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Article

Contamination by Cadmium and Lead in Sugarcane and Its Derived Products in Ecuador

by
María Alcívar
1,
Edwin Vinueza
1,
Beatriz Pernía
1,*,
Xavier Álvarez-Montero
2 and
Alejandro Gallardo
1
1
Facultad de Ciencias Naturales, Universidad de Guayaquil, Av. Raúl Gómez Lince s/n y Av. Juan Tanca Marengo, Guayaquil 090150, Ecuador
2
Departamento de Ciencias de la Vida y Agricultura, Universidad de las Fuerzas Armadas-ESPE, Hda. Zoila Luz, vía Sto. Domingo-Quevedo km 24, Santo Domingo 230118, Ecuador
*
Author to whom correspondence should be addressed.
Agriculture 2024, 14(12), 2121; https://doi.org/10.3390/agriculture14122121
Submission received: 27 October 2024 / Revised: 10 November 2024 / Accepted: 13 November 2024 / Published: 23 November 2024
(This article belongs to the Section Agricultural Product Quality and Safety)
Browse Figures
Versions Notes

Abstract

:
(1) Background: This research examines the contamination levels of cadmium (Cd) and lead (Pb) in sugarcane and its derived products in Ecuador, addressing the significant issue of heavy metal pollution in the country’s agricultural lands. The primary aim of this study was to quantify the concentrations of Cd and Pb in sugarcane and the products derived from it, which are available to the Ecuadorian market. (2) Methods: Samples of the most-cultivated sugarcane varieties in the country, including ECU-01, ECU-02, Cenicaña (CC85-92), and Ragnar, were obtained. To ascertain the source of contamination in the derived products, the brands of panela, white sugar, and brown sugar that are most widely consumed in the country were selected. An atomic absorption spectrophotometry analysis was performed with a graphite furnace. (3) Results: All cane varieties presented Cd and Pb contamination. The variety with the highest levels of heavy metals was Ragnar, with average values of 4.32 mg kg−1 of Pb and 0.15 mg kg−1 of Cd. In the derived products, Pb was found to exceed the maximum limits stipulated in national and international regulations (0.5 mg kg−1) in panela (2.3 mg kg−1) and white sugar (1.6 mg kg−1) sold by one of the brands. (4) Conclusions: It was found that lead (Pb) contamination is directly linked to the use of contaminated sugarcane as a raw material, along with bleaching agents.

1. Introduction

Food safety and human health are directly related to the growing global problem of contamination of food by heavy metals [1]. Studying the metal contents in food is relevant to ensure their quality and safety throughout the production chain, from cultivation and transformation to transport and consumption of the product.
Heavy metals are natural elements in the environment; however, their increased concentrations have been linked directly to sources of anthropogenic origin [2]. Among the activities that lead to heavy metal pollution are those associated with the metal smelting industry, as well as agricultural activities such as irrigation with contaminated water or using phosphate fertilizers and pesticides [3,4,5]. In this regard, the growing use of contaminated water and phosphate fertilizers, including heavy metals, for the growth of crops has induced worldwide concern [6].
Among the heavy metals, cadmium (Cd) and lead (Pb) have been shown to be very toxic to humans [2]. Cd is one of the most dangerous metals due to its effects on the environment and human health [7]. It accumulates in different tissues and organs, causing teratogenic, nephrotoxic, hepatotoxic, and carcinogenic effects [7]. In humans, exposure to cadmium can result in toxic effects such as stunted growth, as well as toxicity in the kidneys and liver. On a molecular level, Cd contributes to the generation of reactive oxygen species, causes DNA damage, and hampers DNA repair processes, which can lead to cancer [8].
Pb, the second-most dangerous element, has persistent distribution characteristics and toxicity in ecosystems [9]. There have been an increasing number of studies on this metal related to food safety due to its bioaccumulation and transference capacity from crops to human beings [8]. Considering anthropogenic causes, the primary Pb sources are agricultural inputs and industrial and municipal discharges [10].
The effects of Pb on human health include damage to the nervous and digestive system, hypertension, kidney failure, hematopoietic disorders, reticulocytosis, and cancer; furthermore, in children, it can cause delayed mental development, attention deficit, and hearing impairment [11,12,13]. Moreover, Pb triggers oxidative stress and increases sensitivity to this type of stress, resulting in higher estrogen levels, which represent a significant risk factor for breast cancer [14]. Additionally, elevated levels of Pb in the blood affect behavior, cognitive function, and postnatal development; cause delays in puberty; and impact the hearing ability of infants and children [15]. Furthermore, anorexia, anemia, brain damage, vomiting, and diseases of the circulatory and nervous systems are notable examples of the adverse effects of Pb contamination [16].
Both metals can accumulate in the body over time, leading to chronic health conditions and increasing the risk of various diseases. Assessing heavy metal levels in food is crucial for public health, as contaminated food is a primary pathway for human exposure to these toxic substances [17,18,19,20]. The consumption of foodstuffs containing elevated levels of Cd and Pb can result in serious health consequences, including developmental delays in children, diminished cognitive function, and increased susceptibility to chronic illnesses. Therefore, monitoring and regulating heavy metal concentrations in food products is essential to safeguard the health of the population and mitigate the risks associated with heavy metal exposure.
In Ecuador, there is evidence of Cd and Pb contamination in agricultural soils. Pernía et al. [21] have stated that studies in the country provide evidence of Cd contamination in coffee, African palm, banana, cocoa, rice, and plantain crops. Pb contamination in rice, coffee, and soybean crops has also been demonstrated [22,23,24,25,26].
One of the most economically important crops in Ecuador is sugarcane, which has multi-purpose properties and plays a vital role in providing food additives and inputs for the sugar and bioenergy industries. Its economic value stands out as it has a high production performance; is easy to handle, store, and transport; and it can be processed locally to generate products with added value, such as white and brown sugar, panela, molasses, ethanol, and energy [27,28,29].
Sugar is of greater importance among cane derivatives, as its worldwide consumption has tripled in the last 50 years and is expected to continue increasing [30]. For this reason, it is of economic and social importance globally to be used as a raw material in most of the products consumed by the world population. Therefore, the concentrations of heavy metals in sugarcane and its derivatives are both a national and international concern [31].
In Ecuador, sugarcane crops and their by-products are the fundamental basis for the national cuisine [32,33]. Nonetheless, there is no information about Cd and Pb contamination in sugarcane, and there are also no national regulations regarding their permitted limits in sugarcane or its by-products. Therefore, it is necessary to delve into health and food safety with respect to heavy metal toxicology in food in order to mitigate their effects on human health.
Considering the history of contamination by Cd and Pb in the agricultural soils of Ecuador, the hypothesis was that sugarcane (and, therefore, their derived products) could be contaminated with these metals. For this reason, the investigation aimed to determine the concentrations of Cd and Pb in sugarcane varieties ECU-01, ECU-02, Cenicaña (CC85-92) and Ragnar, as well as in their derived products (panela, white and brown sugar) marketed in Ecuador. As such, we propose to reduce the incidence of Cd and Pb in sugarcane crops and their derived products.

2. Materials and Methods

2.1. The Study Area for Obtaining Sugarcane

The study area for sugarcane was delimited in El Triunfo Canton, part of the Guayas province, and its lower river basin. It is located in the center of the coastal region of Ecuador, as indicated in Figure 1, and has a population of 50,060 inhabitants [34]. It has a warm and humid climate (Tropical Monsoon), with an average temperature of 26 °C and an extensive plain crossed from east to west by the Bulubulu River, which receives the waters of the rivers Barranco Alto, La Isla, and Culebras [34].
Due to its extraordinary agricultural, commercial, industrial, and livestock development, El Triunfo Canton is considered one of the most critical links in the economy of the Guayas province and the country. El Triunfo Canton has an area of 394.98 km2, of which the industrial sugarcane coverage represents the most significant extent, placing it as the leading economically productive crop by far (Figure 1). It extends over a representative area of 118.38 km2, corresponding to 29.97% of the territory [34].

2.2. Characterization of Sugarcane Varieties

The varieties selected for the present study are widely cultivated in Ecuador and have been described as the most productive and resistant to pests: ECU-01, ECU-02, CC85-92, and Ragnar [35].
The ECU-01 variety (El Triunfo, Ecuador) comes from a cross of the SP81-6215 × SP80-1816 varieties (Sao Paulo, Brazil). In contrast, the ECU-02 variety (El Triunfo, Ecuador) originated from the cross between the V71-51 x SP82-3530 varieties (Sao Paulo, Brazil). Both were bred at the Canavieira Technology Center (CTC) in Brazil [36]. Efficiency inspections were conducted in each selection state to continue improving their performance. They were sown at CINCAE and in the country’s three most crucial sugar mills, with Ingenio San Carlos and Valdez being two of the latest mills.
Cenicaña (CC85-92, Valle del Cauca, Colombia), identified as CC, is a variety of sugarcane that has been produced in Colombia since 1981 by the Centro de Investigación de la Caña de Azúcar de Colombia. Cenicaña was introduced in Ecuador by the Centro de Investigación de la Caña de Azúcar of the Unión Nacional de Cañicultores del Ecuador (UNCE) to create high-yield genotypes and, thus, obtain a certified seed of high genetic and phytosanitary quality [37].
Ragnar (Edmonton, QLD, Australia) is a variety that comes from a cross between CO 270 × 33MQ371 varieties (Ciénaga, Colombia) and is widely distributed in Ecuador. It has been cultivated for 60 years in the country, occupies 70% of sugarcane crops, and has excellent yields and tolerance to pests.

2.3. Obtaining and Collecting Cane Samples

The samples were acquired from plots for sugarcane cultivation in El Triunfo, Guayas Province, Ecuador (Figure 1). The same sugarcane growers donated the varieties ECU-01, ECU-02, CC85-92 (CC), and Ragnar. In addition, sugarcane of the CC85-92 variety with (CC2) and without glyphosate maturing (CC1) was purchased to verify whether this product was a source of heavy metals. Nine samples of each variety of sugarcane in the maturity stage were obtained and analyzed, with an average size of 0.5 ± 0.01 m and an average weight of 0.25 ± 0.02 kg. The samples were collected during May, which corresponds to the dry season.
Once the samples were obtained, they were washed with distilled water and dried in an drying oven (Memmert, Schwabach, Germany) at 80 °C for four days to reduce their moisture levels. They were placed in labeled plastic bags, according to the variety, for conservation and proper transport. In Guayaquil, samples were transferred to the Heavy Metals Laboratory of the Undersecretary of Quality and Safety.

2.4. Sugarcane Derivative Sampling Sites

The study area was delimited to the main cities of Ecuador: Guayaquil and Quito. Ten samples of granulated panela, white, and brown sugar were collected from the most commercialized brands (denoted M1, M2, and M3) in the country.
The Metropolitan District of Quito is one of the eight Cantons in the Pichincha province, located in the western mountain range of the Andes. Quito is one of the most populated cities in Ecuador and may be the most populated Canton by 2020 [38,39]. It has approximately 2,239,191 inhabitants, according to the last population and housing census carried out in Ecuador [30,31]. In terms of mortality data, the leading causes are cerebrovascular diseases, diabetes, and circulatory diseases [40], which could be caused by contamination with heavy metals. In addition, the causes of mortality in children aged 10–19 are nervous system diseases. Regarding the sampling points, supermarkets and a bakery, where the majority of the population goes, were selected.
Guayaquil is the most populated city in the country, with approximately 2,350,915 inhabitants, due to its location, trade, seaport, and other factors that have contributed to the increase in its population and internal migration [40,41]. It occupies 6027.05 km2 of the territory in the central part of the Guayas province in the Coastal Region of Ecuador [41]. Mortality data showed an increase in the incidence of cancer in this city, with eating habits also mentioned as a determining factor in this increasing disease [42]. As for the sampling points, the Municipal Market and the Supermarket were chosen, where the purchases of the different products were made.

2.5. Sample Analysis

The samples of sugarcane and its derivatives were ground in a porcelain mortar. The powder was placed into previously washed containers with a 1% nitric acid solution (Merck, Boston, MA, USA) and plenty of ultra-pure water (0.054 μS cm−1). Then, 0.5 g of each sample was weighed on an analytical balance (Sartorius) in Teflon glasses (CEM Corporation, Charlotte, NC, USA) and digested in Microwave Digestion System (CEM Corporation, Matthews, NC, USA), according to EPA method 3051, placing 6 mL of 65% concentrated nitric acid.
The Cd and Pb concentrations were analyzed using an atomic absorption spectrophotometer with a graphite furnace (Variam 220Z Spectra, Las Vegas, NV, USA), using EPA 7000 A as a reference method.

2.6. Validation

Validation of the methods used for the analysis of cadmium (Cd) and lead (Pb) was comprehensively conducted, following the guidelines established by reputable organizations (AOAC International) [43]. The assessed validation parameters included linearity, limits of detection (LOD), limits of quantification (LOQ), accuracy, and precision, employing sophisticated statistical tests to ensure reliability.
Calibration curves for Pb and Cd were generated using certified standards from Accustandard (Cd: 1 g L−1; Pb: 1000 ± 4 mg L−1). For data validation, a reference material (CRM033, Sigma-Aldrich, St. Louis, MO, USA) was analyzed, yielding recoveries of 98% for Cd and 99% for Pb. The limits of quantification (LOQs) established were 0.035 mg kg−1 for Cd and 0.09 mg kg−1 for Pb. Each analysis also included reagent blanks, duplicate samples, and spike samples to enhance the robustness of the findings.

2.7. Statistical Analysis

The results are shown as the mean ± standard deviation. An Anderson–Darling test was applied to analyze the distributed data, and a Levene test was used to check for homoscedasticity. A parametric one-way ANOVA was conducted to compare the mean concentrations of heavy metals across different sugarcane varieties and their derived products (p < 0.05). To determine the correlations between the heavy metal contents in sugarcane and those found in its derivatives, a Spearman correlation analysis was performed. The graphs and statistical tests were performed using the R and RStudio program, version 4.4.0.

3. Results

3.1. Heavy Metal Concentrations in Sugarcane Varieties

Cd and Pb were observed in every sugarcane sample. In most varieties, Cd was found at lower concentrations than Pb, with Cd levels remaining below the maximum permissible limit (MPL) in plant-based food, according to the Codex Alimentarius FAO/OMS [44], which specifically applies to stem vegetables. However, Pb concentrations were found to exceed this limit (Figure 2). The highest concentration of Cd was observed in the Ragnar variety, with an average of 0.150 ± 0.029 mg kg−1 Cd and a maximum value of 0.2 mg kg−1 of Cd, showing significant differences compared to the varieties ECU-01, ECU-02, and CC (F = 10.57; p < 0.001). In the other varieties, there were no significant differences between them, according to the Tukey test, with values that ranged between 0.026 and 0.043 mg kg−1 Cd. As can be seen in Figure 2A, only the Ragnar variety exceeded the MPL for Cd in plant-based food, according to the Codex Alimentarius (0.1 mg kg−1).
Regarding the Cenicaña variety, which was analyzed with (CC2) and without maturing (CC1), no differences were observed between its means according to the Student’s t-test (t = 0.156; p = 0.883), which implies that the maturing glyphosate did not contaminate the cane with heavy metals.
Conversely, all varieties presented Pb in high concentrations (Figure 2B). Ragnar sugarcane, which is widely cultivated in Ecuador, presented the highest Pb contamination, with a minimum value of 3.99 mg kg−1, a maximum value of 4.72 mg kg−1, and an average of 4.32 ± 0.37 mg kg−1 Pb—significantly higher than those found in the varieties ECU-01 (0.376 ± 0.241 mg kg−1), CC2 (0.150 ± 0.040 mg kg−1), CC1 (0.136 ± 0.073 mg kg−1), and EC-02 (0.122 ± 0.046 mg kg−1). According to Figure 2B, all the concentrations in the reeds were higher than the maximum limit recommended by the Codex Alimentarius FAO/OMS [44] (0.1 mg kg−1 Pb).

3.2. Cd and Pb Concentrations in Sugarcane Derivatives

None of the sugarcane derivatives presented Cd contamination, with all values being lower than the limit of detection (<0.01 mg kg−1) in all the brands studied (Table 1).
Nonetheless, contamination with Pb was observed in brand M1 (Table 1), where a higher concentration was observed in panela and white sugar, which was more significant than that in brown sugar (F = 19.25; p = 0.001).
The average Pb concentrations in panela, white, and brown sugar were 2.3 ± 1.4 mg kg−1, 1.6 ± 0.74 mg kg−1, and 0.3 ± 0.08 mg kg−1, respectively, for the M1 brand. It should be noted that, even though the samples were taken from different lots and in different cities, significant contamination by Pb was observed.

3.3. Comparison of the Concentrations Obtained in the Cane Derivatives with National and International Regulations on the Permissible Limits of Cd and Pb in Food

The considered national regulations included the Ecuadorian Technical Standards of the Ecuadorian Standardization Service for white sugar (NTE INEN 259) [45], brown sugar (NTE INEN 258) [46], and granulated panela (NTE INEN 2332) [47], while the international regulations were the Codex Alimentarius and Regulation Mercosur Technician on Maximum Limits of Inorganic Contaminants in Foods.
Pb concentrations in panela and white sugar of the M1 brand exceeded the MPL established by national and international regulations, thus representing a health risk for consumers, especially children (Figure 3).
Panela exceeded the MPL by 8.6 times, according to the INEN standard and the Codex Alimentarius, and was 43 times the Mercosur limit. White sugar exceeded the INEN/Codex and Mercosur limits by 4.6 times and 23 times, respectively. Moreover, brown sugar did not exceed the INEN/Codex MPL, but it exceeded the Mercosur limit by 2.8 times. Hence, its consumption poses a risk for the population.
Figure 4 displays a significant correlation between the Pb concentration in white sugar and its presence in the CC2 variety (rs = 0.90). Similarly, there was a strong correlation between brown sugar and the Ragnar (rs = 1), CC1 (rs = 0.9), ECU01 (rs = 0.9), and EC02 (rs = 0.70) varieties (p < 0.05). Moreover, there was a perfect correlation between raw cane sugar and the Ragnar, CC1, and ECU01 varieties (rs = 1, p < 0.05). These findings suggest that sugar contamination may originate from the sugarcane itself.

4. Discussion

4.1. Heavy Metal Concentration in Sugarcane Varieties

All cane varieties analyzed contained Cd and Pb, which confirms contamination in the crops of the El Triunfo Canton. Sugarcane and its derivatives can become contaminated with harmful metals due to irrigation water, agricultural soil, and the various fertilizers and pesticides applied during cultivation [3,5,48,49]. Furthermore, in the case of Pb, it can derive from atmospheric contamination due to burning fuels.
The presence of Cd in sugarcane can be explained by the use of phosphate fertilizers containing this metal, with an average concentration of 41.30 ± 1.65 mg kg−1 in Ecuador [24]. It has been shown that, when used in crops, a considerable fraction of this metal accumulates in plants [24]. The Pb concentrations in sugarcane also indicate crops as the source of contamination. This metal bioaccumulates in the plant and is stored in the cane trunk, which is used as a raw material to extract the sugar [5].
The variety with the highest heavy metal accumulation was Ragnar, while Cenicaña had the lowest levels. Differences in the absorption of heavy metals by varieties of the same species have been described previously. According to Shaw [50], varieties of the same plant species exposed to similar concentrations of metals can show differences in the absorption and internal distribution of metals in the plant, according to the differences in the root retention capacity of the element absorbed. For example, metals can reach the xylem through an apoplastic and simplistic pathway linked to ligands such as organic acids or phytochelatins [51]. Other factors that must also be considered are the plant development stage, the time of exposure to the metal, and the chemical species of the element at each sampling point [52].
Several studies have also observed Cd and Pb in sugarcane and its juice. Segura-Muñoz et al. [53] found high concentrations of Cd (0.018–0.067 mg kg−1) and Pb (1.76–2.28 mg kg−1) in sugarcane stems from a cultivation area near the Santa Teresa Protected Forest, as well as higher Cd (0.10–0.32) and Pb (3.5–13.8 mg kg−1) values in sugarcane grown near a municipal landfill in Ribeirao Preto, Brazil. Similarly, in Pakistan, high concentrations of Pb in sugarcane have been determined (at 3.58 mg kg−1) [48], similar to the results in the present study for the Ragnar variety. In addition, it has been determined that cane stem concentrations of Pb in India were 0.01–1.11 mg kg−1 Pb [54], lower than the levels found in this study. In Peru, lower concentrations of Cd (0.001 mg kg−1) and Pb (0.001 mg kg−1) were observed in sugarcane stems from the Moche River Basin [55]. In contrast, higher concentrations of Pb in sugarcane, ranging from 5.92 to 26.98 mg kg−1, have been reported in China [56]; it should be noted that these were irrigated with contaminated water.
Contrary to our results, Cruz-Pons et al. [57] did not find Cd or Pb in sugarcane in Tabasco (Mexico), as the cultivation soils were not contaminated with these metals. Hence, analyzing the sugarcane cultivation soils in Ecuador is essential to determine where the origin is geogenic or anthropogenic (e.g., due to the use of contaminated agrochemicals).
Based on the presented evidence, we hypothesize that the agricultural soils in the El Triunfo Canton are contaminated with heavy metals, specifically Cd and Pb. Previous studies, such as the one conducted by Vieira et al. [58], have reported significant levels of Pb in sugarcane-cultivated soils in Brazil. Additionally, research in Ecuador has indicated heavy metal contamination in agricultural soils [22,23,24,25], supporting the notion that contaminated soils can lead to the subsequent contamination of crops and their final products. Therefore, we propose that the detected concentrations of Cd and Pb in sugarcane samples may originate from these contaminated soils.
Studies carried out in Ecuador have indicated that the origin of contamination by heavy metals in the agricultural soils of the Guayas province is related to the geogenic nature of these metals and anthropogenic activities carried out in the area, as well as their residues, further highlighting the excessive use of agrochemicals as another significant source [22].
Despite genetic improvement processes for sugarcane in Ecuador, the bioaccumulation of heavy metals in crops is not being prevented, which depends directly on the environmental conditions where they are developed. The studied varieties have been introduced by crossing other species over time to obtain crops with higher yields that guarantee long-term sustainable production, such that they adapt to the environmental conditions of the Ecuadorian tropics, as well as the soil and water resource properties. Considering the results obtained in this study, regular cultivation of the Cenicaña variety is proposed due to it having the lowest percentage of both metals.

4.2. Cd and Pb Concentration in Sugarcane Derivatives

After an analysis of the products (i.e., panela, brown, and white sugar) commercialized in Ecuador, it was determined that, in the samples of M1, M2, and M3 brands, the levels of Cd were not detectable (<0.1 mg kg−1). Thus, Ecuadorian sugar does not contain Cd, in contrast to sugar from Pakistan (0.58 mg kg−1) [48], Ethiopia (0.427 mg kg−1) [49], Sudan (0.10–0.99 mg kg−1) [59], and Brazil (0.021 mg kg−1) [60].
On the contrary, high concentrations of Pb were found in the M1 samples and the sugarcane, exceeding the maximum permissible limits established by the national standards NTE INEN 2332, NTE INEN 259, and NTE INEN 258 and the international standard Codex Alimentarius. High Pb values were found in panela, in contrast to national and international regulations requiring that it must be Pb-free [61]. Likewise, in white sugar, the Pb level exceeded the MPL of the regulations by 3.2 times. However, brown sugar was below these limits.
A possible explanation for the high concentrations of Pb in the products analyzed is that the contamination could derive from the crops and the use of additives in production, as suggested by comparisons with the concentrations of Pb obtained in the sugarcane. Furthermore, chemical residues from various stages of sugar processing, such as those derived from bleaching agents like lime, polyelectrolytes, and carbon dioxide, could also introduce toxic metals. Additionally, the equipment and metal components utilized for sugar processing may contribute to the contamination of the final sugar product [5].
As mentioned, heavy metals bioaccumulate in the cane trunk, from which sugar is extracted as a raw material [62]. On the other hand, additives containing heavy metals, such as basic lead acetate or lead subacetate, are used during manufacturing. In this sense, it is well-known that M1 previously used lead subacetate to bleach sugar, but currently uses another compound that—according to its safety data sheet—may contain less than 10 ppm of heavy metals. In contrast, the M2 and M3 brands use sulfur dioxide for bleaching.
Considering these factors, the hypothesis supported an association between the contamination from the chemical additives and the contamination proven from the sugarcane crops. In addition, it is essential to mention that the M1 company mainly uses the Ragnar variety, as it has a higher concentration of sucrose, which may explain the difference with respect to the other brands (besides the use of other bleaching chemicals).
The contamination of panela, white, and brown sugar puts consumers at risk, considering that sugar is one of the most-consumed products, especially by children and young people [63]. Moreover, it is used at home daily by the Ecuadorian population. In the same way, it is used as a raw material for juices, desserts, and other products [63].
The consumers most affected by Pb are children and pregnant women, as it has been shown to lead to mental deterioration and developmental problems such as decreased IQ, hyperactivity, intrauterine death, premature births, and low body weight in newborns [30].
Furthermore, Pb is likely carcinogenic to humans [64], and also causes hypertension, damage to the gastrointestinal system and the central nervous system, damage to the immune system, neuropsychological and neurobehavioral effects, and neurodegeneration potentially leading to Alzheimer’s disease [65,66,67,68]. Its ingestion through contaminated sugar may be related to causes of diseases observed in Ecuadorian children.
Therefore, heavy metal contamination in sugarcane raises concerns from both nutritional and environmental points of view as, in the harvest season, the cane remains are burned. It has been evidenced that traces of metals such as Pb and Cd are present in the particulate material generated by burning [69]. This implies that burning Ragnar-variety crops could have a more significant impact on the health of the inhabitants due to its higher concentrations of Cd and Pb.
Proposal to decrease the occurrence of heavy metals during the production of sugarcane products.
To prevent the accumulation of heavy metals in sugarcane and its products, we propose the following:
  • Do not use fertilizers and pesticides with heavy metals in their composition. As mentioned above, the incidence of fertilizers and pesticides affects the concentrations of heavy metals in the plant [70].
  • Encourage and train farmers on sustainable agriculture and good agricultural practices. Farmers should be trained on heavy metal issues in soils and how to reduce their incidence. In addition, sustainable agriculture should be included with the support of authorities, including international programs such as the UN for Food and Agriculture.
  • Train farmers on the actions they can carry out on site to remediate contaminated soils and prevent contamination by heavy metals. These could include the following:
    -
    pH correction: Apply compounds such as calcium hydroxide to reduce the bioavailability of Pb. The solubility and bioavailability of heavy metals are higher when the pH is acidic [71].
    -
    Organic amendments: To immobilize the metal and reduce toxicity in soils, use organic amendments or increase the organic material of the soil, which reduces its bioavailability for plants [72].
    -
    Composition of irrigation water: Control and analyze the water composition used for irrigation to prevent the excessive accumulation of metals in the food chain [73].
  • Carry out control over the additive chemical products used both in the cane cultivation process and in the production of derived products. Additionally, alternative products that do not have lethal effects on people’s health should be considered. Each company should prepare a toxicity report for the products used in the manufacturing process of food products. The use of bleaches such as Pb subacetate should be avoided and replaced by others that do not contain Pb, such as sulfur dioxide and ozone.
  • Through control authorities, verify that small farmers who sell cane to sugar mills use products that do not contain heavy metals and that their toxicity level is low. Therefore, by ensuring the safety of the product from the beginning of the food chain, it will be possible to ensure its responsible sale to consumers.

5. Conclusions

Cd and Pb were observed in different sugarcane varieties grown in Ecuador. The variety with the highest potential for accumulation of Cd and Pb was Ragnar, while that with the lowest capacity was the Cenicaña variety. Therefore, growing the latter in soils contaminated with heavy metals is recommended to ensure food safety.
The sugarcane derivatives did not present contamination with Cd. On the contrary, in the derivative products of the M1 brand, the levels of Pb exceeded the MPLs established in national and international regulations, representing a health risk for the Ecuadorian population. Pb concentrations in cane and derived products were observed in the following classification pattern: cane > panela > white sugar > brown sugar.
The initial hypothesis was accepted, as sugarcane and its derivatives were found to be contaminated with Pb. Preventive measures were proposed to minimize the presence of Pb in sugarcane products in Ecuador, thus promoting food safety.

Author Contributions

B.P.: conceptualization, methodology, data curation, statistical analysis, writing—original draft preparation; M.A., E.V., X.Á.-M., and A.G.: methodology, investigation, writing—review and editing. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Data Availability Statement

Data are contained within the article.

Conflicts of Interest

The authors declare no conflicts of interest.

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Agriculture 14 02121 g001
Figure 1. The geographical location of the El Triunfo Canton.
Figure 1. The geographical location of the El Triunfo Canton.
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Figure 2. Heavy metal concentrations in sugarcane stems of the varieties ECU-01, EC-02, Cenicaña (CC1), Cenicaña with glyphosate ripening (CC2), and Ragnar. (A) Cd. (B) Pb. Results are shown as means ± standard deviations. Equal letters indicate no significant differences between the means (p > 0.05). Comparison of the Cd concentration in the sugarcane varieties with the maximum permissible limit (red line) of Cd and Pb in vegetables, according to the Codex Alimentarius FAO/OMS [44].
Figure 2. Heavy metal concentrations in sugarcane stems of the varieties ECU-01, EC-02, Cenicaña (CC1), Cenicaña with glyphosate ripening (CC2), and Ragnar. (A) Cd. (B) Pb. Results are shown as means ± standard deviations. Equal letters indicate no significant differences between the means (p > 0.05). Comparison of the Cd concentration in the sugarcane varieties with the maximum permissible limit (red line) of Cd and Pb in vegetables, according to the Codex Alimentarius FAO/OMS [44].
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Figure 3. Comparison of Pb concentrations with national and international regulations. The national regulations used to make the comparisons were the INEN Standards for white, brown, and granulated panela sugar; the international Codex Alimentarius (Codex); and the Mercosur Technical Regulation on Maximum Limits of Inorganic Contaminants in Food (Mercosur).
Figure 3. Comparison of Pb concentrations with national and international regulations. The national regulations used to make the comparisons were the INEN Standards for white, brown, and granulated panela sugar; the international Codex Alimentarius (Codex); and the Mercosur Technical Regulation on Maximum Limits of Inorganic Contaminants in Food (Mercosur).
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Figure 4. Spearman correlation matrix between the Pb concentration in the cane varieties and the lead present in the different types of sugar.
Figure 4. Spearman correlation matrix between the Pb concentration in the cane varieties and the lead present in the different types of sugar.
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Table 1. Cd and Pb concentrations in panela, white, and brown sugar (n = 9).
Table 1. Cd and Pb concentrations in panela, white, and brown sugar (n = 9).
Cd (mg kg−1)Pb (mg kg−1)
DerivedM1M2M3M1M2M3
Panela <0.035<0.035<0.0352.3 ± 1.04 a<0.09<0.09
White sugar<0.035<0.035<0.0351.6 ± 0.74 a<0.09<0.09
Brown sugar<0.035<0.035<0.0350.3 ± 0.08 b<0.09<0.09
Note: M1 = Brand 1; M2 = Brand = 2; M3 = Brand 3. Equal letters indicate no significant differences between the means (p > 0.05).
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Alcívar, M.; Vinueza, E.; Pernía, B.; Álvarez-Montero, X.; Gallardo, A. Contamination by Cadmium and Lead in Sugarcane and Its Derived Products in Ecuador. Agriculture 2024, 14, 2121. https://doi.org/10.3390/agriculture14122121

AMA Style

Alcívar M, Vinueza E, Pernía B, Álvarez-Montero X, Gallardo A. Contamination by Cadmium and Lead in Sugarcane and Its Derived Products in Ecuador. Agriculture. 2024; 14(12):2121. https://doi.org/10.3390/agriculture14122121

Chicago/Turabian Style

Alcívar, María, Edwin Vinueza, Beatriz Pernía, Xavier Álvarez-Montero, and Alejandro Gallardo. 2024. "Contamination by Cadmium and Lead in Sugarcane and Its Derived Products in Ecuador" Agriculture 14, no. 12: 2121. https://doi.org/10.3390/agriculture14122121

APA Style

Alcívar, M., Vinueza, E., Pernía, B., Álvarez-Montero, X., & Gallardo, A. (2024). Contamination by Cadmium and Lead in Sugarcane and Its Derived Products in Ecuador. Agriculture, 14(12), 2121. https://doi.org/10.3390/agriculture14122121

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