Results of this study are shown in Table 6. Caution must be taken in extrapolating these data to other pathogens, however, as poliovirus has been found to be a poor model for the behavior of other pathogens in the environment. Generally, it has been found that bacteria are inactivated more rapidly than either viruses, and that parasites are able to survive for longer than viruses or bacteria. For example, pathogen survival has been found to be longer on root crops and leafy vegetables than on other types of crops due to the protective environment. Temperature is one environmental conditions that has a major impact on the length of time many pathogens remain infective, with relatively shorter survival times observed at high temperatures.
Evidence supporting the spread of disease through irrigation with reclaimed water is scarce.
Table 7 lists outbreaks known to be associated with reclaimed water irrigation. There have been other outbreaks associated with the consumption of contaminated fruits and vegetables, however, the source of the wastewater was not specified in those cases. In addition, there have undoubtedly been outbreaks that have gone unrecognized and unreported. In conclusion, reclaimed water is likely to contain pathogenic microorganisms. Depending on the treatment processes used, the pathogens may be present in high enough concentrations to pose a potential threat to human health.