NO3− The maximum limit of nitrate in drinking water is 50 ppm. Excess nitrate in drinking water can cause disease. Such as methemoglobinemia. SO42−:above 500 ppm of SO42− ion in drinking water causes laxative effect otherwise at moderate levels it is harmless F− Above 2ppm concentration of F– in drinking water cause brown mottling of teeth. ∴ The concentration given in question of SO42– & NO3− in water is suitable for drinking but the concentration ofF– (i.e 10 ppm) make water unsuitable for drinking purpose :