Washington (CNN) -- Health threats from the Gulf oil disaster could last for years, and officials lack knowledge on how long chemicals in the spilled oil and dispersants will remain toxic, health experts told a Senate committee Tuesday.
At the same hearing, a Food and Drug Administration official said seafood from the Gulf of Mexico available to consumers in stores and restaurants now is safe.
"We are confident that Gulf of Mexico seafood that is in the market today is safe to eat," said Mike Taylor, deputy commissioner of the FDA.
The hearing by the Senate Health, Education, Labor and Pensions Committee looked at steps taken so far to monitor and deal with health issues, and what the longer-term threats and effects may be.
Lisa Kaplowitz, a deputy assistant secretary of health and human services involved in preparedness and response, said the spilled oil would cause health concerns for years to come.
"The impacts of this disaster must be considered in the framework in not weeks or months, but years," Kaplowitz said, adding that there is a lack of long-term assessments on the toxicity of oil in the environment.
And another witness at the hearing, Aubrey Miller of the National Institute of Environmental Health Sciences, said the effect of exposure to spilled oil and dispersants "has not been well-studied."
"There is a clear need for additional health monitoring and research to underpin" strategies on responding to health concerns, Miller said.
John Howard, director of the National Institute for Occupational Safety and Health, noted a dearth of scientific literature on oil spills, particularly an unprecedented one like the current situation in the Gulf of Mexico.
"When you look at the world's literature, you may have 40 articles you can turn to, and not all of them of high quality," Howard said.
In addition, Kaplowitz noted that the start of hurricane season raises the possibility of a storm surge carrying the oil slick far onto shore, expanding public exposure to the harmful chemicals.
"We really don't know what's going to happen," Kaplowitz said. "We are very concerned that the oil can be pushed further inland due to a storm surge. ... This is unprecedented, but clearly we have to be concerned."
The main problems from exposure to crude oil and dispersants are "acute irritant effects" to skin, as well as neurological complaints including headache, dizziness and nausea, Howard said.
"Some people are just very sensitive to hydrocarbon odors," according to Howard. "Some people go to the gas station and they get very sensitive to when the gas fumes are there."
The experts noted that most health issues treated so far among workers in the oil spill response and others in the region involved heat stress from the hot, humid weather of the region, as well as respiratory problems, skin irritation and other problems. Kaplowitz described the overall impact on human health so far as generally mild.
Taylor said halting fishing in oil-affected waters had successfully prevented tainted seafood from reaching U.S. markets so far. Now, he said, officials were "collecting and testing a variety of seafood," in particular the shellfish such as crabs, shrimp and oysters that are less likely to escape oil contamination and can retain the toxins for a longer time.
However, committee chairman Sen. Tom Harkin, D-Iowa, asked how confident Taylor could be when small organisms and fish that ingest or otherwise get contaminated by oil and dispersants get eaten by larger fish to spread the toxins up the food chain.
"There is the possibility that this oil will get involved in the streams and the currents to go around, come up the East Coast of the United States," Harkin noted.