Adding a Chemical Substance to Natural Water

Indeed, a Muslim is required by Islam to take great care of the environment. He should make sincere efforts to keep the natural resources intact. He should not cause any harm to natural waters or add any substances to them that are capable of harming him.
Dr. Rif`at Fawzi, former head of the department of Shari`ah at the faculty of Darul-`Ulum, Cairo University, states the following: “The issue is governed by two main legal rulings in the Shari`ah. The first one states that ‘there should be neither harm nor reciprocating harm’. Based on this rule, I can say that a cyber Mufti cannot state whether adding such a substance to natural water is permitted or not. Those who can really judge the situation are the specialists in that field. If they state in clear terms that adding such a substance will cause harm to the health of people, then adding such a substance is prohibited so as to save the lives of people, which is a main objective of the Shari`ah.
Having clarified the above, I should add that if the specialists confirm that adding such substance will cause a bearable harm that people can sustain, then the other legal rule, which states that ‘the lesser harm can be sustained so as to fend off a greater one’, can be applied here. In this later case, adding such a substance will be permissible even with a lesser harm it causes, as the main objective here is to remove the greater harm by adding such a substance.”
Moreover, Sheikh Muhammad Nur Abdullah, President of the Islamic Society of North America (ISNA) and Member of the Fiqh Council of North America, adds:
“The issue of adding chemical substances to water is purely a matter of health. The general rule that governs this is: if adding such substances is going to remove health risks by killing germs and the like, then it should be done, but rather it can reach the level of wujub (mandatory) if the health risk [without the added substance] is inevitable. Such substance is permissible according to the Shari`ah.”