Refinery effluents contribute an estimated 300,000 tons of oil per year to the sea, but the biological effects of continuous but low concentrations of oil and other compounds are not well known. Different approaches to the problem are described, and field and laboratory results summarized. Different ecosystems differ in their capacity to receive and degrade effluents, and speed of dispersion and dilution is a major factor determining amount of biological damage. Changes in distribution and abundance of species are often very localised and in some cases may result from behavioural responses rather than direct toxic effects; areas of influence in terms of sub-lethal absorption of oil or other effluent constituents are not yet known. Biologically acceptable limits for effluents will vary considerably between sites and do not necessarily correspond with the present somewhat arbitrary restrictions.
1 Incorporating work by past and present members of the Oil Pollution Research Unit: Geoffrey Crapp, Brian Dicks, David Levell, Sheila Ottway, Anne Parsons and Roger Parsons.