Uptake of Cadmium, Lead and Arsenic by Tenebrio molitor and Hermetia illucens from Contaminated Substrates

Abstract

Insects have potential as a novel source of protein in feed and food production in Europe, provided they can be used safely. To date, limited information is available on the safety of insects, and toxic elements are one of the potential hazards of concern. Therefore, we aimed to investigate the potential accumulation of cadmium, lead and arsenic in larvae of two insect species, Tenebrio molitor (yellow mealworm) and Hermetia illucens (black soldier fly), which seem to hold potential as a source of food or feed. An experiment was designed with 14 treatments, each in triplicate, per insect species. Twelve treatments used feed that was spiked with cadmium, lead or arsenic at 0.5, 1 and 2 times the respective maximum allowable levels (ML) in complete feed, as established by the European Commission (EC). Two of the 14 treatments consisted of controls, using non-spiked feed. All insects per container (replicate) were harvested when the first larva in that container had completed its larval stage. Development time, survival rates and fresh weights were similar over all treatments, except for development time and total live weight of the half of the maximum limit treatment for cadmium of the black soldier fly. Bioaccumulation (bioaccumulation factor > 1) was seen in all treatments (including two controls) for lead and cadmium in black soldier fly larvae, and for the three arsenic treatments in the yellow mealworm larvae. In the three cadmium treatments, concentrations of cadmium in black soldier fly larvae are higher than the current EC maximum limit for feed materials. The same was seen for the 1.0 and 2.0 ML treatments of arsenic in the yellow mealworm larvae. From this study, it can be concluded that if insects are used as feed materials, the maximum limits of these elements in complete feed should be revised per insect species.

Uptake of heavy metals and arsenic in black soldier fly (Hermetia illucens) larvae grown on seaweed‐enriched media

“…These findings concur with previous studies that provided feeding media spiked with Cd in increasing concentrations to BSF larvae. [35][36][37] In these studies, BSF larvae accumulated higher concentrations of Cd (up to ∼7 mg kg −1 , 37 and up to 170 mg kg −1 , 35 ) compared to this study (highest Cd concentration was 2.3 mg kg −1 ). This difference could be due to higher exposure levels of Cd used in these studies, or because spiked Cd was more available than Cd in the seaweed-enriched media.…”

“…Accumulation of Cd within Dipteran species has been shown before. 35,37 Moreover, Cd has been identified as a potential hazard in fly larvae destined J Sci Food Agric 2018; 98: 2176-2183 © 2017 Society of Chemical Industry wileyonlinelibrary.com/jsfa wileyonlinelibrary.com/jsfa for animal feed, including BSF larvae. 34 In the current study, the retention of Cd was 70-93% at BA0-BA50, showing that this metal readily accumulates in BSF larvae.…”

“…mealworm (Tenebrio molitor) and BSF. [34][35][36][37][38] Similarly, there are limited data available regarding the presence of these compounds in the feeding media currently used to rear farming insects.…”

Sustainable farming of the mealworm Tenebrio molitor for the production of food and feed

“…The larvae accumulated high levels of arsenic, intermediate levels of cadmium, and low levels of lead but were able to excrete arsenic slowly when transferred to a noncontaminated diet [83].…”

“…Food contaminated with cadmium, lead, or arsenic did not influence the development time, dry matter content, or survival time of mealworms, and may therefore remain undetected if the insects are not tested at regular intervals [83]. The larvae accumulated high levels of arsenic, intermediate levels of cadmium, and low levels of lead but were able to excrete arsenic slowly when transferred to a noncontaminated diet [83].…”