Chromium Contamination in Chayote (Sechium edule (Jacq.) Sw.): Health Risk Assessment, Producer Perceptions, and Sustainability Perspectives

Abstract

The bioaccumulation of heavy metals, such as Cr, Cd, Pb, and As, in vegetables irrigated with contaminated water represents a risk to human health. The objective of this study was to evaluate the Cr concentration in chayote fruits in sites irrigated with contaminated water from Lake Chapala and to assess the potential risk to human health using the estimated daily intake (EDI), objective risk quotient (THQ), and carcinogenic risk quotient (TCR). In parallel, interviews were conducted with local producers to understand their perceptions of the quality of irrigation water and their willingness to adopt more sustainable agricultural practices. In two of the sites and seasons, Cr concentrations exceeded the FAO-WHO limit of 2.3 mg·kg⁻¹ (from 2.49 to 4.82 mg·kg⁻¹). In all, 90% of producers used water from Lake Chapala to irrigate their crops, although most did not perform water quality analyses, despite 32% being aware that the water was contaminated. The results highlight the need to implement strategies to increase awareness of the quality of irrigation water, as well as the need for comprehensive public policies that combine technical assessments and producer perceptions to reduce the risks associated with the use of contaminated irrigation water to promote sustainable agricultural production.

1. Introduction

Pollution from heavy metals, such as Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd, and Pb, has become a major global concern as it affects environmental and human health [1]. These pollutants originate from natural sources, such as forest fires, volcanic activity, and biogeochemical cycles [2], as well as from anthropogenic activities, such as industrial operations, mining, fossil fuel use, and the application of inorganic agricultural fertilizers and pesticides [3]. Even at low concentrations, heavy metals can be toxic due to their non-biodegradability, long half-lives, and high potential for bioaccumulation [4]. One of the main routes of heavy metal exposure is through the consumption of contaminated foods [5], with the ingestion of contaminated vegetables and fruits being the primary route of human exposure to these pollutants [6]. Edible plants, a fundamental food source, provide essential minerals, vitamins, and antioxidants [7]. However, research has indicated that some edible plant species absorb and bioaccumulate heavy metals in their tissues, which poses a potential human health risk [8] due to the potential development of various diseases, such as cancer, and disruptions in various body systems [9].

The bioaccumulation pathway for heavy metals in the food chain is complex and begins with the absorption of heavy metals from the soil, with plant roots constituting the main route of absorption, and continues with their transport through different plant organs [7]. It is important to note that the absorption and concentration of heavy metals in plants does not follow a linear pattern, as it is influenced by various physicochemical characteristics of both the soil and the type of crop, as well as by the environmental and production conditions that affect the crop [10,11].

Heavy metals enter the soil from various sources. The high demand for fresh water for agricultural production coupled with its scarcity have led to the use of wastewater, which may contain heavy metals, as an alternative source for crop irrigation [12,13]. In many developing countries, the wastewater discharged from industrial or residential areas is not treated and, in cases where the wastewater is treated, the treatment processes only involve primary methods that often fail to remove heavy metals [14]. The resulting use of domestic and industrial wastewater for irrigation poses a notable threat to agriculture production and is a major concern for food security [15,16] due to heavy metal contamination in the soil-crop system [17]. Thus, water pollution represents a serious risk to public health, requires substantial economic investment for its remediation, and threatens the sustainability of this vital resource for agriculture [18].

In Mexico, agricultural production is primarily carried out by small and medium-sized producers, whose diverse agricultural practices strongly affect food security [19], including the use of irrigation water contaminated with heavy metals [20]. A notable example of this can be found in the municipality of Poncitlán, where chayote (Sechium edule) crops are irrigated with water from Lake Chapala [21]. Chayote is a staple food in many regions of the country due to its nutritional value, low production cost, and accessibility, which also makes this crop an important source of employment [22]. In Poncitlán, the current irrigation practices, which utilize water from Lake Chapala, can expose chayote crops to heavy metal contamination [21]. Lake Chapala, which is fed by the Lerma River and discharges into the Pacific Ocean through the Santiago River, is found within the Lerma-Chapala basin, one of the most important basins in Mexico [23]. Unfortunately, Lake Chapala has been severely impacted by pollution from human activities, as its catchment area includes important urban, industrial, agricultural, and livestock regions, making it one of the most polluted water bodies in Mexico [24]. In addition to the presence of heavy metals, various contaminants have been reported, including polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), pesticides such as glyphosate and malathion, and herbicides like paraquat [25,26,27]. In its upper section, Lake Chapala receives wastewater from the chemical, metallurgical, and textile industries, while its middle section is contaminated by waste from thermoelectric plants, petrochemical plants, fertilizer factories, fruit packing plants, poultry and pig farms, and tanning industries, in addition to untreated sewage and runoff from agricultural areas [28].

Given the potential sources of pollution in Lake Chapala, it is crucial to understand the health risks in the region associated with the presence of heavy metals in crops irrigated with its water [6]. In particular, risk assessment methods, such as those that evaluate the risk quotient [29], estimated daily intake, and risk index [30], should be used to understand the potential effects on human health associated with exposure to these contaminants [2]. Importantly, these methods quantify human exposure to heavy metals in crops, which must be established to properly design prevention and mitigation strategies aimed at lowering the potential impacts on human health. By identifying the concentrations of these contaminants in crops, the risks associated with their consumption in specific regions can be accurately assessed [6]. Identifying contaminant concentrations in crops allows for accurate risk assessment. In Mexican areas irrigated with contaminated water, Cervantes-Trejo and Leal [31] found that the non-cancer risk (THQ) for Cr in apples and the carcinogenic risk (TCR) exceeded acceptable limits, indicating a potential health risk from consuming apples grown in Chihuahua. In areas where crops are irrigated with contaminated water, such as in the region of Lake Chapala, it is essential to analyze and evaluate the risks posed by heavy metals to human health. International regulatory limits have been established for the permissible levels of Cr, with the FAO-WHO setting a maximum limit of 2.3 mg·kg⁻¹ for Cr in vegetables [32].

Therefore, the objective of this study was to evaluate the concentration of Cr in chayote fruits (S. edule) in four sites irrigated with water from Lake Chapala in Poncitlán, Jalisco, Mexico, and the potential risk to human health associated with consumption. In parallel, this study aimed to understand the perceptions of local producers in the municipality of Poncitlán regarding the quality of irrigation water and potential contamination, as well as their willingness to adopt more sustainable agricultural practices.

2. Materials and Methods

2.1. Study Area and Sampling Sites

Agriculture is the main land use type in the municipality of Poncitlán, comprising an important part of its economy [33]. This municipality is located in the Ciénega region of the state of Jalisco and is one of the seven municipalities (i.e., Chapala, Poncitlán, Ocotlán, Jamay, Jocotepec, Tuxcueca, and Tizapán el Alto) that border Lake Chapala. The elevation in the municipality ranges from 1520 to 2350 m.a.s.l., with most of the area experiencing a semi-warm and semi-humid climate. The average annual temperature in the region is 19.8 °C, with minimum and maximum temperatures ranging from 9 °C to 30.3 °C, respectively. The average annual precipitation is 939 mm, while the average accumulated precipitation is 637.72 mm [33]. Approximately 50.22% of the land in the municipality of Poncitlán is used for agricultural purposes. The sampling sites are shown in Figure 1, and the coordinates of each sampling site are shown in

Table 1. Coordinates of the sampling sites in the municipality of Poncitlán, Jalisco.

Site	Identifier	Coordinates
Confluence zone (Lake Chapala-Santiago River)	S1	20°19′59.42″ N, 102°47′80.41″ W
Site 1	S2	20°19′20.99″ N, 102°47′49.59″ W
Site 2	S3	20°18′39.90″ N, 102°48′23.88″ W
Site 3	S4	20°18′37.76″ N, 102°48′27.56″ W

.

2.2. Collection of Plant Material

Chayote samples were collected at sites located in the chayote-producing area on the shores of Lake Chapala. Site selection was based on two main criteria: (1) access to the sampling area was permitted only with the prior consent of producers, and (2) the selected sites had to be irrigated with water from Lake Chapala. Chayote fruits were collected during the dry and rainy seasons; five samples were taken per site (n = 5) (Figure 2). The samples were placed in polyethylene bags and stored at −20 °C until analysis.

2.3. Sample Preparation and Heavy Metal Determination

The Cr content in the samples was determined according to the methodology of Li et al. [34], with some modifications. The samples were first washed with deionized water and then dried in a drying oven at 80 °C (Terlab, Model TE-FH45DM, El Arenal, Mexico) until achieving a constant weight. Each sample was ground and homogenized, and 0.5 g was taken for acid digestion with 5 mL of concentrated nitric acid (HNO₃) on a heating grid (Ika, Model C-MAG HS 4, Wilmington, NC, USA) at 95 °C for 2–3 h until a clear solution was obtained. After digestion, the samples were filtered using Whatman (Whatman PLC, Maidstone, UK) No. 42 filter paper and diluted with deionized water to a final volume of 50 mL. The Cr content was determined by microwave plasma atomic emission spectroscopy (MP-AES) (Model 4200, Agilent Technologies Inc., Santa Clara, CA, USA). Calibration curves were prepared with standard solutions (Sigma-Aldrich, St. Louis, MO, USA) at concentrations of 0, 1, 2, 5, and 10 mg·L⁻¹.

2.4. Health Risk Assessment

2.4.1. Estimated Daily Intake (EDI)

The estimated daily intake (EDI) denotes the estimated daily intake of heavy metals (mg·person⁻¹·day⁻¹) and was calculated with Equation (1) [35]:

$$EDI={\displaystyle \frac{C\times IR\times CF\times EF\times ED}{BW\times AT}},$$

(1)

where C is the concentration of the metal in chayote fruits (mg·kg⁻¹ dry weight); IR is the ingestion rate of the fruit (0.1 kg·person⁻¹·day⁻¹ fresh fruit weight), with a reference consumption value of 100 g per day (specific data on chayote consumption are unavailable for the Mexican population); CF is the conversion factor (0.085) from fresh fruit weight to dry fruit weight [36] given that the water content of chayote is between 90 and 95% [37]; EF is the frequency of exposure (days·year⁻¹); E_d is the exposure duration (women in Mexico: 78.1 years; men in Mexico: 72.4 years) [38]; ED is the average time of exposure for noncarcinogenic substances (365 days·year⁻¹ × years of exposure); and BW is the average body weight (adult women: 68.7 kg [39]; adult men: 76.5 kg [39]).

2.4.2. Target Hazard Quotient

The target hazard quotient (THQ) estimates the noncancer risk due to heavy metal exposure and is the ratio between the EDI and the oral reference dose (RfD). The RfD represents an estimate of daily exposure to which a human population may be continually exposed over a lifetime without an appreciable risk of deleterious effects. The RfD values were based on a value of 9 × 10⁻⁴ mg·kg⁻¹·bw⁻¹ day⁻¹ for Cr [40] (the value of hexavalent Cr was used because only total Cr was analyzed). The THQ was calculated with Equation (2) [35]:

$$THQ={\displaystyle \frac{EDI}{RfD}}$$

(2)

THQ values < 1 indicate a non-carcinogenic risk associated with the ingestion of chayote fruits. If THQ values > 1, then substantial health hazards may exist.

2.4.3. Target Cancer Risk

The target cancer risk (TCR) represents the risk posed to the adult population due to lifetime intake, according to the model proposed by the United States Environmental Protection Agency (EPA). TCR was calculated with Equation (3) [35]:

$$TCR=EDI\times CPSo,$$

(3)

where CPSo is the oral cancer slope factor attributed to the carcinogenic metal equal to 0.16 mg·kg⁻¹·day⁻¹ for Cr [40] (the value of hexavalent Cr was used because only total Cr was analyzed). TCR values ≤ 10⁻⁶ are considered low; values of 10⁻⁴ to 10⁻³ are considered moderate; values of 10⁻³ to 10⁻¹ are considered high; and values of 10⁻¹ are considered very high [41].

2.5. Perceptions and Irrigation Practices of Chayote Producers

We conducted interviews to assess the irrigation practices, perceptions of possible water contamination from Lake Chapala, and willingness to adopt more sustainable agricultural methods of the chayote producers in the municipality of Poncitlán. The interviews allowed us to gather valuable insights into the perceptions and practices of producers to evaluate the relationship between the use of water from Lake Chapala, pollution risks, and the need to promote sustainability and food security in the region.

Interviews were conducted with chayote producers who voluntarily agreed to participate in the study and provided informed consent before completing the questionnaire. Confidentiality and anonymity of responses were established through a privacy notice provided at the beginning of the questionnaire. Total participation (35%) corresponded to 19 producers out of a total of 54 in the representative producer areas. This was a sufficient sample, according to Creswell [42], who mentioned that in qualitative research, sample sizes vary from 1 to 50 cases. The survey was previously reviewed to ensure that the questions related to the perceptions of farmers regarding the contamination problem in the area were clear and well understood. The semi-structured questionnaire, which combined closed and open-ended questions, covered the following topics:

(1)

Use of Lake Chapala water: Do you use Lake Chapala as a water source to irrigate your crops?

(2)

Perception of water contamination: Do you consider Lake Chapala to be a source of contamination?

(3)

Water quality analysis: Do you perform any water quality analysis on irrigation water?

(4)

Impact of pollution on human health: Do you believe that water pollution could be harmful to human health?

(5)

Product marketing: Where are your products primarily marketed?

(6)

Training in sustainable practices: Do you consider it important to receive training in sustainable production? What type of training would be most useful to your production?

2.6. Statistical Analysis

Chromium data are expressed as mean ± standard deviation. Normality was assessed using the Shapiro–Wilk test, and homoscedasticity was evaluated with the Levene test. An analysis of variance (ANOVA) followed by a Tukey test were used to compare groups. Statistical analyses were performed using SPSS Statistics 21.1.0 (IMB, Armonk, NY, USA). A significance level of p ≤ 0.05 was considered for all tests. For the interview data, the analysis focused on identifying patterns and trends in the responses of the producers. Closed-ended questions were analyzed descriptively, while open-ended questions were categorized. This approach allowed us to highlight the perceptions and practices of producers regarding: (1) the use of Lake Chapala water for irrigation, (2) perceptions of contamination, (3) water quality analysis practices, (4) human health concerns, (5) chayote commercialization, and (6) interest in receiving training in sustainable agricultural practices.

3. Results

3.1. Chromium Concentrations in Chayote Fruits

In comparison with sites S1 and S2, sites S3 and S4 exhibited the highest Cr concentrations during the rainy season, with values of 3.64 mg·kg⁻¹ and 2.70 mg·kg⁻¹, respectively, as well as during the dry season, with concentrations of 3.61 mg·kg⁻¹ and 4.82 mg·kg⁻¹, respectively. These results exceed the FAO-WHO limit of 2.3 mg·kg⁻¹ for vegetables [32]. The ANOVA revealed statistically significant differences in Cr concentrations, both between sampling sites and between seasons (p < 0.001). During the dry season, the S4 site had significantly higher Cr concentrations compared to those of the S1, S2, and S3 sites (p < 0.001 for all comparisons). In the rainy season, S3 showed higher Cr concentrations than those of the S2, S1, and S4 sites (p < 0.001, p = 0.006, and p = 0.020, respectively). Additionally, significant seasonal differences in Cr concentrations were observed at the S4 site (p < 0.001) (Figure 3). The results of this study indicate that Cr contamination was present in the chayote fruits sampled from the four study sites. The Cr concentrations varied across different sites and seasons, suggesting that Cr accumulation in chayote fruit is influenced by local and temporal factors. Notably, the S3 and S4 sites showed the highest Cr concentrations, especially during the dry season (Figure 4).

3.2. Health Risk Assessment

The health risk assessment for the consumption of chayote fruits from each of the sampling sites indicated that adults (women and men) were exposed to Cr through chayote consumption. The EDI values for women and men revealed slight variations in intake across different locations, with women generally showing a marginally higher daily intake compared to men. Of the four sites, S4 presented the highest risk of chromium exposure, with the highest EDI values for both women and men. Similarly, S3 also showed elevated EDI levels for both genders, although with slightly lower values. In contrast, S1 and S2 were associated with lower Cr intake among consumers of chayote fruits (

Table 2. Estimation of daily intake (EDI) of Cr from the consumption of chayote fruits of the municipality of Poncitlán.

	S1	S2	S3	S4	Average
Women	0.000298	0.000291	0.000449	0.000465	0.000376
Men	0.000267	0.000261	0.000403	0.000418	0.000337

).

THQ and TCR were calculated assuming a daily intake of 100 g, which corresponds to consumption seven days a week. Given that no specific data on chayote consumption are currently available for the Mexican population, this estimate was made taking into consideration the possibility of higher consumption. The THQ showed the potential risk of chromium exposure for women and men in different sites. Sites S4 and S3 exhibited the highest values, indicating a greater risk for the exposed population. In contrast, sites S1 and S2 had lower values, suggesting a lower risk compared with the other two sites. The overall averages for women and men were 0.41724 and 0.37469, respectively, reflecting moderate chromium exposure among chayote consumers in these sites (

Table 3. Estimation of noncarcinogenic (THQ) and carcinogenic (TCR) risks in adults due to the consumption of chayote fruits contaminated with Cr in the municipality of Poncitlán.

		S1	S2	S3	S4	Average
THQ	Women	0.33063	0.32307	0.49835	0.51691	0.41724
	Men	0.29691	0.29012	0.44753	0.46420	0.37469
TCR	Women	4.76 × 10−5	4.65 × 10−5	7.17 × 10−5	7.44 × 10−5	6.00 × 10−5
	Men	4.27 × 10−5	4.17 × 10−5	6.44 × 10−5	6.68 × 10−5	5.39 × 10−5

RfD = 9 × 10⁻⁴ mg kg⁻¹ day⁻¹ of Cr [35]; CPSo = 0.16 mg kg⁻¹ day⁻¹ of Cr [35].

). Given that the THQ values for both sexes at all sampling sites were <1, a noncarcinogenic risk associated with chayote consumption was identified. The TCR showed the potential cancer risk due to chromium exposure. The average for women and men reflected moderate exposure (10⁻⁵) and cancer risk in the population of chayote consumers. The highest values were found at sites S4 and S3, indicating a higher cancer risk for the population exposed in these locations. On the other hand, sites S1 and S2 had lower values, suggesting a lower risk (Table 3).

Using the Cr concentrations in chayote fruits and the assumed consumption values, the estimation of the potential health risks associated with chayote consumption indicated that the levels of Cr in chayote did not pose a notable risk to the health of the general population. However, variability was observed in Cr concentrations among sampling sites, with sites S3 and S4 exhibiting the highest levels. It is important to note that these estimates were based on a theoretical consumption scenario and did not account for individual factors such as age or specific eating habits.

3.3. Analysis of the Perceptions and Irrigation Practices Among Producers

Overall, 90% of the chayote producers interviewed in the municipality of Poncitlán used water from Lake Chapala to irrigate their crops (Figure 5A). When asked about the potential of the lake as a source of contamination, 32% of producers believed it could be a potential source of contamination, while 58% did not believe it to be an environmental issue (Figure 5B). In addition, 95% of the producers did not conduct any type of analysis on their irrigation water (Figure 5C). With regard to the perceived impact of water contamination on human health, 37% of the producers acknowledged that contaminated water could be harmful, while 48% did not express this concern (Figure 5D).

In all, 63% of the chayote producers interviewed in this study primarily marketed their products in the “Mercado de Abastos” in the municipality of Guadalajara, while 37% relied on intermediaries as their main means of marketing. Of the 19 producers interviewed, 15 (80%) responded affirmatively when asked about the importance of receiving training for sustainable production, while 4 producers stated that such training was not relevant (Figure 6A). Of those open to receiving training, 33% communicated the need to learn about the production of organic fertilizers, 20% preferred training in agricultural practices that promote sustainability, 27% were interested in increasing agricultural production, and the remaining 20% requested general training (Figure 6B).

While most producers recognized the importance of training in sustainable production, none considered the quality of irrigation water to be a key factor for crop sustainability. This revealed an important disconnect between their perceptions, knowledge, and the potential implementation of sustainable agricultural practices.

4. Discussion

The accumulation of contaminants in edible plant parts, particularly heavy metals like Cr, may pose health risks to consumers, raising important concerns regarding food safety worldwide [43]. In this context, the permissible limits have been established by the National Food Safety Standard (GB 2762-2017) [44], which has set a maximum limit of 0.5 mg·kg⁻¹ for Cr in vegetables and plant products. On the other hand, FAO-WHO [32] has established a limit of 2.3 mg·kg⁻¹ for vegetables (fresh weight). Cr is classified as a class A carcinogen due to its high toxicity by the International Agency for Research on Cancer [45,46]. However, its potential toxicity varies depending on its valence. At low concentrations, trivalent chromium (Cr³⁺) is an essential, non-toxic trace element that may enhance insulin activity and reduce the risk of diabetes. However, at excessive levels, Cr³⁺ can exhibit long-term toxicity and carcinogenicity [46,47]. Hexavalent chromium (Cr⁶⁺) is highly mobile and easily transported to cells, making it toxic with carcinogenic and mutagenic effects [48,49,50,51], although Cr⁶⁺ can be converted to Cr³⁺ at the cellular level, which lowers risk [52,53,54].

Overall, excessive Cr consumption can cause adverse health effects, such as hypoglycemia and gastrointestinal discomfort, as well as liver, kidney, and nerve damage, potentially leading to cardiovascular problems [55,56,57]. In humans, exposure to heavy metals, such as Cr, occurs mainly through the consumption of edible plants, which accounts for ~90% of the total intake of these elements [58]. Heavy metals primarily enter plant tissues through their roots, and factors that influence absorption and accumulation include contaminated irrigation water, the use of agrochemicals, and industrial emissions [7,59]. Thus, water pollution, particularly in agricultural areas, can be an important source of contaminants for crops [60].

Lake Chapala, which receives water from 12.5% of all irrigated land in Mexico [61,62], has experienced a notable decline in water quality due to high levels of pollution in the Lerma-Chapala basin, an area with considerable agricultural and industrial activity [63,64,65,66]. In addition to heavy metals, various contaminants related to the use of fertilizers and agrochemicals have been reported [67], as well as waste generated by tourism activity [68]. The basin spans several states and receives water that has been contaminated by various activities [62]. As a result of the diverse water uses and wastewater discharges in the basin, the use of irrigation water from Lake Chapala constitutes the indirect reuse of treated and untreated wastewater [66]. In Mexico, irrigating with wastewater is common due to the scarcity of potable water. Indeed, only 58% of wastewater is treated before being reused or returned to water bodies [69]. In the Poncitlán area, this lack of treatment exposes crops, such as chayote, to pollutants from the industrial and municipal discharges from the Lerma River [70].

Recent studies have detected Cr in the water of Lake Chapala, with concentrations that range from 0.036 to 0.084 mg·L⁻¹ [21] and 0.067 to 0.095 mg·L⁻¹ [60]. These values are below the limits set by the Mexican Official Standard NOM-001-SEMARNAT-2021 [71], which regulates the permissible pollutant levels in wastewater discharges into national water bodies. In contrast, Maldonado-Villegas [21] found no detectable levels of Cr in soil samples from the region, which could indicate that soil contamination may not be a significant source of Cr in chayote fruits. The Cr concentrations present in chayote fruits could be related to the levels present in irrigation water, given that it comes mainly from Lake Chapala. Thus, chayote fruits could bioaccumulate Cr present in irrigation water. The highest Cr concentration was observed at site S4 during the dry season (4.82 mg·kg⁻¹), which was much higher than the lowest levels recorded during the rainy season (2.70 mg·kg⁻¹), suggesting that climatic conditions may influence Cr bioaccumulation in chayote fruits at this site. Compared to sites S3 and S4, the Cr concentrations at sites S1 and S2 were significantly lower, which could be due to differences in agronomic management between plots, including variability in the irrigation frequency. This could be explained by the water quality improving during the rainy season due to a decrease in pollutants, given that seasonal factors affect the natural dynamics of the lake, including the water supply and the recovery period [72]. In other studies, similar concentrations have been reported; for example, Zaragoza et al. [73] found Cr concentrations ranging from 1.98 to 4.47 mg·kg⁻¹ in alfalfa crops irrigated with wastewater in the municipality of Zumpango, state of Mexico. In a study conducted in San Luis Potosí, Loredo-Tovías et al. [74] detected Cr concentrations between 1.22 and 1.36 mg·kg⁻¹ in lettuce plants irrigated with water from a wastewater treatment plant. Cervantes-Trejo et al. [75] observed higher Cr concentrations (8.9 µg·g⁻¹) in walnut fruits from orchards irrigated with river water in the municipality of Aldama, Chihuahua. Similarly, Rayas-Amor et al. [76] analyzed the presence of Cr in water, soil, and strawberry fruits, finding a significant correlation (0.97) between Cr concentrations in irrigation water, its transfer to the soil, and its presence in the fruits.

With the exception of the S1 site in the dry season and the S2 site in the rainy season, Cr concentrations exceeded the FAO-WHO limit of 2.3 mg·kg⁻¹ [32]. However, the daily consumption of 100 g of chayote represents a noncarcinogenic risk, as the THQ values were <1. An increase in chronic kidney disease (CKD) has been recorded, especially in Poncitlán, which has a high CKD mortality rate in people under 20 [77]. While a direct link between chromium and kidney disease has not been proven, the presence of this metal in the water and the high CKD incidence in riverine communities suggest that exposure to heavy metals may contribute. Further studies are needed to assess their specific impact on local health. Based on the TCR values, which were below the threshold of 10⁻⁵ in the present study, and given that values between 10⁻⁴ and 10⁻³ are considered moderate, the estimated carcinogenic risk from consuming Cr-contaminated chayote fruits from Poncitlán is acceptable for the population. In contrast, Cervantes-Trejo and Leal [31] reported a TCR value for apples of 9.58 × 10⁻⁴, which exceeded the threshold limit, indicating a potential carcinogenic risk from ingesting apples over time.

Although the carcinogenic and noncarcinogenic risk estimates were low in the present study, it is important to note that chayote is not the only crop grown in the region. Other crops, such as alfalfa, agave, guava, sorghum, corn, squash, onion, chili, beans, chickpeas, tomatoes, lettuce, and wheat, are also cultivated [78]. Therefore, further studies are needed to assess the impact of using contaminated water for irrigation in other crops in the region and the long-term effects on human health. In this context, policymakers and stakeholders must collaborate to develop and implement strict regulations, monitoring programs, and remediation techniques. Public awareness campaigns are also needed to educate farmers about the associated risks and to promote safe agricultural practices that minimize exposure to contaminants [79]. The results of the present study for the municipality of Poncitlán indicate that there is a lack of awareness among agricultural producers about the importance of conducting water quality analyses for irrigation, although producers expressed interest in receiving training in sustainable practices. This reflects a disconnect between the perceptions of risks and the concrete actions needed to mitigate them. Indeed, although 90% of producers use water from Lake Chapala for irrigation, only 32% were aware that the water was contaminated, and only 37% recognized the health risks associated with water quality.

Given that farmers are the primary users of wastewater, increasing their awareness of the importance of water quality may facilitate an effective transition towards responsible and sustainable agricultural practices. Woldetsadik et al. [80] noted that farmers tended to focus on benefits and market opportunities while often overlooking consumer-related benefits. However, Deng et al. [81] emphasized that improving awareness of water pollution risks among farmers increased their willingness to protect this resource. This contrast in viewpoints highlights the need for strategies to raise awareness that emphasize economic benefits and address broader concerns.

A comprehensive approach that emphasizes collaboration between policymakers and farmers and that goes beyond technical environmental risk assessments to consider the perceptions of producers is needed [82]. Indeed, the lack of knowledge about the quality of irrigation water among chayote producers in Poncitlán underscores the urgent need for educational strategies and awareness campaigns that link sustainability with responsible agricultural practices. Without these strategies, such as those focused on analyzing the quality of irrigation water, current contamination risks will continue to threaten public health and the sustainability of crops and the environment [18]. Furthermore, promoting public policies that entail constant monitoring, remediation, and training—coupled with a participatory approach that values both scientific data and the perceptions of stakeholders—is essential for mitigating health risks [83]. Importantly, decision makers must consider all aspects of sustainability to ensure the long-term health of water resources [84]. To this end, conducting water quality analyses is a fundamental component of a broader strategy aimed at promoting sustainability in the Lake Chapala region, involving all three levels of government, educational institutions, producers, and society as a whole.

5. Conclusions

We found that Cr contamination in chayote fruits varied significantly between sampling sites and seasons. This can be attributed to both the climatic conditions and the management practices of producers in the region, which result in seasons of higher and lower water extraction from Lake Chapala. Although Cr concentrations did not pose a notable risk to human health—in terms of noncarcinogenic and carcinogenic risks—notable variability in the accumulation of this metal was observed, particularly at sites S3 and S4. This variability highlights the need to raise awareness among producers about the risks associated with using contaminated water for crop irrigation, especially given that most of the producers interviewed did not conduct water quality analyses. Consequently, future research could explore the effectiveness of implementing training programs that promote proper water quality management among local farmers. While the estimated risk was low, the consumption of crops irrigated with contaminated water from Lake Chapala warrants comprehensive and coordinated attention.

In Mexico, the absence of adequate regulations and standards that establish maximum permissible limits for elements, such as Cr and other heavy metals, in vegetables poses a threat to public health and the environment. This regulatory gap jeopardizes food security and limits the ability of authorities to control crop quality. Therefore, it is crucial to advocate for the implementation of periodic monitoring programs to effectively enforce regulations regarding the permissible levels of contaminants, including Cr and other metals, in crops in the region. These programs would ensure consistent oversight and facilitate timely actions to reduce contamination risks. It is also crucial to establish regulations that define maximum allowable levels for contaminants, such as Cr and other heavy metals, in crops. Simultaneously, this issue must be addressed by designing public policies that enhance consumer protection and promote responsible agricultural practices. These policies should focus not only on immediate benefits but also on long-term risks. Finally, future research should focus on cost-effective remediation strategies for heavy metal contamination in irrigation water in Lake Chapala. In addition, adopting stricter regulations and implementing continuous water quality monitoring programs in the lake are essential to ensure agricultural sustainability, improve food security, and protect public health.

The lack of detailed information on the health risks posed by heavy metals, such as Cr, in the crops of the Poncitlán area is of critical concern. To promote sustainable chayote production in this area and the broader Lake Chapala region, comprehensive strategies must be implemented that include promoting safer agricultural practices, continuous soil monitoring, water quality monitoring, and adherence to international food safety standards. To this end, collaboration among authorities, scientists, farmers, and the community is vital to safeguarding public health and ensuring the long-term sustainability of agricultural production.