2.3. Coliform
Fecal contamination of drinking water is the major pathway of infection
for humans and several studies correlate the concentration of fecal
coliform with diarrhea [19]. However, the threshold, above which there
is a significant risk of diarrhea, is not yet clear. For example, the current
WHO guidelines recommend that drinking water that is safe for human
consumption should have no detectable amounts (FCU = 0.100 ml−1
).
On the other hand, Moe et al. [33] evaluated the effect of contaminated
source water on diarrhea in the Philippines and found no evidence of an
association between CF and diarrhea at the 1 total coliform (counted as
Escherichia coli) threshold level. However, significant associations with
diarrhea were observed at the 1000 total coliform level. Singh et al.
[48] reported similar results in a study developed in India. In this
sense, some authors suggest that a tolerant drinking water level
(beyond the 1 total coliform threshold) might be acceptable in developing
countries, where better quality sources are not accessible [33,48].
Contrary, Gruber et al. [19] found an elevated risk of diarrhea at a total
coliform threshold of 1. These results support current WHO guidelines,
regardless of location.