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Methodology

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A comprehensive, objective, rigorous testing program for Louisiana seafood, soil and water samples has been underway since April of 2010 to monitor the impact of the Deepwater Horizon oil spill on the ecology in Louisiana. Using federally approved standards of acceptability and the best available technology for an undertaking of this magnitude, our goal is to ensure detection of any potential negative impacts on seafood consumed by residents in the Gulf Coast and beyond.

Location of Testing

In order to achieve certainty despite the number of tests and broad geography, sampling is taking place in many locations off Louisiana's coast to ensure a thorough analysis. Samples are being drawn from both Inshore and Nearshore locations in both state and federal waters.

Types and number of samples

Each month, the team collects 329 species, soil and water samples. Of those 329 samples, 143 are marine life. These include brown and white shrimp, crab, oysters and finfish (grouper, tuna, wahoo, swordfish, gray snapper, butterfish, red drum and croaker).

The breakdown by type and quantity of samples is as follows:

  • 143 Shrimp, Crab and Finfish samples
    • 45 Inshore
    • 98 Nearshore
  • 90 Oyster samples

The remaining 96 samples are taken from coastal sediment and waters. That breakdown is as follows:

  • 56 Inshore
    • 28 Water
    • 28 Sediment
  • 40 Nearshore *
    • 32 Water
    • 8 Sediment

* Nearhore Samples are not being collected at this time; however, the Seafood Safety Plan is working with USGS to acquire the equipment to collect these samples in the near future.

Seafood Sample Collection and Handling

Each sample contains approximately a half-pound of edible flesh. For large species samples, such as some finfish, each sample is taken from the narrow region of the body of the fish, immediately in from the tail. For species that are too small to individually meet the sample size requirements, like shrimp, several can be combined so long as they are taken from the same site. A composite sample of shrimp could include as many as 100 individuals caught in the same location. Collection locations, often referred to as sites, are selected to best represent areas with the greatest recreational and commercial fishing activity.

Samples are collected using strict procedures to ensure that each sample collected remains unaffected by outside contaminants. Here are a few of the sampling guidelines:

Immediately After Harvest:

  • Loose dirt or debris is rinsed from the sample using water from the harvest location.
  • All samples are wrapped in double layers of heavy-duty aluminum foil. The sample never comes in contact with petroleum-based products, such as plastics.
  • Each sample is tagged with a unique identifier, which allows the sampling and testing team to track the sample throughout the chain of custody
  • Exposure to engine exhaust is limited.
  • The samples are immediately chilled to 39 degrees Fahrenheit (or below) and stored in insulated, clean, odor-free shipping containers.
  • Samples may not come in contact with melted ice water or frozen gel packs when storing.

Storage and Shipping:

  • Crab samples are chilled to -4 degrees Fahrenheit for 30 minutes to immobilize.
  • All other samples are immediately placed in a freezer until the product is frozen.
  • Samples, which are still wrapped in double layers of aluminum foil, are double bagged in re-sealable zipper storage bags and the majority of the air is expelled from the bag.
  • Samples are shipped to a state-run laboratory for testing. During shipping, the samples must remain chilled to at least 39 degrees Fahrenheit.

Water & Sediment Sample Collection and Handling

In addition to seafood testing, water and sediment samples are collected to further characterize the chemical profile of the Gulf's marine habitats relative to petroleum contamination.

A total of 60 water samples are collected each month from both inshore and nearshore locations. Using one-quart, glass containers, water is collected within the upper 6" - 12" of the water column.

Thirty six sediment samples are collected each month from both inshore and nearshore locations. Inshore samples are collected using a dredge, targeting the top 2" - 4" of the sediment layer. The samples from the dredge at that collection site are then composited in a stainless steal bucket before being placed in one-quart, wide-mouth jars for storage and transportation.

All water and sediment samples are tagged with a unique identifying number, allowing the sampling and testing team to track each one throughout the chain of custody.

Seafood, Water & Sediment Testing

Samples are distributed between the DHH and DAF laboratories for testing. DHH tests all 90 of the oyster samples and 71 of the seafood samples each month. DAF tests the remaining 72 seafood samples. An independent laboratory contracted through DEQ tests all the sediment and water samples.

Seafood samples received are processed and extracted as needed for the analytical methods listed below. The laboratories also retain samples to allow for re-testing if necessary.

DHH and DAF perform the following tests to detect the presence of dispersants used throughout the oil spill in federal waters.

Smaller samples are extracted before the following tests are performed:

  • Extraction, Cleanup, and Gas Chromatography/Mass Spectrometry Analysis of Sediments and Tissues for Organic Contaminants
  • All seafood samples received will be screened by HPLC-Fluorescence (LC-FLD) for oil contamination through the presence of Polycyclic Aromatic Hydrocarbons (PAH)
  • LC-FLD is an extremely sensitive test that will allow scientists to identify samples that may be contaminated efficiently.
  • In select seafood, samples will also be tested for Dioctylsulfosuccinate using QuEChERS Extraction with Liquid Chromatography-Triple Quadrupole Mass Spectrometry
  • If specimen tests positive in the LC-FLD screen, it will be referred for complete analysis using the seafood testing methods approved by the FDA and NOAA.
  • The complete analysis will determine if there is a presence of PAHs and if so, the amount in parts per million of that compound.

Seafood, Water and Sediment Testing Data Management

Once testing for each sample is complete, the field and laboratory data will be uploaded to a single mainframe database. The database automatically updates the test results on Gulfsource to provide the public access to updated testing results each week.

PAH Levels of Concern

Polycyclic aromatic hydrocarbons, or PAHs, are compounds in oil that can cause cancer when exposed at high doses. As the FDA seafood testing protocol is based on experiments on animals, scientists divided safe animal PAH levels by 10 to get a safe exposure rate for humans. That was then divided by 10 again to ensure safe exposure for vulnerable human populations, such as children, the elderly or the already infirm.

That created what the FDA proudly calls a "100-fold safety level."

Below are the PAH levels of concern determined by the FDA for the Louisiana Seafood Safety Plan's tested compounds.

Compound Levels of Concern1 mg/kg
Oyster Shrimp/Crab Finfish
Anthracene 2,000 1,846 490
Benzo(a)anthracene 1.43 1.32 0.35
Benzo(a)pyrene 0.143 0.132 0.035
Benzo(b)fluoranthene 1.43 1.32 0.35
Benzo(k)fluoranthene 14.3 13.2 3.5
Chrysene 143 132 35
Dibenzo(a,h)anthracene 0.143 0.132 0.035
Fluoranthene 267 246 65
Fluorene 267 246 65
Indeno(1,2,3-CD)pyrene 1.43 1.32 0.35
Naphthalene 133 123 33
Phenanthrene 2,000 1,846 490
Pyrene 200 185 49
Dioctyl sodium sulfosuccinate (DOSS) 500 500 100