Chemical contaminants that may accumulate in insects through their substrate can be broken down into the following categories:
Data on heavy metal uptake by insects is mostly limited to studies on cadmium and lead, but it has been shown that these metals are accumulated in insects through their substrate or from the soil (Vijver et al., 2003; Diener et al., 2011). More research is needed on the uptake of other metals and on the heavy metal content found in different forms of substrate.
Insect toxins are naturally produced by some insect species, but they usually advertise their toxicity through the use of vivid colours to ward of predators. There is no evidence that the most commonly farmed insect species produce these kinds of toxins. Insects do have the ability to accumulate toxins from plants and fungi, so the issue for farmed insects is primarily related to the control of toxin levels in their substrate.
Hormones & Veterinary Drugs
Veterinary drugs, hormones and antimicrobial agents are sometimes added to substrates to fend off disease or promote growth in farmed insect populations, and residues have been found to accumulate in the insects (Charlton et al., 2015). The EU veterinary drug legislation does not currently cater for insect farming, but testing for these kind of compounds can be managed in much the same way as is practised with other foods of animal origin.
Pesticides & Biocides
Very little data exists on the accumulation of pesticides in farmed insects, but most insects tested had levels below the danger threshold (Charlton et al., 2015). Pesticide accumulation is obviously a concern for insect farming, especially if the insects are destined for the plate, but again, close control and traceability of the substrate used should be practised. Similarly, care must also be taken with the use of any biocides for the cleaning and disinfecting of farming equipment.