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The water crisis in Flint, Michigan is a prime example of science being ignored, unknown, or even misused. Here's the chemistry behind how so many things went wrong.

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Lead pipes

Corrosion Protection

Chloride & Chlorine



Lead Poisoning


[♪ INTRO].

In April of 2014, under the control of an Emergency Manager appointed by the state of. Michigan to help the city through an ongoing financial crisis,.

Flint, Michigan switched its water supply. For decades, the city’s water had been piped in from the Detroit Water and Sewerage Department, which got its water from Lake Huron and treated it. But in April of 2013, the decision was made to build a pipeline and connect to a new system, the Karegnondi Water Authority.

This would supply the city with lake water that Flint would treat instead of Detroit, and was estimated to save 200 million dollars over 25 years. In the meantime, as a sort of temporary fix while the pipeline was being built, water would come in from the Flint River and be treated at Flint's water treatment plant. Now, 4 years after that switch, we know that it damaged hundreds of millions of dollars of infrastructure, caused deadly bacterial outbreaks that killed at least 12 people, and exposed thousands of children to high levels of lead in their drinking water.

There are places to learn about the story of how this happened, was covered up, and was eventually recognized, and the underlying situations that caused these massive mistakes to be made. So let's talk about the science of water. And how something as seemingly simple as a switching to a different water source could lead to so many bad, but also seemingly unrelated, outcomes.

Humans have actually been using lead pipes in water systems for hundreds of years, dating back to the ancient Romans. We eventually moved on to using other materials, like iron. But in the late 1800s, engineers in the U.

S. were all about lead, because lead pipes were easier to bend around obstacles and were a bit more durable than iron. People were suffering from lead poisoning, but the public health risks weren’t seriously acknowledged until around the 1920s. And we gradually stopped making new water pipes from lead.

But in lots of cities in the U. S., like Flint, Michigan, there are still several different kinds of metals in pipes for water. In Flint’s case, the pipes are made of lead and iron.

The U. S. Environmental Protection Agency didn’t have any sort of serious regulation about lead pipes until the Lead and Copper Rule was enacted in 1991.

It requires regular monitoring and action plans if old lead pipes start becoming dangerous. So, all that to say, lead water pipes are not that unusual, a 2016 study estimates that there are still millions in use. And even though no amount of lead ingested by a human is considered safe, maybe surprisingly, many of these water systems are usually safe.

A big part of the reason why is anti-corrosion chemicals in the water, like orthophosphate. Orthophosphate helps lead and some other metal pipes from corroding by forming a compound that makes a sort of protective layer on the inside of the pipe. If that layer is patchy or missing, then electron-stealing chemicals called oxidants, like dissolved oxygen gas, can react with the lead.

And when that happens, the lead will dissolve into the water and contaminate it. You’ve probably heard of that. It’s known as leaching, and it’s when things get dangerous for people who need this water to drink or shower or do anything with on their bodies.

Flint, and it is unclear why besides possibly cutting costs, did not add orthophosphate or any sort of anti-corrosion chemicals when switching to Flint River water. Even though the treated water from Detroit had had them. And because Flint was using iron and lead pipes, both iron and lead ended up in the water.

But that’s not the whole story. Not only were these pipes left unprotected, but the water flowing through them also contained higher than average chloride levels. Research has found that chloride helps the process of corrosion along.

When there are enough chloride ions in the water compared to some other ions, they start forming chemical complexes with lead and other atoms. And these chloride complexes are soluble. So, basically, it’s another way that lead can get into the water.

Part of this too-much-chloride problem was from the river water itself. Sodium chloride, which is just table salt, would often wash into the river after being used as a de-icer on roads. But another part of it had to do with the fact that, a couple of months after the switch to the Flint River water, there was also a huge bacterial problem.

The river water wasn’t just, like, extremely dangerous, though. We know how to treat water. We put in disinfectants like chlorine, which can rip open bacteria or mess with the molecules inside them.

But it turns out that chlorine disinfectant can react with metals from corroding pipes, especially iron, to become completely different compounds that do absolutely nothing to control bacteria. So the disinfectants were made useless. Plus, more chloride ions ended up floating around, which only made the corrosion process worse.

And thus, the vicious cycle escalated. By August of 2014, there was a city warning that E. coli and other typically gut-dwelling bacteria, collectively called fecal coliform bacteria, were thriving in the water and could make people sick. The Flint treatment plant upped the amount of chlorine they were using to try to kill off these contaminants.

But because the pipes were already corroding, it wasn’t working. Not only that, but all this extra chlorine they were adding also reacted with some of the organic chemicals from the river water to form disinfection byproducts called trihalomethanes. And, researchers have found trihalomethanes to be linked to health problems and even cancer.

So not only was the chlorine turning into a bunch of non-disinfectant chemicals, one of those was potentially a carcinogen. Trihalomethanes in the water quickly swelled to above the national regulatory limit. So to try and fix that problem, the treatment plant added coagulants that would react with the organic matter in the water to help them filter it out.

Specifically, they used a chemical called ferric chloride. Which took care of the trihalomethanes, but meant they were adding even more chloride to the water. As the pipes got worse and more chlorine was turned into useless compounds, the elevated bacterial levels became deadly.

Between April 2014 and October 2015, at least 12 people died and 91 people got sick from an outbreak of Legionnaires’ disease, the third largest recorded in U. S. history. Before the switch to the Flint River water, there were only a handful of cases per year.

Legionnaires’ disease is basically a really intense pneumonia. It’s caused by breathing in water-borne bacteria that infect the lungs so they get inflamed and lead to other symptoms. This outbreak was caused by a bacterium called Legionella pneumophila, specifically the serogroup 6 strain, which isn’t usually detected in the standard urine test for the disease.

After some extensive studies, most researchers agree that this chlorine inactivation at least played a part in letting these bacteria flourish. On top of that, some of the experts and investigative journalists think that there could have been more deaths than were officially confirmed, because of how tricky it can be to diagnose Legionnaires’ disease. Some deaths caused by these bacterias could have been attributed to pneumonia in general, and thus not counted.

So, counterintuitive as it might seem, not adding corrosion control also deactivated the chlorine disinfectant to basically undetectable levels, resulting in tragic loss of life. In addition to all this, though, there was the ongoing problem of metals leaching into the water supply. Which we definitely know was because of how the Flint River water was treated.

Because of all these chemical reactions, the process by which lead and other metals got into the water was not slow and constant. Sometimes the pipes would leach metal slowly. But sometimes metal compounds, like the protective layer that wasn’t being maintained, flaked off in little hunks, some of which were even visible to the naked eye.

The leached iron made the water look kind of horrible and taste kind of rusty, but it isn’t a big health concern on its own. Lead is. But you can’t see, smell, or taste it in water.

A single tiny lead flake can take water from safe, to far over the EPA’s limit of 15 parts per billion, which requires public action to be taken. And besides randomly super contaminated samples being right next to uncontaminated samples because of flakes, the protocols for testing for lead can be manipulated to make it less likely to record how contaminated the water actually is. Official EPA protocols for measuring drinking water quality involves letting the water sit in pipes for at least 6 hours, and then collecting it after a couple minutes.

City protocols called for pre-flushing the pipes for five minutes before letting them sit for 6 hours. And, according to experts, this pre-flushing can sweep out initial bursts of lead particles so they’re not in the sample. Plus, people don’t just go turning on their water every once in a while, so those samples aren’t necessarily reflective of what they’re using and drinking.

Even still, when the City of Flint tested one resident’s water in February and March of 2015, they found lead levels at 104 ppb and 397 ppb, far above the EPA’s action level. When researchers from Virginia Tech sampled water from the same pipes at low, medium, and high flow rates, they found levels ranging from 220 ppb to a whopping 13,200 ppb. And, to be totally clear about how intense this is, a substance with more than 5,000 parts per billion of lead is considered hazardous waste by the EPA.

By September 2015, those same researchers had collected and analyzed 252 water samples from various Flint homes. 101 of the samples had more than 5 ppb of lead. And they estimated that 90% of homes had a lead level below 25 ppb; 10% were above that. Which, and I can’t say this enough, was a lot of homes above that 15 parts per billion EPA limit for water.

Protocols matter, y'all! So that's how metals ended up in the water. No corrosion control and high corrosive chemical concentrations exposed many thousands of people to lead poisoning.

And lead poisoning can cause incredibly serious health problems. Lead interferes with a lot of different enzymes, can cause cells to die, and can slip past the protective blood-brain barrier to seriously mess with the central nervous system. We don’t know exactly how it interacts with all those systems, but lead ions are chemically pretty similar to calcium ions, which our bodies use all the time in lots of chemical processes.

So that may have something to do with it. In any case, it’s incredibly detrimental to human bodies and brains, in adults and especially in children. All of this was made worse by the fact that the city of Flint has a water system built to deliver water to over 200,000 people.

Since the population peaked at around that in the 1960s, it has declined to less than half that. So in some areas, the water moved through some pipes slowly or sat stagnant. As the Flint River water sat in the pipes and the corrosive chemistry did its thing, metal concentration rose, disinfectant concentration decreased, and bacterial growth increased.

The city of Flint switched back to piping in treated water from the Detroit water system in October 2015, after 18 months. And they’re adding in extra phosphate chemicals to try to build up that protective layer again. But that doesn't just fix the problem that had escalated over that year and a half.

The pipes have already corroded, as have plumbing fixtures and water heaters of many residents. So while the gradual leaching is hopefully going down, metal flakes may still be chipping off. Tests show that lead levels are down, and that’s great news, but many residents have also, understandably, lost faith in the government agencies that are now reporting that the water is safe.

The city is now undergoing a massively expensive process of replacing all of its lead pipes. A step that was taken to save money has ended up costing far more money than it could have saved, not to mention lost health, and lost lives. The way that science was ignored, unknown, or even misused in this story is a lesson that we all have to live with, and one that we at SciShow hope that we can learn from.

Thanks to our patrons on Patreon who support SciShow, so that our team can work on these complex topics that take a lot of research and time to get right. We wouldn’t be able to keep our channel going without their support, and also without everyone who watches and shares our videos. If you want to help us keep making free, educational content, you can go to [♪ OUTRO].