Phenanthrene (Phe) is a 3 ringed poly-aromatic hydrocarbon (PAH) that is an important component of water and air pollution. In air, Phe binds to the surface of fine particulate matter (PM2.5) and in water, it is a major component of crude oil. Previous work with marine fishes shows that Phe has direct negative impacts on the heart including proarrhythmic effects via inhibition of rapid repolarising potassium current (IKr) and L-type calcium current (ICaL) (1, 2). The aim of this study was to further investigate the cardiotoxic effects of Phe using whole-cell patch-clamp in zebrafish (D. rerio) ventricular cardiomyocytes. We show significant cardiotoxic effects of Phe in zebrafish with different pharmacological potency and specificity compared to previous studies on marine fishes. Firstly, 3 µM Phe significantly inhibited isolated peak IKr tail currents by 50% (n=9; N=3; p<0.05, Wilcoxon t-test) with an IC50 value of 2.7 ± 0.1 µM and a Hill slope (nH) of 0.6 ± 0.09 (mean ± S.E.M; n=6-9; N=3) obtained from concentration-response relationship. Also, Phe increased the rate of decay, tau (τ), of peak IKr tail currents showing a significant reduction in mean τfast value in presence of 3 µM Phe. Surprisingly, when the effect of Phe was examined on action potential (AP) generated at 0.5 Hz through whole-cell patch current-clamp recording, it significantly shortened action potential duration at 90% (APD90) at both 3 µM (by 20%; n=4; N=2; p<0.05, paired t-test) and 10 µM Phe (by 41%; n=4; N=2; p<0.05, paired t-test); unlike previous studies in marine fishes that showed AP prolongation at 5 µM and 25 µM Phe. To understand and elucidate the differential effects of phenanthrene on AP and IKr currents, we further tested Phe’s effects using an AP-like voltage-clamp protocol. Interestingly, 3 µM Phe exhibited only 25-30% inhibition of peak total outward current during the AP command. Furthermore, a shift of -6.2 ± 1.7 mV (mean ± S.E.M; n=4; N=3; p<0.05, paired t-test) in mean voltage at which current peaked during repolarization was observed. Lastly, the effect of Phe on L-type calcium channel current, ICaL was assessed by selective recording, using a double-pulse protocol with potassium free solutions and in the presence of 0.5 µM TTX. 10 µM Phe exhibited significant (40%) inhibition of ICaL currents (n=10; N=4; p<0.05, paired t-test) with no shift in the current-voltage relation. Zebrafish are used to model human cardiac electrophysiology. Thus our findings of significant cardiotoxic effects of Phe, a PAH found in air pollution, on zebrafish ventricular cardiomyocytes provide further evidence linking air pollution to cardiovascular toxicology.