Wastewater-based epidemiology (WBE) is a rapidly developing scientific discipline with potential for monitoring real-time data on geographical and temporal trends in illicit drug use, which established itself as a useful complement to existing monitoring tools in the illicit drugs area. It involves sampling a source of wastewater, such as the sewage influent of a wastewater treatment plant. This allows scientists to measure the levels of illicit drugs and their excreted metabolites, which can then be used to estimate the quantity of drugs consumed by a community. This provides a non-invasive, near-real-time analysis of drug use within the area served by the sampled sewer network.
Communicating results in an effective and objective way is a key step in the process, and the list below is just an indicative approach on how this can be potentially achieved.
- Since the approach is non-invasive, and does not allow for identification of drug-using individuals, it does not give rise to any obvious ethical issues. However, thorough study design and cautious management of relationships with research partners (e.g. prisons or forensic authorities) may be needed to protect the anonymity of sample providers and prevent stigmatisation, if studies are performed in small or closed communities.
- Discuss the limitations of the method and results, for example sampling issues, establishing the population size, drugs that can accurately be detected by the method and those that cannot, and the distinction between the detection of the drug and detection of the actual use of the drug.
- Ensure it is clear that back calculations are estimating total amounts of the pure drug consumed. The calculation does not take into account impurities, so total weight of street drug consumed will be greater.
- Triangulate the results with data coming from other indicators (for example, drug surveys, seizures or drug purity) in order to piece together bits of information to obtain a credible whole.
- Provide a certain degree of interpretation to the results. As a researcher, you will be in the best place for it. Use external data to validate your results, where possible.
- Keep the interpretation of the results simple. Inform people in a way they can understand and use the information. Adjust the amount and nature of the given information to your audience. Invite feedback.
- Present the results expressed in daily amounts (or daily doses) per thousand population. Some different calculations may use the same units, for example ‘mass load’ and ‘amount consumed’ both use mg/day/1000 people. It is important to convey clearly what you are calculating so legitimate comparisons may be made with other WBE data.
- Special care is also suggested with regard to ensuring accurate communication of results to the media. The field awaits the establishment of best practices, taking into consideration the ethical aspects of wastewater research.
- WBE is a robust and powerful method, but it cannot and does not need to reply to all questions. There are still several uncertainties: sampling of wastewater, back-calculation methods, accuracy of population estimates, behaviour of biomarkers in sewer systems, etc.
- Keep the focus, don’t oversell or over-interpret the study results. WBE does not provide information on the prevalence of use or information on patterns of use (routes of administration, frequency of use, etc.).
- Do not create ‘league tables’ (e.g. city X is the European cocaine capital). WBE should help to conduct comparative analysis across countries and years, gaining additional understanding on drug-use dynamics and patterns, trends and regional patterns.
- Do not generalise results from one city to a whole country. Different catchment areas in close proximity may have very different drug consumption profiles, and data generated relates only to the catchment area sampled.
- Presenting results showing dosages by translating the total consumed amounts into the corresponding number of average doses is complicated. Drugs may be taken by various routes of administration and in amounts that vary considerably; and purity levels fluctuate on the market. If an end-user of the data requires dosage-estimate calculations, the variables, assumptions and limitations mentioned above should be clearly communicated.
- Do not publish data if the results were likely due to the release/dumping of an unconsumed drug into the sewer system. Specific analyses are available to identify releases and dumping events of unconsumed drugs.
The EMCDDA would like to thank the Sewage Analysis Core Group Europe (SCORE) and Institute of Environmental Science and Research Limited (ESR), New Zealand for their help in drafting this publication
For more information on drugs and wastewater, see our Wasterwater topics page.