BPs (see Table 2). While the ICR focused on the disinfection byproducts, which are currently regulated, the Nationwide Disinfection Byproduct Occurrence Study looked at about 50 other DBPs determined as having a higher potential for toxicity than the currently regulated DBP. Some of these include compounds such as MX (3-chloro-4-dichloromethyl-5-hydroxy-2(5H)-furanone), brominated forms of MX (BMXs), halonitromethanes, iodo-trihalomethanes, and brominated species of halomethanes, haloacetnitriles, haloketones and haloamides.
The results of this study were published in September 2002. The study was conducted by the scientists from the EPA’s National Exposure Research Lab, University of North Carolina (UNC) and the Metropolitan Water District of Southern California (MWDSC).
At the time of the study, no qualitative methods existed for most of the high-priority DBPs; therefore, UNC and MWDSC helped in developing methods for detection and quantitation. Unfortunately, no single method could detect all of the DBPs of concern, so several methods were employed.
At this point, no methods have been approved by the EPA for continued monitoring of these DBPs, but they are continuing to refine methods for future regulations. The results of the study indicated the presence of the high-priority DBPs in the waters that were sampled. Many included in the study were brominated DBPs or iodinated DBPs due to the presence of naturally occurring bromide and iodine in public water supply sources.
Toxicological studies seem to indicate that brominated DBPs are more toxic than chlorinated DBPs, and iodinated DBPs are more toxic than brominated. Significant data of the study found that treatment plants that used chloramination without prechlorination formed the highest levels of iodo-trihalomethanes, and the highest concentrations of dichloroacetaldehyde occurred at plants that utilized chloramine and ozone for disinfection.
Most importantly, the study indicates that while we are trying to use other treatment technologies to reduce the regulated DBPs, we are probably creating other DBPs that are not currently regulated but may be more toxic.
Testing & Disinfection
Disinfection of drinking water is critical to reducing illness and death due to microbiological pathogens that can occur in our water supply sources. The tradeoff is the potential formation of byproducts that can also present a health risk to the public. More studies need to be conducted on the toxicological effects of these emerging DBPs so we have a complete understanding of potential health effects.
In addition to studies that are looking at the ingestion of these DBPs by drinking the water, they are also beginning to look at other routes of exposure including inhalation and dermal absorption.