Municipal pollution consists of wastewater from homes and commercial establishments. Industrial wastewater differs markedly both within and among industries, with its impact depending on characteristics such as biochemical oxygen demand, the amount of suspended solids, and the content of specific inorganic and organic substances. Agriculture is also the source of many organic and inorganic pollutants. These contaminants include both sediment from the erosion of cropland and compounds of phosphorus and nitrogen that partly originate in animal wastes and commercial fertilizers. The combination of toxic substances, the rapid uptake of contaminants by marine organisms, and heavy deposits of materials on the bottom environment near the shore all have very serious consequences for the marine environment.
Oil spills are another major cause of marine pollution.
Most involve supertankers used for oil transport, but other ships also spill oil, and offshore drilling operations contribute a large share of the pollution .