# Uptake and Biotransformation Govern the Toxicity of Reactive Acrylamides in an In Vivo Zebrafish Embryo Model: Implications for NAM-Based Hazard Assessment

## TL;DR

This study uses zebrafish embryos to show that the toxicity of acrylamides depends on how they are taken up and transformed in the body, not just their chemical reactivity.

## Contribution

The study identifies a new detoxification pathway involving mercapturic acid-taurine conjugates for acrylamides in zebrafish embryos.

## Key findings

- Acute toxicity of acrylamides in zebrafish embryos varied over 2 orders of magnitude.
- Toxicity was influenced by hydrophobicity and electrophilic reactivity, but also by biotransformation and uptake.
- Nontarget screening identified 90 transformation products, including mercapturic acid-taurine conjugates for eight compounds.

## Abstract

Acrylamides are widely used in polymer manufacturing
and adhesives,
and their electrophilic nature raises toxicological concerns when
released into aquatic environments. However, their physicochemical
diversity complicates the prediction of environmental fate and toxicity.
To elucidate the main drivers of their toxicity in aquatic organisms,
we investigated ten structurally diverse monomeric acrylamides and
methacrylamides in zebrafish embryos (Danio rerio) (ZFE). Acute toxicity varied over 2 orders of magnitude (0.16–33
mM) and showed a moderate correlation with hydrophobicity (logK
lipw, R
2 = 0.87)
and intrinsic electrophilic reactivity (logk
GSH). Measured bioconcentration factors of highly polar, reactive
compounds (e.g., NMBA) for ZFE deviated up to 16-fold from model predictions,
indicating limited uptake or significant biotransformation. This indicates
an impact of toxicokinetics on their in vivo toxicity.
UPLC-HRMS-based nontarget screening revealed 90 transformation products
across the ten compounds. Glutathione conjugation and mercapturic
acid formation were dominant pathways, with mercapturic acid-taurine
conjugates observed for eight compounds, suggesting a previously undescribed
detoxification mechanism for (meth)­acrylamides in the ZFE. Our results
highlight the need to integrate toxicokinetic data into hazard assessment
of electrophilic compounds, as in vitro assays may
overestimate risks. The ZFE provides a mechanistically informative in vivo model to reduce misclassifications, especially for
polar and reactive chemicals.