Researchers in the Australian city of Adelaide have been sifting through local sewage in order to determine how levels of drug use change over time, finding that concentrations of methamphetamine – also known as crystal meth – in residents’ poop has doubled over the past four years.

The study, which appears in the journal Science of the Total Environment, also reveals that drug use is not constant throughout the year or even the week, with some substances becoming more popular during particular seasons and at weekends.

To conduct their research, the study authors spent one week analyzing sewage samples every two months between December 2011 and December 2015. While this unenviable task may not be how most people imagine scientists spending their time, lead researcher Cobus Gerber told New Scientist “it’s not as bad as you think,” adding that “you get used to it.”

Written into the city’s excrement, the study authors find a tale of dynamic drug markets and social activity, leading to seasonal fluctuations in substance use. MDMA levels, for instance, increased by 90 percent in December – something the researchers put down to the fact that the drug is “conducive to party behavior.”

The drug – which is commonly found in ecstasy tablets – is also much more popular at weekends, when levels tend to rise by 125 percent. Similarly, cocaine was 75 percent more prevalent in weekend poo samples than those obtained on workdays.

Cannabis levels, meanwhile, were found to drop by 45 percent in February, when the marijuana harvest cycle reaches its low point. As such, the researchers propose that this reduction in weed use is probably caused by decreased availability at this time of year.

The social dynamics of life in Adelaide were also discernible in the city’s droppings, which revealed that cocaine use was 45 percent higher in affluent areas than deprived neighborhoods. In contrast, methamphetamine use was 15 percent higher in poorer parts of the city, providing an intriguing insight into which drugs are consumed by members of different socioeconomic groups.

On the whole, crystal meth was found to be the most popular stimulant in Adelaide, in keeping with the trend seen across East and Southeast Asia, where cocaine use is typically low. By contrast, cocaine is the most common stimulant used in Western Europe, which has low levels of methamphetamine consumption.

Alarmingly, use of synthetic opioids like fentanyl rose over the four-year period under consideration. Estimated to be around 10 times stronger than heroin, fentanyl is often sneakily mixed in with street drugs to increase their potency, and has been linked with a number of accidental overdose deaths around the world.

Smelly science at its finest.