The international committees have set some standards for drinking water keeping in mind the body needs which should be followed worldwide.
I will enlist here the international standards for drinking water;
Fluoride
For drinking purpose, water should be tested for fluoride ion concentration. Its deficiency in drinking water is harmful to man and causes diseases like tooth decay, etc. Soluble fluoride is often added to drinking water to bring its concentration up to 1 ppm. The fluoride ions make enamel on teeth much harder by converting hydroxyapatite, the enamel on the surface of teeth to much harder fluorapatite.
However, fluoride ion concentration above 2 ppm causes brown mottling of teeth. At the same time, excess fluoride concentration (above 10 ppm) causes damage to bones and teeth as reported in some parts of Rajasthan.
Lead
Drinking water gets contaminated by lead when lead pipes are used for transportation of water. The prescribed upper limit concentration of lead in drinking water is about 50 ppb. Lead can damage liver, kidney, reproductive system, etc.
Sulphate
Excessive sulphate (>500 ppm) in drinking water causes laxative effects, otherwise at moderate levels, it is harmless.
Nitrate
The maximum limit of nitrate in drinking water is 50 ppm. Excess nitrate in drinking water can cause disease such as methaemoglobinemia which is also termed as Blue Baby Syndrome.
Other metals
The maximum prescribed concentration of other metals in drinking water are
Iron : 0.2 ppm
Manganese : 0.05
Aluminium : 0.2
Copper : 3.0
Zinc : 5.0
Cadmium : 0.005
Thank You.