Lake Erie Is Green Again. Did the Phosphate Ban Fail?

Western Lake Erie turned a thick, paint-like green again this September. On 14 September NOAA’s bloom bulletin put the cyanobacteria bloom at about 260 square miles, down from roughly 320 the week before, with toxin concentrations still elevated between Toledo and Monroe. Two weeks later, northeast winds had pushed the bloom against the Maumee Bay shoreline, and University of Toledo Lake Erie Center director Tom Bridgeman told The Blade that the bloom had been “remarkably bright green and ‘healthy’ looking, which is unusual for mid-September, at least it used to be.”

Every green September brings back the same question in hardware stores and comment sections: didn’t we ban the phosphates? We did, and the bans worked. The answer to why the lake is green anyway is a chemistry story about which phosphate was in the box, where the phosphorus goes, and why a bag of trisodium phosphate is the most famous and least guilty compound in it.

This is a chemistry and history explainer. It does not tell anyone how to farm, it takes no position on any policy proposal before the governments involved, and it makes no environmental claim about any phosphate product.

What is happening on Lake Erie this fall?

The 2026 western Lake Erie bloom is a moderate bloom that has peaked long and late. NOAA forecast it in June at 3.5 on its 10-point severity index, with a likely range of 3 to 4.5, and NOAA oceanographer Rick Stumpf told The Blade on 28 September that the season is still on track to be moderate overall — “nothing that rivals the 2011 record or the 2015 runner-up.” The index measures biomass during the bloom’s peak 30 days, not the look of any one beach.

So the honest summary is: a moderate bloom, an unusually long peak, a drinking-water system that has handled it, and a shoreline that looks alarming. That is enough to make people ask what happened to the phosphate bans of the 1970s.

Why did people say Lake Erie was “dead”?

Lake Erie was never literally dead; it was over-fertilized. The “dead lake” phrase spread through national press coverage in the late 1960s without any one originator, and the Cleveland Historical project calls it “more sensational than factual.” What the science actually described was eutrophication: too much nutrient, too much algae, oxygen stripped from the bottom water of the central basin as the algae decayed, and fish kills.

The International Joint Commission, the US–Canada body that reports on boundary waters, put it plainly in its 1970 report: the lake, “particularly its Western Basin, is in an advanced state of eutrophication.” Burrowing mayflies, a classic indicator of oxygen in the bottom sediments, disappeared from western Lake Erie in the 1950s and did not come back in numbers until the early 1990s, according to the US Geological Survey.

Where did the phosphorus come from in 1967?

In the late 1960s most of Lake Erie’s phosphorus came out of sewage pipes, and most of the phosphorus in American sewage came from laundry detergent. The International Joint Commission’s 1970 report tabulated it: in 1967, United States municipal sources sent 35.7 million pounds of phosphorus into Lake Erie, “of which 25 million came from detergents.” Canadian municipal sources sent 2.5 million pounds, 1.3 million of it from detergents. The commission concluded that “detergents are by far the greatest single source of total phosphorus input into the Lakes.”

Compare that with the present. The EPA’s 2025 Milestone Report, published in June 2026, says Lake Erie now receives a phosphorus load “varying from about 7,000–12,000 metric tons each year.” The load fell by more than half. The bans and the sewage limits did what they were designed to do.

Was trisodium phosphate the detergent phosphate?

No. The workhorse laundry phosphate was sodium tripolyphosphate (STPP, Na₅P₃O₁₀), a chain of three phosphate units that grabs calcium and magnesium out of hard water so the surfactant can do its job. The American Chemical Society’s landmark history of Tide records the 1946 formula as one part surfactant to three parts STPP. That ratio is the whole phosphate story in one line: the builder, not the soap, was most of the box.

Trisodium phosphate, Na₃PO₄, is a single orthophosphate unit, a much stronger base, and a different product. It went into heavy-duty cleaners, paint-prep washes and some dishwasher formulas, sometimes in a chlorinated form. When the House of Representatives held hearings on Phosphates in Detergents and the Eutrophication of America’s Waters in 1969, the record noted that trisodium phosphate “contributed about 5 percent” of the phosphate, counted as P₂O₅, consumed by the soap and detergent industry in 1958 and 1967. The rest was the polyphosphates.

That sentence is why TSP took the blame. The regulators counted every phosphorus atom the same way, whatever compound it arrived in, so the laws that followed were written against phosphorus content by weight, and any product with “phosphate” in the name was caught in the net. TSP had the most recognisable name on the shelf. It was the face of a problem that was mostly made of something else.

The last row is worth a second look. Trisodium phosphate is usually sold as the dodecahydrate, CAS 10101-89-0, which carries twelve waters of crystallisation. Its formula weight is 380.1, of which phosphorus is 30.97, so a 2-pound bag of the crystals holds about 0.16 pounds of phosphorus. A pound of STPP holds about three times as much.

Why does phosphorus, and not nitrogen or carbon, turn a lake green?

Because in most fresh water phosphorus is the nutrient that runs out first, so adding it is what lets algae grow. The EPA’s June 2026 report states it directly: “Phosphorus (P) is the growth-limiting nutrient in the Great Lakes and the primary driver of these issues.”

That was not settled science in 1969. Detergent makers argued that carbon, not phosphorus, limited algae, which would have made phosphate removal pointless. The question was answered with a sheet of plastic. At the Experimental Lakes Area in northwestern Ontario, the ecologist David Schindler’s team strung a vinyl curtain reinforced with nylon across the narrows of Lake 226 in 1973, and fertilized both halves with carbon and nitrogen but only one half with phosphorus. By late summer the phosphorus side was green with a cyanobacteria bloom and the other side was clear. Schindler published the result in Science in May 1974. The photograph of a lake split down the middle, green on one side, became one of the most persuasive images in environmental science.

What did the phosphate bans actually change?

They removed most of the phosphorus from household detergent and forced sewage plants to strip out much of what was left. It happened in layers.

The sewage half of that table runs on chemistry Alliance Chemical sells. A treatment plant meets a phosphorus limit by precipitating dissolved phosphate as an insoluble metal phosphate, usually with an aluminum salt such as aluminum sulfate (alum) or an iron salt such as ferric chloride, then settling and filtering the solids. Our ferric chloride versus alum comparison covers how plants choose between them, and our alum dosing guide works through phosphorus removal at small-system scale.

The result showed in the lake. Burrowing mayflies returned to western Lake Erie in the early 1990s. In 1971 Dr. Seuss had written into The Lorax that “things are just as bad up in Lake Erie”; after two graduate students in Ohio Sea Grant’s education program wrote to him in 1986, Ohio’s Year of the Lake, he took the line out of later printings, a story Ohio Sea Grant still tells.

If the bans worked, why is the lake green again?

Because the phosphorus moved from the pipe to the field. Point sources such as sewage plants can be fitted with chemical precipitation; runoff from millions of acres cannot. The blooms came back, and in 2011 they set a record, when a bloom covering more than 5,000 square kilometres followed long spring storms, according to a 2013 study in the Proceedings of the National Academy of Sciences. On 2 August 2014 Toledo told roughly 400,000 to 500,000 water users not to drink tap water after microcystin was detected in treated water.

The EPA’s June 2026 report identifies the Maumee River, which enters the lake at Toledo, as the largest phosphorus source of any Lake Erie tributary, contributing nearly half of the lake’s total load from a watershed of 6,571 square miles in Michigan, Indiana and Ohio. Its key sentence:

The same report says the bulk of that load “originates from agricultural fertilizers being applied to cropland each year and building up over time in the soil and streambeds,” and lists streambank erosion, atmospheric deposition and residential fertilizers as further contributors. In 2016 the two countries adopted a target of a 40 percent cut in phosphorus loads to the western and central basins from 2008 levels. The report records progress: the blooms of 2020–2024 “were mild in comparison to the 2010s,” and farmers in the western basin have installed nearly 13,000 conservation practices since 2013. It also cautions that “a single wet year or a few intense storms could deliver high loads.”

So the 2026 bloom is not evidence that the phosphate bans failed. It is evidence that the source changed. In 1967 the problem was mostly in the laundry room; in 2026 it is mostly in the soil.

Is trisodium phosphate banned now?

Not under US federal law. Trisodium phosphate is still made, sold and used: in metal cleaning and surface preparation before painting, in industrial and institutional cleaners, as a laboratory buffer and reagent, and in water and boiler chemistry. What exists are state laws limiting phosphorus in particular consumer products, mostly laundry and dishwasher detergent, and in a few states household cleaning agents more broadly. Washington’s statute is typical in shape: it bars laundry and dishwashing detergent containing 0.5% or more phosphorus by weight and states that the rule “does not apply to the sale or distribution of detergents for commercial and industrial uses.”

That is why hardware-store shelves now carry products labelled “TSP substitute.” Their makers reformulated around the consumer limits with phosphorus-free alkaline builders, of which sodium carbonate (soda ash) is the classic. Trisodium phosphate itself never went away; it moved to the commercial, industrial and laboratory side of the counter. If you plan to use TSP as a household cleaner, check your own state’s rule first, and follow local requirements for disposing of the rinse water, which carries the phosphate with it.

Our complete guide to TSP cleaner covers how TSP is used, mixed and handled. This piece is the history and the 2026 context behind it.

What this means on a specification

None of the history changes which grade a process needs. It does explain why buyers increasingly ask about phosphorus content, and which compound to reach for when phosphorus is or is not wanted in the waste stream.

A word on what this article does not say. It describes what regulators measured in 1967, what they require now and what the EPA reports about the sources of Lake Erie’s phosphorus. It does not say any product is harmless to water, it does not tell anyone how to manage a farm or a treatment plant, and it makes no claim about ours beyond what is printed on the product listing and the certificate.

Common questions

Did trisodium phosphate cause Lake Erie’s algae blooms?

Only in a small way. In 1967 detergents supplied 25 million of the 35.7 million pounds of US municipal phosphorus reaching Lake Erie, but the main detergent phosphate was sodium tripolyphosphate. A 1969 House hearing record puts trisodium phosphate at about 5 percent of the phosphate the detergent industry consumed. Today’s blooms are driven mainly by nonpoint runoff, which the US EPA says supplies 90 percent of the phosphorus load in the Maumee watershed.

Is trisodium phosphate banned in the United States?

No. There is no federal ban on trisodium phosphate. Several states limit phosphorus in laundry and dishwasher detergent, and a few limit it in household cleaning agents more broadly; laws such as Washington’s exempt commercial and industrial uses. Check your own state’s rule before using TSP as a household cleaner.

Why is Lake Erie green again in 2026?

Phosphorus runoff from the land, mainly through the Maumee River, combined with warm, shallow water in the western basin. NOAA forecast a moderate 2026 bloom at 3.5 on its 10-point severity index; the bloom measured about 260 square miles on 13 September and stayed thick in Maumee Bay into late September as northeast winds pushed it toward shore.

Did the 1970s phosphate bans work?

Yes. Detergent limits in Canada and the US states, plus the 1978 requirement that large Lake Erie basin sewage plants reach 0.5 milligrams per litre total phosphorus, cut the lake’s phosphorus load from about 27,300 tonnes in 1967 to the 7,000 to 12,000 tonnes a year the EPA reports now. Burrowing mayflies returned to western Lake Erie in the early 1990s.

How much phosphorus is in trisodium phosphate?

Trisodium phosphate dodecahydrate, Na₃PO₄·12H₂O, is 8.15% phosphorus by mass because more than half its weight is water of crystallisation. Anhydrous trisodium phosphate is about 18.9% phosphorus, and sodium tripolyphosphate, the old laundry builder, about 25.3%.

How do sewage plants remove phosphorus?

Mostly by chemical precipitation: an aluminum salt such as aluminum sulfate or an iron salt such as ferric chloride is dosed into the wastewater, binds dissolved phosphate into an insoluble solid, and the solid is settled and filtered out. Biological treatment can remove part of it as well. The dose depends on the phosphate concentration, the pH and the discharge limit, and is set by jar testing.

The phosphates and phosphorus-free alternatives we stock

Trisodium Phosphate Dodecahydrate, ACS Reagent Grade

The crystal at 8.15% phosphorus, for buffers, reagent work and heavy cleaning where permitted. 2 lb to 50 lb.

Soda Ash Technical Grade

Sodium carbonate, the classic phosphorus-free alkaline builder for cleaning where phosphate is restricted.

Aluminum Sulfate 50%

Liquid alum, the aluminum salt used to precipitate phosphate in wastewater.

Ferric Chloride 40% Water Treatment Grade

The iron-salt route to phosphorus removal. Also listed at 10%.