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The activity of e-waste recycling often causes the combined pollution of tetrabromobisphenol A (TBBPA) and cadmium (Cd) in soils. In this study, the effects of their co-existence on each other's fate, further reflecting the bioavailability, were analyzed in the presence of two ecologically different earthworm species, endogeic Metaphire guillelmi and epigeic Eisenia fetida. Mineralization of 14 C-TBBPA combined with 10 mg Cd kg -1 was suppressed by the presence of M. guillelmi, whereas a facilitating effect was produced by the combination of 1 mg Cd kg -1 in the soil-E. fetida system after a 14-day exposure. The uptake of 14 C-TBBPA by M. guillelmi (17% of initial amount) and by E. fetida (10%) dominantly contributed to significant (P < 0.05) decrease of extractable (more bioavailable) 14 C residues in soils both with and without Cd spiked, while the mineralization of 14 C-TBBPA in the soils was negligible (<0.4%). Meanwhile the amendments of the two earthworm species exerted different impact on 14 C distribution in bound residues. In general, co-exposure to Cd did not significantly (P > 0.05) influence the accumulation and metabolism of TBBPA in the earthworms. Both earthworms accumulated only ~7% of Cd in soil, however, the bioavailable Cd determined by the diffusive gradients in thin films technique declined by ~46% in the presence of M. guillelmi, and a much smaller decrease was determined in the presence of E. fetida. Amendment of TBBPA at environmental levels did not alter the accumulation and subcellular distribution of Cd in both earthworms unless that at high doses. The results highlighted the importance of considering the difference of the earthworm species and the interaction of pollutants in soil-risk assessments of such combined contamination. CAPSULE: M. guillelmi displayed greater effect on the fate of TBBPA and Cd co-existed in soils than E. fetida, while the accumulation, metabolism, or distribution of the two pollutants in earthworms did not significantly alter due to interactions between the two pollutants., (Copyright © 2018. Published by Elsevier B.V.)

Cadmium (Cd) and tetrabromobisphenol A (TBBPA) are two ubiquitous pollutants in soils and are often found together at electronic waste recycling sites. In this study, their toxicity as well as the accumulation and subcellular partitioning of Cd were determined in two ecologically different earthworms Eisenia fetida and Metaphire guillelmi exposed for 14 days to Cd (1 mg kg -1 ) and TBBPA (10, 50, 100, and 500 mg kg -1 ) alone and in combination. In general, Cd-TBBPA co-exposure resulted in synergistic effects in terms of acute toxicity, growth inhibition, histopathological changes in body walls, and oxidative stress responses to earthworms, moreover, M. guillelmi showed higher sensitivity than E. fetida. Principal component analysis showed that the two earthworm species differed in their biomarker expression patterns. In addition, Cd accumulation was significantly (P < 0.01) reduced in E. fetida co-exposed to TBBPA but significantly (P < 0.05 and 0.01) enhanced in M. guillelmi. The difference in bioaccumulation between the two earthworm species may be made by their different exposure routes despite the decrease of Cd bioavailability (assessed by the diffusive gradients in thin films technique) in the soils. High doses of TBBPA also altered the subcellular distribution of Cd in the earthworms. These findings demonstrate the need to include more ecologically relevant earthworm species, represented in this study by M. guillelmi, in soil risk assessments of Cd and TBBPA co-exposure., (Copyright © 2018 Elsevier Ltd. All rights reserved.)