Is polio virus suspectibile to chlorination
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Here is a thorough answer based on the textbook source and water disinfection data:
Poliovirus Susceptibility to Chlorination
Yes - poliovirus is susceptible to chlorination, but with important caveats about context and concentration.
In Pure Water (Purified Virus)
According to Jawetz, Melnick & Adelberg's Medical Microbiology (28th Ed):
"Purified poliovirus is inactivated by a chlorine concentration of 0.1 ppm (mg/L)."
This means that under ideal laboratory conditions - clean water, no organic matter, neutral pH - a very low chlorine level suffices to kill poliovirus.
In Real-World Conditions (Sewage / Fecal Matter)
The textbook immediately qualifies this:
"Much higher concentrations of chlorine are required to disinfect sewage containing virus in fecal suspensions and in the presence of other organic matter."
This is the critical practical point. Organic matter (feces, proteins, debris) rapidly consumes free chlorine, drastically reducing disinfection efficacy. This is why simple chlorination of sewage or heavily contaminated water often fails to adequately control poliovirus.
Quantitative Benchmarks (from water treatment literature)
| Disinfectant | Condition | Requirement for ~99.7% inactivation |
|---|---|---|
| Free chlorine (HOCl) | pH 7.0, 25°C | ~0.3 mg/L, 30 min contact time |
| Combined chlorine (chloramines) | pH 7.0, 25°C | ~9.0 mg/L (much less effective) |
| Ozone | - | Far more effective than chlorine |
- Free hypochlorous acid (HOCl) is the active species - it is more than 50 times more virucidal than hypochlorite ion (OCl⁻), so pH matters greatly (lower pH = more HOCl = better kill).
- Combined chlorine (chloramines) are substantially less effective against poliovirus than free chlorine.
- Among enteric viruses tested, Poliovirus 1 (Mahoney/MK-500 strain) was among the most chlorine-resistant strains, while coxsackievirus B5 was the most sensitive.
Why Poliovirus is Relatively Chlorine-Resistant
- It is a non-enveloped virus - no lipid membrane to disrupt with chlorine.
- Its protein capsid provides greater protection to the RNA genome.
- Enveloped viruses (influenza, SARS-CoV-2) are far more easily killed.
- Note: poliovirus is not affected by ether or sodium deoxycholate, consistent with its non-enveloped nature (Jawetz, Melnick & Adelberg's Medical Microbiology, 28th Ed, p. 539).
Public Health Implications
- Standard municipal water treatment (filtration + chlorination to 0.2-0.5 mg/L residual) is effective at inactivating poliovirus in clean, treated water.
- Raw sewage or heavily contaminated water sources cannot be reliably disinfected by chlorination alone - the chlorine demand of the organic load far exceeds what is practical.
- The WHO/NCBI data on drinking water disinfection confirms that at pH 7.0 and 25°C, a minimum of 0.3 mg/L free residual chlorine with at least 30 minutes contact time is needed for reliable enteric virus inactivation.
Summary
| Condition | Chlorination Effective? |
|---|---|
| Purified/clean water | Yes - even 0.1 ppm is sufficient |
| Treated municipal water | Yes - standard disinfection works |
| Sewage / high organic load | Largely inadequate - much higher doses needed |
| Combined chlorine alone | Unreliable - 9 mg/L needed for 99.7% kill |
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