The human risk perception system evolved to deal with simple dangers, like wolves and bad guys with clubs and the dark, not complex long-term threats involved in the unsustainable way we live on the planet.
The dispersants used to break up the oil from the Gulf of Mexico spill are indeed toxic, but no more so than the oil itself. They reduce the mechanism by which the oil suffocates or harms some wildlife.
As an environmental writer, I see parallels between religious End Timers and increasingly apocalyptic Greens. Original sin among fundamentalists is easily translated into pollution among environmentalists.