Chloroxylenol is a disinfectant that sees widespread use around the globe, yet it has raised concerns regarding eco-toxicological risks in water environments. This is largely due to its high chemical stability and significant levels of usage. Researchers from the School of Engineering at the Hong Kong University of Science and Technology (HKUST) have identified an exciting alternative called 2,6-dichlorobenzoquinone (2,6-DCQ). This new disinfectant is more effective against various common bacteria, fungi, and viruses, and it can swiftly break down and be detoxified in water.
This groundbreaking research is spearheaded by Prof. ZHANG Xiangru from the Department of Civil and Environmental Engineering at HKUST, who has extensive experience in studying disinfection byproducts (DBPs). During the recent pandemic, Prof. Zhang observed that chloroxylenol shares a structural similarity with several halo-phenolic DBPs that his team had previously investigated, which are known to degrade rapidly through solar photolysis.
Taking inspiration from the structure and degradability of these halo-phenolic DBPs, the research team successfully identified an efficient broad-spectrum disinfectant that can be quickly broken down and detoxified in aquatic environments. The team evaluated the effectiveness of 10 different DBPs at neutralizing various pathogens, including E. coli (linked to colorectal cancer), Staphylococcus aureus (a type of bacteria), Candida albicans (fungi), and the bacteriophage MS2 (a virus). They discovered that 2,6-DCQ is 9 to 22 times more efficient than chloroxylenol in neutralizing these pathogens.
Moreover, the developmental toxicity of 2,6-DCQ for marine polychaete embryos diminished rapidly due to its swift hydrolytic degradation in seawater, even without sunlight. After two days in seawater, 2,6-DCQ displayed 31 times lower developmental toxicity compared to chloroxylenol.
“We found that the chosen DBP had significantly greater antimicrobial power than chloroxylenol, and its concentration along with related developmental toxicity in seawater diminished quickly, even in the dark,” Prof. Zhang stated.
He highlighted the urgent need for effective and environmentally friendly disinfectants, especially following the COVID-19 pandemic. “Chloroxylenol has been frequently found in aquatic systems; for example, its concentration in river water in Hong Kong can reach as high as 10.6 μg/L. Toxicological studies have indicated harmful effects of chloroxylenol on aquatic life, such as endocrine disruption, embryonic death, and deformities. Prolonged exposure to chloroxylenol at environmental levels (~4.2 μg/L) can lead to gene regulation changes and physical deformities in rainbow trout.”
The identification of 2,6-DCQ as a viable alternative represents a crucial advancement in addressing this global issue. The findings indicate that 2,6-DCQ could serve as a disinfectant in various applications, including personal care products (like hand sanitizers and soap), paints, textiles, metal working fluids, medical garments, and for sanitation in homes, food processing equipment, surgical tools, and public areas.
“This innovative research not only offers a potential solution for enhancing human biosecurity while maintaining environmental sustainability, but it also has far-reaching implications for the creation of eco-friendly disinfectants and other sustainable industrial products by leveraging the slightly alkaline properties of seawater. For instance, scientists might design and produce additional industrial items like pesticides, pharmaceuticals, and personal care products that can be swiftly broken down by hydrolysis in seawater,” Prof. Zhang explained.
The team’s results have been published in the prestigious journal Nature Communications. The research group also included Dr. HAN Jiarui, a current Research Assistant Professor at HKUST, and Dr. LI Wanxin, who is now an Assistant Professor at Xi’an Jiaotong-Liverpool University. Both are PhD graduates from HKUST’s Department of Civil and Environmental Engineering and were postdoctoral researchers in Prof. Zhang’s team during this study.
Looking to the future, Prof. Zhang aims to investigate the connections between the efficiency of disinfection and the degradability of halo-phenols in relation to their molecular signatures using machine learning. He hopes that future studies will provide insights for developing optimal disinfectants.
