Wastewater Reveals What People Eat and Drink

Scientists have found a new way to learn about the habits of city residents by looking at their sewage. The technique, called wastewater‑based epidemiology, usually tracks drug use but now also measures food and drink markers. A fresh laboratory test can spot more than 40 different substances in raw city water, from alcohol and nicotine to artificial sweeteners and vitamins. The test mixes a few simple steps. First, tiny cartridges pull out low‑concentration food markers from the water. Then, most other chemicals are measured directly after a quick dilution. The key to separating the many compounds is a special liquid‑chromatography machine that uses a small amount of acetic acid and another solvent called acetonitrile. The machine watches for specific fingerprints of each marker, allowing scientists to count them accurately.The method was checked by running many experiments. Most markers were recovered well, and the numbers matched what was expected. The limits of detection are low enough that even rare chemicals can be seen in real samples. When researchers kept the sewage at 4 °C for a day, almost all markers stayed stable; however, repeated freezing and thawing caused some loss. This means samples should be kept cold and not repeatedly frozen. To test the real‑world usefulness, researchers collected 24‑hour sewage samples from four cities in Croatia. The new test worked reliably on all of them, showing it can be used to monitor what people are eating and drinking in different urban areas. This could help public health officials understand diet trends, food safety issues, and the overall well‑being of communities. The approach opens a door to studying community health without asking individuals directly. By watching what ends up in the pipes, scientists can get a broad picture of lifestyle choices and nutritional habits that would otherwise be hard to track.