Chemical contamination has been decreasing. In the 1920s, spillage from the on-shore oil industry was widespread in southern California and San Francisco Bay. In the 1950s, radionuclides from atmospheric testing and releases from the Columbia River began showing up in clams and mussels along the coast. The combined chemical contamination of West Coast marine life, water and sediments reached an overall peak in the early 1970s, followed by dramatic decreases during the late 1970s and early 1980s. Most of the decreasing contamination has come as a result of controls on the sale and use of specific chemicals and as a result of pre-treatment or industrial source control.
Chemical contaminants continue to cause problems to marine life.
However, whether these are serious or not depends on your point of view. Compared to the past, today's problems are minor, are localized and are not caused by controllable inputs such as sewage or industrial outfalls. As we now realize, there were very serious and large-scale ecological problems a quarter century ago. These effects were reversed during the 1970s. Nevertheless, significant problems remain, due largely to seepage of toxic chemicals from submerged historical deposits.