Investigating the correlation between wastewater analysis and roadside drug testing in South Australia
Graphical abstract
Introduction
Wastewater analysis (WWA) has become a standard means of assessing population-scale use of illicit drugs and other substances of interest (European Monitoring Centre for Drugs and Drug Addiction, 2016). In Australia, the approach has been applied to estimate drug use in several regions over a period of six years (Irvine et al., 2011, Lai et al., 2013, Lai et al., 2011, Tscharke et al., 2016) and, more recently, has been applied nationally (Australian Criminal Intelligence Commission, 2017). Although WWA can reflect the relative scale of drug use in a community, it cannot distinguish between heavy use by a small number of habitual users from occasional use by a large number of drug takers. Consequently, if the scale of drug use changes over time in an area, as measured by WWA, it is not possible to determine whether the change is due to a shift in users in the community, a change in frequency of use, or changes in the purity of available drugs or the amount of pure drug consumed.
Increases in the use of an illicit drug in a population are associated with a number of adverse consequences. In general, the precise consequences depend on the nature of the drug but may include increased harm and increased criminality associated with intoxicated behaviour (Walters, 2014). One consequence that is associated with use of all illicit drugs is impairment of driving. For a range of drugs, there are a number of epidemiological and experimental studies showing driving impairment as a result of use of the drugs at the doses normally consumed, and the epidemiological evidence shows that this impairment results in an increase of both fatal and non-fatal crashes (Elvik, 2013).
Based on this evidence, roadside driver testing (RDT) for a limited range of drugs has been implemented in a number of countries, including Australia. After the compulsory oral swab tests are conducted, confirmatory analyses in a forensic laboratory are performed on oral fluid to establish whether or not the driver had consumed drugs and was driving under the influence. In Australia, tests are only carried out for methamphetamine, MDMA and cannabis (alongside alcohol).
If drug use increases in a population, and particularly if that increase in total use is due in part to an increase in number of users, then this may be reflected in the rate of positive detections in RDT for that drug. It would therefore be expected that for each drug, rates of use measured by WWA would correlate with RDT detections. However, a limitation of RDT is that targeted policing captures drug ‘hotspots’, creating the risk of sampling bias, although the number of drug tests and sites covered over a year provides a sample that is close to random. In Finland, driving under the influence of drugs and drug seizure information was compared to results from WWA from 2008 to 2015, and there were relatively good correlations for the drugs investigated (Kankaanpää et al., 2016). In Norway, methamphetamine and amphetamine use were compared across drug seizures, RDT, WWA, forensic autopsies, and urine from prisoners with similar trends observed in all data sources (Bramness et al., 2015).
Currently, there is limited data showing positive correlations between driver test positive numbers and WWA trends (Bramness et al., 2015, Kankaanpää et al., 2016, Kankaanpää et al., 2014, Reid et al., 2012). These included a significantly lower number of tests compared to the present study and were limited to comparisons between data of different time scales; one or two-week periods of WWA were compared to the overall positive-test rate in each year. This paper, to the best of the authors’ knowledge, is the first to investigate the potential complementarity of WWA and RDT outside Europe. The correlation between the temporal trends for these two measures of drug use was evaluated for methamphetamine, cannabis, and MDMA in bimonthly sampling from December 2011 − December 2016.
Section snippets
Wastewater analyses
Wastewater samples from four wastewater treatment plants in Adelaide, Australia were collected and analysed for methamphetamine, MDMA, and cannabis. Seven consecutive days of wastewater samples were collected every two months during the first week of the month (or the second week to avoid public holidays) from December 2011 to December 2016. All information regarding sample preparation and analysis is described elsewhere (Irvine et al., 2011, Tscharke et al., 2016).
Roadside drug testing
The manner of roadside drug
Results of wastewater analysis
Bimonthly analysis of four wastewater treatment plants of Adelaide has been carried out since 2011. In the period up to the end of 2016 clear trends have been observed: methamphetamine use has increased significantly, MDMA has steadily declined, and cannabis has remained relatively stable, albeit with seasonal fluctuations each year coinciding with the growing/harvesting seasons (Tscharke et al., 2016).
Roadside drug testing
All data pertaining to the roadside drug tests are presented in Table S1. The number of RDTs
Role of funding source
This work was supported in part by Drug and Alcohol Services South Australia, SA Health.
Contributors
RB, BT, JW and CG planned and designed the study. BT performed wastewater analysis. ML and RC acquired roadside drug testing data. RB and BT interpreted the results from both sets of data with contribution from all co-authors. RB and BT wrote initial draft with input from JM and CG, which was critically revised by all co-authors.
All authors are aware of the content of and accept responsibility for the manuscript. All authors contributed to and approved of the final version of the manuscript.
Conflict of interest
None.
Acknowledgements
The authors gratefully acknowledge support from SA Health, South Australia Police and the Australian Criminal Intelligence Commission. We would also like to thank the wastewater plant operators for their assistance in sample collection.
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Cited by (0)
- 1
Richard Bade and Benjamin J. Tscharke are joint first authors.
- 2
Queensland Alliance for Environmental Health Sciences (QAEHS) University of Queensland 39 Kessels Rd Coopers Plains Queensland Australia 4108.