86331.8571.458CA30.81022.9771.635Self-efficacySE10.74115.800AVE: 0.663CR: 0.885a: 0.8371.352SE20.93446.1721.526SE30.91160.4021.635SE40.6338.2641.458IntentionIN10.77118.051AVE: 0.560CR: 0.836a: 0.7381.638IN20.75817.4741.963IN30.71414.1081.846IN40.74919.6181.634
Reliability is a key characteristic of measurement tools, especially for Likert-scale and quantitative studies. Various methods exist to calculate reliability, with Cronbach's alpha being one common approach. This method bases reliability on the variability of data and collected responses [67]. If the Cronbach's alpha coefficient is above 0.7, the questionnaire or similar tools are considered reliable [68]. A second method is composite reliability (CR), which assesses the model's internal consistency based on the alignment of questions designed to measure each factor [69]. This type of reliability closely resembles convergent validity and uses the same parameters for its calculation [69]. Composite reliability is confirmed when CR exceeds 0.6. While Cronbach's alpha depends on data dispersion with standard deviation as a primary measure, composite reliability measures the internal consistency of items for each factor, making it a more precise measure [68]. As shown in Table 2, both Cronbach's alpha and composite reliability for all constructs exceeded the thresholds of 0.7 and 0.6, respectively, indicating suitable reliability of the questionnaire.
To analyze the relationships among the research components outlined in the theoretical framework, Structural Equation Modeling (SEM) was employed to predict farmers' willingness to use TWW for irrigation. Data analysis was performed using Smart PLS with maximum likelihood estimation, enabling the calculation of the direct effects of psychosocial factors influencing the adoption of TWW in agriculture. SEM was utilized to assess how well the data fit the proposed theoretical model by examining the relationships between latent variables (constructs) and their corresponding observed variables (indicators). Since constructs are not directly measurable, they were operationalized through survey-based indicators [69]. These indicators were derived from the questionnaire responses provided by the study participants [67]. PLS-SEM, the third generation of structural equation modeling, is particularly well-suited for structural analyses due to its robustness against sample size limitations and non-normal data distributions. One of the key advantages of this version of PLS-SEM is its redesigned, user-friendly graphical interface, which allows for streamlined analysis [69]. For this study, SEM was employed to test the theoretical framework (Fig. 1) and assess the hypothesized associations between the key variables.
The participants' age distribution revealed an average age of 43.67 ± 13.85 years. The educational background of the participants was varied, with 29 % having completed middle school and only 5.6 % possessing a university degree. On average, farmers had 17.16 years of experience in agriculture and managed approximately 8.63 ha of land. When asked about their understanding of the impacts of UTWW on agriculture, most farmers demonstrated a limited to moderate level of knowledge. Moreover, a significant portion, 74.67 %, reported that they had not attended any training sessions related to the use of TWW for irrigation purposes.
The assessment of the measurement model involves three essential unidimensionality, reliability, validity, and discriminant validity. These stages must be evaluated to ensure the accuracy and robustness of the measurement model [69]. The following outlines the procedures for each stage.
The first step in evaluating the measurement model is to confirm the unidimensionality of the indicators and measurement items. Unidimensionality was assessed using standardized factor loadings (ƛ) and t-values [69]. Given that the standardized factor loadings for all indicators were above 0.5 and statistically significant at the 1 % level (P < 0.01), it can be concluded that all measurement items meet the criterion for unidimensionality, confirming their validity (Table 2).
The second stage involved the assessment of reliability and validity using Cronbach's alpha (α), composite reliability (CR), and average variance extracted (AVE) (Table 2). The results demonstrated that all indices met the required thresholds for validity and reliability, with composite reliability exceeding 0.60, Cronbach's alpha above 0.70, and AVE greater than 0.50.
An important parameter for detecting multicollinearity or collinearity is the Variance Inflation Factor (VIF), which measures the extent to which a variable's behavior is influenced by other variables (Cheng et al., 2022). In essence, the VIF index quantifies the degree to which estimated coefficient variations are amplified due to multicollinearity [74]. A VIF value below 5 indicates the absence of multicollinearity or collinearity [74]. The analysis results indicated no multicollinearity issues among the research constructs, as the VIF values for all variables were below the standard threshold of 5 and fell within the acceptable range. This confirms that the independent variables are not highly correlated, thereby validating the suitability of the regression analysis.
The third stage involved assessing discriminant validity. To confirm discriminant validity, the average variance extracted (AVE) for each construct must exceed the correlations between constructs [63]. As shown in Table 3, the square root of the AVE (ranging from 0.724 to 0.839) was greater than the correlations between the constructs (ranging from 0.317 to 0.694). This result confirms the discriminant validity of the measurement model.Table 3Discriminant validity of research constructs.Table 3Constructs1234567Cue to action0.839Intention0.6940.748Perceived barriers0.5870.5080.839Perceived benefits0.6580.6780.5100.816Perceived severity0.6130.6510.5410.7980.724Perceived susceptibility0.6090.5760.5540.6030.5470.822Self-efficacy0.3860.5380.3170.5170.5500.4300.814
HTMT is a technique used to assess the divergent validity of measurement models by determining whether there is sufficient differentiation between constructs. It has been proposed as a more accurate alternative to the classic Fornell-Larcker method. This approach calculates the ratio of the average correlations between different constructs (Heterotrait) to the average correlations within a single construct (Monotrait). If the HTMT value falls below the accepted threshold (typically <0.85), the constructs can be considered to exhibit adequate divergent validity. The findings of this study confirm that the research instruments meet this criterion (Table 4).Table 4HTMT value for research constructs.Table 4Constructs1234567Cue to actionIntention0.748Perceived barriers0.6950.715Perceived benefits0.4780.7410.777Perceived severity0.7480.6850.6280.744Perceived susceptibility0.6930.8150.8110.5630.741Self-efficacy0.7150.6330.6990.6380.5280.744
The results of the SEM analysis are presented in standard and t-value formats in Fig. 3, Fig. 4. The HBM explains 72.1 % of the variance in farmers' intentions to use TWW for irrigation. According to the path analysis, perceived barriers (β = −0.133, P < 0.005) negatively and significantly affected farmers' intentions. In contrast, perceived severity (β = 0.194, P < 0.001), perceived susceptibility (β = 0.187, P < 0.005), perceived benefits (β = 0.325, P < 0.001), self-efficacy (β = 0.107, P < 0.005), and cues to action (β = 0.225, P < 0.005) all had positive and significant effects on farmers' intentions to use TWW for agricultural irrigation.Fig. 3Model with standard factor loadings.Fig. 3Fig. 4Model with t-value.Fig. 4
Prior to assessing the structural model, the variance inflation factor (VIF) was calculated to distinguish any potential issues arising from high correlations between latent variables. The results confirmed that all VIF values, both for inner and outer variables, were within acceptable limits, indicating no concerns regarding multicollinearity. For model evaluation, the study adhered to the procedures outlined by Hair et al. [68], which involved estimating path coefficients (β values) and calculating their respective t-statistics. To assess their significance, a bootstrapping procedure with 4000 samples was employed using partial least squares (PLS) analysis (Table 5). The findings indicated that the proposed framework was effective in explaining 72.1 % of the variance in farmland owners' intentions to adopt TWW for irrigation. In addition, it was observed that perceived benefits had a more substantial influence on the farmers' behavioral intentions compared to other factors.Table 5Hypothesis testing and model evaluation.Table 5HypothesisƛtResultR^2^Q^2^H1: PS→Intention0.1942.742Confirm0.7210.325H2: PSV→Intention0.1872.442ConfirmH3: PB→ Intention0.3253.057ConfirmH4: PBR →Intention−0.1332.188ConfirmH5: SE →Intention0.1071.972ConfirmH6: CA →Intention0.2252.606Confirm
A Q^2^ value greater than zero indicates the model's predictive relevance for endogenous constructs. This means the structural model is capable of accurately reconstructing omitted data and predicting dependent variables.
The growing issue of water scarcity has led to the increased use of untreated sewage for agricultural irrigation in many developing countries, resulting in considerable health and environmental challenges. In Iran, the practice of using raw wastewater for irrigation purposes is becoming more common, though it carries significant risks. In contrast, Treated Wastewater (TWW) offers a sustainable alternative, mitigating many of these negative effects and providing a range of economic, environmental, and social benefits. However, despite these advantages, farmers' adoption of TWW remains limited, highlighting the need to investigate the underlying factors influencing their decisions. This study contributes to the One Health approach by addressing the interconnected risks and benefits of wastewater reuse across human health, environmental sustainability, and agricultural productivity. By exploring behavioral drivers behind farmers' irrigation choices, the research supports integrated solutions that promote safe water use, reduce disease transmission, and enhance ecosystem resilience.
The application of TWW is increasingly recognized as a viable solution to address global water scarcity issues [12]. In addition to its potential to alleviate water stress, TWW can enhance crop productivity, mitigate water contamination, and reduce the strain on freshwater resources [75]. The United Nations has encouraged the widespread adoption of TWW as part of the effort to meet the Sustainable Development Goals (SDGs) by 2030. In Iran, although considerable progress has been made in wastewater treatment efforts aligned with sustainability, the use of treated wastewater in agriculture has yet to gain significant acceptance among farmers. This study sought to explore the psychosocial factors influencing farmers' intentions to adopt TWW for irrigation. The HBM served as the conceptual framework for this research. A review of existing literature revealed that, globally, the HBM has not been applied to the context of TWW utilization in agriculture, marking this study as a significant contribution to the field. The findings have important implications for policymakers working to promote TWW adoption in agricultural practices.
The hypothesis testing results revealed that the perceived susceptibility factor had a significant and positive impact on farmers' intentions to utilize TWW for irrigation (hypothesis 1 confirmed). This is consistent with previous studies [76,77]. This suggests that when individuals perceive a personal risk, they are more inclined to adopt behaviors aimed at reducing that risk, such as engaging in protective measures [78,79]. The HBM postulates that individuals are motivated to minimize health risks, but they first need to recognize that they are at risk [77]. Farmers must comprehend the potential of UTWW to meet crop nutritional needs, but it is equally critical to assess the ecological and health implications, particularly regarding its impact on soil and crop properties [80]. A major concern in using UTWW for irrigation is the possible accumulation of heavy metals in the soil, which could eventually contaminate crops [29]. Additionally, UTWW harbors pathogens, such as bacteria, viruses, and fungi, which pose health hazards to farm workers, consumers, and those handling agricultural products [81]. It is crucial to inform farmers that adequate treatment of wastewater can reduce the economic, environmental, and health risks linked to using substandard wastewater [82]. Therefore, enhancing farmers' awareness of the dangers associated with UTWW is pivotal. This knowledge can increase their sensitivity to the potential consequences of their actions on both human health and the environment, which, in turn, may improve their willingness and motivation to use TWW in agricultural irrigation.
In line with prior research [34,35,55,83], the findings of this study demonstrate that perceived severity has a positive and statistically significant impact on farmers' willingness to consume TWW for crop irrigation (hypothesis 2 supported). From a psychological standpoint, people are more likely to get involved in precautionary behaviors when they believe the consequences of inaction are severe [84]. In the context of agricultural practices, the perception of risk severity, such as the use of UTWW for irrigation, significantly influences farmers' safety-related decisions, motivating them to adopt safer alternatives [43]. Previous studies have shown that increased awareness about the poor quality of raw wastewater decreases the likelihood of its use among farmers, leading them to prefer TWW as a safer option [85]. As farmers' concerns about the potential negative impacts of UTWW grow, they are more likely to opt for TWW as an irrigation solution [86]. It is essential for farmers to understand that heavy metals can accumulate in both soil and crops, ultimately entering the food chain and potentially harming both farmers and consumers [87]. Globally, heavy metal contamination in environmental media such as water, soil, and plants presents a critical environmental issue, as these metals can infiltrate the food supply [88]. These substances are known to pose health risks, including mutagenic and carcinogenic effects [89]. In Tehran province, for example, farmers often rely on UTWW for irrigation due to its abundant availability. However, they must be made aware of the potential irreversible health consequences of this practice. Increasing farmers' awareness about these risks could encourage them to adopt TWW, even if it requires additional investment.
The results for Hypothesis 3 showed that the perceived benefits of using TWW positively and significantly influence farmers' intention to adopt this method for crop irrigation. This result is consistent with numerous research in both environmental and agricultural research that highlight the role of perceived benefits in shaping farmers' intentions to adopt environmentally sustainable practices [3,4,44,49,53,54]. Specifically, when farmers are more aware of the financial, environmental, and social advantages of TWW, they are more likely to consider its use [4]. Previous research has emphasized that perceived benefits often play a more considerable role in shaping behavior than perceived risks [54]. These benefits not only influence farmers' attitudes but also drive behavioral changes, as attitudes are central to adopting safe agricultural practices [90]. Additionally, farmers who reduce their use of untreated sewage often gain recognition as environmentally conscious, which further motivates the adoption of sustainable practices [6]. Therefore, raising awareness about the benefits of TWW is essential. For example, studies by Muamar et al. [91] have demonstrated that using TWW improves both the physical and chemical features of soil. Furthermore, replacing groundwater with TWW in arid and semi-arid areas reduces dependence on freshwater resources and minimizes the use of chemical inputs in agriculture [92]. When adequately managed, TWW is not only more cost-effective than groundwater but also reduces the need for chemical fertilizers while maintaining environmental standards. Additionally, TWW irrigation allows for better monitoring and control of pollutants, such as heavy metals, introduced into the soil [93]. Despite these advantages, many farmers remain unaware of TWW's potential, leading to its limited use. To address this knowledge gap, it is recommended that targeted training and educational programs be implemented to raise awareness and motivate farmers to adopt TWW for irrigation purposes.
On the other hand, the results from Hypothesis 4 supported the idea that perceived barriers negatively and significantly influence farmers' willingness to utilize TWW for irrigation. These results align with those of previous research [42,55,94]. Perceived barriers refer to factors that hinder the adoption of health-related behaviors, such as using TWW in irrigation practices. For example, when the costs of adopting a new behavior outweigh its perceived benefits, farmers may be less likely to make the switch [49]. According to the HBM, people are more inclined to participate in behaviors when they perceive the advantages to outweigh the costs [82]. Our study further confirmed that when farmers perceive more barriers, they are less likely to incorporate TWW into their irrigation practices. This trend is observed globally, with significant proportions of urban wastewater remaining unused due to cost-related challenges [85]. In countries like Iran, these challenges are particularly pronounced, as the financial burden associated with wastewater treatment often exceeds the capabilities of small-scale farmers [95]. Many Iranian farmers work on a smaller scale and lack the resources to invest in new agricultural technologies [96]. Furthermore, a lack of motivation and positive attitudes toward TWW adoption further contributes to its slow uptake. As such, psychological barriers represent a significant challenge to the widespread use of TWW [82]. For instance, a study in Fars Province found that most farmers held unfavorable views toward the use of TWW, which hindered its adoption [4].
Hypothesis 5 also demonstrated that cues to action had a positive and significant impact on farmers' willingness to utilize TWW. This finding is align with earlier studies [55,56,73]. Cues to action are strategies designed to prompt individuals to adopt health-related behaviors by acting as motivators for healthier practices [56]. These cues may include activities such as attending training programs, seeking advice from experts, or receiving information through promotional materials like posters and banners. Such cues serve as reminders for farmers, increasing their awareness of the risks associated with using UTWW and highlighting the benefits of TWW [97]. Ultimately, these strategies help cultivate a perceived need for action and motivate farmers to adopt more sustainable irrigation practices. It is, therefore, crucial to maintain ongoing communication through both local and national channels that emphasize the dangers of UTWW. Such efforts would provide farmers with the necessary motivation to transition to using TWW for irrigation.
Finally, the results from Hypothesis 6 confirmed that self-efficacy has a significant and positive impact on farmers' intention to use TWW for crop irrigation. Self-efficacy, defined as an individual's belief in their ability to organize and execute the necessary actions to achieve specific goals [55], plays a crucial role in motivating protective behaviors. In this context, farmers are more likely to adopt behaviors that they believe they can successfully perform. This suggests that when farmers feel confident in their skills and capabilities, they are more inclined to take action toward using TWW for irrigation [8]. The strength of this belief correlates closely with their perception of the task's when a task appears difficult, individuals may hesitate or avoid undertaking it [98]. Conversely, higher self-efficacy is linked to greater persistence and success in engaging in desired behaviors [99]. Previous studies have underscored the importance of self-efficacy in shaping farmers' intentions and behaviors, reinforcing the finding that self-efficacy significantly influences the decision to adopt agricultural innovations such as TWW [34,35,38,55,56]. This influence is especially pronounced in developing countries like Iran, where many farmers lack the necessary knowledge and skills to use TWW effectively, often leading to reluctance in adopting this practice. Therefore, improving farmers' professional competencies is critical for facilitating the broader use of TWW.
This study highlights critical behavioral factors influencing farmers' intention to use TWW for irrigation, with perceived benefits emerging as the most significant determinant. To promote safe and sustainable irrigation practices aligned with the One Health framework, policymakers should consider the following -Emphasize the benefits of TWW: Design targeted awareness campaigns that clearly communicate the economic, environmental, and health advantages of TWW to farmers, focusing on increased crop yields, reduced water costs, and minimized disease risks.-Integrate TWW into agricultural extension Equip agricultural advisors with training and resources to educate farmers on safe TWW usage, addressing misconceptions and building trust in water quality.-Improve infrastructure and Invest in decentralized wastewater treatment systems and distribution networks to ensure reliable access to high-quality TWW, especially in water-scarce regions.-Incentivize adoption through subsidies and Offer financial incentives, such as reduced water tariffs or equipment grants, to encourage farmers to transition from raw wastewater to treated sources.-Monitor and certify water Establish transparent monitoring systems and certification programs to reassure farmers about the safety and reliability of TWW.
By implementing these measures, decision-makers can reduce the harmful impacts of untreated wastewater use, enhance agricultural sustainability, and protect public and environmental health—advancing the goals of the One Health approach.
This study provides novel insights into the behavioral drivers influencing farmers' willingness to adopt TWW for agricultural irrigation in Tehran Province, Iran. By applying the HBM, the research demonstrated that farmers' perceptions—particularly perceived benefits—play a pivotal role in shaping their intention to use TWW. The model explained 72.1 % of the variance in intention, highlighting its strong predictive power. However, while the findings confirm the relevance of HBM constructs, they also suggest that farmers' decisions are shaped by a complex interplay of psychological, contextual, and possibly structural factors. The dominance of perceived benefits underscores the importance of communicating the tangible advantages of TWW, yet the presence of perceived barriers and varying levels of self-efficacy indicate that awareness alone may not be sufficient. A more holistic approach—combining education, infrastructure support, and trust-building—may be necessary to translate intention into actual behavior.
Despite its contributions, this study has several limitations that open avenues for future -Model Although the HBM accounted for a substantial portion of the variance in intention, it did not capture all influencing factors. Future studies could enhance explanatory power by integrating HBM with other behavioral models such as the Theory of Planned Behavior (TPB) or the Technology Acceptance Model (TAM).-Methodological The exclusive use of quantitative methods limited the depth of understanding regarding farmers' motivations and concerns. Incorporating qualitative approaches—such as interviews or focus groups—could provide richer, context-specific insights.-Behavior vs. This study focused on behavioral intention rather than actual adoption. Future research should investigate the gap between intention and real-world behavior, possibly through longitudinal studies or observational methods.-Policy and institutional factors**:** Future work could also explore the role of institutional trust, regulatory frameworks, and water governance in shaping farmers' decisions, particularly in regions where treated wastewater infrastructure is under development.
By addressing these areas, future research can contribute to more effective strategies for promoting sustainable water reuse in agriculture—advancing both environmental resilience and public health in line with the One Health framework.
Moslem Savari: Writing – review & editing, Writing – original draft, Visualization, Validation, Supervision, Software, Resources, Project administration, Methodology, Investigation, Funding acquisition, Formal analysis, Data curation. Mohammad Shokati Amghani: Writing – review & editing, Writing – original draft, Visualization, Validation, Supervision, Software, Resources. Ashraf Malekian: Investigation, Funding acquisition, Formal analysis, Data curation, Conceptualization.
We confirm that the submitted work is my own and that copyright has not been breached in seeking its publication. Also, we declare that the submitted work has not previously been published in full, and is not being considered for publication elsewhere.