N,N-dimethylamphetamine can arise during methamphetamine heating, but it can also occur as a manufacturing impurity. That dual origin complicates its proposed use as a community marker of methamphetamine smoking. A 2018 study by Been and colleagues investigated the problem by comparing wastewater, seized drugs and smoking-device residues.
What evidence was compared?
The researchers analyzed wastewater from eight Australian treatment-plant catchments, including urban and rural locations. Wastewater observations covered 2011–2016, with the multi-year temporal analysis concentrated in one catchment. They also obtained forensic data on 794 methamphetamine seizures from 2006–2007 and nine smoking-device residues analyzed in 2016–2017.
These were different materials collected during different periods. The study did not administer a standardized smoked dose to people or directly measure the fraction of residents who smoked methamphetamine.
Were all reported ratios measured the same way?
No. Wastewater compounds were analyzed with chromatographic mass-spectrometric methods. For comparison with consumed material, wastewater concentrations were adjusted using assumed unchanged urinary-excretion fractions: 17.0% for dimethylamphetamine and 28.5% for methamphetamine.
Seizure and pipe-residue ratios were semi-quantitative estimates based on normalized GC-MS peak responses. They were not uniformly obtained by the same quantitative wastewater assay. The comparison combines analytical information with assumptions about metabolism and excretion.
The adjusted wastewater DMA/MA ratios had a median of 0.007, compared with 0.0004 in the seizure data. Pipe-residue ratios ranged from 0.031 to 3.37. These distributions supported investigating sources beyond impurities, but they did not define a validated percentage-smoking calculation.
How common was the impurity?
Dimethylamphetamine was detected in 459/794 seizures, approximately 58%. Among positive seizures, 87% had an estimated DMA/MA ratio below 0.0025. The compound’s presence therefore was not specific to material that had already been smoked.
A marker can be chemically informative without having a unique origin. Establishing that a compound is produced during heating does not establish that every detection arose through that pathway.
Did it form inside wastewater during the experiment?
The researchers tested raw wastewater over twenty-four hours at room temperature with methamphetamine, dimethylamphetamine or both added. Dimethylamphetamine was not detected when methamphetamine alone was added. The tested conditions therefore did not demonstrate conversion of methamphetamine into dimethylamphetamine within wastewater.
This negative result narrows one explanation but does not validate every sewer environment. The authors identified unexamined influences such as microbial degradation, sorption and biofilm conditions. A limited stability experiment is not a comprehensive simulation of all catchments.
Why was the historical seizure comparison a major limitation?
The seizure data preceded the wastewater observations by several years. Manufacturing methods, purity and impurity profiles could change during that interval. Without contemporary seizure data, a falling wastewater ratio could reflect changing impurities rather than fewer people smoking methamphetamine.
Indeed, the temporal series showed declining ratios alongside increasing methamphetamine loads. That divergence should not automatically be interpreted as declining smoking prevalence. Changes in the numerator, denominator and source composition all require consideration.
The study supports further investigation using simultaneous wastewater and seizure measurements. It does not establish an individual route of administration, prove smoking from one positive marker, or convert a community wastewater ratio into a clinical or impairment conclusion.
Source
Been F, O’Brien J, Lai FY, et al. Analysis of N,N-dimethylamphetamine in wastewater—a pyrolysis marker and synthesis impurity of methamphetamine. Drug Testing and Analysis. 2018;10(10):1590–1598. doi:10.1002/dta.2419.
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