There is disagreement on the potential health hazards of the spilled oil polluting the Gulf of Mexico.
Some scientists predict medical problems among workers involved in the cleanup and even the general public. Others expect safety precautions ordered by the federal government to protect cleanup workers and the public from harm.
Concerns over the health effects of the spill grew this week as more workers and residents of the coastal areas reported symptoms such as headaches and breathing problems. So far, about 60 exposure-related complaints have been filed with the Louisiana Department of Health and Hospitals.
In one of the more publicized incidents, late last week seven workers performing skimming operations from boats were taken to hospitals because of sudden illness. An investigation is underway, but it appears the symptoms may have resulted from exposure to a cleaning substance, said Dr. David Michaels, assistant secretary of labor for the federal Occupational Safety and Health Administration.
A mobile public health clinic opened Tuesday in Venice, La., to serve cleanup workers. The clinic, which will be available for all their health needs, has not been overrun, said U.S. Rep. Charlie Melancon (D-La.), who helped establish the facility.
"If we have stations to clean the birds, we ought to have stations to help humans," he said.
Crude oil contains a brew of dangerous chemicals, including ones such as benzene that are known to cause cancer in humans, and others that are toxic to the central nervous system, such as polycyclic aromatic hydrocarbons.
"There is overwhelming evidence that many of the compounds found in crude oil are dangerous," said James Giordano, director of the Center for Neurotechnology Studies at the Potomac Institute for Policy Studies in Arlington, Va.
Brief contact with crude oil is not considered harmful, but sustained exposure or high doses can sicken people rapidly, said Dr. Cyrus Rangan, assistant medical director for the California Poison Control System.
"If you breathe them or ingest them or absorb them through skin, they can cause headaches, fatigue, dizziness, even changes in mental status," Rangan said. "The longer you're out there and being exposed, the higher the risk."
Though the flu-like symptoms reported by some cleanup workers in recent days have been dismissed by some authorities as the result of heat, fatigue or food poisoning, they are similar to what would be expected from crude oil toxicity, Rangan added.
"They shouldn't be dismissed," he said. "You should pretty much presume these symptoms are from the crude oil before assuming otherwise."
Timing of exposure makes a big difference, said toxicologist LuAnn White, director of the Tulane Center for Applied Environmental Public Health in New Orleans.
"Oil changes over time," she said. "When it's first released, it comes up and sits on the water. Volatile compounds in the oil, such as those that would go into gasoline or solvents — the most toxic components — evaporate on top of the water."
The oil drifting to beaches and wetlands — "weathered oil" — has lost most of the volatile components and is not as toxic. So have the tar balls, weathered oil that has been shaped by wind and waves into clumps.
"The workers on the beach picking up the tar balls and gooey stuff should wear gloves and boots and not let it come into contact with the skin. But they don't need a respirator based on what compounds are there," White said.
One of the trickiest issues in assessing probable health effects is the poor record from prior spills.
A 2007 study following cleanup workers more than a year after a 2002 oil tanker spill off the coast of Galicia, Spain, showed that some workers experienced respiratory symptoms one to two years after exposure.
"Several people who worked on the Valdez spill complained of health problems," added Dr. Stephen Cunnion, medical director for the Center for Health Policy and Preparedness at the Potomac Institute for Policy Studies. Skin and respiratory problems were the most common complaint. Little is known about longer-term effects.
"Not following up on people in these situations has always been a problem," Cunnion said.
The Valdez spill and gulf disaster are different, in any case, because of factors such as water temperature, weather conditions and density of human population along the coast, experts said.
This time, several agencies, including gulf state public health departments, the Centers for Disease Control and Prevention and the American Assn. of Poison Control Centers have said they will conduct long-term surveillance on health issues related to the gulf spill.
Predictions vary depending on with whom you speak.
"This crisis will be an environmental crisis, not a public health crisis," White said.
"You may not see symptoms for weeks to months following exposures," Giordano said. "It's very insidious."