You are what you eat, the saying goes. It therefore follows that what you excrete gives away a lot about you.
Writ large, that information might yield useful demographic clues about particular neighbourhoods.
This, at least, is the thinking behind a study by Saer Samanipour of the University of Amsterdam, in the Netherlands.
Dr Samanipour has been analysing sewage, and has shown that it gives a pretty good profile of an area's population.
To make sure that his analysis reflected the most up to date demographic information Dr Samanipour timed it to coincide with a census.
The one he chose was that conducted in Australia, in 2016, so he called on the assistance of a group of colleagues from the University of Queensland.
As they describe in a paper in Environmental Science and Technology Letters,
正如他们在《Environmental Science and Technology Letters》的一篇论文中所述，
team members collected samples from more than 100 sewage-treatment plants for five to seven consecutive days around the time of the census.
They analysed these for 40 chemicals that past research has suggested have socioeconomic significance.
Nicotine, for example, is associated more with rural populations than urban ones, because people living in the countryside are more likely to smoke.
Caffeine consumption correlates with education levels. Amphetamine use tracks levels of crime.
In total, the team looked at the concentrations of six legal recreational drugs, caffeine and nicotine among them,
two illegal recreational drugs (amphetamine and methamphetamine),
seven opioids (the legality of which depends on the circumstances), eight antidepressants and antipsychotics,
nine other pharmaceuticals, two artificial sweeteners and six markers of diet,
such as enterolactone, a substance that shows how much fibre people are consuming.
All of the chemical information collected from each treatment plant was paired with data from the census
to create a model of what the wastewater chemistry of populations with particular socioeconomic characteristics looks like.