Pathogens can be destroyed by various treatments, such as heat (high temperature) generated by physical, chemical or biological processes. Sufficient temperatures maintained for sufficiently long time periods can reduce bacteria, viruses, protozoan cysts and helminth ova to below detectable levels (helminth ova are the most resistant to heat treatment). Chemical processing with disinfectants (e.g., chlorine, ozone, lime, etc.) can also reduce bacteria, viruses and vector attraction. High pH conditions, for example, may completely destroy viruses and bacteria but have little or no effect on helminth eggs. Gamma and high energy electron beam radiation treatment depends on dosage with viruses being most resistant. Reduction of pathogenic organisms can be measured using microbiological analysis directly or by monitoring non-pathogenic organisms-indicators.