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Twenty thousand workers are currently cleaning up the oil spill in the Gulf of Mexico. Of those, about a dozen have gone to the hospital with symptoms that could have been caused by exposure to crude oil or the chemicals used to clean it up. Many others have described similar symptoms, including nausea and dizziness. All that is a reminder that oil is toxic stuff.
But as NPR's John Hamilton reports, experience with previous spills suggests that the health risk to workers is usually small.
JON HAMILTON: So far, 11 cleanup workers have been taken to West Jefferson Medical Center, just south of New Orleans.
Damon Dietrich is a doctor in the emergency room there.
Dr. DAMON DIETRICH (West Jefferson Medical Center): One patient I treated was burning oil for seven days and then had two days off and then burned oil again for seven days. And 14 days into burning the oil, that's when he had, you know, headache, dizziness, lightheadedness, chest pains, shortness of breath.
HAMILTON: Dietrich says if only one or two cleanup workers had gotten sick, he might have put it down to chance.
Dr. DIETRICH: Given we've seen 11, and theyve all pretty much had similar symptoms, we got to believe it's either the burning of the oil or working around the oil spill or the dispersant that are causing their symptoms.
HAMILTON: Eleven is a pretty small number, and it includes people who probably had some of the highest exposures. They've all recovered. Air quality measurements around the Gulf have generally shown very low levels of pollutants.
Joseph Hughes from the National Institute of Environmental Health Sciences has been touring the parts of Louisiana where oil is reaching the beaches. He says at the moment, chemicals aren't even the biggest problem facing cleanup workers: it's temperatures in the mid-90s.
Mr. JOSEPH HUGHES (National Institute of Environmental Health): We were out in (unintelligible) yesterday, looking at beach cleanup operations, and they're dealing with, number one, heat stress right now.
HAMILTON: Hughes says the powerful effects from heat and fatigue make it hard to know if chemicals are contributing to the overall health threat.
Mr. HUGHES: You have the physiological conditions of people working under incredible stress for incredible numbers of hours, and then you may have chemical exposure as part of it.
HAMILTON: Scientists say one reason oil itself isn't causing more problems is that some of the worst chemicals, like the carcinogen benzene, tend to dissipate within a day or two of exposure to air and sunlight.
That was one of the lessons learned after the Exxon Valdez tanker dumped more than 10 million gallons of oil into Alaska's Prince William Sound in 1989. Eleven thousand workers were involved in the cleanup, yet government scientists found little evidence of health problems from so-called volatile chemicals.
Bob Emery of the University of Texas Health Science in Houston says the scientists' finding is somewhat comforting.
Mr. BOB EMERY (University of Texas Health Science Center): They concluded that this - what they referred to as weathered crude oil, the exposures from volatiles were insignificant. But nonetheless, the situation in New Orleans and the climatic conditions might be very different in Louisiana than it would be in Alaska.
HAMILTON: Higher temperatures, for example, may release toxins that otherwise would have stay locked inside tarballs. And nearly a million gallons of chemical dispersants have been used to break up the oil in the Gulf, far more than in Alaska. Emery says that could pose a health risk for people actually applying the dispersant.
Mr. EMERY: But once it's distributed on the water or wherever it's distributed, the relative concern there, I think, goes down compared to the just sheer volume of oil that people will be potentially exposed to.
HAMILTON: Emery says whether cleanup workers need respirators depends on what job they're doing and where they are. He says contractors and the government should continue monitoring air quality to make sure that the unprotected workers are breathing air that's safe.
Jon Hamilton, NPR News.
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