Cocaine contamination

From cash to creatures – cocaine is running wild

A large number of studies have found traces of drugs – especially cocaine – on banknotes. But it’s not only cash that can be contaminated. Bank cards, door handles and photocopiers often retain traces of the substance. Residues of cocaine have even been detected in animals.

Following the powder trail

Smooth surfaces like desks and photocopiers are ideal for “doing a line”. A bank card serves as a precision tool for shaping the powder into even lines so that none goes to waste. Finally, a seemingly harmless banknote can be rolled up into a tube through which the “line” is snorted into the nose. In this way, drug residues that are invisible to the naked eye are deposited on everyday surfaces and objects.

Clean bank notes are rare

Cocaine-contaminated banknotes are frequently reported on in the media. Shortly after the introduction of the euro in early 2002, only a small number of banknotes in Germany had such residues. However, just seven months later, nine out of ten did. Smaller notes were found to be more contaminated. One study in Ireland in 2007 even found traces of cocaine on every single banknote tested.^1, 2

Polymer versus paper notes

The material from which notes are made plays a role in the transfer of residues, with polymer banknotes much more likely to transfer cocaine particles than paper notes. Paper notes consist mainly of cotton, making them more porous so that they act like a sponge. As a result, cocaine residues adhere better to them and are less likely to be transferred to other surfaces. Euro notes are still made from cotton. In contrast, some countries – such as Australia – have adopted polymer banknotes in recent years.^3, 4

Trace levels compared

Levels of cocaine contamination on banknotes vary widely across the globe. The highest concentrations have been found in the United States, with over 1300 μg per note detected in some studies. On average, however, the values detected are in the single to double-digit microgram range. Within Europe, Spain is clearly leading the pack – with up to 889 μg of cocaine residues per note, Spanish banknotes are the most contaminated. On average, they carry around five times more traces of cocaine than German euro notes – which is no coincidence, given that Spain is a key point entry point for the drug into Europe.⁵

Animals on drugs

In 2024, Brazilian researchers discovered higher concentrations of cocaine and its main metabolite benzoylecgonine in the tissues of sharpnose sharks than had previously been found in other marine animals.⁶ The European eel is also suffering from the effects of exposure to cocaine in river water. Numerous studies from around the world have detected residues of drugs and their metabolites in samples taken from bodies of water. This can be explained by the widespread use of drugs and by variations in the effectiveness of waste water treatment.⁷

Cocaine is in the air

Drugs and psychoactive substances are becoming a focal point for air analysis. Cocaine, among other substances, has been detected in air measurements taken in almost all large cities around the world. A nationwide study in Italy also found that cocaine was the most prevalent drug in the air in both urban and rural areas, with Milan top of the list. However, the concentrations detected aren’t sufficient to make people “high” or unfit to drive.⁸

A rising trend

According to the 2025 report by the European Union Drugs Agency (EUDA), the ready availability of cocaine is steadily increasing in Europe. As a result, rising concentrations of residues are to be expected.⁹