He is worried about the health effects of the Gulf of Mexico tar balls and oil dispersants, a Rhode Island biomedical scientist has said.

The saturated hydrocarbons found in crude oil, methane, hexane and octane, evaporate quickly once in the ocean when exposed to sunlight and heat because of their low boiling points, said Bongsup Cho, a professor at the University of Rhode Island.

Cho said in a statement, "These are the chemicals that can cause the respiratory problems in people involved in cleanup operations, but they are not the ones necessarily known as carcinogens."

Cho, however, said that the tar balls and thick ooze washing up on beaches and into marshes cause more worry.

Cho said, "The tar balls contain the non-volatile, benzene-like, heavily unsaturated hydrocarbons with high boiling points. That's where there are a lot of toxins, such as benzoapyrene. This is a known human carcinogen, and it is used as a biomarker to detect human exposure to toxins."

According to Cho, another worry is the orange sheen seen on the surface of the gulf water, the result of a chemical reaction involving the sun, crude oil and oil dispersants.

Cho further said, "Nobody knows what's in that color and how toxic the chemicals are. Companies keep the chemical makeup of the dispersants secret." (With Inputs from Agencies)