Until recently, the toxicity of dispersants approved for use in U.K. waters was evaluated by a static bioassay on the dispersant alone.

Following the 1974 Dumping at Sea Act, dispersant evaluation methods were reviewed and dispersants are now licensed for sea (offshore) or for beach use, based on two tests to assess the environmental effect of the dispersant use.

The “sea” test assesses the toxicity to Crangon crangon of a chemically dispersed oil and compares it with the toxicity of the oil alone. Mortality is measured over a period of 100 min at an oil concentration of 1000 ppm.

The “beach” test assesses the toxicity of the dispersant alone to a typical intertidal organism, Patella vulgata, by spraying with dispersant and rinsing in a simulated tidal cycle. Mortalities are measured after 72 h and compared with those of an oil control.

The rationale behind the development of these tests is described, together with the experimental results. The U.K. criteria for licensing products on the basis of these test results are also discussed.