Out of sight, out of mind?

With surface oil slicks fading from view in the Gulf of Mexico, courtesy of the capped Macondo well, we'd be out of our minds to think that the oil still isn't there, warn forensic toxicologists.

"We're finding less and less oil as we move forward," disaster response chief Thad Allen said last week, noting skimmer boats having trouble finding slicks. The retired Coast Guard admiral also pointed out that some 40% of the leaked oil, more than 90 million gallons of crude by U.S. Geologic Survey scientist estimates, is missing. "There's the issue of whether or not we may find oil under the water," Allen added.

Under the water is where the oil is, say environmental chemists such as Jeffrey Short of the conservation group, Oceana, and not just in deep sea clouds of oil reported by National Oceanic and Atmospheric Administration (NOAA) scientists. "Oil tends to congeal and where you saw a broad slick, you now have a lot of droplets and tarballs," he says. Whether floating as tarballs, buried under Mississippi River mud or carried off in currents to the Atlantic, much of the spilled oil remains in the water, Short says.

"A chemical spill in the ocean is what this (Gulf of Mexico) leak is, really," says chemist Kim Anderson of Oregon State University in Corvallis. "The crude oil contains diesel, it contains gasoline, it contains kerosene, it contains methane and it contains chemicals that are unfortunately, carcinogenic. Literally there are hundreds of chemicals in crude oil."