Soil Contamination and Bioaccumulation of Heavy Metals by a Tropical Earthworm Species (Alma nilotica) at Informal E-Waste Recycling Sites in Douala, Cameroon

Brian Nfor, Patricia Bi Asanga Fai, Simon Awafor Tamungang, Julius N. Fobil, Niladri Basu

Research output: Contribution to journalArticlepeer-review

13 Citations (Scopus)

Abstract

Soil contamination at electronic waste (e-waste) recycling sites is pervasive, though many locations have yet to be studied. While such contamination can present risks to soil organisms, little is known on the risks to native species. The objective of the present study was to assess soil contamination by heavy metals at e-waste recycling sites, and the potential of Alma nilotica, a native earthworm species, to bioaccumulate these metals. Soil samples collected from eight informal e-waste recycling sites and two non-e-waste sites in Douala, Cameroon, were analyzed for metal content. Metal concentrations in earthworm juveniles exposed to the soils for 21 days followed by a 14-day post-exposure period were measured weekly. Mean soil metal concentrations at e-waste sites ranked as Cu > Pb > Zn > Hg > Ni > As > Cd > Co > Cr. Based on contamination factors, soil contamination ranged from “moderate” (Cr), through “considerable” (Co and Cd), to “very high” for the rest of the metals. Based on the modified degree of contamination and risk index, all e-waste sites had “ultra-high” contamination with Ni, Pb, and Zn posing very high ecological risks and Bonaberi being the most contaminated site. There was a positive correlation between soil metal concentrations and metal accumulation (retention) by eathworms, but Hg and Co had the highest bioaccumulation factors (BAFs) despite having low soil concentrations. These results document that e-waste sites in Douala are contaminated with metals and that native earthworm species can bioaccumulate the studied metals at levels that could account for the toxic effects earlier recorded. With e-waste recycling growing worldwide, there is a need for more data, especially from understudied locations. Environ Toxicol Chem 2022;41:356–368.

Original languageEnglish
Pages (from-to)356-368
Number of pages13
JournalEnvironmental Toxicology and Chemistry
Volume41
Issue number2
DOIs
Publication statusPublished - Feb 2022

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