What’s Really in Your Water? Tap Water, Bottled Water and the Chemicals We Leave, 08/08/2026

Professor Emma Schymanski reveals what water carries, why bottled may offer no advantage, and how our daily choices flow back into every glass. We turn on a tap, fill a glass, make a cup of tea (many cups, in my case) dozens of times a day without thinking twice. But our water carries traces of everything around it: the medication we take, the cosmetics we wear, even the flame retardants in our sofas. Some of it is monitored closely. Some of it we're only just learning to detect. And water, of course, doesn't stop at a border. To unpack all of this, I sat down with Prof. Emma Schymanski, Head of Environmental Cheminformatics at the Luxembourg Centre for Systems Biomedicine, University of Luxembourg, and an FNR ATTRACT Fellow. Her work combines chemical detective work with high resolution mass spectrometry to find chemicals hiding in water that nobody knew to look for, and to trace them back to their source. The Water Cycle Ignores Borders Water moves the way weather does: without any concern for what is a political border. Rain falls, rivers carry it across countries, and it sinks into groundwater that doesn't recognise a map. For Luxembourg, sitting downstream of its neighbours, that means inheriting chemical traces long before they reach a Luxembourg tap. Even in the Alps, even in Antarctica, contamination that starts on one continent eventually cycles back down in rainwater on another. Your Water's Fingerprint When people hear "water contamination," pesticides usually come to mind first. But that's a small part of the picture. Emma's team also finds pharmaceuticals, cosmetics, flame retardants, anti icing agents and dyes, everyday traces of everyday life. During the pandemic, her team watched caffeine levels in wastewater drop as the working population stayed home, and medical imaging dyes vanish almost entirely as routine cancer diagnostics paused. Antidepressant levels rise every winter. Antihistamines spike every spring. The Detective Work So how do you find a chemical when you don't know it's there? Emma's team runs water samples through mass spectrometry and looks for anomalies: a signal spiking above baseline, or one that suddenly disappears (in one case, tracing back to a factory shutting down for a six week holiday). It's forensic work, applied to a glass of water. That same technique now underpins wastewater epidemiology, used across Europe to trace drug use, and even, in one memorable case, to work out how drugs were getting into a prison. Tap Water vs Bottled Water Now here's a way to save money and perhaps stress. Emma's own research compared tap and bottled water across Luxembourg and found no statistically significant difference between them. The only real difference was between filtered and unfiltered tap water, and even filtering introduced its own new, if fewer, unknowns. She drinks from the tap herself, no filter at home. Even reverse osmosis, often floated as the ultimate fix, has a catch. It strips out almost everything, including the minerals your body needs, meaning treated water then has to have things added back in. "If you're drinking snow only, it won't quench your thirst, because it will actually start to strip the salt from your body," Emma explained. What You Can Actually Do This isn't a call to panic. It's a case for informed, small choices: Let the tap run cold for a couple of minutes before drinking, especially in older buildings, to clear water that's been sitting in the pipes. Favour metal, ceramic or glass over soft plastics for reusable bottles and cups. Don't assume "eco" means chemical free. Some paper straws are treated with solvents to stop them going soggy. Wash new clothing before wearing it. The New Frontier: Data Centres AI and water is a massive discussion right now. Emma noted that the cooling systems have their own knock on contamination risks. This is perhaps a conversation for another episode. Where to find the show: The Lisa Burke Show airs on RTL Today, RTL Play, and RTL Today Radio, and is available on Apple Podcasts and Spotify. Guest links Prof. Emma Schymanski, LCSB profile: http://www.uni.lu/lcsb ORCID: https://orcid.org/0000-0001-6868-8145 PubChemLite for Exposomics: https://pubchemlite.lcsb.uni.lu/ NORMAN Suspect List Exchange: https://www.norman-network.com/nds/SLE/ MassBank: https://massbank.eu/MassBank/ MetFrag: https://msbi.ipb-halle.de/MetFrag/ patRoon: https://rickhelmus.github.io/patRoon/