Techniques used to clean oil spillages in the sea are more dangerous for fish than the spills themselves, a study shows.

The research by the Canadian Queen's University revealed that detergents used to treat oil spills harm aquatic wildlife. They decrease the surface tension between the oil and the water so that oil is able to mix with the water and form droplets, instead of a surface film. Although this helps reduce the impact which oil spills have on surface-dwelling animals and speeds up the oil's biodegradation, at the same time it increases the negative effect on creatures below the water level.

“The detergents may be the best way to treat spills in the long term because the dispersed oil is diluted and degraded,” says Biology professor Peter Hodson. “But in the short term, they increase the bioavailability and toxicity of the fuel to rainbow trout by a hundred-fold.”

Hydrocarbons mixed with water easily pass into living tissue, which can be deadly to juvenile fish.

Researchers say that turbulent river currents can have a similar effect on oil spills.

The study was published in the journal, Environmental Toxicology and Chemistry.