With approximately 2.2 billion people around the world lacking access to clean drinking water, the emergence and advancement of water purification systems in the 20th century is crucial to global health outcomes.
However, despite efforts to better standards of living through water purification, in recent years, scientists have uncovered increasing health risks associated with water treatment, which take the form of environmental contaminants known as disinfection by-products (DBPs).
While DBPs are less noticeable than environmental challenges like pollution or deforestation, their impact is just as important to the future of our health.
In fact, DBPs are estimated to be one of about seven environmental contaminants that are associated with human health implications.
DBPs are also very common with relatively high DBP levels detected in our water supplies.
Researchers are therefore working to uncover their severity, how to control them and in the future, how best to regulate them.
The Role of DBPs In Drinking Water Treatment
Water quality wasn’t previously as high a priority, with the focus being more about the quantity of water rather than the quality itself.
It wasn’t until 1974 that scientists first discovered DBPs in drinking water, even though chemical disinfection had been used since the early 1900s.
Current water disinfection processes involve the addition of disinfectants, usually chlorine or chloramine to public water supplies to eliminate pathogens which are responsible for waterborne diseases such as typhoid and paratyphoid fevers, cholera and salmonellosis.
How do DBPs Fit Into the Process?
DBPs are an unintended consequence of trying to make drinking water safe, and are formed as a result of the reaction of disinfectants with naturally occurring organic and anthropogenic organic matter, bromide, and iodide. These contaminants form during drinking water treatment and are transported through underground pipes from drinking water plants to our homes.
Disinfectants such as chlorine, chloramine, ozone, chlorine dioxide and even UV light can react with organic matter naturally present in our rivers, lakes and groundwater to form DBPs.
While water contaminants, such as pesticides, pharmaceuticals, per- and polyfluorinated alkyl substances (PFAS), brominated flame retardants, and UV filters are often present in natural water sources, they are usually not detected in drinking water. In comparison, DBPs are always present in drinking water, and at significantly higher levels — 1,000 times higher than the other contaminants to be exact. This is alarming because research has found that long-term exposure to DBPs has the potential to cause adverse health outcomes such as bladder and colorectal cancer, as well as miscarriages and birth defects. Minimizing DBPs is therefore critical for the improvement of future health outcomes.
Putting DBPs On the Map and the Future of Regulation
Initial studies that sought to categorize the adverse effects of DBPs focused on a very small number of regulated DBPs, measured using the early methods developed at the time by the United States Environmental Protection Agency (U.S. EPA).
As technology and research methods in this field have advanced, scientists have identified over 700 DBPs through target and non-target unknown identification, over half of which our lab at the University of South Carolina is responsible for.
DBPs that have been identified include: trihalomethanes, haloacetic acids, haloacetonitriles, haloacetamides, halonitromethanes, haloaldehydes, haloketones, and nitrosamines.
By working closely with toxicologists, researchers can decipher which of these pollutants are toxic, and those that require quantitative analytical methods for analysis to understand their concentration levels.
The identification of toxic DBPs has not led to the development of new regulations, as further hard data is often required to create enforced regulations, but this research has influenced decision making around the control of DBP levels.
A clear example of this is the EPA’s decision to tighten their regulations in relation to the Stage 1 and Stage 2 DBP Rule, which led to new regulations around the use of haloacetic acids and lowered the allowable limits of trihalomethane exposure. As a result of this, many treatment plants switched from chlorine to chloramine in their disinfection process to lower the level of these regulated DBPs by as much as 90 percent.
As technology evolves in the identification and analysis of DBPs, laboratories can work toward providing further advanced data to influence the implementation of more concrete regulations to control the presence of DBPs in water supplies.
Emerging Technology and Identification Methodology
Previously, DBPs and other environmental contaminants of concern were limited by the technological advancement of analytical instruments and methods that could detect and quantify them.
Over the last 10 years, instruments such as the LC mass spectrometer and the LC high resolution mass spectrometer have been developed to be more sensitive and advanced in software, allowing researchers to identify unknown compounds faster than ever before.
Advances in chromatography have progressed research needs, allowing for better separations of complex water samples. Some of these samples are composed of hundreds and thousands of new components, which can be analyzed to further inform research.
DBPs consist of numerous compound classes, with different chemical and physical properties, which makes it difficult to analyze them with a single method.
Utilizing a combination of GC mass spectrometry and LC mass spectrometry is crucial to understanding the bigger picture of what we’re being exposed to in drinking water. GC mass spectrometry will produce more volatile and semi-volatile lower molecule weight compounds, whereas LC mass spectrometry will uncover higher molecular weight and more polar molecules.
Adopting a combination of targeted and non-targeted analysis approaches enables us to not only identify which potentially harmful DBPs are present in these samples, but additionally, the levels we’re exposed to. It’s this type of data which is likely to support decision-making policies around the control of DBPs in our water supplies.
By partnering with laboratory equipment providers, the quality of our research has significantly progressed, allowing us to meet and expand our research goals.
Why is the Future of this Research so Important?
The future of DBP research is likely to be filled with a myriad of challenges, as we witness the way in which climate change continues to impact our source waters, leading to the development of further DBPs and DBP precursors, but equally, other emerging environmental contaminants.
DBPs are permanently present in our water supplies, therefore continuing to understand how to control and mitigate the presence of these contaminants will be essential for the wellbeing of global populations.
Most research to date has focused on the human health effects of these contaminants, with very few studies conducted on how these DBPs could impact ecological species. This untapped area of research is likely to increase in study, ultimately providing further data and understanding on how to control these contaminants.
Our Latest Research
Our latest research involves investigating hydraulic fracturing wastewater impacts on DBP formation and determining the forcing factors of toxicity in drinking water. For our hydraulic fracturing research, we used GC and LC with high resolution-MS to identify new DBPs formed, including more than 300 novel sulfur-containing compounds.
Our forcing factors study is revealing that DBPs other than what we currently regulate are the important drivers of toxicity in drinking water.
Conclusion
Identifying unknown contaminants and determining their impact on human health and our ecosystem is no small undertaking, but it is one that is of critical importance to our public health. Through further advancing our methods of research, we hope to be able to paint a clearer picture of the potential consequences of DBPs, ultimately allowing us to understand and control them more effectively. WW
About the Author: Susan D. Richardson is the Arthur Sease Williams Professor of Chemistry in the Department of Chemistry and Biochemistry at the University of South Carolina. Prior to coming to USC in January 2014, she was a Research Chemist for several years at the U.S. EPA’s National Exposure Research Laboratory in Athens, Ga. For the last several years, Richardson has been conducting research in drinking water — specifically in the study of toxicologically important disinfection by-products (DBPs).
