Knoll and Cappai 2024 — Honey bee foraging and cadmium exposure: review
This comprehensive review synthesizes the literature on the pathway by which environmental cadmium enters honey bee (Apis mellifera) colonies through foraging activity and ultimately appears in honey and bee products consumed by humans. The paper traces the chain from soil Cd pollution sources through plant uptake into pollen and nectar, to bee foraging behavior, Cd accumulation in bee body tissues, and carryover into honey. Bees are presented both as sensitive environmental Cd bioindicators and as vectors by which Cd reaches the human food chain through honey consumption.
Key numbers
- LD50 for oral Cd exposure in adult honey bees: 3.51 µg/bee (cadmium chloride, 48-hour acute toxicity test).
- LC50 for Cd in honey bee larvae: 0.275 mg/L — larvae are substantially more sensitive than adults.
- Cd concentrations in honey from Cd-contaminated agricultural areas exceed background levels in honey from unpolluted zones, with the review documenting a statistically significant spatial correlation between soil Cd levels and honey Cd content in multiple European and Asian studies.
- Forager bees accumulate Cd primarily in body fat and cuticle; workers near smelters or heavily fertilized cropland show body Cd burdens 5–10× background.
- Pollen collected near Cd-contaminated soils can contain Cd at concentrations that approach or exceed EU maximum levels for food (0.050 mg/kg fresh weight for honey under EU Regulation 2023/915 framework context); specific values vary by study and region cited in the review.
- Seasonal patterns documented: spring and early summer pollen loads carry higher Cd in some regions, attributed to early-season soil Cd mobility.
Methods (brief)
Narrative review methodology. No primary data collection. Synthesizes published studies on (1) Cd sources and plant uptake mechanisms, (2) bee exposure pharmacokinetics, (3) honey and pollen Cd residue surveys, and (4) bee colony-level and individual-level toxicological endpoints. Published in a Springer journal (REVIEW format). No PRISMA flow or systematic search protocol described.
Implications
Certification: Provides mechanistic and empirical basis for treating honey and bee pollen as food matrices of concern for Cd; the review supports including honey in HMT&C product scope where bee pollen or honey ingredients appear in product formulations. Courses: Useful for supply-chain modules illustrating how soil Cd enters the food chain via non-crop vectors (bees/pollination products); also illustrates spatial biomonitoring using bee products as passive samplers. App: Honey ingredient page should flag Cd as the primary metal of concern given this review’s explicit food-chain linkage; bee pollen and propolis products share the same exposure pathway. Microbiome: Not applicable directly, but Cd disrupts gut microbiota; relevant if a honey-gut-microbiome interaction page is developed.