Unfortunately, this sort of law is different all over the world, and may or may not be present in the laws that are applicable to you. The best place to look would be in any laws that apply to drinking water in your area.
I received the following question:
2. Is the WHO (World Health Organization) may include in our Legal & Other requirements?
The WHO may show up in your interested parties if they have resolutions that apply to you. The real test of any organization being an interested party is when you determine the needs and expectations of that organization on your company. If they do not have any needs and expectations, then they are very likely not an interested party.