Chapter 3: Builders and water softeners · Part 1: Phosphates
Sodium tripolyphosphate (STPP)
No badge
The worst fact: phosphorus feeds algae. In late 1991, blue-green algae covered 1,000 km of the Darling–Barwon river system, then called the world's largest recorded river bloom, and up to 1,600 sheep and 40 cattle deaths were suspected. The NSW task force estimated that up to 55% of the phosphorus from sewage plants could be from detergents and cleaners, though it said that figure was derived and needed confirming. The bloom came during very low flow and hot, still weather, and researchers later suggested much of the phosphorus came from the river's own sediment. In rural catchments, farm runoff is generally the main source of phosphorus; sewage plants matter most in dry years.
Why brands use it: it locks up the calcium and magnesium in hard water and keeps the wash alkaline.
Take care if: you get it in your eyes. About 4 in 10 company reports to Europe's chemicals agency class it as an eye irritant; about a third say it isn't hazardous. A 1% solution is about pH 9.8, mild compared with TSP.
Comes from: phosphate rock, attacked with sulfuric acid to make phosphoric acid, then neutralised with caustic soda and heated.
Myth check: "Phosphates are banned in Australia": no. Under a voluntary deal, in 2011 all major laundry manufacturers and supermarkets committed to removing phosphates from laundry detergents by 2014, and by 2024 all mainstream laundry products carried the "NP" logo. They're still legal. A 2017 campaign audit found phosphates in 62% of dishwasher tablets sold in Coles and Woolworths over a year; dishwasher brands began removing them after that campaign.
Contaminants: nil.
Fair to say: the industry's risk assessment rates it low concern for people, and it's an approved food additive (E451). In the US, phosphorus in raw sewage rose from about 3 to 11 mg per litre as phosphate detergents took over, then fell to about 5 after bans. The industry points out that no case has been documented where cutting detergent phosphate alone, without better sewage treatment, fixed an algae problem.
We use this ingredient. It's in our Laundry Powder and Dishwasher Powder, to soften hard water so it doesn't leave a film. We don't claim either powder is phosphate-free.
Correct as of November 2026. What the badges mean
Sources
- Safe Work Australia. Hazardous Chemical Information System (HCIS): classifications for each chemical, and for formaldehyde.
- NSW Blue-Green Algae Task Force. Final report summary (1992).
- Environment Australia / National Pollutant Inventory. Aggregated nutrient emissions to the Murray-Darling Basin (2000).
- European Union. Regulation (EU) 259/2012 (phosphates in detergents); Detergents Regulation (EC) 648/2004, Annex VII; Regulation (EU) 2023/2055 (microplastics); EU Ecolabel decisions 2017/1216 and 2017/1218.
- HERA. Risk assessments: STPP (2003) and STPP eutrophication note (2003); phosphonates (2004); zeolite A (2004); soluble silicates (2005); polycarboxylates parts I and II (2014).
- HSDB (US National Library of Medicine), via PubChem: production, pH and impurity data for each chemical.
- InsideFMCG. Dishwasher tablets and phosphates (2017).
The full source list is at the end of Chapter 3.