Harmful algal blooms are a growing concern in the Great Lakes. The toxins they produce can close beaches, and even poison drinking water. What’s fueling these blooms? Phosphorus, a key ingredient in agricultural fertilizers. But the way it’s being used comes at a cost.

By Patrick Shea 

The following story is adapted from an episode of Points North, a narrative podcast about the land, water, and inhabitants of the Great Lakes. Listen to more episodes at pointsnorthpodcast.org.

Listen along while you read below.

Lake Erie turns a bright green as cyanobacteria blooms across large portions of the lake’s western basin. (credit: Tom Archer / Michigan Sea Grant)

PATRICK SHEA, HOST/BYLINE: On a late summer morning in 2014, residents of Toledo, Ohio woke up to some troubling news.


“The governor declares a state of emergency after Ohio’s fourth largest city is told not to drink its water…Residents in Toledo and nearby communities on Saturday quickly bought up water bottles, leaving store shelves empty…”

SHEA: Tests at a water treatment plant showed dangerously high levels of a toxin produced by blue green algae in Lake Erie. The toxin is known to cause nausea, vomiting, and even liver disease, so a “do not drink” order was quickly put out. Half a million people were unable to drink, bathe or brush their teeth with tap water for three days. The culprit: an overload of phosphorus – an element that’s critical for all life on earth. It’s in our DNA, and in the membrane of every single living cell. It’s also essential for agriculture. But the same element we need to grow our food can make our water poisonous. This is Points North: a show about the land, water and inhabitants of the Great Lakes. I’m Patrick Shea, in for Dan Wanschura.

Today, I’ll be talking with Dan Egan about his new book “The Devil’s Element: Phosphorus and a World Out of Balance.” Dan is an award-winning author and journalist. In the early 2000s, he left his job as a reporter in Salt Lake City, and moved back to his home state of Wisconsin, where he spent about 20 years reporting for the Milwaukee Journal Sentinel.

Author Dan Egan (credit: Mike De Sisti)

DAN EGAN: I came back with a whole new appreciation for these inland seas after living in the desert for a decade. So that launched me on doing long stories about the Great Lakes, and that eventually was put between a couple of covers and made into a book in 2017.

SHEA: And that book, if you don’t know, is “Death and Life of the Great Lakes.” It’s a great read. You do such a good job of distilling dense scientific concepts, and making them into a really compelling story.  That book was a two-time finalist for the Pulitzer Prize and a winner of the Los Angeles Times Book Prize. How did that change your career?

EGAN: It was received better than I expected, and I think better than the publisher expected. You know, I can look at it and say, “Yeah it dramatically changed my professional career,” but it was on the way to changing anyway because of what’s gone on with newspapers. But the book did open doors, and the most important door I guess it opened was they wanted another book. And so, from 2018 until a couple months ago, that’s what I’ve been doing.

SHEA: And that led to your latest work – again it’s called “The Devil’s Element: Phosphorus and a World Out of Balance.” It was a real page turner, Dan, and that’s coming from someone who was never a very strong chemistry student – or really that interested in it.

EGAN: Me neither.

SHEA: Yeah, so I’m guessing as you first got into journalism you never imagined you’d be writing a whole book about element 15 on the periodic table.

EGAN: No, no…But, you know, it’s about phosphorus but it’s about a lot of stuff. It’s kind of phosphorus as, like the vehicle. And I knew going in that it might be a heavy lift to write for the general public. So, I came out the gate pretty hard as far as the introduction. You know, it starts with a police chase and a guy practically drowning in an algae-smothered canal down in Florida, and off we go with the book.

SHEA: Right, and that individual was poisoned by toxins from a blue green algae in that water – which is a result of phosphorus pollution, which we’ll get into. But to start at a really basic level, what is phosphorus?

EGAN: It’s one of the elements, and critically it’s one of the three elements that sustain modern agriculture – the other two being potassium and nitrogen. And since the early 1900s, we’ve had the technology to pull nitrogen out of the air to put it into fertilizer form. Potassium – there’s oodles of deposits of potassium still and nobody’s talking about ever running out of it, but phosphorus is a different story. Most of the phosphorus we get for agriculture, for fertilizer, comes from these rocks. And there’s not a lot of these rock deposits, and we’re burning through them at an unsustainable pace. And, you know, in the U.S., we’re looking at running out of our mineable reserves in three decades. Maybe more; probably not less. But it’s coming, and then we’re going to have to figure out – you talk about energy security – that pales compared to food security.

SHEA: So there’s a huge global demand for phosphorus, which is a very limited resource, and that demand has been there for a long time. Some of the history you get into in this book really blew my mind, especially some of the drastic and kind dark means people have gone to get this stuff. Let’s start in England in the 1800s.

EGAN: Farmers in England, primarily, there was a lot of agricultural experimentation going on there because it’s an island and so it’s got finite crop land. And they found that bones were a really rich source of phosphorus so they started using animal bones. And there’s only so many animal bones, so then they started looking for other sources and they ended up looting battlefields. Like the Battle of Waterloo in 1815 – within 10 years there were no bones to be found on that battlefield. Because the British went back and just stripped the battlefield of all its bones and built these bone crushing mills to create this miraculous, fertilizing, crunchy powder that they just spread across the landscape. So, they were looting the Catacombs; it was just anywhere they could find bones, they would go get them and they would grind them up and use them to grow turnips.

SHEA: And then eventually another really potent source of phosphorus is discovered on the other side of the planet, right?

EGAN: Yeah, so then they realized that guano – which isn’t just bat poop, it’s bird poop – is also a very rich source of phosphorus. Particularly these deposits on the west coast of South America. Fish-eating birds need to take a breather once in a while so they’d go out to these islands and you had mountains of bird poop that became recognized as mountains of fertilizer. So, there we go, you know, from Waterloo over to the west coast of South America. And they thought they had an inexhaustible supply of this stuff, and this was in the 1840s and 50s, and by the 1890s it was all played out.

SHEA: And as you mentioned earlier, these days with advancements in chemistry we get phosphorus for fertilizer from rock deposits. But those are limited, too. So there’s this recurring theme of scarcity. But now, at the same time, there’s this overabundance of phosphorus in our water. It’s running off of farm fields through fertilizers and manure and getting into waterways. What’s the impact of that?

EGAN: Well, it’s just a fertilizer boost. I mean, it’s just like dumping fertilizer into a body of water instead of onto a crop – a farm field. Instead of corn, you’re going to get aquatic life. And now, increasingly the type of aquatic life we get are these blue green algae outbreaks, which are – they’re literally poisonous.

SHEA: Right, and you spend a good portion of the book talking specifically about manure and the phosphorus runoff that can happen there. But there’s been phosphorus in cow and pig manure for as long as there’s been pigs and cows, right? Why is this becoming a bigger issue now?

An algal bloom in Lake Erie seen from above. (credit: NOAA / Great Lakes Environmental Research Laboratory)

EGAN: So, for forever, phosphorus molecules – in the form of phosphates – they were recycled. They don’t go away. It’s just like, a cow poops, grass grows, cow eats grass, poops, grass grows, and on and on and on for thousands of years. It’s the circle of life, literally. And we got rid of that with these big farms.

SHEA: Big farms, as in really, really big farms – at least big in terms of the number of animals: confined animal feeding operations. Dan says by the mid 2000s, those dominated the livestock industry in the United States. One dairy farm near Dan, in Wisconsin, has 8,000 cows on just a few acres. And that means a lot of concentrated manure – and phosphorus.

EGAN: So, phosphorus is this critical, critical nutrient, but it’s also a real nasty pollutant because its fertilizing properties don’t stop when it washes off a cropland.

SHEA: That’s what Dan calls the phosphorous paradox. We need this stuff to grow food, and we can’t get enough of it. On the other hand, there’s too much in our water. But the thing is, back in the 1970s, we found a way to deal with phosphorus pollution. Dan, there’s a section in the book called “dirty soap.” It’s about how soap and detergent manufacturers were loading their products with phosphates. That led to a lot of problems in Lake Erie – similar to what’s happening today. But there was some pretty direct action taken against these soap companies. How did that happen?

EGAN: It wasn’t a national ban right off the bat. It was basically, I think maybe even Chicago was the first city. But cities started banning phosphate detergents and then states. And the turnaround was just incredible. You know, Dr. Suess was, in 1972 or something, writing about Lake Erie and its smeary water. It was in “The Lorax.”


“No more can they hum for their gills are all gummed. So, I’m sending them off. Oh, their future is dreary. I hear things are just as bad up in Lake Erie…” 

EGAN: And after these reductions were put in place in the mid and late 70s, by ‘85 the lake had so recovered that Dr. Suess pulled the line out of “The Lorax.” You won’t find it in the modern Lorax books. Dr. Suess wrote about Lake Erie and its smeary water in “The Lorax.”

Dr. Suess wrote about Lake Erie and its smeary water in “The Lorax.”

SHEA: The dirty soapy era in Lake Erie changed more than just popular children’s books, too. It played a big part in passing the Clean Water Act. That reduced pollution in the Great Lakes and all over the county. The act put strict limits on what’s called point source pollution – that means pollution you can easily trace back to a point. Think of a pipe coming out of a factory and right into the water. But now, Dan says most of the phosphorus pollution that’s fueling harmful algal blooms is coming from farm fields – specifically from manure – and that’s spread out across the landscape. In the Clean Water Act, that’s called nonpoint source pollution, and it’s much harder to regulate.

EGAN: Agriculture was given a pass because its pollution was so diffuse. It was spread across pastures. And it wasn’t “pollution” – it was fueling more grass. But it’s no longer a nonpoint source pollution, you could argue. There’s a point where this stuff is, and it’s in a sewage lagoon on a factory farm.

SHEA: Yeah, I’m glad you brought up the sewage lagoon. Basically, at these really large farming operations, there’s typically a sort of pond that contains animal manure, right? And then when that pond is full, what’s typically done with the excess material?

EGAN: It’s spread on the land, you know? So, it is regulated under the Clean Water Act as long as it’s in that lagoon or in the production facilities of a farm. But it’s gotta go somewhere, and once it goes out on to the landscape it becomes bureaucratically, magically, nonpoint source pollution. So, it’s much less – if regulated at all.  But it’s politics, I understand the importance of agriculture; I had breakfast this morning. But we don’t have to be doing it the way we’re doing it. And this book doesn’t really – it’s not a call to action or anything like that. It’s more just connecting dots and trying to give people a picture of what’s happening, and I’ll leave it to others to come up with a recipe for the fix.

SHEA: You’re saying it’s not a call to action. There is a part where you sort of say, “It seems that it’s time to revisit the agricultural exemption from the Clean Water Act.” Do you see that as a call to action, or do you see that as a suggestion?

EGAN: Yeah, I mean I guess, what is a call to action? I don’t want to be a crusader here for agriculture reform. I just want to point out that the system we have right now is not serving too many people. I mean it works great for producing food. It’s not working to protect our water. And so, anybody who cares about water – the only call to action I guess I’ll say I have is to read the book, and then get educated and let’s start moving forward. We’re just kind of stuck with a system that’s been around for a hundred years that’s worked marvelously but isn’t working so well now.

SHEA: That was Dan Egan, his new book is “The Devil’s Element: Phosphorus and a World Out of Balance.” I highly recommend reading it – thanks so much for joining us, Dan.

EGAN: Sure, I appreciate it. So, have a good day.