Cadmium bioaccumulation and gastric bioaccessibility in cacao: A field study in areas impacted by oil activities in Ecuador

Assessing the cadmium content of cacao crops in Arauca, Colombia

The district of Arauca is the second-largest producer of cacao in Colombia. However, despite its quality, it faces issues for export due to levels of cadmium (Cd) higher than the regulatory thresholds. A central question is how it may impact agricultural performance in the presence of Cd in cacao and chocolates. This study quantified Cd in cacao plantations from Arauca. Thus, 180 farms were assessed in the municipalities of Arauquita, Fortul, Saravena, and Tame. Five sample types (soil, irrigation channel sediment, soil litter, cacao seeds, and chocolates) were assessed for Cd. As a technological innovation, the new MXRF technology was used for Cd in chocolates. The sequence of Cd content was soil litter > chocolate > soils > cacao seeds > irrigation-channel sediment. A gradient north-south of Cd content in soil was observed, where highest content was found in farms near the Arauca River, and lower farther away. In irrigation channel sediment, Cd levels averaged 0.07 mg kg-1. The Cd content in cacao seeds was 0.78 mg kg-1 on average. Cd content in chocolates was above the threshold (1.10 mg kg-1 on average, including several cacao mass percentages). These artisanal chocolate bars produced by single farms were near the limit of Cd set by the European Union (up to 0.8 mg kg-1). Therefore, mixing beans from different farms could reduce their Cd content. The present study underscores the complexity of Cd distribution, emphasizing the importance of integrating soil, crop, and landscape features in managing and mitigating Cd levels in cacao.

Cadmium (Cd) distribution and soil-plant relationship in cacao farms in Costa Rica

The current cadmium (Cd) regulations in chocolate threaten the cacao supply chain in several Latin American countries. The factors contributing to Cd accumulation in cacao beans have been poorly studied in Central America. The objective of this research was to identify the location of Cd hotspots as well as soil properties and management practices influencing the Cd concentration in cacao beans. A survey was carried out and soil, leaf, and beans were sampled from 150 farms in the three principal cacao-producing regions in Costa Rica. Total soil Cd concentration ranged from <0.1 to 1.05 (average 0.22 mg kg-1) which is typical of uncontaminated soils. Bean Cd concentration ranged from 0.12 to 3.23 (average 0.56 mg kg-1) and 22% of the samples exceeded the selected threshold of 0.80 mg kg-1, located mostly in the Huetar Caribe and Huetar Norte regions. Variability in bean Cd concentration was better explained by total soil Cd and soil organic carbon (SOC) (R2 = 0.62, p < 0.05). In addition, bean Cd concentration was affected by leaf nutrient content and management practices. Leaf Zn and P were positively correlated with bean Cd while K and Mn were negatively correlated (p < 0.05). Farm altitude and orchard age were also negatively correlated with bean Cd. Overall, this study shows that bean Cd contamination does not reach the extent observed in other Latin American countries such as Ecuador, Colombia, or Honduras. Nevertheless, research is needed in hotspot areas to assess the feasibility of potential mitigation strategies, particularly the use of mineral or organic soil amendments, which may allow better for planning in existing plantations or the expansion into new cacao-growing areas in the country.

Unveiling Cacao Rootstock-Genotypes with Potential Use in the Mitigation of Cadmium Bioaccumulation

The accumulation of high cadmium (Cd) levels in cacao beans (Theobroma cacao) generate several commercial and health issues. We hypothesized that cacao phenotypic and genotypic diversity could provide new insights to decrease Cd accumulation in cacao beans. Nine cacao rootstock genotypes were evaluated for up to 90 days under 0, 6, and 12 (mg·kg-1) of CdCl2 exposure and Cd content and plant growth dynamics were measured in leaves, stems, and roots. Data revealed that all cacao genotypes studied here were highly tolerant to Cd, since they presented tolerance index ≥ 60%. In shoots, EET61 and PA46 presented the higher (~270 mg·kg DW-1) and lower (~20 mg·kg DW-1) Cd concentration, respectively. Accordingly, only the EET61 showed an increase in the shoot cadmium translocation factor over the 90 days of exposure. However, when analyzing cadmium allocation to different organs based on total plant dry mass production, none of the genotypes maintained high Cd compartmentalization into roots, since P46, which was the genotype with the highest allocation of Cd to the roots, presented only 20% of total cadmium per plant in this plant organ and 80% allocated into the shoots, under Cd 12 (mg·kg-1) and after 90 days of exposure. Thus, genotypic/phenotypic variability in cacao rootstocks may provide valuable strategies for maximizing the reduction in Cd content in shoots. In this sense, IMC67 and PA46 were the ones that stood out in the present study.

Cadmium up Taking and Allocation in Wood Species Associated to Cacao Agroforestry Systems and Its Potential Role for Phytoextraction

Trees in cacao Agroforestry systems (AFS) may present a high potential for cadmium (Cd) phytoextraction, helping to reduce Cd in cacao (Theobroma cacao L.) plants grown in contaminated soils. To assess this potential, four forest fine-woody species commonly found in cacao high-productive sites in Colombia (Tabebuia rosea, Terminalia superba, Albizia guachapele, and Cariniana pyriformis) were exposed to contrasting CdCl2 contamination levels (0, 6, and 12 ppm) on a hydroponic medium. Growth dynamics, tolerance index (TI), and Cd concentration and allocation in leaves, stems, and roots were evaluated for up to 90 days after initial exposure. T. superba, A. guachapele, and C. pyriformis were classified as moderately tolerant (TI > 0.6), and T. rosea was considered a sensitive species (TI < 0.35) under 12 ppm Cd contamination. Despite showing a high stem Cd concentration, C. pyriformis also showed the lowest relative growth rate. Among the evaluated forest species, A. guachapele exhibited the highest Cd accumulation capacity per plant (2.02 mg plant-1) but also exhibited a higher Cd allocation to leaves (4%) and a strong decrease in leaf and stem dry mass after 90 days of exposure (~75% and 50% respectively, compared to control treatments). Taking together all the favorable features exhibited by T. superba as compared to other CAFS tree species and recognized phytoextractor tree species in the literature, such as Cd hyperaccumulation, high tolerance index, low Cd concentration in leaves, and high Cd allocation to the stem (harvestable as wood), this species is considered to have a high potential for cadmium phytoextraction in cocoa agroforestry systems.

Soil amendments to reduce cadmium in cacao (Theobroma cacao L.): A comprehensive field study in Ecuador

The new EU regulations on maximum levels of cadmium (Cd) in cacao products sparked research on countermeasures to reduce Cd concentrations in cacao beans. This study was set up to test the effects of soil amendments in two established cacao orchards (soil pH 6.6 and 5.1) in Ecuador. Soil amendments included: 1) agricultural limestone at 2.0 and 4.0 Mg ha^-1 y^-1, 2) gypsum at 2.0 and 4.0 Mg ha^-1 y^-1 and 3) compost at 12.5 and 25 Mg ha^-1 y^-1, all amendments were applied at the surface during two subsequent years. Lime application increased the soil pH by one unit down to 20 cm depth. On the acid soil, leaf Cd concentrations decreased by lime application and the reduction factor gradually rose to 1.5 after 30 months. No effects of liming or gypsum on leaf Cd was found in the pH neutral soil. Compost application in the pH neutral soil reduced leaf Cd concentration with factor 1.2 at 22 months but that effect was absent at 30 months after application. Bean Cd concentrations were unaffected by any of the treatments at 22 months after application (acid soil) or 30 months (pH neutral soil) suggesting that any treatment effects on bean Cd might be even more delayed than in leaves. Soil columns experiments in the laboratory showed that mixing lime with compost largely enhanced the depth of lime penetration compared to lime only. Compost + lime reduced 10^-3 M CaCl₂ extractable Cd in soil without lowering extractable Zn. Our results suggest that soil liming has the potential to lower Cd uptake in cacao in the long term in acid soils and that the compost + lime treatment should be tested at field scale to accelerate the effects of the mitigation.

Revealing the pathways of cadmium uptake and translocation in cacao trees (Theobroma cacao L.): A 108Cd pulse-chase experiment

The pathways through which cadmium (Cd) is taken up and loaded into cacao beans (nibs) are yet to be revealed. Previous work suggested that Cd loading into cacao nibs may occur via direct xylem uptake rather than phloem-mediated redistribution from the leaves. A stable isotope (¹⁰⁸Cd) pulse-chase experiment was set up to identify the pathways of Cd loading into cacao nibs. The topsoil beneath two mature cacao trees in the field was enriched in ¹⁰⁸Cd via surface irrigation with a spiked solution. The increase in ¹⁰⁸Cd isotopic abundance (IA) in the plant tissues was followed up for 548 days after spiking. The ¹⁰⁸Cd IA in the plant tissues increased from natural abundance (0.89 %) to 7.0 % (tree A) and 10.1 % (tree B) at equilibrium. The tracer was taken up in the plant tissues in the order immature leaves > mature leaves > nibs in both trees, while tracer uptake in flowers and cherelles was less consistent between the trees. Half of the equilibrium ¹⁰⁸Cd IA was reached in the nibs at 191 days after spiking, significantly later than corresponding values for mature (151 days) and immature leaves (117 days). Pod maturation from flower stage takes about 6 months with most Cd entering the nibs at the last stage of development. The rather slow rise in the ¹⁰⁸Cd IA in the nibs compared to the leaves hence suggests that Cd in cacao nibs likely originates from phloem-redistribution from the stem, branches or mature leaves and not from direct root-to-nib transport via the xylem.

An investigation of zinc isotope fractionation in cacao (Theobroma cacao L.) and comparison of zinc and cadmium isotope compositions in hydroponic plant systems under high cadmium stress

This study aims to establish whether zinc (Zn) and cadmium (Cd) share similar physiological mechanisms for uptake and translocation in cacao plants (Theobroma cacao L.). Multiple-collector ICP-MS was used to determine the Zn stable isotope compositions in the roots, stems and leaves of 19 diverse cacao genotypes grown in hydroponics with 20 µmol L^-1 CdCl₂. Additional plants of one genotype were grown in hydroponic solutions containing lower Cd concentrations (0 and 5 µmol L^-1 added CdCl₂). Regardless of the Cd concentration used in the exposures, the Zn stable isotope compositions show the same systematic patterns in plant organs, with δ⁶⁶Zn_root > δ⁶⁶Zn_stem > δ⁶⁶Zn_leaf (δ⁶⁶Zn denotes relative differences in ⁶⁶Zn/⁶⁴Zn ratios in parts per thousand). The mean Zn stable isotope fractionation between the plants and the hydroponic solutions was ε⁶⁶Zn_uptake = -1.15 ± 0.36‰ (2SD), indicating preferential uptake of isotopically light Zn by plants from the hydroponic solution. The mean  stable isotope fractionation factor associated with translocation of Zn from roots to shoots, ε⁶⁶Zn_seq-mob =  + 0.52 ± 0.36‰ (2SD), shows that isotopically heavy Zn is preferentially sequestered in the cacao roots, whilst isotopically light Zn is mobilised to the leaves. A comparison with the Cd stable isotope compositions of the same plants shows that both isotopically light Zn and Cd are preferentially taken up by cacao plants. In contrast to Zn, however, the cacao roots retain isotopically light Cd and transfer isotopically heavy Cd to the leaves.

From soil to cacao bean: Unravelling the pathways of cadmium translocation in a high Cd accumulating cultivar of Theobroma cacao L

The research on strategies to reduce cadmium (Cd) accumulation in cacao beans is currently limited by a lack of understanding of the Cd transfer pathways within the cacao tree. Here, we elucidated the transfer of Cd from soil to the nib (seed) in a high Cd accumulating cacao cultivar. Here, we elucidated the transfer of Cd from soil to the nib (seed) in a high Cd accumulating cacao cultivar through Cd stable isotope fractionation, speciation (X-Ray Absorption Spectroscopy), and localization (Laser Ablation Inductively Coupled Plasma Mass Spectrometry). The plant Cd concentrations were 10-28 higher than the topsoil Cd concentrations and increased as placenta< nib< testa< pod husk< root< leaf< branch. The retention of Cd in the roots was low. Light Cd isotopes were retained in the roots whilst heavier Cd isotopes were transported to the shoots (Δ ^114/110 Cd _shoot-root = 0.27 ± 0.02 ‰ (weighted average ± standard deviation)). Leaf Cd isotopes were heavier than Cd in the branches (Δ ^114/110 Cd _{IF3 leaves-branch} = 0.18 ± 0.01 ‰), confirming typical trends observed in annual crops. Nibs and branches were statistically not distinguishable (Δ ^114/110 Cd _nib-branch = -0.08‰ ± 0.06 ‰), contrary to the leaves and nibs (Δ ^114/110 Cd _{nib-IF3 leaves} = -0.25‰ ± 0.05 ‰). These isotope fractionation patterns alluded to a more direct transfer from branches to nibs rather than from leaves to nibs. The largest fraction (57%) of total plant Cd was present in the branches where it was primarily bound to carboxyl-ligands (60-100%) and mainly localized in the phloem rays and phelloderm of the bark. Cadmium in the nibs was mainly bound to oxygen ligands (60-90%), with phytate as the most plausible ligand. The weight of evidence suggested that Cd was transferred like other nutrients from root to shoot and accumulated in the phloem rays and phelloderm of the branches to reduce the transfer to foliage. Finally, the data indicated that the main contribution of nib Cd was from the phloem tissues of the branch rather than from leaf remobilization. This study extended the limited knowledge on Cd accumulation in perennial, woody crops and revealed that the Cd pathways in cacao are markedly different than in annual crops.

Sustainability of Cocoa (Theobroma cacao) Cultivation in the Mining District of Ponce Enríquez: A Trace Metal Approach

Historically, cocoa (Theobroma cacao) has been one of Ecuador's most important export crops. In the Ponce Enriquez district, artisanal and small gold mining (ASGM), and quarrying account for 42% of economic activities, while agriculture and livestock farming account for 30%, making the analysis of their synergy and interaction key to understanding the long term viability of the different activities. In this study, we evaluated the concentration of potentially toxic metals in different parts of the cocoa plant and fruit, in relation to mining activities within the area. Gold extraction generates pollution, including potentially toxic metals such as mercury (Hg), cadmium (Cd), arsenic (As), copper (Cu), lead (Pb) and zinc (Zn). In order to understand the mobility of these metals within the cocoa plant and fruit, the analysis was conducted separately for leaves, pod, husk and cocoa bean. Concentrations of the target metals in the different plant parts and soil were measured using ICP-MS, and the mobility and risk factors were calculated using the transfer factor (TF) and the risk ratio (HQ). The results suggest that Zn, Cd and Cu are indeed moving from the soil to cocoa leaves and beans. Furthermore, the results show that the concentrations of toxic metals in the different parts of the cocoa fruit and plant, particularly in the cocoa bean, which is used for chocolate manufacture, are not higher than those regulated by FAO food standards, as is the case of Cd, which is limited to 0.2 mg Cd/kg and in the samples analyzed does not exceed this limit. Even though the concentration of these metals does not exceed the safety standard, the presence of these potentially hazardous metals, and the fact they are absorbed by this important local crop, are worrying for the long-term sustainability of cocoa cultivation in the area. Therefore, it is fundamental to monitor the local environment, understanding the distribution of heavy metal pollution, and work with the local authorities in landscape management to minimize the exposure of crops to ASGM pollution.

Sustainability Dimensions Assessment in Four Traditional Agricultural Systems in the Amazon

Although traditional agriculture carried out by ethnic groups is considered for its high biodiversity and important for food security and sovereignty, few studies have investigated the potential of these systems in the interest of promoting a sustainable agricultural development policy according to United Nations Sustainable Development Goals. Using the FAO's Sustainability Assessment of Food and Agriculture (SAFA) methodology, this study analyzed the sustainability of four traditional agricultural systems, three indigenous (Waorani, Shuar, and Kichwa) and one migrant settler populations in the Yasuní Biosphere Reserve (YBR) and identified synergies and trade-offs among the dimensions of sustainability. The results showed different dynamics in all dimensions of sustainability-specifically, trade-offs in the dimensions of good governance with environmental integrity and social well-being, economic resilience, and social well-being. It was identified that the differences in terms of sustainability are narrowing between the indigenous Shuar people's traditional agricultural systems and those of migrant settlers, which provides policymakers with specific information to design sustainable development policies and rescue traditional agricultural systems in the Amazon region.

Rootstock-Mediated Genetic Variance in Cadmium Uptake by Juvenile Cacao (Theobroma cacao L.) Genotypes, and Its Effect on Growth and Physiology

Grafting typically offers a shortcut to breed tree orchards throughout a multidimensional space of traits. Despite an overwhelming spectrum of rootstock-mediated effects on scion traits observed across several species, the exact nature and mechanisms underlying the rootstock-mediated effects on scion traits in cacao (Theobroma cacao L.) plants often remain overlooked. Therefore, we aimed to explicitly quantify rootstock-mediated genetic contributions in recombinant juvenile cacao plants across target traits, specifically cadmium (Cd) uptake, and its correlation with growth and physiological traits. Content of chloroplast pigments, fluorescence of chlorophyll a, leaf gas exchange, nutrient uptake, and plant biomass were examined across ungrafted saplings and target rootstock × scion combinations in soils with contrasting levels of Cd. This panel considered a total of 320 progenies from open-pollinated half-sib families and reciprocal full-sib progenies (derived from controlled crosses between the reference genotypes IMC67 and PA121). Both family types were used as rootstocks in grafts with two commercial clones (ICS95 and CCN51) commonly grown in Colombia. A pedigree-based best linear unbiased prediction (A-BLUP) mixed model was implemented to quantify rootstock-mediated narrow-sense heritability (h 2) for target traits. A Cd effect measured on rootstocks before grafting was observed in plant biomass, nutrient uptake, and content of chloroplast pigments. After grafting, damage to the Photosystem II (PSII) was also evident in some rootstock × scion combinations. Differences in the specific combining ability for Cd uptake were mostly detected in ungrafted rootstocks, or 2 months after grafting with the clonal CCN51 scion. Moderate rootstock effects (h 2> 0.1) were detected before grafting for five growth traits, four nutrient uptake properties, and chlorophylls and carotenoids content (h 2 = 0.19, 95% CI 0.05-0.61, r = 0.7). Such rootstock effects faded (h 2< 0.1) when rootstock genotypes were examined in soils without Cd, or 4 months after grafting. These results suggest a pervasive genetic conflict between the rootstock and the scion genotypes, involving the triple rootstock × scion × soil interaction when it refers to Cd and nutrient uptake, early growth, and photosynthetic process in juvenile cacao plants. Overall, deepening on these findings will harness early breeding schemes of cacao rootstock genotypes compatible with commercial clonal scions and adapted to soils enriched with toxic levels of Cd.

Land Use and Land Cover Changes in the Diversity and Life Zone for Uncontacted Indigenous People: Deforestation Hotspots in the Yasuní Biosphere Reserve, Ecuadorian Amazon

Land use and land cover change (LULC) is an essential component for the monitoring environmental change and managing natural resources in areas of high natural and cultural biodiversity, such as the Amazon biome. This study was conducted in in the northern Amazon of Ecuador, specifically in the Diversity and Life Zone (DLZ) of the Yasuní Biosphere Reserve (YBR). The general aim was to investigate the territorial dynamics of land use/land cover changes to support policies for environmental and sociocultural protection in the DLZ. Specific objectives included (i) mapping LULC spatial and temporal dynamics in the DLZ in the period from 1999 to 2018, (ii) identifying sensitive LULC hotspots within the DLZ, and (iii) defining the possible policy implications for sustainable land use in the DLZ. Multitemporal satellite imagery from the Landsat series was used to map changes in LULC, which were divided into three-time stages (1999–2009, 2009–2018, 1999–2018). We adopted open-access Landsat images downloaded from the United States Geological Survey (USGS). The processes for assessing LULC in the DLZ included (1) data collection and analysis, (2) data processing for remote sensing, (3) thematic land cover, and (4) homogenization and vectorization of images. The results showed that in the period 1999–2018, most of the uses and land cover were transformed into pastures in the DLZ. Therefore, it is important to improve territorial planning, to avoid conflicts between indigenous populations, migrant settlers, and uncontacted indigenous populations that live in the DLZ, within the YBR.

Cadmium-tolerant bacteria: current trends and applications in agriculture

Cadmium (Cd) is considered a toxic heavy metal; nevertheless, its toxicity fluctuates for different organisms. Cadmium-tolerant bacteria (CdtB) are diverse and non-phylogenetically related. Because of their ecological importance these bacteria become particularly relevant when pollution occurs and where human health is impacted. The aim of this review is to show the significance, culturable diversity, metabolic detoxification mechanisms of CdtB and their current uses in several bioremediation processes applied to agricultural soils. Further discussion addressed the technological devices and the possible advantages of genetically modified CdtB for diagnostic purposes in the future.

Growth and nutritional responses of wild and domesticated cacao genotypes to soil Cd stress

Cadmium (Cd), a toxic non-essential metal, is easily accumulated in cacao tissues. This represents a risk for cacao exportation, and consequently it affects the economic well-being of the resource-poor-small-producers in Latin America. A greenhouse experiment was conducted with 53 wild and domesticated cacao genotypes to determine their response to Cd in terms of growth and Cd and essential nutrients accumulation. Cacao seedlings were grown for 6 months in an acidic soil with or without added Cd. The total concentration of macro (Ca, K, Mg, N and P) and micronutrients (B, Cu, Fe, Mn and Zn) as well as Cd were measured in shoots along with growth (biometric) parameters after harvest. The results revealed that even if there was a wide range of Cd concentrations among genotypes, there was a reduction in the concentration of essential nutrients in genotypes grown in Cd spiked soils, however these concentrations were not significantly different from the control. In the case of growth parameters, the effects of Cd were diverse across all genotypes some of them being more tolerant to Cd stress than others. Thus, different growth responses to Cd stress are related to a genotype effect. Based on their lower Cd concentration, a total of 11 cacao genotypes (AYP-22, PAS-105, UGU-126, ICT-1026, ICT-1087, ICT-1189, ICT-1292, PH-17, CCN-51, ICS-39 and TSH-565) are proposed here as low Cd-accumulating genotypes. Therefore, these genotypes are potentially useful as rootstock to reduce uptake and transport of Cd, especially in economically important cacao cultivars.

Simultaneous determination of cadmium, lead and copper in chocolate samples by square wave anodic stripping voltammetry

In this work, an effective and simple method is proposed for the simultaneous determination of cadmium, lead and copper in chocolate samples by Square Wave Anodic Stripping Voltammetry (SWASV). An ultrasonic bath was used for the extraction of cadmium, lead and copper from fourteen chocolate samples using HNO₃ solution (7 mol L^-1). The electrochemical system consisted of a cell with three electrodes and HCl solution (10 mmol L^-1) as the supporting electrolyte. An efficient extraction of the metals (~100%) was attained after 1 h of ultrasonic pre-treatment. Quantitative analysis was carried out by the standard addition method. Good linearity, precision and accuracy were obtained in the range of concentrations examined. The accuracy was evaluated by means of a reference sample of spiked skim milk powder (BCR 151) to prove the reliability of the method. Detection limits (LOD) of 0.089, 0.059 and 0.018 µg g^-1 were found for cadmium, copper and lead, respectively, in the chocolate samples. Concentrations in chocolate samples were 4.30-138 µg g^-1 for Cu and 0.83-27.9 µg g^-1 for Pb, with no significant Cd. The simultaneous determination brings advantages to other methods already reported for chocolate analysis and the samples preparation proposed avoids the traditional sample mineralization step. These characteristics show this new method is especially attractive for case studies and routine analysis.

Beyond cadmium accumulation: Distribution of other trace elements in soils and cacao beans in Ecuador

Since cacao beans accumulate Cd in high levels and restrictions have been imposed on safe levels of chocolate consumption, concern about whether or not cacao trees store other toxic elements seems to be inevitable. Following a previous study in Ecuador examining Cd content in five cacao varieties collected in pristine areas and in places impacted by oil activities, we present here the concentrations of 11 trace elements (TEs) (As, Ba, Co, Cu, Cr, Mo, Mn, Ni, Pb, V and Zn) in soils, cacao tissues (leaves, pod husks, beans) and cocoa liquor (CL). Several TEs showed concentrations in topsoils above the Ecuadorian limits, and may have a mixed natural and anthropogenic origin. Ba and Mo concentrations in cacao tissues are slightly higher than those reported in other surveys, but this was not the case for toxic elements (As and Pb). TE contents are lower in CL, than in beans, except for Pb and Co, but no risk was identified for human health. Compared with control areas, Enrichment Factors were below 2 in impacted areas, except for Ba. Transfer factors (from soils to cacao) indicated that cacao does not accumulate TEs. A positive correlation was found between Cd and Zn in topsoils and cacao tissues for the CCN-51 variety, and between Cd and Ni for the Nacional variety. Identifying patterns of TE distribution and potential interactions in order to explain plant internal mechanisms, which is also dependent on the cacao variety, is a difficult task and needs further research.

Perspective on Cadmium and Lead in Cocoa and Chocolate

Cocoa and chocolate can contain cadmium (Cd) and lead (Pb) from natural and anthropogenic sources. This perspective provides background on the origin, occurrence, and factors affecting Cd and Pb levels in chocolate products as well as ongoing international efforts to mitigate Cd and Pb in these popular foods, particularly the higher Cd levels observed in some cocoa and chocolate originating from parts of Latin America. Information on factors contributing to higher Cd levels in Latin America, including elevated soil Cd, is increasing, but more work is needed to identify successful mitigation methods.

Surface soil liming reduces cadmium uptake in cacao seedlings but subsurface uptake is enhanced

Cadmium concentrations in cacao (Theobroma cacao L.) beans from South America often exceed trade limits. Liming soil is advocated as a remediation option, but amendments cannot be incorporated into the entire root zone without harming the trees. An experiment was set up to identify how Cd uptake varies within the root zone when surface and subsurface soil layers are either limed or not. The experiment used 22-cm-height pots with top and bottom layers using surface and subsurface soil samples from a cacao field. The potted soils were either surface limed or not or fully limed and layers spiked with stable ¹⁰⁸ Cd isotope in various combinations to trace the plant Cd provenance. The root distribution was neither affected by liming nor by soil source; 70% of the root biomass was present in the top layer. Plants grown on the fully limed surface soil had 1.7 times lower Cd concentrations in leaves than the unlimed treatments, whereas this concentration was 1.2 times lower when only the top layer was limed (surface soil used in both layers). The isotope dilution data showed that surface soil liming enhanced Cd uptake from the unlimed bottom layer compared with the unlimed soil, suggesting compensating mechanisms. The pots containing surface soil over subsurface soil also showed that compensating effect but, due to lower phytoavailable Cd in the subsurface soil, surface liming still effectively reduced foliar Cd. We conclude that liming might be a feasible mitigation strategy, but its effectiveness is limited when Cd phytoavailability remains untreated in the subsurface layer.

Determination of cadmium and lead in tomato (Solanum lycopersicum) and lettuce (Lactuca sativa) consumed in Quito, Ecuador

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Cadmium content was lower than 0.100 mg/kg (tomato) and 0.200 mg/kg (lettuce).

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Lead content above or close to 0.100 mg/kg was found in 25 % of tomato samples.

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Organic products had similar lead and cadmium content as nonorganic ones.

Vegetables are one of the most important components in the human diet, but despite their multiple nutritional components, studies have demonstrated the presence of trace metals in their edible parts. In Ecuador, two of the most consumed crops are tomato (Solanum lycopersicum) and lettuce (Lactuca sativa). The importance of these two crops in the Ecuadorian diet, especially in large and touristic locations like the Metropolitan District of Quito, implies food safety-related concerns for locals and visitors. However, no previous studies have quantified the cadmium and lead levels in these two vegetables using samples from Quito markets. Thus, the aim of this study was to determine the cadmium and lead content in both tomato and lettuce products from main nonorganic and organic markets in Quito using a graphite furnace atomic absorption spectrophotometer. The results showed that the cadmium levels were lower than 0.058 in tomatoes and 0.034 mg/kg in lettuce, which are under the respective threshold values (0.100 and 0.200 mg/kg). Regarding lead, levels lower than 0.066 mg/kg were detected in lettuce, which did not exceed the CXS 193–1995 threshold value, while levels in tomatoes were near or exceeded the threshold value (0.100 mg/kg) from four markets (0.209, 0.162, 0.110, 0.099 mg/kg), suggesting a possible risk from tomato consumption. In addition, most vegetables marketed as organic had higher metal content than those coming from nonorganic markets. Based on these results, local health and commercial control authorities should monitor contaminants in food products sold in Quito and other places in Ecuador to ensure their safety.

Cocoa-laden cadmium threatens human health and cacao economy: A critical view

In the recent decades, Cd burden in cocoa-based products threatened global food safety, human health and the future of chocolateries. Increased Cd bioavailability is an acute problem in cacao-based horticulture. Poverty, poor maintenance, unjustified traditional farming, and paucity of knowledge on Cd-binding propensity in cacao discourage the application of risk-mitigation measures. Progressive accumulation of Cd, with a half-life of 10-30 years, in the human body even at ultra-trace levels may lead to serious health complications. If Cd accumulates in the food chain through cocoa products, consequences in children, who are the primary consumers of chocolates, include morbidity and mortality that may result in a significant demographic transition by the year 2050. Developing cacao clones with an innate capability of taking up low Cd levels from soils, and site-specific Cd-cacao research might contribute to limiting the trophic transfer of Cd. This review highlights the possible routes for Cd uptake in cacao plants and discusses the measures to rescue the chocolateries from Cd pollution to promote "healthy" cacao farming. The potential human health risks of chocolate-laden Cd and mitigation strategies to minimize Cd burden in the human body are also presented. The challenges and prospects in Cd-cacao research are discussed as well.

Public health issues from crude-oil production in the Ecuadorian Amazon territories

Crude oil production (COP) is a high-pollution industry but the vast Amazon rainforest has been an active COP zone for South America. Although COP has been associated with a variety of health effects among workers around the world, such effects have not been adequately investigated in the Amazon region, especially at the community level. Therefore, this review was conducted to provide a report about COP in the Amazon of Ecuador and about its association with health status of indigenous human populations. Some epidemiological surveys in the Amazonian Territories indicate that COP has been associated with health problems in the surrounding populations, e.g. cancers in the stomach, rectum, skin, soft tissue, kidney and cervix in adults, and leukemia in children. In addition, some biomarkers and mechanistic studies show exposure effects. However, due to limitations from these studies, contradictory associations have been reported. Our review indicates that COP in the Amazonian territories of northern Ecuador was characterised by contamination which could have affected the indigenous and non-indigenous populations. However, there have not been dedicated investigations to provide relationships between the contamination and the subsequent exposure-health effects. Since indigenous populations have different lifestyle and cultures from regular city dwellers, systematic studies on their potential health hazards need to be conducted. Due to the remote locations and sparse populations, these new studies may involve the use of novel and genomic-based biomarkers as well as using high technology in the remote regions.

The effectiveness of soil amendments, biochar and lime, in mitigating cadmium bioaccumulation in Theobroma cacao L

Cocoa (Theobroma cacao L.) is an important neotropical tree crop grown for its seeds or beans used in global chocolate and confectionary industries. Following studies showing ill effects of long-term dietary exposure of cadmium (Cd) on human health, a number of countries including the European Union (EU) have developed stringent regulations to protect consumers from exposure to cadmium. Cocoa is capable of bioaccumulating Cd in the cocoa beans when grown in soils high in cadmium and hence livelihood of cocoa farmers can be at risk if methods to mitigate the bioaccumulation of Cd are not developed. In vitro, greenhouse and field experiments were established with four, three and three replications respectively to evaluate the effectiveness of soil amendments, biochar and lime, at various application rates (0, 0.5×, 1×, 1.5× and 2× of the recommended rate), on soil pH, Cd phytoavailability and Cd bioaccumulation in Theobroma cacao L. For the in vitro study, Cd-containing soil was amended with 5 levels of biochar and lime, while for the greenhouse and field study four application rates were tested. The study showed that while lower rates were effective under in vitro conditions as you progressed from in vitro to greenhouse to field conditions the application rates and application frequency had to be increased, as the effectiveness and longevity of the treatments were compromised by environmental factors. Our study implies that the two amendments were complementary in their action and can be used in the recommended rated to reduce Cd bioaccumulation. However further studies are required on the placement of amendments to improve their effectiveness and longevity particularly under field conditions.

Method validation and determination of heavy metals in cocoa beans and cocoa products by microwave assisted digestion technique with inductively coupled plasma mass spectrometry

In this article, an easy and quick method based on microwave assisted acid digestion technique prior to quantification using inductively coupled plasma mass spectrometry for the analysis of heavy metals in cocoa beans, cocoa powder and chocolate was established and validated for arsenic (As), cadmium (Cd), lead (Pb), and antimony (Sb). Limit of quantification for all elements were product dependent and varies from 7.84 to 194.52 µg/kg. The recoveries of the heavy metals at 250 and 1000 µg/kg spiking levels were ranged between 96.27-108.75%, 90.43-101.97% and 89.72-106.26% for cocoa beans, cocoa powder, and chocolate, respectively. Relative standard deviation values obtained were all below 20% and the expanded uncertainty measurements for the elements were less than 25%. The analysis of real samples found that the concentration level is far from the national alarming level except for cadmium in cocoa beans.

Cadmium accumulation and allocation in different cacao cultivars

Cadmium (Cd) is a biologically non-essential heavy metal that can cause toxic effects in plants, animals and humans already at low concentrations compared to other metals. After Cd concentrations in cacao beans of various provenances, particularly from Latin America, were found to exceed the new regulations enforced by the European Union in 2019, there is an urgent need to find measures to lower Cd accumulation in cacao beans to acceptable values. In this research, the long-term cacao cultivar trial CEDEC-JAS in northern Honduras was used to investigate differences between 11 cultivars in Cd uptake and translocation. Sampling of various plant parts, including rootstocks, scions, leaves and beans, from three replicate trees per cultivar and the soil around each tree was conducted at this site. Results indicate that concentrations of available soil Cd were more closely correlated with Cd concentrations of the rootstocks (R² = 0.56), scions (R² = 0.59) and leaves (R² = 0.46) than with bean Cd concentrations (R² = 0.26). In addition, Cd concentrations of rootstocks, scions and leaves showed close relationships to available soil Cd concentrations, with no significant differences between the cultivars. In contrast, bean Cd concentrations showed only weak correlations to available soil Cd and Cd concentrations in the vegetative plant parts, but significant variation among cultivars. Three cultivars, which were analysed in more detail, showed significant differences in Cd concentrations of mature beans, but not of immature beans. These results suggest that cultivar-related differences in bean Cd concentrations primarily result from differences in Cd loading during bean maturation, possibly due to cultivar-specific differences in the xylem-to-phloem transfer of Cd. The results show that selection of cultivars with low Cd transfer from vegetative parts into the beans has high potential to keep Cd accumulation in cacao beans at levels that are safe for consumption.

Using cadmium bioavailability to simultaneously predict its accumulation in crop grains and the bioaccessibility in soils

Single extraction procedures (SEPs) have been extensively conducted to determine Cd bioavailability (Cd-Bav) in soils. However, whether SEPs can simultaneously predict Cd accumulation in crop grains and bioaccessibility (Cd-Bac) in soils remains unclear. To assess their suitability, the Cd-Bav in 20 contaminated soils (containing 0.27-56.59 mg/kg Cd) determined by four SEPs (including DTPA, EDTA, HOAc and HCl) was compared with Cd concentrations in crop grains (wheat and rice) and Cd-Bac in soils (based on SBET and PBET assays). The results indicated that both Cd-Bav (0-103.2%) and Cd-Bac (0-110.4%) in soils varied greatly with the methods used. The Cd-Bav obtained from chelators (DTPA and EDTA) was generally greater in low-Cd soils but lower in high-Cd soils as compared to those obtained from acid solutions (HOAc and HCl). Regression analysis revealed that bioavailable Cd concentrations in soils were linearly correlated with Cd concentrations in wheat grains (R² = 0.88-0.91); however, no significant correlation was found for rice grains. The Cd-Bac in soils was significantly correlated with Cd-Bav obtained from HOAc (R² = 0.55-0.59) or HCl (R² = 0.60-0.68), but not with those obtained from chelators (DTPA and EDTA). Our data suggest that SEPs, particularly the HCl method, have great potential to simultaneously predict Cd accumulation in wheat grains and Cd-Bac in contaminated soils.

Soil properties and agronomic factors affecting cadmium concentrations in cacao beans: A nationwide survey in Ecuador

Recent cadmium (Cd) regulation in chocolate threatens the sustainability of cacao production in Southwest America. Cadmium contamination in cacao beans has not been assessed at a country level. A nationwide survey was conducted in Ecuador to identify the spatial distribution of Cd in cacao beans, as well as soil and agronomic factors involved. Paired soil and plant samples (pods and leaves) were collected at 560 locations. Information on agronomic practices was obtained through a prepared questionnaire for farmers. Total soil Cd averaged 0.44 mg kg^-1 which is typical for young and non-polluted soils. Mean Cd concentration in peeled beans was 0.90 mg kg^-1 and 45% of samples exceeded the 0.60 mg kg^-1 threshold. Bean Cd hotspots were identified in some areas in seven provinces. Multivariate regression analysis showed that bean Cd concentrations increased with increasing total soil Cd and with decreasing soil pH, oxalate-extractable manganese (Mn_ox) and organic carbon (OC) (R² = 0.65), suggesting that Cd solubility in soil mainly affects Cd uptake. Bean Cd concentration decreased a factor of 1.4 as the age of the orchard increased from 4 to 40 years. Bean Cd concentration was inconsistently affected by genotype (CCN-51 vs. Nacional), pruning or application of fertilizers. It is concluded that the relatively larger bean Cd concentrations in Ecuador are related to the high Cd uptake capacity of the plants combined with their cultivation on young soils, instead of Cd depleted weathered soils. Mitigation strategies should consider the application of amendments to modify such soil properties to lower soil Cd availability. There is scope for genetic mitigation strategy to reduce bean Cd, but this needs to be properly investigated.

Cadmium isotope fractionation in the soil – cacao systems of Ecuador: a pilot field study

The often high Cd concentrations of cacao beans are a serious concern for producers in Latin America due to the implementation of stricter Cd limits for cocoa products by the European Union in 2019. This is the first investigation to employ coupled Cd isotope and concentration measurements to study soil – cacao systems. Analyses were carried out for 29 samples of soils, soil amendments and cacao tree organs from organic farms in Ecuador that harvest three distinct cacao cultivars. The majority of soils from 0–80 cm depth have very similar δ^114/110Cd of about −0.1‰ to 0‰. Two 0–5 cm topsoils, however, have high Cd concentrations coupled with heavy Cd isotope compositions of δ^114/110Cd ≈ 0.2%, possibly indicating Cd additions from the tree litter used as organic fertilizer. Whilst cacao leaves, pods and beans are ubiquitously enriched in Cd relative to soils there are distinct Cd isotope signatures. The leaves and pods are isotopically heavier than the soils, with similar Δ^114/110Cd_leaf–soil values of 0.22 ± 0.07‰ to 0.41 ± 0.09‰. In contrast, the data reveal differences in Δ^114/110Cd_bean–leaf that may be linked to distinct cacao cultivars. In detail, Δ^114/110Cd_bean–leaf values of −0.34‰ to −0.40‰ were obtained for Nacional cacao from two farms, whilst CCN-51 hybrid cacao from a third farm showed no fractionation within error (−0.08 ± 0.13‰). As such, further work to investigate whether Cd isotopes are indeed useful for tracing sources of Cd enrichments in soils and to inform genetic efforts to reduce the Cd burden of cocoa is indicated.

Cd isotope composition in cacao seems to be cultivar-specific whereas Cd in soil is probably due to tree litter recycling.