OIL AND RELATED CHEMICALS - Marine Pollution: What Everyone Needs to Know - page 80

to clean up. Methods for cleaning up include skimming,
which requires calm waters and removes the oil quickly with-
out damaging the environment. Bioremediation is the use of
microorganisms or biological agents to break down or remove
oil. It can be effective, but takes a long time. Controlled burn-
ing can effectively reduce the amount of oil in the water if done
properly, but it can only be done in low wind and can cause
air pollution and kill surface dwelling animals. Dispersants
act as detergents, clustering around oil globules and allowing
them to dissolve in the water. This improves the surface aes-
thetically and mobilizes the oil. Smaller oil droplets, scattered
by currents, may cause less harm and may degrade more eas-
ily. However, the dispersed oil droplets penetrate into deeper
water and can affect marine organisms, since they are toxic.
Another approach is to just wait; in some cases, natural attenu-
ation of oil may be most appropriate, because of the potential
harm associated with some of the methods of remediation,
particularly in ecologically sensitive areas. Remedial actions
after oil spills are controversial, and some of them (e.g., aggres-
sive cleaning with large heavy equipment) may be worse than
the original problem, as was seen with some of the attempted
clean up techniques after the Exxon Valdez oil spill. However,
an oil company advocating for natural attenuation instead of a
cleanup would have a major public relations problem.
What are the trends in oil spills over the decades?
The number of spills from tanker ships has decreased greatly
over the past three decades. There were about three times as
many spills in the 1970s as in the 1990s. However, the number
of spills does not consider the volume of oil; the frequency of
large spills has decreased as well as the frequency of small
ones. Although more oil is being transported in larger super-
tankers, technical, political, and legal experience in managing
the problem has been gained in many countries and interna-
tionally through conventions initiated by the International