Persistence of methamphetamine after cleaning of dwellings formerly used as clandestine laboratories

Abstract

Methods used for the manufacture of methamphetamine in New Zealand often generate semi-volatiles that contaminate houses used as clandestine laboratories. There is uncertainty as to how effective current cleaning methods are for removing methamphetamine. Surface swabs and air samples were collected from suspected former clandestine methamphetamine laboratories in New Zealand prior to and following remedial cleaning. Surface wipe samples were collected, extracted, derivatised and analysed by GCMS. A deuterated methamphetamine internal standard was spiked onto swabs immediately upon return to the analytical laboratory to enable reliable quantitation. A variety of surface materials from floors, ceilings, walls, doors, windows and built-in shelving were sampled throughout each dwelling. Air was tested using solid-phase micro-extraction (SPME) with GCMS analysis. Analysis of surface swabs showed that methamphetamine was the primary drug residue along with smaller amounts of pseudoephedrine. Several surface methamphetamine levels exceeded 1.5 ug/100 cm2, with some exceeding100 ug/100 cm2, even after several cleaning episodes. Surfaces that had been stripped of wallpaper and washed also showed methamphetamine contamination, indicating either penetration of methamphetamine through wall coverings,recontamination from cleaning activities, or redistribution of volatile methamphetamine. Air testing showed that most of the volatile organic compounds detected prior to cleaning decreased in concentration following cleaning. However, when methamphetamine had been detected in a dwelling during initial testing, it continued to be present at similar concentrations during subsequent air testing after cleaning. These findings suggest that while manual washing of former clandestine methamphetamine laboratories reduces concentrations, there may still be significant methamphetamine contamination remaining.