Transformation of organophosphate esters (OPEs) in natural
ambient
air and potential health risks from coexposure to OPEs and their transformation
products are largely unclear. Therefore, a novel framework combining
field-based investigation,
in silico
prediction,
and target and suspect screening was employed to understand atmospheric
persistence and health impacts of OPEs. Alkyl-OPE transformation products
ubiquitously occurred in urban ambient air. The transformation ratios
of tris(2-butoxyethyl) phosphate were size-dependent, implying that
transformation processes may be affected by particle size. Transformation
products of chlorinated- and aryl-OPEs were not detected in atmospheric
particles, and atmospheric dry deposition might significantly contribute
to their removal. Although inhalation risk of coexposure to OPEs and
transformation products in urban ambient air was low, health risks
related to OPEs may be underestimated as constrained by the identification
of plausible transformation products and their toxicity testing
in vitro
or
in vivo
at current stage. The
present study highlights the significant impact of particle size on
the atmospheric persistence of OPEs and suggests that health risk
assessments should be conducted with concurrent consideration of both
parental compounds and transformation products of OPEs, in view of
the nonnegligible abundances of transformation products in the air
and their potential toxicity
in silico
.
Benzo[a]pyrene (BaP) is ubiquitously present in the aquatic environment and has been identified as a bone toxicant. Previous studies have demonstrated that ancestral BaP exposure can cause transgenerational bone deformities in fish. Transgenerational effects are thought to be caused by heritable epigenetic changes, such as DNA methylation, histone modification, and non-coding RNAs. To investigate the role of DNA methylation in BaP-induced transgenerational skeletal deformities and the related transcriptomic changes in deformed vertebrae, we examined the vertebrae of male F1 and F3 medaka fish using high-throughput RNA sequencing (RNA-seq) and whole-genome bisulphite sequencing (WGBS). The histological results revealed that osteoblast numbers at the vertebral bone decreased in the BaP-derived F1 and F3 adult males in comparison with the control group. Differentially methylated genes (DMGs) associated with osteoblastogenesis (F1 and F3), chondrogenesis (F1 and F3), and osteoclastogenesis (F3) were identified. However, RNA-seq data did not support the role of DNA methylation in the regulation of genes involved in skeletogenesis since there was very little correlation between the level of differential methylation and gene expression profiles related to skeletogenesis. Although DNA methylation plays a major role in the epigenetic regulation of gene expression, the dysregulation of vertebral gene expression patterns observed in the current study is most likely to be mediated by histone modification and miRNAs. Notably, RNA-seq and WGBS data indicated that genes related to nervous system development are more sensitive to ancestral BaP exposure, indicating a more complex transgenerational phenotype in response to ancestral BaP exposure.
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