Evaluation of Oil Spill Dispersants with a focus on their toxicity and Biodegradability

Abstract

Abstract Oil spill dispersants (OSD) are known to be efficient tools needed to clean and disperse many oil spills. Dispersants are used to disperse oil and prevent them from reaching the shorelines. There are two major concerns in the use of dispersants on our environment. Their toxicity, because the synergistic toxicity effects of these chemicals is of great concern as different chemicals that combine together in the same effluent can have toxic effects even when each of the individual chemicals is known to be non-toxic. Also their biodegradability, as every product whose final fate is in our environment should biodegrade quickly in order to avoid irreparable damage and disruption of the natural ecosystem. This work reviewed literature on oil spill dispersants from 1994–2014 focusing on their toxicity and biodegradability. From the review, many researchers however reported that dispersed oil is more toxic than the crude oil while very few were able to show that the dispersed oil was less toxic or equal in toxicity to the crude oil. They also showed that the dispersant increased the concentration of PAHs in the water column, this some accredited to be the cause of the increased toxicity. The effect of the toxicity on the various organs of the organism was noted as some recorded lesions on the gills of fish, drop in heart rate and so on. Many studies proved that dispersants do actually increase the biodegradability although to some it was restricted to some components of the crude oil. Some researchers however showed that the dispersant reduced the biodegradability of the crude oil. Also noted was the fact that various crude oils reacted differently when mixed with a dispersant and aquatic organisms reacted differently to different combinations of the dispersed oil. Temperature was shown to play a role in rate of biodegradability. More work needs to be done here in Nigeria to determine the cumulative impact oil spill dispersants have on the different organisms in the ecosystem when mixed with our various crude oils. Since the window of opportunity for use of a dispersant after an oil spill is recorded to be between hours to 2 days, this will aid timely decision making on the use of dispersants in our waters.