Sentence:It was also felt necessary at this time to draw up a similar document, dealing not with the prevention of marine [e1]pollution[/e1] by [e2]dumping[/e2], but instead with the prevention of marine pollution by discharges of dangerous substances from land-based sources, watercourses or pipelines.
 e1: pollution. 
 e2 : dumping.
Answer: Cause-Effect(e2,e1)