Chapter 3: Builders and water softeners · Part 4: Chelating agents
Trisodium NTA
- Made from a hazardous chemical
- Contaminant risk
The worst fact: Australia classes it as "Suspected of causing cancer", and the World Health Organization's cancer agency rates it "possibly carcinogenic to humans". In rats it caused kidney, ureter and bladder tumours, and in mice kidney tumours. In December 1970 the US detergent industry voluntarily stopped using it, after an unpublished government report suggested it could cause birth defects. Australia's regulator now says it doesn't, and US use resumed in the 1980s. It's banned in EU cosmetics.
Why brands use it: it was the main phosphate replacement: it locks up calcium and magnesium.
Take care if: you get it in your eyes. Australia classes it as "Harmful if swallowed", "Causes serious eye irritation" and "Suspected of causing cancer". It's a Schedule 6 Poison only in products with more than 20%, and known household uses overseas are up to 5%. Australia's drinking-water guideline is 0.2 mg per litre.
Comes from: ammonia, formaldehyde and hydrogen cyanide. 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: "NTA doesn't biodegrade": it does. In German river water, half was gone in 2.3 days at 25°C and 9.9 days at 2°C. It breaks down poorly in salty estuary water.
Contaminants: manufacturing by-products such as hexamethylenetetramine and glycolic acid. They're unlikely to matter in a well-made product, but it's a factor you can't see on the label.
Fair to say: the tumours came at high doses: from 80 to 100 mg per kg of body weight a day for trisodium NTA in rats. They're linked to the way it grabs zinc and calcium in the urinary tract. Australia's regulator rates the public health risk as "not unreasonable".
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.
- AICIS. Evaluation statement EVA00169: EDTA and its salts (2025). IMAP assessments: trisodium phosphate (2016); etidronic acids (2013); soluble silicates (2016); nitrilotriacetic acid and salts (2017).
- IARC. Monographs vol. 73: nitrilotriacetic acid and its salts (1999).
- US National Toxicology Program. Report on Carcinogens, 15th ed.: nitrilotriacetic acid; Technical Report 6 (1977).
- HSDB (US National Library of Medicine), via PubChem: production, pH and impurity data for each chemical.
The full source list is at the end of Chapter 3.