Which of the following is the source of a pathogen, a major water pollutant?

The water pollutants are as follows:
1. Suspended impurities like sand, mud, clay and organic matter.
2. Dissolve gasses like CO2, NH3, N2, H2S. 
3. Dissolve minerals like Ca2+, Na+ and Mg2+ salts. 
4. Dissolved chemicals, pesticides, domestic wastes, etc.
5. Micro-organisms of pathogenic or non-pathogenic nature like bacteria, virus, protozoa, etc.
6. Isotopes or radiologically activated substances.