Table of Contents
Background
Haloacetic acids (HAAs) refer to a group of chemical compounds formed when chlorine or other halogenated chemicals are used in the disinfection of drinking water during the treatment process. These chemicals can also be found in the environment due to various industrial and agricultural activities. HAA5 is a general term that refers to the sum of the five most commonly found haloacetic acids comprising monochloroacetic acid (MCA), dichloroacetic acid (DCA), trichloroacetic acid (TCA), monobromoacetic acid (MBA) and dibromoacetic acid (DBA). The total HAA5 concentration in the environment may vary depending on various factors such as water source, treatment methods used, and the surrounding land use. Because of their wide application in the disinfection of drinking water, HAA5 can be found in drinking water in varying concentrations.
Therefore, USEPA has regulated their levels and established a maximum contaminant level goal (MCLG) for HAA5 in drinking water to be zero and an MCL of 60 ppb (µg/L) for public health safety. However, the actual HAA5 levels in drinking water may show variability based on the location and water source and therefore it is important to regularly monitor the drinking water for HAA5 levels. Moreover, public water systems are required to test water for HAA5 in the US and report the generated results to the state and EPA. These compounds are mainly formed as a byproduct of the disinfection process and can be found in both ground and surface water reservoirs. Further, the activities involving pesticides, herbicides, and other chemicals used in agriculture may significantly contribute to the elevated HAA5 levels in drinking water. Another important HAA5 source in drinking water can be the presence of naturally occurring organic matter in water including algae, decaying plants, and other microorganisms.
When chlorine is used for disinfection, these organic substances react with chlorine to generate HAA5 in drinking water. Importantly, the major drinking water source in the US comes from surface water which can be contaminated by pollutants from the surrounding land use such as surface runoff from agriculture and industries. According to EPA, the majority of public water systems in the US are in compliance with the HAA5 MCL. However, private wells are not regulated by the EPA and therefore not required to test for HAA5. Regular water testing for HAA5 is recommended for private wells to ensure safe drinking water consumption. The EPA guidelines for HAA5 also recommend that if a public water system exceeds the MCL, the public must be informed and necessary steps must be taken to bring the levels back into compliance. While the HAA5 levels in drinking water are typically low and are regulated by the EPA in the US, exposure to high concentrations of HAA5 over a long period can have adverse impacts on human health. Studies have shown that long-term HAA5 exposure through drinking water can result in increased cancer risk mainly including colon and rectal cancer.
Further, these chemicals can also negatively affect other organs including the liver and central nervous system as well as developmental and reproductive effects. Few studies also support the link between HAA5 exposure and an increased birth defects risk, low birth weight, and developmental delays. However, the data is limited in this regard and demands additional research to support the link between HAA5 exposure through drinking water and disease development by conducting cross-sectional population studies that report an association between their detected levels in drinking water and human health. It is also important to use water testing services for HAA5 levels and implement suitable treatment methods to reduce or eliminate their presence to ensure a safe drinking water supply and public health safety. In case of any concerns about the drinking water quality, the consumers are recommended to have their water tested for HAA5 levels and take necessary treatment steps if the detected levels in drinking water exceed the MCL.
Limited epidemiological evidence exists for HAA5 toxicity and metabolism in humans therefore the detailed mechanisms are not well understood so far, and more research is needed to determine how the body processes and eliminates these compounds. It has been proposed that the body can metabolize and excrete some of these compounds. Once ingested, HAA5 gets absorbed in the gastrointestinal tract and distributed throughout the body. Some of the HAA5 may be metabolized by the liver and excreted mainly through the urine. Studies suggest that multiple mechanisms may be involved and associated with the toxicity of HAA5. This mainly includes oxidative stress, DNA damage, and disruption of cellular signaling pathways.
One of the main ways that HAA5 is thought to trigger toxicity is through reactive oxygen species (ROS) production leading to DNA and protein damage (Craven et al. 2021; Plewa et al. 2010). HAA5 can also result in DNA damage by forming adducts (chemical modifications) with DNA that leads to mutations and result in increased cancer risk (Li and Mitch 2018). HAA5 can also disrupt normal cellular functioning by interacting with and altering the activity of signaling pathways that control cell growth and differentiation (Chaves et al. 2019). These disruptions can lead to changes in cell behavior and contribute to the development of cancer and other diseases.
Studies have also shown an association between HAA5 and epigenome-wide changes including histone protein modifications and DNA methylation (Salas et al. 2015; Yang et al. 2017). These changes have been reported to cause altered gene expression that controls cell growth and differentiation hence leading to cancer development. Further, HAA5 can also impact the transcriptome by altering the gene expression of various genes involved in cell growth, metabolism, and DNA repair leading to various disease development (Plewa et al. 2010). However, more research is required to explore detailed mechanisms involved in the toxicity of HAA5 in drinking water.
Detection Methods and Removal Strategies
A variety of analytical methods are available to detect and quantify HAA5 in drinking water. This includes liquid chromatography coupled with mass spectrometry (LCMS) and gas chromatography-mass spectrometry (GCMS) being the most sensitive and reliable methods to quantify these compounds (Postigo et al. 2020; Prieto-Blanco et al. 2012). These methods involve the separation of HAA5 compounds from other contaminants in the water samples followed by identification and quantification using mass spectrometry. Rigorous sample extraction and clean-up protocols are required to treat the water sample before it is subjected to a chromatography instrument for quantification. Several methods for extraction and clean-up have been developed so far for LCMS and GCMS analysis.
This includes solid phase extraction (SPE) and liquid-liquid extraction. In the first one, the sample is passed through a solid-phase material that selectively absorbs the HAA5 and is then washed and eluted before being passed through GC or LC system for detection. While in liquid-liquid extraction, organic solvents are used to separate the HAA5 from water samples and then analyzed using chromatography systems. Some other methods are also available for HAA5 quantification including ion chromatography (Paull and Barron 2004; Yang et al. 2022) and UV/VIS spectrophotometry. However, chromatography-based analysis is the most widely used approach for HAA5 quantification in drinking water.
HAA5can be removed from drinking water using a variety of methods. Chlorination is the most commonly used method to remove these compounds by adding chlorine to the water that reacts with HAA5 to generate less harmful compounds. Ozonation is also an effective way to remove HAA5 from drinking water in which Ozone is added to the water to react with HAA5 and form less toxic/harmful compounds (Lou et al. 2009). Advanced oxidation processes (AOPs) comprise a group of technologies that use various oxidizing agents to treat water such as hydrogen peroxide. These processes can be more efficient compared to chlorination and ozonation for HAA5 removal from drinking water (Chen and Wang 2012; Sinha et al. 2021). Granular activated carbon filtration (GAC) is another method for HAA5 removal that uses a porous material to absorb HAA5 from the water resulting in the effective removal of HAA5 compounds (Kim and Kang 2008).
Further, reverse osmosis (RO) is also a widely used strategy to remove avariety of contaminants from drinking water including HAA5. The method uses a semi-permeable membrane to pass through the water sample with pressure resulting in the removal of HAA5. Moreover, application of nanofiltration membranes for HAA5 removal from drinking water has also been effectively used (Chalatip et al. 2009). More recently, the use of biochar for treatment of various contaminants in drinking water has gained broad attention due to its cost effective and environment friendly nature. Although limited information is available regarding their application for HAA5 removal and additional studies need to be conducted to explore their efficiency related to HAA5 removal from drinking water.
Public Perspective
Following frequently asked questions (FAQs) try to address some general public concerns in the US, especially the NYC and NJ region.
Haloacetic acids (HAAs) are a type of chlorination disinfection by-products (CDBPs) that are formed when the chlorine used to disinfect drinking water reacts with naturally occurring organic matter (NOM) in water. Haloacetic acids are a relatively new disinfection by-product.
Haloacetic acids (HAAs) are a group of compounds that can form when chlorine or halogens are used to disinfect drinking water and they reacts with naturally occurring organic matter (e.g., decaying leaves and vegetation).
Haloacetic acids (HAA) and trihalomethanes (THM) are two groups of disinfection byproducts (DBP) that form when water disinfectants such as chlorine or ozone react with other naturally occurring chemicals in the water. There are five significant regulated HAA potentially found in disinfected drinking water.
Remember, boiling water does not remove HAA5. As a matter of fact, boiling water increases the concentration of HAA5 in your water.
When people consume haloacetic acids at high levels over many years, they increase their risk of developing bladder cancer. Other health effects that may be associated with haloacetic acids include rectal and colon cancer, and adverse developmental and reproductive effects during pregnancy.
HAA5 can potentially impact on various organs. Studies have shown that high concentrations of haloacetic acids given to animals impact adversely on organs including the liver, testes, pancreas, brain and nervous system. The U.S. Environmental Protection Agency (EPA) considers DCA and TCA to be potential human carcinogens.
Various types of home filters including Reverse Osmosis and Granular Activated Carbon treatment technologies have been shown to reduce exposure to disinfection byproducts (e.g., mono-, di-, and trichloroacetic acids and mono-and dibromoacetic acids, collectively referred to as “HAA5”).
HAA5 are five haloacetic acid compounds and TTHM are four volatile organic chemicals that form when chlorine, which is used for disinfection, reacts with dissolved natural organic matter (NOM) found in surface water supplies,
Haloacetic acids (HAAs) are organic compounds containing chlorine and/or bromine.
Haloacetic acids (HAA) are a type of disinfection byproduct used in water treatment to disinfect water from various environmental contaminants.
Conclusion
EPA and there is a prescribed MCL of 60 ppb in drinking water. Although the detected levels of HAA5 in the US Total halo acetic acids (HAA5) refer to the five most commonly found disinfection by-products in drinking water that are formed when chlorine or halogens are used for the disinfection of drinking water. These compounds are regulated by drinking water and lie within the permissible limits however, it should be taken into account that regular monitoring of their levels in drinking water must be done to ensure a safe drinking water supply to US consumers.
Studies suggest various health risks associated with elevated exposure to HAA5 mainly cancers through various proposed cellular and molecular mechanisms. Therefore, any drinking water supply containing levels of HAA5 above MCL should be subjected to proper treatment to lower the levels before its supplied to the consumers for public health safety.
References
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- Yasir A. Rehman, Ph.D.
Dr. Rehman was born in Rawalpindi, Pakistan. He completed his MSc from PMAS – Arid Agriculture University Rawalpindi in 2011 where his thesis comprised a health risk assessment of subjects living in the vicinity of wastewater channels in urban settings and its relationship with the incidence of Malaria.
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OTHER RESEARCH ON WATER CONTAMINANTS BY DR. YASIR
