Toxic Pollutants in Water: Health Risk Assessment and Removal

1. Introduction

Clean water is a fundamental human right; however, it is increasingly under threat from toxic pollutants that infiltrate rivers, lakes, groundwater, and even treated drinking water supplies [1]. As industrialization accelerates and agricultural practices intensify, these contaminants originate from multiple sources, such as industrial effluents, agricultural runoff, improper waste disposal, aging infrastructure, and household products [2,3]. Once released into environment, many of these pollutants do not degrade easily and can bioaccumulate in aquatic organisms, eventually entering the human food chain and causing global public health crises [4,5]. Challenges lie not only in identifying these toxins but also in assessing their risks to human health and implementing effective strategies for their removal [6]. Water pollution is no longer confined to visible signs, such as oil slicks or floating debris. Modern pollutants are often invisible, insidious, and persistent in nature. Chronic occurrence of toxic pollutants, including heavy metals (HMs; Pb, Ni, As, Hg, Cd, Co, and Cu), dyes, and organic contaminants such as pharmaceutical residues, pesticides, and perfluoroalkyl and poly-fluoroalkyl substances (PFAS; perfluorooctanoic acid (PFOA) and perfluorosulfonic acid (PFOS)), in water is a significant environmental concern due to their persistence, toxicity, and potential risks to humans and ecosystems [7,8,9].

The health consequences of long-term exposure to low levels of toxic pollutants are profound [10]. Unlike acute illnesses caused by pathogens, the effects of chemical contamination often manifest over years or decades. Exposure to HMs has been linked to neurological disorders, kidney damage, developmental delays in children, and cancer [11]. Organic compounds and PFAS, known as forever chemicals, are associated with immune dysfunction, hormonal disruption, and increased cancer risk [12,13]. In many developing regions, contaminated water remains a primary source of disease and mortality, particularly among children [14]. Assessing the health risks posed by these pollutants requires robust scientific methodologies.

One of the major hurdles in managing water pollution is the sheer diversity and evolving nature of the contaminants. Regulatory frameworks often lag behind scientific discoveries, leaving many emerging pollutants unregulated. For instance, while some countries have set limits on certain organic compounds, thousands of them remain unmonitored. Moreover, detection technologies must keep pace with this rapidly evolving landscape. Traditional water testing methods may not be sufficiently sensitive to detect trace amounts of emerging contaminants. Advanced analytical techniques can help to bridge this gap; however, their widespread implementation remains costly and technically demanding. Addressing the issues of toxic pollutants in water requires a multi-pronged approach that combines prevention, treatment, and policy reform [7]. Adsorption with biochar and activated carbon [15,16], reverse osmosis [17], membrane filtration [18], bioremediation [19], and advanced oxidation processes [20] have proven effective in removing a wide range of contaminants. Nanotechnology [21] and (bio)remediation [22], which use microbes or plants to absorb or break down toxins, are promising frontiers in sustainable water purification. Furthermore, community-based solutions, such as rainwater harvesting, decentralized filtration systems, and green infrastructure, can help to reduce reliance on centralized water treatment plants and mitigate contamination at the local level.

As an effort to promote sustainable water management and environmental protection, this Special Issue, titled “Toxic Pollutants in Water: Health Risk Assessment and Removal”, of Water aimed to advance our understanding and remediation of water contamination by bringing together multidisciplinary research on pollutant sources, health risks, and innovative removal techniques. This Special Issue covered a range of topics related to toxic pollutant (HMs, dyes, and organic contaminants) contamination in water, approaches for toxic pollutant sources, environmental fate, health risk assessment, environmental composites/nanoparticles for toxic pollutant removal, and water treatment techniques, i.e., adsorption, desalination, catalytic reduction, advanced oxidation, bioremediation, and membrane filtration.

2. Findings Reported in This Special Issue

This Special Issue comprises nine articles, including eight research articles and one review article. The topic of “Toxic Pollutants in Water: Health Risk Assessment and Removal” is discussed in the following articles: Ikizoglu et al. (2024) investigated the pollution of two PFAS types, namely PFOA and PFOS, both of which are banned by the Stockholm Convention, in surface waters and surface water fish in the most densely populated and industrial region in Turkey [contribution 1]. Shaffique et al. (2024) explored research developments in migratory water birds, focusing on indicators of HM (Ni, Cu, Co, Zn, Pb, Cd, and Mn) pollution in the inland wetland resources of Punjab, Pakistan [contribution 2]. Jing et al. (2024) evaluated the ecological impact of wastewater discharges on microbial and contaminant dynamics in rivers to optimize wastewater treatment processes to better comply with Chinese environmental quality standards [contribution 3]. Piccardo et al. (2024) assessed the first evidence of the water bioremediation potential of Ficopomatus enigmaticus (Fauvel 1923), both living and dead, to remove contaminants and enhance water quality [contribution 4]. Medina Salas et al. (2023) explored the ZnO-CuO nanocomposite’s potential as an efficient adsorbent for As(III) removal from water, showing that the straightforward and energy-efficient production of nanocomposite makes it promising for real-world water treatments [contribution 5]. Alhamzah et al. (2023) studied the control of bromate, a potentially carcinogenic disinfection by-product; its formation in desalinated seawater production; and its transmission with ammoniation in Makkah, Saudi Arabia [contribution 6]. Cáceda Quiroz et al. (2023) studied cyanide bioremediation carried out by Bacillus subtilis under alkaline conditions using cyanide concentrations and experimental conditions demonstrative of real mining wastewaters [contribution 7]. Mahringer et al. (2023) evaluated the redox behavior of Cr with redox-active substances (O₂, NO₃⁻, Fe²⁺, MnO₂) in reduction, coagulation, and biotic filtration drinking water treatment at pilot-scale [contribution 8]. Liang et al. (2023) reviewed the literature on the pollution components of pulp and paper wastewater, their environmental and health impacts, and the sustainable treatment, recycling, and utilization of pulp and paper wastewater [contribution 9].

3. Conclusions and Future Directions

Toxic pollutants in water represent a complex and urgent challenge that demands immediate attention from scientists, policymakers, industry leaders, and civil society. Researchers have developed eco-friendly and cost-effective materials and methods for the efficient removal of pollutants from contaminated water, wastewater regeneration and reuse, and reducing toxicant levels, paving the way for scalable and adaptable wastewater treatment and sustainable water management [23,24,25]. Although progress has been made, much work remains to be completed to ensure that everyone has access to safe and clean water. As we face the growing pressures of climate change, population growth, and resource scarcity, protecting our water resources is not just an environmental imperative; it is also a moral one. The health of future generations depends on the choices that we make today. Let us act decisively, collaboratively, and with a shared commitment to preserving our most vital natural resources.

Effective regulation is essential to curb the release of toxic pollutants at source. Governments must enforce stringent industrial discharge standards, invest in wastewater treatment infrastructure, and promote sustainable agricultural practices. Transparency in reporting water-quality data and setting enforceable maximum contaminant levels are critical steps toward ensuring accountability. International cooperation is equally important in this regard. Water pollution knows no borders, especially in transboundary river basins and coastal waters. Agreements such as the Stockholm Convention on Persistent Organic Pollutants [26] and the Paris Agreement [27] provide a framework for global action, but stronger enforcement and funding mechanisms are needed.

The future of water pollution control depends on our capacity to innovate, collaborate, and educate. By leveraging cutting-edge technologies (such as artificial intelligence and the Internet of Things), responding to challenges posed by climate change, modernizing governance frameworks, and increasing public awareness, we can build a robust and sustainable approach for protecting surface water and groundwater resources. As we progress, it is crucial to remain flexible and proactive in addressing new and evolving threats. Emphasizing integrated strategies that combine scientific research, community engagement, and informed policy decisions will be key to ensuring the long-term health and resilience of essential water systems and resources.