Effects of Electronic and Electrical Waste–Contaminated Soils on Growth and Reproduction of Earthworm (Alma nilotica)

Informal recycling of electronic waste (e-waste) contaminates local environments with metals and other organic compounds. The adverse effects on native earthworm populations are poorly understood. The objective of the present study was to determine metal concentrations in soils from e-waste activity sites in Douala (Cameroon) and assess the effects of these soils on the growth and reproduction of the local earthworm, Alma nilotica. Concentrations of nine metals (arsenic [As], cadmium [Cd], cobalt [Co], chromium [Cr], copper [Cu], mercury [Hg], nickel [Ni], lead [Pb], and zinc [Zn]) were measured in soil samples collected from eight e-waste activity and two non–e-waste sites. Earthworms were then exposed to these soils in the laboratory following test guidelines of the Organisation for Economic Co-operation and Development. Metal concentrations in the e-waste–contaminated soils were significantly higher than in the non–e-waste soils. The e-waste soils were found to have a different soil metal profile (Cu > Pb > Zn > Cr > Ni > Co > As > Cd > Hg) from that of the non–e-waste soils (Zn > Cr > Cu > Pb > Ni > As > Cd > Co > Hg). Earthworm growth and reproduction were significantly inhibited in organisms exposed to soils from e-waste sites. Reproduction was particularly affected, with a mean of 8 ± 5.6 offspring/10 worms in the e-waste–exposed worm groups compared with 90.5 ± 0.7 in non–e-waste soil worms. Notably, earthworm growth recovered during depuration in clean soil, indicating the possibility of remediation activities. The results demonstrate that soils at e-waste sites can affect the health of resident worm populations, which may be more sensitive than temperate species. They also highlight the potential of a bioassay-based approach in monitoring risks at e-waste sites. Environ Toxicol Chem 2022;41:287–297.