44. Water | The Pathogen, the Plastic & What's in Your Glass

In this episode of Mohivate, Dr Mohi Sarawgee follows the remarkable story of water, from the cholera-stricken streets of Victorian London to the microplastics turning up in the water we drink today.

We meet John Snow and the Broad Street pump, explore how clean water and sanitation became one of the greatest advances in human health, and look at just how much science and human effort sits behind something as ordinary as turning on a tap.

Then we come to the question facing us now. Microplastics and nanoplastics are being found in drinking water, bottled water, and even human tissues. But what do those findings actually mean for our health? And how much should we really be worried?

Along the way, we look at bottled versus tap water, what water filters can and cannot do, simple ways to reduce unnecessary plastic exposure, and what to do if the water coming from your own tap suddenly looks, smells, or tastes different.

This episode is a story about a pathogen, plastic, uncertainty, and the extraordinary science hidden inside an ordinary glass of water.

References: 

1.John Snow, cholera and the Broad Street pump (1854) — London Museum: https://www.londonmuseum.org.uk/collections/london-stories/john-snow-cholera-broad-street-pump/

2.Clean water and sanitation voted the greatest medical advance since 1840 — BMJ readers’ poll (2007): https://pmc.ncbi.nlm.nih.gov/articles/PMC1779856/

3.The Brixham cryptosporidium outbreak and record fine — Drinking Water Inspectorate (2026): https://www.dwi.gov.uk/2-june-2026-south-west-water-fined-a-record-1-853-million-for-drinking-water-failures-in-brixham/

4.Microplastics in drinking water: WHO assessment (low risk at current levels, more research needed) — World Health Organization: https://www.who.int/news/item/22-08-2019-who-calls-for-more-research-into-microplastics-and-a-crackdown-on-plastic-pollution

Just a gentle reminder: this episode is for information, education, and inspiration only. It’s not a substitute for your doctor’s advice. For any personal health concerns, always seek guidance from your doctor.

Transcript

SPEAKER_00 0:08

Hi everyone, welcome back to Mohivate. I'm Dr. Mohi Saraugi, a GP by profession, but here I'm swapping prescriptions for perspective. I want to begin today by taking you to the southwest of England. A few years ago, I lived in Cornwall. For those who don't know it, Cornwall is that long finger of coastline reaching out into the Atlantic, right at the very tip of the country, where the land finally gives way to the sea. And I was fortunate enough to watch that sea in all its moods and in all its times, always teaching me that each time the waves fall, they never fail to rise again. I think water has always been more than a substance to us. Long before we understood the first thing about it, we felt it. Almost every culture on earth has treated water as sacred, a symbol of life, of purity, of renewal, of washing clean and beginning again. People are baptized in it, we are cleansed by it. We speak of being swept away, of feeling flooded, of washing the slate clean, of calm waters and troubled ones. Water has always been the mirror. We hold up to our own emotions and to our own longing to start afresh. It carries our deepest ideas about beginnings and about being made new. And of course, it is not only a symbol, it is the most literal life there is. You are yourself mostly water. You cannot go more than a few days without it. And you have almost certainly been told more times than you can count to drink more of it. So water is life. That is the oldest truth we have. And yet, for almost all of human history, that same life-giving water, the very symbol of purity, could quietly kill you, and you would never have known why. Because water has two faces. It can sustain life and it can carry death. It can be calm and it can be chaos. And for all the meaning we pour into it, water might also be the single most underrated, most overlooked, most miraculous thing we have. The plain glass we barely give a second thought to. So today, let's follow water a little differently. This episode is a story in two halves. First, what was hidden inside our water that we never knew and how we made it safe. And then what has found its way back into it today. So let's begin. First, let's understand what a miracle safe water really is. And to do that, I'll ask you to picture a world without it. So let's go to London in the summer of 1854. London then was the largest city on earth and it was buckling under its own weight. More than 2 million people were crammed into a city built for a fraction of that, and there was no real system to carry away everything a city of 2 million people produces. Beneath the houses sat cesspools, great brick pits of human waste sitting right there under the floorboards. When they overflowed, which was often, it seeped into the cellars, ran through the streets, and soaked into the ground. The river Thames itself had become little more than an open sewer. The smell of London in summer was so famous that a few years later it earned its own nickname, The Great Stink. Now, into this crowded, filthy, sweltering city came a visitor that the 19th century had learned to dread above almost any other. And thus begins the story I want to tell you today. It starts with a baby. At number 40 Broad Street in Soho, London, a little girl, only a few months old, felt terribly ill at the end of August 1854. Her exhausted mother washed out the baby's soil clothes in a bucket of water and tipped that dirty water into the cesspool in front of the house. That was all. One tired mother emptying her bucket. But that cesspool sat just a few feet from a well, and that well fed the most popular water pump in the neighborhood: the Broad Street pump. Cool, clear, sweet-tasting water that people walked streets out of their way to collect. Within 10 days, more than 500 people in that small tangle of streets were dead. People collapsed in their homes, in the road, at their workbenches. The killer was cholera. And cholera is a horror. A person could be perfectly well at breakfast and dead by dinner. It works to sudden, violent, unstoppable diarrhoea, so severe that the body pours out liters of fluid in a matter of hours. In the outbreaks of that century, tens of thousands died. And what made it even more terrifying was this. Nobody knew how it spread. The explanation everyone trusted had a name. Almost everyone, including the finest doctors and scientists of the age, believed that cholera rose out of foul, poisonous air. The stink itself from the sewage and the rot was thought to be what made you ill. And honestly, you can see why they believed it. The poorest, most crowded, worst-smelling districts were reported to have the most disease. So the logic seemed to close neatly. Bad air, bad disease. And it was completely wrong. But it was believed so deeply that to question it was to sound like a crank. Until one man was about to question it. His name was John Snow. He was a physician living in Soho in the very heart of London, right where the outbreak was unfolding. He was already well known for his work with anesthesia. In fact, he had given chloroform to Queen Victoria for the birth of two of her children. So he was no fringe figure. He was a respected doctor. But he had a nagging, unfashionable idea. He simply did not believe the bad air theory. He had watched cholera closely in earlier outbreaks and the pattern never fit. He kept asking the same questions. If this disease was breathed in from the air, why did it strike the gut so violently and so specifically? Why did one person fall ill while the person beside them, breathing the very same air, stayed perfectly well? Years earlier, in 1849, he had actually published his answer. He suspected cholera was not in the air at all. He suspected it was in the water, something you swallowed, and his idea had been more or less ignored. The world was quite happy with its bad air. And then at the end of August 1854, cholera exploded in his own neighborhood and it became one of the first outbreaks the country had ever seen. So Snow began to investigate. He walked the streets, knocked on doors, and asked the grieving families one question. Where did you get your water? And he marked every death on a map. Slowly, a shape appeared. The deaths clustered thickest around one single point. The broad street pump. The further you walked from it, the fewer the dead. But the truly clever part of his work was the exceptions, the cases that looked wrong until you look closer. There was a large workhouse sitting right in the middle of the dead zone, packed with hundreds of people. By the logic of the map, it should have been devastated. Yet barely a soul inside it died. Why? Because Snow discovered the workhouse had its own private well. Its residents never drank from the Broad Street pump at all. And then there was a puzzle in the opposite direction. A widow living miles away in the clean, breezy suburb of Hampstead, far from any so hosting, died of cholera. It made no sense. So Snow went and asked her family, and the answer was extraordinary. The widow had once lived on Broad Street years before, and she had so loved the taste of that pump's water that even after moving across London, she had it fetched for her by cart in large bottles, delivered to her door. She had drunk from her last delivery just before she died. She had, in the saddest possible way, imported her own death from across the city. Bad Air could not comfortably explain these patterns. Snow's water theory could, and the evidence was becoming very difficult to ignore. So Snow took his map and his evidence to the local parish officials and he asked them for one simple thing. Take the handle off the Broad Street pump. Make it impossible to draw the water. Of course, they thought he was probably wrong. They were not scientists, and like everyone else, they believed in bad air. But the sheer weight of his evidence and perhaps the sheer scale of the dying all around them made them reconsider. And so, with far more reluctance than faith, they agreed. The very next morning, the handle of the Broad Street pump was unscrewed and carried away. Now I must be honest with you here because Snow was honest about it himself. By the time that handle came off, the outbreak was already fading in large part because so many terrified people had already fled the area. So we cannot really say the pump handle stopped the epidemic in one heroic stroke. That part has become a little more legend than truth. But it does not matter because of what that moment represented. For the first time, someone had taken an invisible killer that everybody misunderstood, traced it to its exact source using nothing but patient questions and a map, and then acted, That is the moment a whole science was born. The study of how disease moves through populations, and it is why Jon Snow is remembered the way he is today. Many of you will already know him as the father of modern epidemiology. There's one last part of this story I have to tell you because it is my favorite. There was a local clergyman, Reverend Henry Whitehead, who knew the people of Soho well, and he thought Snow was completely wrong. He was fond of that pump and he set out to prove the water theory was nonsense, going door to door to clear the pump's name. But the deeper he dug, the more the evidence pointed exactly where Snow said it would. And here is a measure of the man. Whitehead followed the truth instead of his pride. He changed his mind and then he did something important. Because he knew the neighborhood so well, it was Whitehead who traced the whole outbreak back to its very beginning. Back to number 40 Broad Street, back to a sick baby and a bucket and a cesspool beside a well. He found the sauce of the sauce. And I love this because a man who set out to prove someone wrong had the honesty to admit it when he found they were right. There's something rather beautiful in that, and it is partly why I wanted to share this story with you. Because it is, in one person, the whole spirit of good science. Jon Snow died in 1858 at just 45 before the world fully accepted what he had shown. But accepted, eventually it did, and in the decades that followed, cities began the enormous, unglamorous work of separating their sewage from their drinking water, building proper sewers, filtering and cleaning what people drank. And the results were extraordinary. Cholera, typhoid, and the other waterborne killers that had haunted humanity for centuries began in these cities to fade away because of clean water. In fact, when the British Medical Journal once asked more than 11,000 readers to choose the greatest medical advance since 1840, they did not choose antibiotics, vaccines, or surgery. They chose the sanitary revolution, clean water, and sewage disposal. But let's discuss the honest other half of that truth. This is not a solved problem and it is not shared equally. Even today, around 1 in 4 people on Earth, more than 2 billion of us, still live without safely managed drinking water. And unsafe water, sanitation, and hygiene still contribute to at least 1.4 million preventable deaths every year. Waterborne diseases are not distant history. They are still here. This gift, so much of the world is still waiting for. In the summer of 2024, in Brixham in Devon, a tiny parasite called Cryptosporidium found its way into the drinking water. Tens of thousands of people were suddenly told to boil their water before they could safely drink it. People fell ill, and it was serious enough that two years later the water company was fined a record amount for the failure. And in late 2025, Tunbridge Wells faced a different kind of water crisis. A failure at its treatment works left thousands affected by loss of supply and subsequently a boiled water notice. And this is not in the 19th century. Here, now, in one of the wealthiest countries on earth. And I do not say this to frighten you or to point a finger at any country. Water in most developed places is overwhelmingly safe, and it is safe because everything snow set in motion. I say it because it is worth remembering that the clean glass of water in your hand is not a law of nature. It is a gift built and maintained and defended every single day by people you will never meet, and most of us have maybe never once stopped to be grateful for it. And yet there's a strange twist in our story because even though our water, for the most part, is now clean, we have started to worry about the water all over again. Only this time, the thing we are worried about is not a germ, it is something we made ourselves. Plastic, or to be precise, microplastics, and their even smaller cousins, nanoplastics. Microplastics are simply very small pieces of plastic. Anything under 5mm, right down to particles smaller than a single cell. They break off from the ocean of plastic we have made, the bottles, the packaging, the bags, the clothes, as it slowly wears and crumbles. And over the last few decades, they have spread absolutely everywhere. They are on the highest mountains, in the deepest sea, in the soil, the rain, and the air. They have been found in human blood, even in the placenta. And yes, they are in our tap water too. And it turns out in even greater amounts in plastic bottled water. The numbers here may sound a little alarming. So let me give them to you honestly, and then let me be a careful doctor about what they actually mean. Researchers have tried to estimate how many of these particles we take in, but the numbers vary enormously depending on how you measure them and particularly on how small a particle your equipment is able to detect. Bottled water is certainly not exempt. One widely cited study estimated that someone drinking only bottled water could take in tens of thousands more microplastic particles over a year from water alone than someone drinking only from tap. Some of those particles may come from the packaging itself. Studies suggest that the bottle, the cap, and the repeated mechanical stress of opening and closing it can contribute particles, while heat and prolonged sunlight can increase their release. There's a certain irony in that the bottled water we sometimes reach for because it feels cleaner, purer, and safer is not necessarily giving us less plastic at all. I want to say that clearly because it matters and because it is so often left out. Scientists have become very good at finding these particles and very good at counting them. What they have not yet done is prove that the amounts we meet in ordinary life are actually making us ill. The World Health Organization looked carefully at microplastics in drinking water and concluded that on the evidence we have so far, there was no clear sign of a risk to health at the levels we typically encounter. While being honest, that the science is still young and incomplete. And more recently, food safety bodies in Europe and America have said much the same thing. The evidence so far is simply not strong enough to draw firm conclusions. And this is where I want to be a steady voice because this is a subject that pulls people to two extremes, and in my perspective, both of them are wrong. On one side, there are the frightening headlines that studies have reported microplastics in your blood, your brain, your mother's placenta. That is genuinely sobering, but detecting a material is not the same thing as demonstrating it is causing disease. On the other side, there are voices keen to reassure you that there is absolutely nothing to think about here at all. And the honest, grown-up truth sits quietly in the middle holding two ideas at the same time. The first idea is this we have not shown that these particles are harming us at the levels we meet in daily life. So there is no good reason to lie awake at night or to feel afraid of a glass of water. Fear that runs ahead of the evidence helps no one. But the second idea is just as important. Reports of man-made plastic particles turning up in human tissues, a material that essentially did not exist in our bodies a century ago is reason enough to pay attention and to want to understand it properly. Because absence of proof of harm is not the same thing as proof of safety. Those are two very different statements, and it would be a mistake to confuse them. A person can hold both of those thoughts together without collapsing into either panic or dismissal. And here is where our story comes full circle because there is a real echo of Jon Snow in all of this. In his day, the danger in the water was invisible too. People could see the deaths, but they could not yet prove how, because the science to understand it did not exist yet. They were living inside the question before anyone had the answer. We are standing in a strangely similar place with microplastics. We can now see the particles and count them, but we cannot yet fully read what they mean for us. That work is happening right now in laboratories all over the world, and it may be a few years before we truly know. And perhaps the most honest thing I can tell you is that this chapter has not been written yet. And in the meantime, well, I think we all know a few people who have declared war on plastic. The ones at war in the kitchen, guarding the glass jars, refusing to let the children near a plastic cup, plate or bottle, and yet their own phone sits wrapped in a plastic case. Half the bathroom is plastic bottles, shampoos, and lotions. The children's toys are almost entirely plastic, and the entire fridge is full of food wrapped in plastic. The war, it turns out, has very specific borders. I say all of this, of course, as someone whose own life is hardly plastic free. So take my perspective for what it is worth. And finally, where does all of this leave you standing in your kitchen holding a glass of water? Let me give you some very calm practical things so that a great deal of worry can safely be set down. First, and this is a big one if your tap water is already known to be safe, drink it. In most developed countries, such as the UK, your tap Water is held to good standards. It is tested again and again all the way to your kitchen. So the idea that bottled water is somehow purer or cleaner or better for you is mostly a feeling that has been sold to us, not a fact. And as we have seen, the plastic bottle may quietly be adding the very thing you were hoping to avoid. Second, if you do use plastic, keep it away from heat. A plastic bottle left in a hot car or in direct sunlight all afternoon will shed more particles into the water. And in the kitchen, this is the one I would underline. Use glass or ceramic rather than plastic containers when heating or microwaving food. It's a small, simple change if reducing your plastic exposure is something you want to do. Third, if you'd like to go a step further, a simple water filter can help. Some filters can reduce the microplastic particles in water, although how well they work depends on the type of filter. And honestly, for most people with a safe, regulated water supply, this is an optional extra rather than a necessity. A nice to have, not a must. And finally, one genuinely useful thing because knowledge is a quiet kind of power. If your tap water suddenly changes color, smell or taste, here is what to do. First, check another tap or two in your home. If it is only the one, the problem is probably your own plumbing, not the supply. Then, if you can ask a neighbor if their water is or two, that points to something in the wider network, not just your home. And that is exactly when you contact your water company. In most places, and certainly in the UK, every home is served by one. Their number is on your water bill, the internet, and they are obliged to investigate. And here is the reassuring part: the thing that ties back to Brixum. When Cryptosporidium caught into that supply, the contamination itself was a failure. We should be clear about that. But what happened around that failure matters too. The problem was quickly detected, people were warned, the supply was investigated, and ultimately the company was held to account. Safe water does not mean nothing can ever go wrong. It means we build systems designed to detect when it does. One last thing worth knowing: if you are ever curious, you can look up the water quality report for your own postcode, usually online. Your water company publishes it and it will tell you exactly what is in the water, where you live. Most of us never think to look, but it is there if you ever want the reassurance of seeing it for yourself. And if the taste is ever really strong, if it smells of fuel, solvents, or chemicals, or if a few people around you are falling unwell, please don't try to make it safe by boiling it. Stop using it for drinking and contact your water company immediately. That watchfulness, that testing again and again, all the way to your tap is the quiet machinery that keeps the water safe. It is Jon Snow's map still being drawn every single day. So here we are, back where we began with water. Something so ordinary that most of us barely notice it. We turn a tap, fill a glass, take a sip, and carry on with our day. And yet, behind that simple act lies a remarkable human story. The people who asked better questions, the people who were willing to change their minds, the engineers who built the sewers, the scientists who learned what to look for, and the thousands of people, even now, whose work allows the rest of us to turn a tap without giving any of it a second thought. I think about that scene Cornwall sometimes and the thing it seemed to teach me over and over again that each time the waves fall, they never fail to rise again. Perhaps water has been teaching us something all along to pay attention to what sustains us, to care for it, and every so often to begin again. I hope something today stirred a thought or simply made you look at the next glass of water in your hand a little differently. Thank you for listening. I'm Dr. Mohi. Until next time, remember this. Some of the things that sustain us are so familiar that we stop seeing them. And perhaps paying attention to them again is one small way of coming home to ourselves.