Building upon the extensive testing and protocols already in use by federal, state and local officials for the fishing waters of the Gulf, NOAA and FDA have developed and are using a chemical test to detect dispersants used in the Deepwater Horizon-BP oil spill in fish, oysters, crab and shrimp. Trace amounts of the chemicals used in dispersants are common, and levels for safety have been previously set.
Experts trained in a rigorous sensory analysis process have been testing Gulf seafood for the presence of contaminants, and every seafood sample from reopened waters has passed sensory testing for contamination with oil and dispersant. Nonetheless, to ensure consumers have total confidence in the safety of seafood being harvested from the Gulf, NOAA and FDA have added this second test for dispersant when considering reopening Gulf waters to fishing.
Using this new, second test, in the Gulf scientists have tested 1,735 tissue samples including more than half of those collected to reopen Gulf of Mexico federal waters. Only a few showed trace amounts of dispersants residue (13 of the 1,735) and they were well below the safety threshold of 100 parts per million for finfish and 500 parts per million for shrimp, crabs and oysters. As such, they do not pose a threat to human health.
The new test detects dioctyl sodium sulfosuccinate, known as DOSS, a major component of the dispersants used in the Gulf. DOSS is also approved by FDA for use in various household products and over-the-counter medication at very low levels. The best scientific data to date indicates that DOSS does not build up in fish tissues.
"The rigorous testing we have done from the very beginning gives us confidence in the safety of seafood being brought to market from the Gulf," said Jane Lubchenco, Ph.D., under secretary for commerce and NOAA administrator. "This test adds another layer of information, reinforcing our findings to date that seafood from the Gulf remains safe."
"This new test should help strengthen consumer confidence in Gulf seafood," said Margaret A. Hamburg, Ph.D., commissioner of the Food and Drug Administration. "The overwhelming majority of the seafood tested shows no detectable residue, and not one of the samples shows a residue level that would be harmful for humans. There is no question Gulf seafood coming to market is safe from oil or dispersant residue."
The 1,735 samples tested so far were collected from June to September and cover a wide area of the Gulf. The samples come from open areas in state and federal waters, and from fishermen who brought fish to the docks at the request of federal seafood analysts. The samples come from a range of species, including grouper, tuna, wahoo, swordfish, gray snapper, butterfish, red drum, croaker, and shrimp, crabs and oysters.
Previous research provided information about how finfish metabolize DOSS, and at FDA's Dauphin Island, Alabama lab, scientists undertook further exposure experiments on fish, oysters and crab; similar experiments on shrimp were held at NOAA's Galveston, Texas lab. These exposure studies further support that fish, crustaceans and shellfish quickly clear dispersant from their tissues, and provided samples with known concentrations for use as standards for validating the methodology. Samples undergoing chemical analysis are always accompanied by standards with known concentrations of DOSS, to verify the equipment continues to measure the compound accurately.
Nearly 9,444 square miles, or about 4 percent of the federal waters in the Gulf are still closed to commercial and recreational fishing.