Resource Hub / ChromaBLOGraphy / Human Exposure to Toxic Unregulated Disinfection By-Products

Human Exposure to Toxic Unregulated Disinfection By-Products

8 Jan 2024

Identifying Unknown Disinfection By-Products (DBPs) and Why We Should Continue the Quest for New DBPs

In my last blog,  we discussed a comprehensive study to quantify 60 regulated and priority disinfection by-products (DBPs)  in three popular teas in the United States. In this blog we’ll review unregulated and unknown DBPs and why they matter, as well as analytical techniques.

Disinfection by-products (DBPs) continue to be important environmental contaminants. Unlike industrial solvents and persistent organic pollutants (POPs), DBPs are formed when organic matter comes into contact with chlorine, bromine or iodine. While drinking water may contain other contaminants the DBP’s are orders of magnitude higher in concentration and have a direct impact on aquatic organisms following release of treated water into the environment. In addition to their impact on the environment, epidemiological studies have documented adverse effects on human health which include bladder cancer, colorectal cancer, miscarriage, and birth defects¹. While some DBPs such as the trihalomethanes (THMs) which include chloroform, bromoform, dichlorobromomethane, dibromochloromethane are considered “legacy contaminants” and have been regulated for decades, more than 700 additional DBPs have been identified.  Globally very few DBPs are regulated for instance: 11 in the US & Canada, 14 in China, 12 in Japan, 13 in Australia and 5 in the European Union (EU). The World Health Organization (WHO) recommends testing for 15 DBPs.  Of the >100 unregulated DBPs that have been studied for toxicity, many are more toxic than those currently regulated2.

Identifying unknown volatile DBPs is challenging. To be truly ‘identified’, a match of the mass spectrum and retention time is required with a certified reference standard. This is especially important with isomers and other compounds with similar mass spectra.

Identification of unknown DBPs in drinking water and environmental samples uses both liquid chromatography (LC) and gas chromatography (GC) techniques. The emergence of mass spectrometers with high resolving power, high mass accuracy and sensitivity are required especially when analyzing complex matrices. For example, the Orbitrap and quadrupole-time of flight (QTOF) mass spectrometers have demonstrated the ability to detect iodo-DBPs, and accurate mass identification of other halogenated contaminants GC-MS and Electron Capture Detectors (ECD) have historically been used to determine DBPs, however higher molecular weight / non-volatile compounds can be analyzed using LC-MS. A comprehensive analytical screening of unknowns would require the use of both techniques3.

Table 1. Examples of Unknown DBPs Identified using Restek Rxi-5ms GC column (30 m × 0.25 mm ID × 0.25 μm) and a Restek Rxi-17Sil MS column (0.48 m × 0.1 mm ID × 0.1 μm) in Simulated Tap Water Brewed Tea.

Examples of Unknown DBPs Identified using Restek Rxi-5ms GC column (30 m × 0.25 mm ID × 0.25 μm) and a Restek Rxi-17Sil MS column in Simulated Tap Water Brewed Tea

“Unknown DBPs were detected in all tea samples; however, DBP-3 was not detected in brewed tea. DBP-7/8/9 showed one peak in GC-HRTTOF-HRMS but showed three isomers using GCxGC-TOF-MS. The isomers of DBP-1/2, DBP-3/4, DBP-5/6, and DBP-7/8/9 were confirmed by the retention time and mass spectra of standard in GCXGC-TOF-MS. Reference: Environ. Sci. Technol. 2021, 55, 12994-13004

Toxicity data is critical to understanding the significance of new DBPs. Toxicological studies of treated whole waters enables different treatments to be evaluated and different cities’ drinking water to be compared. By evaluating the whole water, the toxicity of both known compounds can be measured to the unknown compounds in the complex mixture 2. We can help you identify unknown DBPs with columns and consumables, below are some examples of research in this area done with our products.

Additional DBP articles using Restek Columns and consumables;

Analysis of tea for disinfection byproduct exposure to include the identification of unknown compounds. Agilent 7890 GC-MS instrument described below with electron ionization. Sample extracts (1.0 μL) were injected into a multimode inlet in pulsed splitless mode using a Restek Rtx-200 column; 30 m × 0.25 mm × 0.25 μm. For analyses in single-GC mode, the type of column (Restek Rxi-5ms GC column; 30 m × 0.25 mm ID × 0.25 μm). For analyses in GC × GC mode, the primary column was the same as above, and the secondary column was a Restek Rxi-17Sil MS column (0.48 m × 0.1 mm ID × 0.1 μm)

The analysis of 60 disinfection byproducts in swimming pools. Analytes were chromatographically separated using a Restek Rtx-200 column (30 m × 0.25 mm × 0.25 µm film thickness; Restek Corporation, Bellefonte, PA). This column provides improved separation and detection limits for iodo-THMs and haloacetamides, which tend to tail and give lower responses using a DB-5 column.

The presence of specific algae can more than double concentrations of DBPs in water. Used an Rtx-200 column (30 m × 0.25 mm × 0.25 μm; Restek Corporation, Bellefonte, PA).

The analysis of halogenated compounds and 61 unregulated DBPs were studied in Flint Michigan. Samples were injected onto a Restek Rtx-200 column (30 m × 0.25 mm ID × 0.25 μm film thickness; Restek Corporation, Bellefonte, PA)

Used an Rxi-5ms (30 m × 0.25 mm ID × 0.25 μm film thickness; Restek Corporation, Bellefonte, PA)