Chapter 10: Acids and alkalis · Part 1: Alkalis
Sodium metasilicate
- Poison schedule (Australia)
The worst fact: Australia classes it as "Causes severe skin burns and eye damage", and even a 0.5% solution has a pH of about 12.5. Australia took alkaline dishwasher products above pH 12.5 (2 products at the time) off the home market from 1 September 2006. A submission to the poisons committee reported 96 children under 4 treated in 6 years for swallowing dishwasher detergent, about a third needing a camera down the throat. One Queensland toddler was left with lifelong scarring of the oesophagus.
Why brands use it: a high pH helps dishwasher and laundry detergents break down food and grease.
Take care if: you have toddlers. In a Victorian Poisons Information Centre study of 61 children who swallowed dishwasher detergent, 50 (82%) took it from the dispenser in the door, most of them from leftover detergent after a wash. A parent was in the room 78% of the time. Keep the dishwasher closed and wipe out the dispenser.
Comes from: sand (silica) fused with washing soda.
Myth check: nil.
Contaminants: nil.
Fair to say: when Australia banned the strongest powders in 2006, the remaining home dishwasher products usually had a pH below 11.5. Australia's regulator rates the risk from home use as "not unreasonable" with normal care.
We use this ingredient. It's in our Laundry Powder and Dishwasher Powder, as an alkaline builder that lifts grease and food. It works inside a closed machine and is rinsed away before you open the door. As with any dishwasher detergent, keep the powder away from children, and wipe out the dispenser if any is left after a wash.
Correct as of November 2026. What the badges mean
Sources
- Australian Government. Poisons Standard October 2026 (SUSMP), F2026L01327: sodium hydroxide, potassium hydroxide, alkaline salts, monoethanolamine, sulfamic acid, hydrochloric acid, acetic acid; Appendix B (sodium bicarbonate).
- Safe Work Australia. Hazardous Chemical Information System (HCIS): classifications for each chemical, and for ethylene oxide, carbon monoxide and acetaldehyde.
- AICIS / NICNAS. IMAP assessments: soluble silicates; ethanolamine (2013); hydrochloric acid (Tier II 2014, Tier III 2018); acetic acid (2013).
- HSDB (US National Library of Medicine), via PubChem: production and impurity data for each chemical.
- Cornish LS et al. Automatic dishwasher detergent poisoning. Aust N Z J Public Health 1996.
The full source list is at the end of Chapter 10.