Toxic effects of a methanolic coal dust extract on fish early life stage.

Coal dust is a contaminant that impacts the terrestrial and aquatic environment with a complex mixture of chemicals, including PAHs and metals. This study aims to evaluate the toxic effect of a methanolic coal dust extract on a fish early life stage by analyzing phenotypic alterations, transcriptome changes, and mortality in zebrafish (ZF) embryos. ZF embryos were exposed to methanolic coal dust extract at 1-5000 mg·L-1 and monitored using bright field microscopy 24 and 48 hpf to determine malformations and mortality. In situ hybridization, RNA sequencing, and qRT-PCR were employed to identify transcriptome changes in malformed embryos. Three malformed phenotypes were generated in a dose-dependent manner. In situ hybridization analysis revealed brain, somite, dorsal cord, and heart tube development biomarker alterations. Gene expression profile analysis identified changes in genes related to structural constituent of muscle, calcium ion binding, actin binding, melanin metabolic process, muscle contraction, sarcomere organization, cardiac myofibril assembly, oxidation-reduction process, pore complex, supramolecular fiber, striated muscle thin filament, Z disc, and intermediate filament. This study shows, for the first time, the malformations generated by a mixture of pollutants from a methanolic coal dust extract on a fish early life stage, constituting a potential risk for normal embryonic development of other aquatic vertebrate organisms. Furthermore, we establish that phenotypes and changes in gene expression induced by the extract constitute a target for future studies about mechanical toxicity and their utility as sensitive tools in environmental risk assessments for biota and humans exposed to coal mining activities.