Methadone Linked to NDMA Contamination in Drinking Water

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Methadone, a drug prescribed for managing the symptoms of heroin withdrawal and chronic pain, has been linked to the formation of the carcinogenic compound N-Nitrosodimethylamine (NDMA) in drinking water.¹ Understanding which compounds contribute to NDMA formation in water could lead to tailored wastewater treatment approaches to remove the risk of contamination.

NDMA is a carcinogenic compound that can contaminate drinking water, and is thought to enter drinking water in recycled wastewater that has been disinfected using chloramination. Lead author David Hanigan told The Column: “Previously people thought that natural organic matter in the water was responsible but that has slowly been disproven, as we typically see no correlation between organic carbon (representative of natural organic matter) in the water and NDMA formation in disinfected waters.”

Wastewater is a very complex sample, making it difficult to identify factors important to NDMA formation. Research has previously suggested that candidate compounds can react to form NDMA when chloramines are added, but this approach does not show if the precursors are actually in the surface water or the wastewater. With funding from the Water Research Foundation, researchers from Arizona State University (Arizona, USA), the University of Colorado at Boulder (Colorado, USA), and the University of Toronto (Ontario, Canada) collaborated to screen surface waters and the secondary effluent of a wastewater treatment plant from across the United States and Canada.

Samples of wastewater and secondary efluent were screened using liquid chromatography coupled to quadrupole time-of-flight mass spectrometry (LC–QTOF-MS), looking for candidate compounds with tertiary amine groups. Methadone was identified as a potential candidate and was quantified using gas chromatography coupled to mass spectrometry (GC–MS). Methadone was detected in samples at concentrations ranging from 32–2256 ng/mL.

A methadone standard was then used in a NDMA formation assay to determine the rate of formation. Hanigan said: “The novelty is that methadone forms a lot of NDMA, 6 of 10 molecules are reacted, and that we have already inherently shown occurrence by the original discovery. Thereby, we can account for its contribution and estimate the risk.”

So what is next? Hanigan told The Column that the team will continue to investigate NDMA formation to find other candidate compounds that could be contributing factors. He said: “We are sure there are others out there as we are not yet able to account for the total NDMA formation, and if we are able to determine which are the most important, we can begin to propose tailored treatment technologies.” - B.D.

Reference
1. D. Hanigan et al, Environmental Science & Technology Letters DOI: 10.1021/acs.estlett.5b00096 (2015).

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