The Home Chemical Almanac · Chapter 3
Builders and water softeners
Correct as of November 2026.
If the label says "builders", "water softeners", "sequestrants" or "phosphate-free"
Hard water is full of calcium and magnesium, which stop surfactants working and leave scale on glasses and machines. Builders grab those minerals (chelating agents hold onto them; others swap them out or keep them suspended), so the detergent can do its job. US laundry powders once held up to 60% STPP by weight.
In Europe, phosphates, phosphonates, EDTA, NTA, zeolites and polycarboxylates are official label groups, shown in a percentage band above 0.2%. EU laundry detergents must have under 0.5 g of phosphorus per wash (since 30 June 2013), and dishwasher detergents under 0.3 g per dose (since 1 January 2017). Australian cleaning products don't have to list all their ingredients. Only a scheduled poison must be named on the label, with its strength, and a disinfectant must name its active ingredients.
"Phosphate-free" doesn't mean phosphorus-free. Many phosphate-free products use phosphonates instead, which also contain phosphorus. The EU counts total phosphorus "to preclude a mere substitution of other phosphorus compounds for phosphates". Australia has no law limiting phosphorus in detergents. Removal was voluntary, and the industry retired its "P" logo (up to 7.8 g phosphorus per wash) on 22 March 2024. Laundry products can still carry the voluntary "NP" logo, which means under 0.5% phosphorus.
Washing soda, citric acid and sodium metasilicate are builders too. They're in Chapter 10.
Cheat sheet
| Chemical | Badges | Also on labels as | Worst fact | Take care if |
|---|---|---|---|---|
| STPP | — | sodium tripolyphosphate, phosphates | Detergent phosphorus helped feed the 1991 Darling bloom | eyes |
| Trisodium phosphate | ☠ | TSP | Splashes have permanently clouded the cornea | eyes, skin |
| Pyrophosphates | — | tetrasodium / tetrapotassium pyrophosphate | Can cause serious eye damage | eyes |
| HEDP | — | etidronic acid, phosphonate | Barely breaks down in sewage treatment | eyes |
| ATMP | 🛢 | phosphonate | Made with formaldehyde; adds phosphorus to rivers | eyes |
| DTPMP | 🛢 | phosphonate | Can turn into glyphosate in lab tests with wastewater | eyes |
| Zeolite A | — | zeolite, sodium aluminium silicate | Dust inflames the lungs in animal tests | breathing dust |
| Silicates | 💧 | sodium silicate, disodium disilicate | A woman died within an hour of deliberately drinking 500 mL | eyes, children |
| Tetrasodium EDTA | 🛢 💧 | EDTA, edetate | Europe's highest-concentration man-made organic compound in rivers | eyes |
| Trisodium NTA | 🛢 💧 | NTA | Possibly carcinogenic to humans | eyes |
| MGDA | 💧 | trisodium methylglycinediacetate | "Green" chelator; maker's patents use formaldehyde and cyanide | — |
| GLDA | 💧 | tetrasodium glutamate diacetate | Only 56% of its carbon is bio-based | eyes |
| Sodium polyacrylate | 💧 | polycarboxylate, polyacrylic acid | Doesn't readily biodegrade; mostly ends up in sewage sludge | — |
| Acrylic/maleic copolymer | 💧 | polycarboxylate | Doesn't readily biodegrade; mostly ends up in sewage sludge | — |
☠ Poison schedule (Australia) · ⚠ Officially classed skin allergen · 🛢 Made from a hazardous chemical · 💧 Contaminant risk
The chemicals
Part 1: Phosphates
- Sodium tripolyphosphate (STPP)
- Trisodium phosphate (TSP) ☠
- Tetrasodium and tetrapotassium pyrophosphate
Part 2: Phosphonates
These are what many "phosphate-free" products use instead.
Part 3: Zeolites and silicates
Part 4: Chelating agents
- Tetrasodium EDTA 🛢 💧
- Trisodium NTA 🛢 💧
- MGDA 💧
- GLDA 💧
Part 5: Polycarboxylates
Safer alternatives
In the United States, bar soap was the main cleaning agent until the end of the Second World War. Phosphate detergents then took over, and by the late 1960s Lake Erie was being called a "dead lake". Today's readily biodegradable builders come from fermentation or break down quickly after use.
Look for these on the label:
- Sodium citrate and citric acid (made by fermenting sugar)
- Sodium gluconate (made by fermenting glucose)
- Tetrasodium iminodisuccinate (IDS): made from maleic acid, a petrochemical, but readily biodegradable and not classed as hazardous (the US Safer Choice list gives it a yellow triangle, not a green circle)
- Washing soda (sodium carbonate)
- "Phosphate-free and phosphonate-free" on the pack. The NP logo alone doesn't rule out phosphonates.
Sources
Regulators and official lists
- Australian Government. Poisons Standard October 2026 (SUSMP), F2026L01327: alkaline salts; trisodium nitrilotriacetate.
- 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).
- NSW Blue-Green Algae Task Force. Final report summary (1992).
- CSIRO. Toxic algal blooms the new normal for Australia's major rivers (2016).
- Environment Australia / National Pollutant Inventory. Aggregated nutrient emissions to the Murray-Darling Basin (2000).
- Accord Australasia. Phosphorus Standard and P-logo retirement Q&A (2024).
- 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.
- European Commission CSTEE. Opinion on the EU risk assessment of EDTA (2003).
- 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).
- US Geological Survey. Litke DW, Review of phosphorus control measures in the United States (WRI 99-4007, 1999).
- ILO/WHO International Chemical Safety Card: trisodium phosphate.
- OECD SIDS. Gluconic acid and its derivatives (2004).
- 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.
Studies and technical sources
- Donnelly TH, Grace MR, Hart BT. Algal blooms in the Darling-Barwon River. Water Air Soil Pollut 1997;99:487-496.
- Rott E, Steinmetz H, Metzger JW. Organophosphonates: a review. Sci Total Environ 2018;615:1176.
- Moedritzer K, Irani RR. The direct synthesis of α-aminomethylphosphonic acids. J Org Chem 1966.
- Röhnelt et al. Glyphosate formation from aminopolyphosphonates. Nat Commun 2025.
- Sigrist T, Flury K. Death by peroral ingestion of soluble glass (sodium silicate). Z Rechtsmed 1985;94:245-250.
- Nörtemann B. Biodegradation of EDTA. Appl Microbiol Biotechnol 1999;51:751-759.
- Lanigan RS, Yamarik TA. Final report on the safety assessment of EDTA. Int J Toxicol 2002;21 Suppl 2:95-142.
- Pinto IS et al. Biodegradable chelating agents: a review. Environ Sci Pollut Res 2014;21:11893.
- Cokesa Z et al. Biodegradation of iminodisuccinate. Appl Environ Microbiol 2004;70:3941.
- BASF SE. US patents 5,849,950 and 8,802,894 (MGDA). Akzo Nobel / Nouryon. US patent 8,399,705 (GLDA). Nouryon, Dissolvine GL Premium launch (2023).
- InsideFMCG. Dishwasher tablets and phosphates (2017).