Gulf of Mexico oil spill: clean-up boats recalled after crews suffer health problems
The crew members aboard three separate vessels "reported experiencing nausea, dizziness, headaches and chest pains" midafternoon Wednesday, the US Coast Guard said in a statement.
"No other personnel are reporting symptoms, but we are taking this (recall) action as an extreme safeguard," said Robinson Cox, the Coast Guard Chief Petty Officer.
The move raises questions over the safety of the clean-up operation in and around the Gulf in Mexico, in particular the protection workers have been given as they mitigate the oil, and the toxicity of the controversial chemical dispersants being used by BP in an attempt to break up the slick.
One of the workers had to be evacuated by air ambulance to a nearby hospital for treatment, another followed by boat and the other two were transported by ground, the statement added.
Safety officers for BP along with US officials with the Coast Guard and the Environmental Protection Agency are investigating the incident.
A ruptured well from BP's sunken Deepwater Horizon offshore drilling rig has spewed millions of barrels of crude over the five weeks, encroaching on prized southern US coast wetlands and wildlife preserves, as well as billion-dollar fishing and tourism destinations.
BP has said that efforts to plug the ruptured Gulf of Mexico oil rig with mud were going to plan.
"What you've been observing coming out of the top of that riser is most likely mud," Doug Suttles, BP's chief operating officer, said at a news conference broadcast from a Louisiana command centre. "We can't fully confirm that because we can't sample it. And the way we know we've been successful is it stops flowing."
Residents along the Gulf Coast have been watching video of the leaking well since the process, known as "top kill", began about 1pm CDT (1800 GMT). The effort involves pumping tons of heavy drilling mud down the well bore to overcome the oil and gas flowing out. The mud is twice the weight of water, and it is hoped it will sink into the well to stop the massive flow of oil.
Mr Suttles and US Coast Guard Admiral Mary Landry said they were cautiously optimistic about the effort to stop the leak that began with a drilling rig explosion April 20. The leak threatens the ecology of the US Gulf of Mexico and the economies of four US states.
"We've all been here a long time and been trying a lot of things and ridden a roller coaster," Mr Suttles told reporters in Robert, Louisiana. "I think we just need to take the next 24 hours and see what the results are."
The goal is to halt the flow of oil long enough so cement can be pumped in to shut it off.
The mud, a substance specially created for the oil drilling industry and used in all wells drilled, is being pumped in by 30,000 horsepower compressors.
"Ultimately, what we need to see is that the well can't flow to surface," Mr Suttles said. "That will be the way we know it's successful."
The mile-deep underwater gusher began flowing after the Deepwater Horizon drilling rig exploded on April 20, claiming the lives of 11 workers.