Ecotoxicity of bromate and human health risks resulting from wastewater treatment units' effluents associated with some key physicochemical parameters in two hotspots connected to the Egyptian Mediterranean Sea

Abstract

This study is the first of its kind in terms of focusing on the seasonal monitoring of bromine species (bromide⁻ and bromate) and some of the main physicochemical parameters in the surface water of stations inside and in front of the El Noubareya and El-Umum drains that flow directly or indirectly to the Egyptian Mediterranean coast at A (El Noubareya Drain) and B (El-Mex Bay) sites. Among the bromine species, bromate (BrO₃⁻) is a disinfection byproduct considered by many international agencies to have a potential carcinogenic effect in humans and is also known to be ecologically toxic to aquatic organisms. Drain water samples collected from the studied sites A and B had a bromide/chlorinity ratio (3.85E-03 - 6.25E-03 and 3.27E-03 - 6.97E-03, respectively) significantly higher than the typical value for open seawater (3.50E-03), showing significant dilution with wastewater at drain stations in the investigated sites. The source and origin of bromine species and the major ions studied associated with the wastewater units were identified and tracked by calculating the ion/chlorinity ratio and multivariate analysis. The total hazard quotient (THQ) for bromate intake and dermal exposure in children, females, and males demonstrates negligible harm to human health. The toxic unit (TU) and the sum of toxic units (STU) values of the three trophic levels in the surface water for the two sites under investigation yielded approximately comparable values for risk quotient (RQ) and mixture risk characterization ratios (RCR_{mix(MEC/PNEC)}), indicating that invertebrates are more sensitive to bromate dangers than fish and algae. The study highlights the importance of conducting large-scale laboratory tests on the effluents resulting from wastewater treatment units, including bromide levels, to prevent the formation of dangerous side compounds such as bromate, which may have negative effects on populations and may lead to the toxicity of trophic levels in ecosystems.