Chapter 3: Builders and water softeners · Part 2: Phosphonates
ATMP
- Made from a hazardous chemical
The worst fact: it barely breaks down in standard tests: only 0.5 to 2% was fully broken down over 210 days. Sunlight breaks it down slowly, releasing phosphorus that feeds algae. A 2018 review notes that phosphonate breakdown products such as aminomethylphosphonic acid (AMPA) and glyphosate are "regarded as being particularly critical".
Why brands use it: it stops scale and locks up hard-water minerals at very low doses.
Take care if: you get it in your eyes. Most company reports class it as an eye irritant.
Comes from: phosphorous acid, an amine and formaldehyde. Australia classes formaldehyde as "May cause cancer". That doesn't mean it's in the product, but it's not a great starting point for something you clean with.
Myth check: "Phosphonates pull heavy metals out of river mud": not at real levels. It takes more than 50 parts per billion (the industry says 100 to 300), and measured river levels are lower; the industry predicts under 1.
Contaminants: nil.
Fair to say: lab tests show over 90% sticks to sewage sludge. Workers have reported only irritation in over 20 years of use.
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.
- HERA. Risk assessments: STPP (2003) and STPP eutrophication note (2003); phosphonates (2004); zeolite A (2004); soluble silicates (2005); polycarboxylates parts I and II (2014).
- Rott E, Steinmetz H, Metzger JW. Organophosphonates: a review. Sci Total Environ 2018;615:1176.
The full source list is at the end of Chapter 3.