García Porras et al. 2025 — Cadmium in cacao farmland: sources, uptake, and mitigation
This review consolidates current knowledge on cadmium (Cd) sources in cacao agroecosystems, the factors driving Cd uptake into cacao beans, and mitigation strategies, with particular attention to the challenge posed by the EU’s 2019 Cd limits for cocoa products (Regulation EU No. 488/2014, setting 0.10 and 0.80 mg Cd/kg dry matter depending on cacao content). Latin American cacao-producing soils — particularly in Colombia, Ecuador, Peru, Costa Rica, and Honduras — naturally contain elevated Cd due to geogenic sources (volcanic parent materials, sedimentary rocks) compounded by anthropogenic inputs (phosphate fertilizers, mining). The review synthesizes a meta-analysis of 785 paired soil-plant data points showing that soil total Cd, lower pH, and reduced soil organic carbon are the primary predictors of bean Cd concentration, and discusses promising mitigation approaches including beneficial element amendments (Mn, Zn), low-Cd accumulator genotype selection, and rhizosphere microbiota manipulation.
Key numbers
Table 1 — Cadmium concentrations in cacao-cultivated soils and beans by country:
| Country | Soil Cd (mg/kg) | Method | Soil pH | Bean Cd (mg/kg DW) |
|---|---|---|---|---|
| Colombia | <0.20 to >1.12 | ICP-MS/XRF | 5.5–6.0 | 0.78 |
| Colombia | 0.01 to 27 | ICP-OES | — | — |
| Colombia | 8 to 90 | XRF | — | — |
| Costa Rica | <0.1 to 1.05 (avg 0.22) | ICP-OES | 4.50–7.49 | 0.41 and 0.56 |
| Costa Rica | 0 to 4.0 (avg 0.38) | ICP-OES | 4.8–6.3 | 0 and 8.70 |
| Ecuador | 0.44 | ICP-OES | <5.5 | 0.55 and 0.90 |
| Ecuador | 0.88–2.45 (surface) | ICP-OES | 4.92–7.97 | 0.02 to 3.0 |
| Peru | — | GFAAS | — | 0.2–12.56 (avg 2.46) |
| Honduras | 0.25±0.02 (0–10 cm) | GFAAS | 4.6–7.8 | 1.1±0.1 |
| Brazil | — | — | — | — |
Regional averages reported in literature: South and Central America 1.39 mg/kg⁻¹ DW (average), East/West Africa 0.51 mg/kg⁻¹ DW and 0.09 mg/kg⁻¹ DW, Asia 0.33 mg/kg⁻¹ DW. Latin American cacao up to 7× higher than other regions.
EU regulation trigger: 53% of cacao bean samples from six provinces in Ecuador exceeded the 0.80 mg/kg DW threshold. Average Cd in Honduran beans: 1.1 mg/kg DW (n=55 farms).
Meta-analysis (785 paired data points, 7 studies): soil total Cd, lower pH, and reduced soil organic carbon are significant predictors of bean Cd. Rainfall negatively correlates with soil Cd in Peru (higher rainfall = increased leaching = lower soil Cd).
Methods (brief)
Systematic review of published literature on Cd in cacao agroecosystems. Synthesizes empirical concentration data from multiple studies across Latin America (Colombia, Ecuador, Peru, Honduras, Costa Rica, Brazil). Review covers Cd uptake and transport mechanisms in Theobroma cacao (root absorption via TcNRAMP5 transporter, xylem and phloem loading, remobilization), soil chemistry factors governing Cd bioavailability, and agronomic and genetic mitigation strategies. No original laboratory measurements; all numbers are extracted from cited primary sources.
Limitations
Review rather than primary study; concentration ranges represent multiple methods, geographic scopes, and sampling periods across the cited literature. EU regulatory limits cited are Regulation (EU) No. 488/2014 as updated; verify current limits against the regulations wiki page as EU limits for cacao were revised again in 2023 (Regulation (EU) 2023/465). Costa Rica values showing 0 to 8.70 mg/kg DW range reflect extreme within-country variance from different altitude and geology combinations. Uncontaminated soil range (0.1–1.0 mg/kg, average 0.1–0.3 mg/kg) is a useful background comparison.
Implications
- Certification: Directly supports HMT&C’s geographic variance tracking for cocoa/cacao Cd. The enormous bean Cd range (0.02 to 12.56 mg/kg DW across Latin America) makes geographic sourcing a primary determinant of certified-product eligibility. The EU 0.10–0.80 mg/kg DW tiered limit by cacao content is the most stringent current regulatory framework.
- Courses: Comprehensive review of why cacao Cd varies geographically — geology, rainfall, soil pH, organic matter, fertilizer inputs — and what mitigation strategies exist. Excellent for supply-chain education.
- App: Note only — contamination_profile for cocoa Cd geographic breakdown. This review aggregates regional bean Cd data that could populate the geographic_breakdown sub-field for cocoa Cd.
- Microbiome: Mentions rhizosphere microbiota as a mitigation strategy vector; not a primary metals-microbiome mechanism paper.