Estimation of the bioaccumulation potential of a nonchlorinated bisphenol and an ionogenic xanthene dye to Eisenia andrei in field‐collected soils, in conjunction with predictive in silico profiling

Abstract

In silico-based model predictions, originating from structural and mechanistic (e.g., transport, bioavailability, reactivity, and binding potential) profiling, were compared against laboratory-derived data to estimate the bioaccumulation potential in earthworms of 2 organic substances (1 neutral, 1 ionogenic) known to primarily partition to soil. Two compounds representative of specific classes of chemicals were evaluated: a nonchlorinated bisphenol containing an -OH group (4,4′-methylenebis[2,6-di-tert-butylphenol] [Binox]), and an ionogenic xanthene dye (2′,4′,5′,7′-tetrabromo-4,5,6,7-tetrachloro-3′,6′-dihydroxy-, disodium salt [Phloxine B]). Soil bioaccumulation studies were conducted using Eisenia andrei and 2 field-collected soils (a clay loam and a sandy soil). In general, the in silico structural and mechanistic profiling was consistent with the observed soil bioaccumulation tests. Binox did not bioaccumulate to a significant extent in E. andrei in either soil type; however, Phloxine B not only accumulated within tissue, but was not depurated from the earthworms during the course of the elimination phase. Structural and mechanistic profiling demonstrated the binding and reactivity potential of Phloxine B; this would not be accounted for using traditional bioaccumulation metrics, which are founded on passive-based diffusion mechanisms. This illustrates the importance of profiling for reactive ionogenic substances; even limited bioavailability combined with reactivity can result in exposures to a hazardous substance not predictable by traditional in silico modeling methods.

Deriving in vivo biotransformation rate constants and metabolite parent concentration factor/stable metabolite factor from bioaccumulation and bioconcentration experiments: An illustration with worm accumulation data

“…With the proposed framework for characterizing biotransformation, a forward step would be to revisit the existing bioaccumulation or biotransformation literature on well‐studied organic contaminants such as energetic compounds and polycyclic aromatic hydrocarbons as well as on chemicals of growing environmental concern . The application of the MPCF for next‐generation chemical assessment and management practices has yet to be further explored and developed.…”

Review of laboratory‐based terrestrial bioaccumulation assessment approaches for organic chemicals: Current status and future possibilities

“…For plant bioaccumulation testing, soil fertility also must be known, given the important influence of nutrient availability to plant roots. The importance of soil type was demonstrated by Princz et al (2014) in an earthworm bioaccumulation study in which uptake of the test chemical in tissue of earthworms exposed in a sandy soil was significantly greater than that in earthworms exposed to the chemical in clay loam soil where organic matter and clay content were significantly higher. The choice of test soils must be considered during the experimental design phase to ensure that critical parameters such as soil pH and organic matter content are not outside the tolerance limit of the test organism.…”

“…The test is applicable to stable neutral organic chemicals, metallo‐organics, metals, and other trace elements. Recent testing with an ionogenic organic chemical proved challenging for test endpoint determination because the chemical was highly water‐soluble, had low lipophilicity, and did not depurate from the earthworm tissue during the elimination phase of the test (Princz et al ). These results suggest the need for additional research on the use of the earthworm bioaccumulation test guideline or other bioaccumulation tests when evaluating the potential bioaccumulation of ionogenic compounds.…”