Assessing the bioaccumulation of lead by black soldier fly (Hermetia illucens) larvae from contaminated hotel waste from urban areas of Kampala

Abstract

Urban organic waste streams in Kampala pose a growing challenge for sustainable waste management and safe feed production. This study aimed to assess the bioaccumulation of lead in Black Soldier Fly (Hermetia illucens) larvae reared on hotel waste substrates spiked with varying concentrations of lead, simulating contamination levels typical of urban environments. A composite organic waste sample from three hotels in Kampala with codes HO1, H02 and H03 was characterized and it revealed background lead level of 5.75mk/kg. Using a controlled laboratory experiment, four substrate treatments were prepared: control (0 g), low-level spike (5 g), mediumlevel spike (10 g), and high-level spike (45 g). The larvae were then analyzed for lead content using inductively coupled plasma mass spectrometry (ICP-MS). Results revealed a clear dosedependent accumulation pattern, with larval lead concentrations increasing from 374.35 ± 1.50 mg/kg in the low-level spike group to 595.20 ± 11.25 mg/kg in the high-level spike group. In comparison, the control group showed minimal accumulation (5.77 ± 1.5 mg/kg). Statistical analysis confirmed significant variation across treatments (F = 436.06, P < 0.001), indicating that substrate contamination directly influences larval lead uptake. The study concludes that although H. illucens demonstrates resilience to lead exposure, current waste handling practices in Kampala compromise the safety of BSF larvae for food and feed applications. To mitigate these risks, the study recommends mandatory waste pre-sorting, prioritization of safer substrate sources, establishment of community-level treatment hubs, integration of lead monitoring into insect farming standards, and targeted public awareness campaigns to reduce lead-containing waste at the source.