The National Oceanic and Atmospheric Administration (NOAA) has released a summary of the chemical composition of the Gulf oil
The oil is slightly less toxic than most crude oil. As NOAA notes:
[The Gulf] oil is less toxic than crude oils generally because it is relatively much lower in polyaromatic hydrocarbons (PAHs). PAHs are highly toxic chemicals that tend to persist in the environment for long periods of time, especially if the spilled oil penetrates into the substrate on beaches or shorelines. Like all crude oils, [the Gulf] oil contains volatile organic compounds (VOCs) such as benzene, toluene, and xylene.
This is a little bit of good news for a change, especially since hurricanes could spread oil inland.