Tar balls and liquid oil from the Gulf spill taint Florida's Pensacola Beach on July 1. Exposed oil, though, may be the least of the worries.
Even without cleanup crews, surface oil disappears fairly quickly as oxygen, sunlight, and oil-eating microbes break it down. Buried oil can persist much longer, particularly deep down, where oxygen is in short supply.
"If [oil's] buried and you have a five-year-old out here next summer building a sand castle and they uncover a layer of tar and oil, that's not going to be good," said Tiffany Roberts, a University of South Florida Ph.D. student.
Contact with oil can cause skin irritation, and inhaling evaporated oil particles may cause nausea, headache, and dizziness—ailments already reported by some Gulf oil spill cleanup workers, according to the U.S. Department of Health and Human Services.