Our study involved the measurement of N-nitrosamines, and their chloramine- and ozone-reactive precursors in different greywaters (e.g., laundry waters and sink waters) and blackwaters (e.g., urine and feces) contributing to sewage. On the basis of previous research suggesting that the pharmaceutical, ranitidine, serves as a chloramine-reactive precursor for Nnitrosodimethylamine (NDMA), our study included the collection of one urine and one fecal sample from each of two volunteers after the consumption of one 150 mg tablet of ranitidine. Our results indicated the occurrence of NDMA in the two urine samples collected after consumption of ranitidine, but not in the five samples collected without ranitidine consumption. We did not detect NDMA in the fecal samples. We had employed gas chromatography mass spectrometry (GC/MS) to measure NDMA. GC/MS has been a standard technique for the analysis of NDMA in water and wastewater samples by EPA Method 5211 and by the U.S. Food and Drug Administration (FDA) for the analysis of NDMA in pharmaceuticals as recently as January 25, 2019.2 However, research has since identified the potential for an analytical artifact that could have contributed to the levels of NDMA measured in urine samples containing ranitidine in our study. Specifically, research has demonstrated that ranitidine is thermally unstable, and can convert to NDMA under high temperature conditions, such as might be encountered within GC injection ports.3 For our GC/MS method, the injection port temperature started at 37 °C but was ramped to 230 °C over the first 20 s after injection. Unfortunately, given the potential for this analytical artifact, our NDMA measurements within urine samples collected after consumption of ranitidine are not reliable, since NDMA could have been formed during the sample analysis from any ranitidine present in the urine. Although the detection of NDMA in these specific urine samples was not reliable, this does not affect the conclusions of the study, since we did not conclude that ranitidine consumption was associated with an important contribution of NDMA or its chloramine- or ozone-reactive precursors to sewage. The FDA has since developed two analytical methods to measure NDMA levels in pharmaceuticals that avoid this temperature-dependent analytical artifact by using liquid chromatography mass spectrometry (LC/MS).4,5.
ASJC Scopus subject areas
- Environmental Chemistry