This summer has seen huge amounts of volatile or "low boiling" petroleum fractions released into the Gulf of Mexico, including dispersants. These 'volatiles' are aromatic (strong smelling), and rapidly evaporate when warm. Evaporation can take place directly from sea water.
Once in the air, volatiles can react to form photochemical smog, which contains ozone. Ground-level zone is known for irritating bronchial tubes and eyes.
Last week, the EPA said that residents of two hard hit coastal communities in Louisiana - Grand Isle and Venice - face a "moderate health risk" due to hydrocarbon fumes.