Environmental pollution主语,is系动词,a term表语,that后的句子为term的定语
主句是Environmental pollution is a term。that refers to all the ways是定语从句,that 代替a term做定语从句的主语,也可以使用which,不能省略。by which man pollutes his surroundings是第二个定语从句,修饰先行词ways。环境污染是一个术语,指的人类污染其周边环境的种种途径和方式。