Not all things claimed to pollute the environment are prohibited
1-10-2015 | IslamWeb
Question:
assalaamu alaykum. I read a fatwa on your website that says that a business that pollutes and harms the environment is not allowed, but I want to ask about t-shirt printing. T-shirt cotton printing wastes gallons of water, and it contributes to pollution by other means. My question is the following: there is a group in facebook, and in this group, there are thousands of people who sell t-shirts online (print on demand T-shirt), and I am a member of this group because I wanted to do so at first, but I gave up on the idea. So should I leave the group and tell them about that? I am afraid that if I tell them about that they would go in a haram business and something evil. You can see more about the impact of pollution here: https://www.youtube.com/watch?v=g5rGm6veAhg
Answer:
All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah and that Muhammad 
is His slave and Messenger.
A well-established Fiqh rule in Islam asserts that all things are deemed lawful in principle (unless proven otherwise by valid evidence). Allaah, The Exalted, says (what means): {It is He Who created for you all of that which is on the earth. Then He directed Himself to the heaven [His being above all creation] and made them seven heavens, and He is Knowing of all things.} [Quran 2:29]
Ibn Taymiyyah 
wrote:
"I do not know of any difference of opinion among past scholars that things that are not proved unlawful by means of religious evidence are lawful in an absolute, unrestricted manner. Many scholars of Usool Fiqh (Fundamentals of Fiqh) and branches of Fiqh stated that rule. I believe that some of them asserted that a scholarly consensus has been reached in this regard with certainty, or strong assumption that amounts to certainty."
Hence, the basic principle is that all things that Allaah has created as well as the benefits derived from them are permissible. Nothing is deemed unlawful except what is prohibited by a sound and explicit religious text. This is a manifestation of the Mercy of Allaah for His slaves and an indication of the ease celebrated in Islam and the elimination of hardships intended by the Sharee'ah.
As for environmental pollution, you should know that not all the things or practices labeled as environmental pollutants are religiously prohibited. Rather, prohibition is only ascribed to the causes that are considerable in the Sharee'ah, such as inflicting harm on people without right, wasting resources, and the like.
However, the fact that a certain matter is said to pollute the environment, or is environmentally unfriendly, in their terminology, is irrelevant with regards to the religious ruling. Many of the things that are deemed lawful according to the collective consensus of the Muslims are labeled (by some) as environmentally unfriendly. Moreover, some environmentalists fall into excessiveness, immoderation, and obsessive whisperings because of that.
In brief, the basic principle is that manufacturing cotton clothes such as T-shirts and printing on them are deemed lawful by the Sharee'ah, and the opinions suggesting that they pollute the environment and the like are not a valid reason for deeming them prohibited.
Allaah knows best.