Bioaccumulation and elimination kinetics of metals and polycyclic aromatic hydrocarbons in Hermetia illucens larvae: Implications for risk mitigation of selected contaminants in insect farming

Rapidly expanding insect farming industries worldwide are raising concerns about introducing contaminants into food chains. One of the dominant species in this new bioindustry, the black soldier fly (Hermetia illucens), offers diverse benefits ranging from protein production to waste management, biofuel, and pharmaceutical applications. Recent studies have highlighted the ability of insects to accumulate metals; however, knowledge of their ability to eliminate contaminants is needed. Similarly, information regarding the accumulation of polycyclic aromatic hydrocarbons (PAHs) is lacking. This study aimed to understand how H. illucens larvae accumulate and eliminate metals and PAHs from contaminated substrates. We performed two-phase bioaccumulation experiments followed by toxicokinetic modelling to estimate uptake and elimination rate constants and half-lives in H. illucens. During the uptake phase, insects were exposed for five days to contaminated substrates at EU maximum feed concentrations: 2 mg kg−1 for As and Cd, 10 mg kg−1 for Pb, and 12.5 μg kg−1 for each of four PAHs (benzo[a]pyrene, benz[a]anthracene, benzo[b]fluoranthene, chrysene). In the second phase, insects were exposed to non-contaminated substrates for five days to evaluate elimination. Results showed metal accumulation with kinetic bioaccumulation factors of 4.26, 1.16, and 1.31 for Cd, As, and Pb, respectively. A one-day depuration reduced As and Pb below regulatory thresholds; Cd required three days. Minimal to no accumulation was observed for B[a]P and B[b]F, with higher uptake for B[a]A. PAH half-lives were under one day. These findings, from controlled experiments with limited contaminants, support incorporating a depuration phase for risk mitigation in H. illucens waste-to-protein systems.

Highlights: We examined the toxicokinetics of metals and PAHs in Hermetia illucens larvae; Increased chemical exposure to insect feed may lead to excess insect contamination; Insects consistently and rapidly eliminated the chemicals studied; Integrating 3-day elimination periods within the rearing process is recommended; Findings promote safer insect farming and sustainable use of waste as insect feed.