Disinfection Byproducts: Production and Health Effects
DBPs are a group of compounds that are produced during the process of disinfecting drinking water, swimming pool water, and wastewater. In the disinfection process, disinfectants, such as chlorine, chloramines, chlorine dioxide, or ozone, are used to kill pathogens in water. However, during this process, disinfectants can react with halogen-containing compounds and natural organic matter (NOM) to form DBPs.
Early pool water disinfectant studies focused on the safety and stability of chlorine and iodine treatments. Although the U.S. Public Health Service tentatively approved iodine as a disinfectant for swimming pools in 1959, iodine was not used as a sanitizer for swimming pools because it failed to kill algae. DBPs only became a concern in 1974 when Rook and Bellar independently found DBPS, such as chloroform (one of the trihalomethanes) and other carcinogens in natural waters treated by chlorination. More recently these DBPs were found in the blood and breath of swimmers (aka - shark food or NOM NOM) and of non-swimmers at indoor swimming pools.
It is estimated that more than 600 known DBPs are produced during drinking water disinfection. The most common DBPs and their health effects are summarized in the table below.
Generally recent findings suggest bromine-containing compounds are more toxic than chlorine-containing compounds, although they are less toxic than iodine- and nitrogen-containing DBPs. Thankfully, iodine was not used as a disinfectant for public swimming pools in the 1970s, as, unknowingly, much more toxic DBPs would have been produced.
Regulations of Disinfection Byproducts
Most regulatory bodies or organizations (EPA, European Union, and WHO) provide either regulatory standards or guidance for monitoring some of common DBPS in found in treated drinking water. However, evaluation of the emerging DBPs, such as nitrogen- or iodine-containing DBPs, is still at an early stage. Collection of data regarding the health effects, occurrence, level of frequency as well as development and validation of analytical methods are necessary before regulatory determinations are considered for these emerging DBPs. Below you will fill find a summary of EPA regulatory initiatives for DBP’s based on compound type.
Total Trihalomethanes (TTHMs): TTHMs are regulated by the EPA at a Maximum Contaminant Level (MCL) of 80 ppb (µg/L). The European and National Drinking Water Quality Standards sets THMs at 100 ppb.
HAAs: Currently, only HAA5 are regulated by the EPA at an MCL of 60 ppb. HAA6Br and HAA9 are on the recent monitoring list of UCMR 4, a program the EPA uses to evaluate unregulated drinking water contaminants. You can also find the detailed list of these HAAs here.
Chlorate: Although chlorate was evaluated in the UCMR 3 program, no regulatory determinations have been made. Read the chlorate review to learn more.
Chlorite: the EPA currently regulates chlorite at a MCL of 1 ppm (mg/L).
Bromate: regulated by the EPA at a MCL of 10 ppb. The European and National Drinking Water Quality Standards also set bromate at 10 ppb as the health-based chemical standard.
The EPA and International Organization for Standardization (ISO) have developed a variety of analytical methods to quantify common DBPs in drinking water some of which are listed below.
There are many techniques that can be used to identify and quantitate known DBPs; unknown DBP compounds create a specific challenge that current technologies cannot easily navigate. The recent introduction of high resolution accurate (HRAM) mass spectrometry coupled with gas chromatography (GC) has introduced advanced capabilities that provide new tools for approaching this challenge. The benefits of this novel technique have recently been demonstrated in the analysis of nitrogen-containing and iodinated DBPs. Using the Q Exactive™ GC Orbitrap™ GC-MS/MS simultaneous screening and identification of both known and unknown compounds can be accomplished with great accuracy. If you are interested in learning more about the application of this technology, you can register for the May 13 webinar by Dr. Cristina Postigo discussing the characterization of the iodinated disinfection byproducts.
Protecting Yourself from Disinfection Byproducts in Swimming Pools
Now let’s jump back in to the swimming pool. The intent of this blog is to raise awareness about the potential dangers of exposure to DBPs, not to convince you to stop swimming. After all summer is right around the corner! Because swimming is the third most popular sport in the U.S. according to the data from the U. S. Census Bureau in 2010, with more than 52 million people swimming at least 6 times a week the risk for exposure is high. Since many DBPs (both known and unknown) can be produced in swimming pools when treated by chlorination swimmers must take precautions to protect themselves and others from the potentially harmful effects of these compounds. A few steps that can help include the following:
Shower with soap before and after swimming
Avoid drinking swimming pool water
Bring children to the restroom before swimming and instruct them not to urinate in the pool
When swimming indoors, make sure the pool area has the appropriate amount of air circulation
Follow these guidelines to help ensure it is “safe to go back into the water”, but the dangers that DBP exposure present should be taken seriously.
Learn more about other DBP analysis methods for bromate and HAAs.