Developmental exposure to ethylbenzene: Elucidating the effects of volatile organic compounds on phenotypic and transcriptomic endpoints using zebrafish (Danio rerio).

Volatile organic compounds (VOCs) are ambient anthropogenic pollutants prevalent in urban environments; sources include vehicle exhaust and industrial emissions. Ethylbenzene, a 'possible human carcinogen' is of public health concern due to high levels in residential drinking water wells near waste sites and leaking underground sources entering indoor air through vapor intrusion. Exposure has also been linked to non-cancer adverse health outcomes, yet few studies focus on the immediate effects of ethylbenzene exposure. In this study, we utilized the zebrafish model to carry out controlled VOC exposures during the critical window of early development. Our novel, validated method using sealed glass vials was employed for optimized chemical delivery. Phenotypic data collection was conducted following 0.001-10 ppm ethylbenzene exposure after 5 days post fertilization (dpf) and tissue samples were collected for transcriptomic endpoints. Behavioral assays were carried out at 1 and 5 dpf to characterize very early signs of neurotoxicity. At 5 dpf, exposure to ethylbenzene was significantly associated with a decrease in larval behavior at almost every concentration (p < 0.001) during the dark periods and significantly associated with a decrease in behavior at 10 ppm (p < 0.001) in the light periods. Mortality and swim bladder inflation were significantly affected at 1 and 10 ppm ethylbenzene. Dysregulated genes (including crtc2 and pdca) and pathways of interest are associated with carcinogenesis, the endocrine systems, neurological system, and reproductive system. The high conservation of molecular pathways between zebrafish and mammals provides further insight into potential mechanisms and adverse health impact associated with volatile organic compound exposure.