Dispersing Agents

Dispersing agents, also called dispersants, are chemicals that contain surfactants, or compounds that act to break liquid substances such as oil into small droplets. In an oil spill, these droplets disperse into the water column where they are subjected to natural processes - such as wind, waves, and currents - that help to break them down further. This helps to clear oil from the water surface, making it less likely that the oil slick will reach the shoreline.

Heavy crude oils do not disperse as well as light- to medium-weight oils. Dispersants are most effective when applied immediately following a spill, before the lightest materials in the oil have evaporated.

Environmental factors, including water salinity and temperature and conditions at sea, also influence the effectiveness of dispersants. Studies have shown that many dispersants work best at salinities close to that of normal seawater. The effectiveness of dispersants also depends on water temperature. While dispersants can work in cold water, they work best in warm water.

Some countries rely almost exclusively on dispersants to combat oil spills, because frequently rough or choppy conditions at sea make mechanical containment and cleanup difficult. However, dispersants have not been used extensively in the United States because of difficulties with application, disagreement among scientists about their effectiveness, and concerns that dispersants are toxic.

These problems are being overcome, however, as new technologies that improve the application of dispersants are being designed. The effectiveness of dispersants is being tested in laboratories and in actual spill situations, and the information collected is being used to help design more effective dispersants. Dispersants used today are much less toxic than those used in the past.