Table 1.

Characteristics of studies of tap water versus tap water re‑treated at POU.

Study	Location	Source water	Treatment plant	Distribution system	Design	Comparison exposure	Effect estimate (95% CI)
Payment et al. 1991	Canada	River receiving sewage; coliforms and viruses detected	Conventional treatment with ozonation and chlorination; effluent in compliance with regulations; no coliforms or viruses in effluent	Negative pressures; inadequate residual	CRT, nonblinded	RO-treated water	IDR = 1.36 (1.10, 1.69)a
Payment et al. 1997	Canada	Same river as for Payment et al. 1991; coliforms, parasites, and viruses detected	Conventional treatment with ozonation and chlorination; effluent in compliance with regulations; no coliforms, parasites, or viruses in effluent	Same system as for Payment et al. 1991; no fecal coliforms; coliforms detected in 0.6% of samples	CRT, nonblinded	Ozonated bottles of RO-treated plant water or spring water	IDR = 1.14 (0.91, 1.42)a
Semenza et al. 1998	Uzbekistan	Not reported	Two-stage chlorination	Pressure-loss events; inadequate residual	Cohort,b nonblinded	Chlorinated water	IDR = 2.61 (1.71, 4.00)a
Hellard et al. 2001	Australia	Protected forest catchments; fecal coliforms detected	Chlorination; no coliforms in effluent	Inadequate residual; no fecal coliforms; coliforms detected in 19% of samples	CRT, blinded	Microfiltration + UV	IDR = 1.00 (0.86, 1.15)
Colford et al. 2002	USA	River receiving agriculture and industry runoff; pathogens detected	Conventional treatment with chloramination; effluent in compliance with regulations	Not reported	CRT, blinded	Microfiltration + UV	IDR = 1.32 (0.75, 2.33)
Colford et al. 2005b	USA	River receiving sewage; parasites and viruses detected	Conventional treatment with chlorination; effluent in compliance with regulations; no coliforms, parasites, or viruses in effluent	No negative pressures; adequate residual; no coliforms	CRT, blinded	Microfiltration + UV	IDR = 0.96 (0.85, 1.08)
Abbreviations: CRT, cluster-randomized trial; IDR, incidence density ratio; POU, point of use; RO, reverse osmosis; UV, ultraviolet. aCalculated from data reported in study. bObservational arm within cluster-randomized trial.