- Giardia cysts are highly resistant to chlorination because the cyst wall protects them from the oxidative damage caused by chlorine.
- In contrast, methods like boiling, ultraviolet irradiation, and filtration effectively inactivate or remove Giardia cysts by disrupting their structure or physically removing them from water.
- Therefore, chlorination alone is insufficient for safe water treatment against Giardia.

Reference: Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases, Volume 2, Chapter 304