Chapter 4: Bleaches and brighteners · Part 2: Chlorine bleaches (and ammonia)
Sodium dichloroisocyanurate (NaDCC)
- Poison schedule (Australia)
The worst fact: Australia's classification list includes "Causes serious eye damage" (the EU's is "Causes serious eye irritation"), and safety references warn of permanent eye damage, including blindness. It reacts with ammonium compounds, which "can cause a very vigorous reaction".
Why brands use it: it's a stable tablet that releases chlorine slowly and may kill germs even better than liquid bleach at the same strength, according to the US CDC.
Take care if: you have children, or for your eyes. In Australia it's a Schedule 5 Poison up to 40% available chlorine, and a Schedule 6 Poison above that. The pure chemical is about 60%.
Comes from: cyanuric acid (made from urea) reacted with chlorine.
Myth check: nil.
Contaminants: nil.
Fair to say: it's widely used in emergencies to make drinking water safe.
Correct as of November 2026. What the badges mean
Sources
- Australian Government. Poisons Standard October 2026 (SUSMP), F2026L01327: chlorinating compounds, dichloroisocyanuric acid, hydrogen peroxide, sodium percarbonate, peracetic acid, ammonia.
- Safe Work Australia. Hazardous Chemical Information System (HCIS): classifications for each chemical, and for borax. hcis.safeworkaustralia.gov.au
- US CDC. Guideline for Disinfection and Sterilization in Healthcare Facilities (2008); Chloramines and pool operation.
The full source list is at the end of Chapter 4.