pH-Dependent Developmental and Behavioral Toxicity of Diethanolamine in Zebrafish (Danio rerio)

Amine-based compounds are used in petroleum and gas processing for CO2 capture and gas sweetening. Diethanolamine (DEA), a water-soluble alkaline compound, can alter exposure-medium physicochemical properties. Its industrial use and potential release into aquatic environments highlight the need to characterize its aquatic toxicity. However, data on DEA developmental toxicity remains limited, particularly regarding the distinction between intrinsic chemical toxicity and pH-mediated effects. This study investigated the developmental and behavioral toxicity of DEA in zebrafish (Danio rerio) under pH-adjusted and unadjusted exposure conditions to examine the contribution of exposure-medium pH to the observed effects. Acute toxicity assays determined the median lethal concentration (LC50), followed by sublethal assessments of spontaneous tail coiling, heart rate, morphology, and larval locomotor activity. Under pH-adjusted conditions, heart rate increased, indicating a sublethal effect on cardiac function. In contrast, unadjusted exposures caused a concentration-dependent increase in medium pH associated with adverse effects on survival, development, and behavior, despite no morphological abnormalities. For statistical analyses, individual measurements were averaged within each vessel, and vessel-level means were used to assess concentration–response relationships and estimate concentration–response trend rates. Responses differed between DEA-Adj and DEA-Unadj under their respective testing conditions, highlighting the importance of considering exposure-medium pH when assessing alkaline chemical toxicity. pH alterations caused by chemical releases may also contribute to adverse effects in aquatic organisms and should be considered when evaluating the environmental implications of DEA contamination.