Sensitive screening for second-hand marijuana exposure

Constant debate and controversy surrounds the legalization of marijuana for medicinal and recreational purposes, with a growing interest in potential health effects of both first- and second-hand smoking.

A multifunctional method has been developed and validated by researchers at the US Centers for Disease Control and Prevention (GA, USA) to monitor marijuana exposure from both active and passive use. Their findings were recently published in Analytical Chemistry.

The method enables the detection of tetrahydrocannabinol (THC; the psychoactive marijuana component) and its metabolites in urine. While currently available tests are able to detect large amounts of THC and its metabolites in active users, monitoring marijuana exposure from second-hand smoke – in which only trace levels of substances can be found in urine – requires a more sensitive detection technique.

Wei B and colleagues at the U.S. Centers for Disease Control and Prevention used a UHPLC–MS/MS technique to analyse urinary THC (and its metabolites). To reach the sensitivity required to screen for second-hand marijuana exposure, positive electrospray ionization (ESI) was used.

The limits of detection (LOD) were 10–100 times more sensitive than methods currently reported in literature, and laboratory investigations demonstrated detection of substances at low levels – akin to those that would be found in second-hand marijuana exposure.

The method boasts a potential for large-scale population studies, owing to the fact sample preparation throughout was enhanced using an automation liquid-handling system.

Sources: Testing for secondhand marijuana exposure; Wei B, Wang L, Blount BC. Analysis of cannabinoids and their metabolites in human urine. Anal. Chem. 87(20), 10183–10187 (2015).