BP oil spill Fermi estimates

This isn't meant to minimize the environmental horror of the BP oil spill, but I can't resist some rough estimates. (I did this quickly, so please correct my errors.)

100 days x 50k barrels/day x 150 liters/barrel = 750 million liters

Call it a billion liters of oil: 10^9 liters

Gulf of Mexico: over 2M cubic kilometers of water, or 2 x 10^18 liters

Suppose the spill is concentrated in 1 percent of the Gulf's area (a region 10% by 10% of the Gulf's linear dimensions - about 50 miles by 100 miles). This would presumably only be the case for a limited amount of time, and concentrations would fall off as the oil disperses further. Of course, if the oil is concentrated on a 2-dimensional surface slick, that would be quite bad for anything in the slick.

Then, assuming uniform dispersal within this sub-region, the oil concentration is about 1 part in ten million, or .1 ppm.

Googling around (e.g., ppm oil toxic), I couldn't find evidence of toxicity at any concentrations lower than 1 ppm.

So, aside from shocks to otherwise already endangered species, it seems the long-run effects of the spill won't be that bad. Don't yell at me -- I'm an environmentalist! But numbers don't lie...