RO purifier water has merits as well de-merits, and while it may pose some negative health effects over short and long terms, it cannot be categorised as “very dangerous for us”.First let’s see the merits (assuming its use for household level drinking water purification). The membrane is a non-chemical, non-residue leaving, physical process of removal of contaminants from water. The removal of contaminants is dependent on the size of the pores in the RO membrane. Because of its very small size (of the order of 0.001 microns) the membrane is capable of removing practically everything from water, giving highly purified water. This water could also be used for surgical and pharmaceutical purposes.Reverse osmosis is a highly economical and efficient way of obtaining drinking water from sea through desalination. Other methods like distillation are highly energy intensive, for desalination.The demerits arise in the process of reverse osmosis, which must necessarily reject a concentrated solution containing all the contaminants.