Pooled data from six case-control studies suggest that higher consumption of tap water-based drinks may slightly increase the risk of bladder cancer among men.
The increased risk of bladder cancer with tap water consumption was "consistently found in all six studies, making chance an unlikely explanation," write investigators in the International Journal of Cancer.
They caution, however, that for now, the study finding that tap water "is associated with a slight increased risk of bladder cancer" does not readily translate into public health recommendations.