The two pie charts compare the percentage of different pollutants that entered a particular part of the ocean in 1997 and 2007.
Overall, it is clear that domestic sewage and offshore oil increased their proportions significantly, whereas most other sources declined. Pollutants from the air remained almost unchanged during the period.
In 1997, air pollution was the most serious contributor, making up 30% of the total. This figure showed only a slight fall to 29% ten years later. Marine pollutants accounted for 22% in 1997, but this share decreased moderately to 17% in 2007. A sharper decline was seen in industrial waste, which dropped from 17% to only 9%. Likewise, farm waste was halved, moving from 4% to 2%, while litter completely disappeared from the chart.
By contrast, the proportion of domestic sewage rose markedly, from 18% in 1997 to 29% in 2007, becoming the joint-largest category. Offshore oil also experienced a considerable increase, almost tripling from 5% to 14%.