people are used to heararing about oil spills from ththe "exxon v valdez" o or abot the recent spill in the gulf of mexico that brititish petreum mn illing provokeked. you're talking about a whole differenent set of problems. how do they compmpare with thosese big spills? micah: it's a great question. i think we all get our attention awn to the big dramatic moment. explosion of an oil rig, the sinking of a giant oil tanker. but in fact, over time, if you look at the total cumulative effect of that, it's only about 20% of the oil that goes into the ocean frfrom human sources. the much larger component is this relar, everyday, intentional dumping overboard, getting rid of oil, waste products, sludge. ships--commerciaial ships tend o burn very low-grade oil, and thatat produces this messy slud. and the question is, what do you do w with that? well, by law, you're supposed to bring it to port, you're supposed to offload it. it takes t time, it takes money, it takes energy to properly dispose of this stuff. or, if you're not trying to obey the law,ou can jusust dump it overboard, which th