*Article* **Comparison of Joint Effect of Acute and Chronic Toxicity for Combined Assessment of Heavy Metals on** *Photobacterium* **sp.NAA-MIE**

**Nur Adila Adnan 1, Mohd Izuan Effendi Halmi 1,\*, Siti Salwa Abd Gani 2, Uswatun Hasanah Zaidan <sup>3</sup> and Mohd Yunus Abd Shukor <sup>3</sup>**


**Citation:** Adnan, N.A.; Halmi, M.I.E.; Abd Gani, S.S.; Zaidan, U.H.; Abd Shukor, M.Y. Comparison of Joint Effect of Acute and Chronic Toxicity for Combined Assessment of Heavy Metals on *Photobacterium* sp.NAA-MIE. *Int. J. Environ. Res. Public Health* **2021**, *18*, 6644. https://doi.org/10.3390/ ijerph18126644

Academic Editors: Pasquale Avino, Massimiliano Errico, Aristide Giuliano and Hamid Salehi

Received: 24 April 2021 Accepted: 8 June 2021 Published: 21 June 2021

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**Abstract:** Predicting the crucial effect of single metal pollutants against the aquatic ecosystem has been highly debatable for decades. However, dealing with complex metal mixtures management in toxicological studies creates a challenge, as heavy metals may evoke greater toxicity on interactions with other constituents rather than individually low acting concentrations. Moreover, the toxicity mechanisms are different between short term and long term exposure of the metal toxicant. In this study, acute and chronic toxicity based on luminescence inhibition assay using newly isolated *Photobacterium* sp.NAA-MIE as the indicator are presented. *Photobacterium* sp.NAA-MIE was exposed to the mixture at a predetermined ratio of 1:1. TU (Toxicity Unit) and MTI (Mixture Toxic Index) approach presented the mixture toxicity of Hg2+ + Ag+, Hg2+ + Cu2+, Ag+ + Cu2+, Hg2+ + Ag+ + Cu2+, and Cd2+ + Cu2+ showed antagonistic effect over acute and chronic test. Binary mixture of Cu2+ + Zn2+ was observed to show additive effect at acute test and antagonistic effect at chronic test while mixture of Ni2+ + Zn2+ showing antagonistic effect during acute test and synergistic effect during chronic test. Thus, the strain is suitable and their use as bioassay to predict the risk assessment of heavy metal under acute toxicity without abandoning the advantage of chronic toxicity extrapolation.

**Keywords:** toxicity assessment; luminescent bacteria; acute and chronic toxicity
