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Researchers: Wei Wang, Yichao Qian, Jessica M. Boyd, Minghuo Wu, Steve E. Hrudey, Haiying Du, Jinhua Li, Birget Moe, Claire F. McGuigan, Shengwen Shen, and Xing-Fang Li, University of Alberta (Edmonton, Alberta, Canada) & Jilin University (Changchun, Jilin Province, China)
Researchers at the University of Alberta recently published some insightful findings on what is lingering in the waters of one of summer's favorite pastimes. Wei Wang, and her coworkers in the Division of Analytical and Environmental Toxicology in Edmonton, Canada embarked on a study using the SCIEX API 5000™ LC/MS/MS System to quantify halobenzoquinones (HBQs), a class of disinfection byproducts (DBPs) of health relevance, in swimming pool waters.
It is essential for drinking water to undergo some disinfection process to inactivate pathogenic microbes and prevent waterborne diseases. Common disinfection processes include chlorination, chloramination, ozonation, and UV. While these processes function effectively to remove microbial risks, these disinfecting agents can also react with the natural organic matter that might be present in the water, resulting in the creation of disinfection by-products (DBPs).
There are numerous types of DBPs that can be formed, depending on the composition of the organic matter in the water and the treatment process used, and significant scientific research has been focused on identifying and understanding DBPs that are toxicologically significant. Halobenzoquinones (HBQs) are one of five DBP classes that have been predicted to have toxicological importance. In a recent study published by Du, Li, and co-workers, the cytotoxicity of four HBQ compounds was evaluated (1). The research team identified that HBQs are, in fact, cytotoxic to T24 bladder cancer cells, with cytotoxicity impacted by oxidative stress. The comprehensive study produced significant results for identifying the toxicological significance of HBQ compounds as well as beginning to formulate the cellular mechanism of that toxicity.
The formation of assorted disinfection by-products in swimming pools is a complex chemical process. Swimming pool waters usually contain significantly more organic matter than regular tap water (consider cosmetics, lotions, and sunscreens), and may also contain other contaminants (urine or sweat), among a variety of other residues. Swimming pools very commonly utilize chlorine as the primary means of disinfection, and the chlorine dose applied in swimming pools is usually higher than the residual chlorine in regular tap water to control waterborne disease. UV irradiation may also be used as secondary disinfection treatment. So, the variety of DBPs that could be present in swimming pool waters can be vast.
Wang and coworkers sought to identify and quantify assorted HBQ compounds in swimming pool waters, with a goal to better understand how those compounds are formed as well as the potential human health risks associated with exposure to these HBQ compounds (2). The team utilized solid-phase extraction (SPE) to extract HBQ residues from swimming pool water samples, with additional washes to remove excess salinity or other matrix residues. Samples were analyzed using LC/MS/MS, with LC separation performed using a Phenomenex Luna C18(2) column and MS analysis using an API 5000™ System triple quadrupole mass spectrometer using negative electrospray ionization (ESI) mode and with multiple reaction monitoring (MRM).
Several sample types were evaluated in the study, including:
Of all HBQ compounds studied, 2,6-DCBQ (2,6-dichloro-1,4-benzoquinone) had the most elevated concentration in pool waters relative to tap water (increased by a factor ranging from 5- to 100-fold), and three other HBQ compounds were detected in the pool waters but not detected in the tap water. The team then investigated what factors led to the increase of these HBQ compounds in the pool waters, looking into effects of water temperature and chlorine dose. The results showed that higher water temperatures and increased chlorine content both contributed to an increase in the presence of HBQ residues, particularly 2,6-DCBQ.
The team followed up with an investigation of what caused the increased concentration of HBQs in the swimming pool waters, evaluating whether the formation occurred from biological fluids (e.g., urine) or from personal care products (e.g., sunscreens and lotions). The results showed that lotions and sunscreens introduced by swimmers could increase the concentration of HBQs in the swimming pool waters, but it is dependent on the type of lotion or sunscreen present (most likely due to differences in formulations and active ingredients in different products). Urine did not seem to serve as a precursor to the formation of HBQs.
This study using the API 5000™ System to identify and quantify HBQ compounds in swimming pool waters was very insightful in showing that multiple HBQ residues of toxicological significance do form in swimming pools as a result of the reaction between the disinfection agents used in the pool and the organic residues introduced by swimmers. What is the relevance of all of this? Epidemiological studies have indicated a potential association of consumption of chlorinated water with an increased risk of bladder cancer. The results showing the cytotoxicity induced by HBQs at micromolar concentrations to T24 bladder cancer cells could potentially be the first steps in understanding the toxicity of these compounds. While cytotoxicity testing is done at micromolar concentrations, HBQs in treated water are at ng/L levels. The effects of long term exposure to the trace HBQs are unclear. Therefore, additional research is certainly warranted.
However, one thing is clear – enjoy your time at the pool this summer, but you must take a shower before jumping into the pool. The mass spectrometer can tell. Keep the swimming pool clean for your health!
Read more about this incredible work.
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