Chapter 7: Disinfectants and antibacterials · Part 1: Quats
DDAC
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The worst fact: in a French survey of 543 hospital workers, those exposed to quats had 7.5 times the odds of reporting doctor-diagnosed asthma, and the highest risk came from mixing disinfectants by hand. A US occupational-clinics list names DDAC as a cause of work-related asthma. In a US study, median quat levels in blood were 77% higher in samples taken during the COVID-19 pandemic than before it, and quats were found in over 90% of 40 house-dust samples.
Why brands use it: it kills bacteria and enveloped viruses, keeps working in hard water and also cleans.
Take care if: you have asthma, or for your eyes. Australia classes it as "Harmful if swallowed; Harmful in contact with skin; Causes severe skin burns and eye damage". It's a Schedule 6 Poison unless it's 1% or less and labelled "Avoid contact with eyes"; household products have been reported at under 5%.
Comes from: a didecyl amine with a methyl group added. The only published route we found, a patent, uses methyl chloride (Australia: "Suspected of causing cancer"); without a chemistry reference, this book gives no 🛢 badge.
Myth check: "Disinfectant kills everything": no. Quats don't kill spores, and generally don't kill tuberculosis or non-enveloped viruses such as norovirus.
Contaminants: nil.
Fair to say: Australia's regulator found household use "not unreasonable" risk if you avoid eye contact and breathing the spray. Birth-defect and fertility effects have been reported only in rodents, and the regulator found no specific reproductive toxicity. Whether household quat use drives antibiotic resistance is debated and unproven.
Correct as of November 2026. What the badges mean
Sources
- Australian Government. Poisons Standard October 2026 (SUSMP), F2026L01327: didecyldimethylammonium salts; quaternary ammonium compounds; triclosan; o-phenylphenol; chlorocresol; p-dichlorobenzene; thymol; methanol; Appendix B.
- Safe Work Australia. Hazardous Chemical Information System (HCIS): classifications for each chemical, and for benzene and benzyl chloride.
- NICNAS. IMAP: cationic surfactants (2015). Priority Existing Chemical Assessment Report No. 30: triclosan (2009).
- US CDC. Guideline for disinfection and sterilization (2008); Hand sanitizer guidelines (2024).
- Gonzalez M et al. Asthma among workers in healthcare settings: role of disinfection with quaternary ammonium compounds. Clin Exp Allergy 2014;44:393-406.
- Zheng G et al. Quaternary ammonium compounds in human blood during the COVID-19 pandemic. Environ Sci Technol 2021;55:14689-14698.
- Zheng G et al. Elevated levels of QACs in indoor dust during the COVID-19 pandemic. Environ Sci Technol Lett 2020;7:760-765.
- Arnold WA et al. Quaternary ammonium compounds: a chemical class of emerging concern. Environ Sci Technol 2023;57:7645-7665.
- Boyce JM. Quaternary ammonium disinfectants and antiseptics: tolerance, resistance and potential impact on antibiotic resistance. Antimicrob Resist Infect Control 2023.
The full source list is at the end of Chapter 7.