Yes we can...and should. My husband and I have in fact taught our daughter that littering in many ways is a sin and not to be taken lightly. It's a sin against the environment, it's breaking laws, it's causing harm to others, and actually in the case of Muslims an action that directly affects your faith cos in Islam removing something harmful to others is a part of our faith so imagine then being the perpetrator of spreading harm?Audubillah! Keep it clean, people!