In 2013, the Ministry of Health, Welfare and Sport asked the National Institute for Public Health and the Environment (RIVM) to estimate the extent of the illegal market in Viagra tablets. RIVM has conducted sewage research to come up with an answer to this question. Data from pharmacies indicated how much Viagra had been sold legally, and sewage analysis revealed how much of the drug was actually being used.

Insight into illegal market  

Sewage research revealed that much more Viagra was being used than was being sold through pharmacies. Illegally obtained Viagra accounts for the difference. In 2013, the illegal market for Viagra accounted for about 65% of total usage.1 By 2017, this had increased to almost 80% (see figure below). 

This shows how sewage research can give a clearer insight into the scale of the illegal market for a particular medicine. If necessary, measures can then be introduced in response. RIVM regularly conducts research of this type into various other medicines. Current events often trigger the research. 

But sewage research is not just about understanding the nature of illegal markets. Medicine residues in sewage also reveal how medicines are processed in the human body. Sewage research offers great potential for detecting substances and understanding how much of our medicine residues eventually end up in the environment.  

1.    Venhuis BJ, de Voogt P, Emke E, Causanilles A, Keizers PHJ. Success of rogue online pharmacies: sewage study of sildenafil in the Netherlands. Br Med J 2014; 349: g4317.