NEW ORLEANS -- With a huge and unpredictable oil slick drifting in the Gulf of Mexico, state and federal authorities are preparing to deal with a variety of hazards to human health if and when the full brunt of the toxic mess washes ashore.
The list of potential threats runs from temporary, minor nuisances such as runny noses and headaches to long-term risks such as cancer if contaminated seafood ends up in the marketplace. While waiting to see how bad things will get, public health agencies are monitoring air quality, drinking water supplies and seafood processing plants and advising people to take precautions.
"We don't know how long this spill will last or how much oil we'll be dealing with, so there's a lot of unknowns," said Dr. Jimmy Guidry, Louisiana's state health director. "But we're going to make things as safe as humanly possible."
Oil has been spewing into the Gulf at a rate of at least 200,000 gallons a day since an offshore drilling rig exploded on April 20, killing 11 people. Little if any has reached land thus far, but shifts in wind speed and direction could propel the slick toward populated areas.
In a possible hint of things to come, a foul stench drifted over parts of southwestern Louisiana last week. The oil probably was the culprit, said Alan Levine, secretary of the Louisiana Department of Health and Hospitals, whose office heard about dozens of complaints -- even from state legislators in New Orleans, some 130 miles from the leaky undersea well.
"Their eyes were burning, they felt nauseated, they were smelling it," Levine said.
Farther up the coast at Shell Beach, marina operator and commercial fisherman Robert Campo said the smell gave him a headache as he collected oysters 20 miles offshore. "It was rotten," he said.
The U.S. Environmental Protection Agency has began round-the-clock air monitoring in Gulf coastal areas and posting online hourly readings for ozone and tiny particles such as soot. Both can cause respiratory problems and are particuarly aggravating for people with chronic conditions such as asthma.
Crude oil emits volatile organic compounds that react with nitrogen oxides to produce ozone. Fires being set by the Coast Guard to burn off oil on the water's surface would produce sooty, acrid smoke.
"We don't know what the impacts are going to be yet," said Dave Bary, an EPA spokesman in Dallas. "We don't know in what direction this oil will go."
The potential for unhealthy air quality depends on a variety of factors, particularly the speed and direction of winds that could disperse fumes and determine where they go, said Jonathan Ward, an environmental toxicology professor at the University of Texas Medical Branch at Galveston.
With the leaky Gulf well some 50 miles offshore, Ward said much of the oil vapor likely wouldn't reach land, although the potential for air pollution from the slick will remain as long as the leak continues.
Public health agencies in Alabama, Louisiana and Mississippi advised people near the coast who experience nausea, headaches or other smell-related ailments to stay inside, turn on air conditioners and avoid exerting themselves outdoors.
In addition to air pollution, officials also were guarding against health problems from tainted drinking water and seafood.
Some communities, including New Orleans, get their supplies from the Mississippi River. Its southerly currents will prevent oil from drifting upstream to city intake pipes, and the Coast Guard is making sure that any ships with oil-coated hulls are scrubbed down before proceeding up the river, Guidry said.
Even so, the state health department has ordered testing of municipal water systems near the Gulf for signs of oil.
"It's next to impossible that a high amount would get in," Guidry said. "Even if some got through, more than likely the treatment system would eliminate it."
The department this week began taking samples at seafood processing plants. Officials have ordered a temporary moratorium on fishing in federal waters from the Mississippi River to the Florida Panhandle, but sampling will provide benchmarks enabling scientists to track any increases in contaminant levels once fishing is allowed to resume.
Louisiana health officials said they believe fish, shrimp and other Gulf delicacies already on the market are safe.
"If we see increases in hydrocarbons or other contaminants, we'd stop the flow of seafood," Levine said.
Even after the immediate crisis passes, risks could linger for years, said Gina Solomon, an associate professor at the University of California-San Francisco medical school and a senior scientist with the Natural Resources Defense Council.
"Exposure to some of the chemicals in oil has been linked to cancer," Solomon said. "Those chemicals can get into sediments in the Gulf, build in the food chain and be a long-term problem in fish and shellfish."
The U.S. Centers for Disease Control and Prevention is working with epidemiologists in the Gulf states to develop studies of health repercussions from the oil spill, Guidry said.
Yet another hazard is direct contact with oil-saturated water -- particularly for cleanup crews and volunteers involved in animal rescue operations.
When the container ship Cosco Busan hit a bridge and released 53,000 gallons of highly toxic bunker fuel into San Francisco Bay in November 2007, officials managing the cleanup ordered volunteers to wear protective suits, gloves and masks that later were discarded at a hazardous waste dump. Some oil fouled beaches, which were closed to prevent danger to the public.
People working around the Gulf spill should be equipped with respirator devices and wear heavy-duty gloves and protective clothing to guard against painful skin rashes, said Solomon, who has treated patients exposed to oil fumes.
"The workers absolutely need to be protected," Solomon said.