Refuse is household waste and sewage is mainly human excreta. These waste are organic in nature, people living in undeveloped areas which are close to the sea end up dumping these substances into the water and still people drink and bath from that water and this will spread diseases.

People living in such evironsay not even understand it. They release their sewage inside the water/stream and also drink from same source.

@jammyroberts, i love this post. Keep it up