Gulf Spill: How Bad Is It? Really!

I think it's bad, really bad. But maybe some genius math guy out there can help me with some number crunching.

The Gulf of Mexico contains 6.43 x 10 to the 17th power or 643 quadrillion gallons of seawater. Even if we consider an absolute worst case estimate of 100,000 barrels per day, the total spill at day 78 (today) is 327,600,000 gallons or 3.27 x 10 the 8th power. I'm not sure of the math but doesn't this make the spill approximately 50 billionths of the total volume? What would that be in parts per million, e.g. the standard by which the EPA figures toxic threshold values?

Anyway, I realize this is a horrendous disaster of monumental proportions, and the spill is not an easily calculable thing. I just wanted to add another perspective.

~seabgb