Clostridium perfringens
Cities measured
87
Detected in
2 / 87
Elevated / alert
2
Highest
4 CFU/100mL — Beirut
Overview
C. perfringens spores are used as indicators of ancient faecal contamination and as surrogates for Cryptosporidium and Giardia — protozoa resistant to chlorine. Their heat-resistant spores survive conventional treatment, so their presence indicates either source breakthrough or old contamination.
Health Relevance
C. perfringens causes food poisoning but is not a primary waterborne pathogen concern at drinking water concentrations. Its value is as a process performance surrogate for protozoan parasites.
Regulatory Limits
Drinking Water Directive 2020/2184
0 per 100 mL (used in surface water source characterisation).
Controversy & Contested Science
The C. perfringens/Cryptosporidium surrogate relationship is imperfect — it over- or under-predicts protozoan risk depending on source characteristics. The EU has not established a specific Cryptosporidium limit in drinking water (unlike the US, which has a specific Treatment Technique Rule). Several Cryptosporidium outbreaks in Ireland (2007, Galway, ~240 cases) and the UK highlight this regulatory gap — protozoa can breach UV and chlorine treatment at levels undetected by C. perfringens monitoring.