An environmental study made headlines this spring as it drew a distinct parallel between the growing PPCP epidemic and a poisonous disinfection byproduct (DBP) making its way into drinking water. The culprit in this case is methadone, which reacts to chloramination by forming large amounts of N-Nitrosodimethylamine (NDMA), a probable human carcinogen.
Using a mass spectrometry screening procedure, a team of researchers assembled from Arizona State, the University of Colorado at Boulder, and the University of Toronto discovered the connection and published their findings in Environmental Science & Technology Letters.
The study found a median methadone concentration of 23 mg/L and determined the drug was responsible for 1 to 10 percent of NDMA formation potential (FP) in most raw surface waters in which it was detected, and up to 62 percent of NDMA FP in wastewater.
“The conclusion is that pharmaceuticals, in particular methadone, are responsible for at least some of the formation of a carcinogen in drinking water,” said David Hanigan, the study’s lead PhD student. “This adds to mounting evidence that loading pharmaceuticals to our wastewater plants, which are not designed to remove them, is damaging ecosystem health and human health.”
Hanigan pointed to the unnatural phenomenon of fish feminization as an example of this damage to our ecosystem health. While he believes the water industry is aware of the presence of NDMA in water, a conclusive treatment method hasn’t been developed to combat it.
“Early indications suggest that activated carbon, pre-oxidation with ozone or chlorine dioxide, and changing primary or secondary disinfectants to free chlorine from chloramines will reduce or eliminate NDMA formation,” Hanigan said, when asked what treatment plants might do to avoid NDMA forming in the first place. But he noted that pre-oxidation and disinfectant switching can form other byproducts that may be harmful.
“Therefore my suggestion would be for plants to use activated carbon prior to disinfection,” he said. “This is, unfortunately, likely the most expensive option for most water treatment plants. It is the only one, though, that removes organic matter rather than simply transforming it to something that is not reactive in forming NDMA.”
He may be a preeminent scholar on the risk that methadone runoff is introducing to our waters, but Hanigan remains tempered in his stance on the drug.
“Although this is carcinogen exposure that could be in part or entirely due to upstream prescription use, I still view this as relatively low risk,” he said. “Rather than think about removing methadone from physicians’ toolsets, we should work to find a way to remove methadone from water.”
Due in no small part to its attention-grabbing focus on methadone and the possibility that our water is giving us cancer, the study was seized by media outlets upon its release, including this one. Coverage resulted from PBS, The U.S. Finance Post, and a slew of scientific publications. But Hanigan feels that many readers are drawing the wrong conclusion and don’t realize the power they have to change things for the better.
“Sometimes I see people saying they are switching to bottled water, which I think really misses the point,” he said. “Whether it’s methadone, sucralose, synthetic estrogen, we are all responsible for surface water pollution with pharmaceuticals and anthropogenic chemicals, and thus are all responsible to find ways to fix these issues.”
Image credit: "weekend supply," Mr Cumbo © 2007, used under an Attribution 2.0 Generic license: https://creativecommons.org/licenses/by/2.0/