By: Muhammad Raznisyafiq Razak; Ahmad Zaharin Aris and Azim Haziq Zainuddin

Moderated for Web By: Farah Izana binti Abdullah

Per- and polyfluoroalkyl substances (PFAS) are synthetic organic chemicals comprising fluorinated carbon chains and can be grouped into endocrine disrupting chemicals (EDCs). PFAS are employed in various applications such as surface coating, industrial surfactant, corrosion resistance agents, and fire-fighting foams. This is due to PFAS features distinct physicochemical properties such as water and oil repellency, high surface activity, heat and acid resistance, as well as weak intermolecular interactions. These characteristics cause PFAS to remain in the environment and allow for bioaccumulation and biomagnification in the food chain. This study aimed to assess the adverse effects at different levels of organisations such as organ, individual and population. This study were also aimed to utilise an acute toxicity test to assess the toxicities of PFOS and PFOA at various concentrations on M. micrura.

Organ level endpoint could be an early indication before the organisms are immobilised or killed. The data indicated that exposure to 5000 μg L^{− 1} PFOA lowered M. micrura heart rate by 38.4 beats per 30 s, while exposure to 5000 μg L^{− 1} PFOS lowered the heart rate by 35.5 beats per 30 s. Another study reported contradictory findings which exposure to increasing PFOS concentration enhanced the heart­ beat of Daphnia magna until 66,000 μg L^{− 1}, but inhibited the heart rate. Similar findings were shown by Jeong et al (2018) during the exposure of propanolol towards D. magna, even at the concentration as high as 1,755,000 μg L^{− 1}. A previous study highlighted the toxicity pathway of the particular chemicals from organ level towards the upper level of biological organisation such as individual and population levels.

This study investigated the toxicological effects of PFOA and PFOS on M. micrura at different levels of organisation consisting organ, individual and population, following the acute toxicity tests. Both compounds severely decreased the heartbeat of M. micrura, indicating the heart rate endpoints are sensitive to be employed as an ecological endpoint. The results revealed PFOA was more toxic compared to PFOS towards M. micrura. The PNECAF values for PFOA and PFOS were 0.4747 and 0.5496 μg L^{− 1}, respectively. Meanwhile, the PNECSSD values found were 1077.0 μg L^{− 1} (PFOA) and 172.5 μg L^{− 1} (PFOS). The toxicity and the risk assessment such as the PNEC values of PFOA and PFOS are valuable decision-making tools for developing environmental quality criteria, serving as the baseline for screening assessments, and estimating ecological risks in freshwater ecosystems.

Web: https://doi.org/10.1016/j.chemosphere.2022.137377

Date of Input: 27/04/2023 | Updated: 11/05/2023 | s_humaira