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The buoy and the water crib for the city of Toledo, rear right. At far left is the Davis-Besse Nuclear Power Station.
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Clean water a complex issue

THE BLADE

Clean water a complex issue

The discovery of microscopic pathogens in the early 19th century was a medical mystery finally solved. This important information explained the cause of many different illnesses, such as cold, flu, infections, food poisoning, and a long list of other diseases that affect the majority of us at one time or another during our life. Microscopic pathogens include different bacteria, viruses, yeast, and other tiny organisms that can only be seen under a microscope.

Soon after the discovery of tiny pathogens, it was then discovered that many pathogens can travel by water. Exposure to pathogens that cause cholera and typhoid fever by drinking contaminated water is a worldwide problem even in highly developed countries such as the United States. For example, you may recall the major outbreak of illness caused by water-borne pathogens in Milwaukee in 1993. Even more memorable to all of us in the Toledo area was the 2014 alert to stop drinking the city water to avoid exposure to a toxic product produced by blue-green algae or cyanobacteria.

Once the important discovery of water-borne pathogens was made, another major breakthrough was the introduction of water chlorination; now a standard procedure for disinfecting water. Raw water is chlorinated by adding different molecular forms of chlorine. We now know that water chlorination ensures clean drinking water by killing bacteria and other pathogens that might be within it. While these chlorination solutions could be harmful to us in high doses, when they are added to water, they are safely diluted, but still retain their ability to make our city water safe for us and our pets to drink.

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No one can disagree that water chlorination is important for human health. My studies are focused on other specific effects of water chlorination. The water purification process produces chemicals that are known as disinfection by-products. Chlorine and other disinfectants can react with natural organic matter in water to generate a complex mixture of disinfection by-products. Potential effects of long-term exposure to disinfection by-products are not known. This subject has been an ongoing focus of research for many scientists, including myself.

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These disinfection by-products are divided into two families depending on whether they have a molecule called a halogen group attached to them. Halogens are from salts or minerals. Two disinfectant by-product chemicals that are in highest amounts in our drinking water within the halogen-containing family are dichloroacetate (DCA) and trichloroacetate (TCA).

Previously, a lot of studies have been done to measure the toxicity of DCA and TCA. Both rat and mouse models have been used to study the effects of these and other disinfection by-products. The major obstacle with these investigations is that there are many different disinfection by-products that are normally in water as mixtures, because there are different types of natural organic matter in water for the disinfectant to react with. Studies that involve mixtures of chemicals are always a novel challenge. We are still at the learning stage of understanding the behavior of mixtures of different disinfection by-products.

One of the main goals of my research is to study how DCA and TCA disinfection by-products affect developing embryos. I use a Zebrafish embryo model. I used this animal model because zebrafish embryos are produced weekly, and allows me to monitor the embryos after I add single chemicals or chemical mixtures during the growth period, which is very rapid compared to human embryos.

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The first step of my investigation has been to assess the harmful effects of TCA; one of the more abundant disinfection by-products on growing zebrafish embryos. Our research laboratory has previously assessed the effects of DCA, the other abundant disinfection by-product, in this same experimental model. My results were in agreement to the previous studies of DCA. I found that increased amounts of TCA causes comparable toxic effects in zebrafish. Unlike DCA however, the toxic effects of increased amounts of TCA did not depend on any specific time of exposure (hours post-fertilization) nor on the concentration.

Because we now had well documented effects of the two disinfection by-products studied separately, I then studied mixtures of these compounds in the zebrafish embryos. These studies are still ongoing and are in the initial phases.

My goal is to continue to investigate the effects of DCA and TCA, as well as their mixtures on the development of embryos. Publishing this important information in scientific journals will be essential when assessing the risks to unborn children of any chemicals in our environment.

Omar N. Issa is a PhD candidate in the Developmental and Environmental Toxicology track at the University of Toledo College of Pharmacy and Pharmaceutical Sciences in the Experimental Therapeutics Program. Omar is studying for his doctoral degree in the laboratory of Frederick E. Williams, PhD and Ezdihar A. Hassoun, PhD. To learn more about his research, contact him at omar.issa@rockets.utoledo.edu or go to http://www.utoledo.edu/pharmacy/depts/pharmacology/experimentaltherapeutics.html

First Published June 3, 2019, 2:53 a.m.

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The buoy and the water crib for the city of Toledo, rear right. At far left is the Davis-Besse Nuclear Power Station.  (THE BLADE)  Buy Image
Omar Issa is in the University of Toledo College of Pharmacy and Pharmaceutical Sciences - Experimental Therapeutics Program.  (JAMES MOLNAR)
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