Dispersants, a mixture of chemicals that break up the oil and send it into the water column, are being used as a remedy on oil that is leaking from the Deepwater Horizon disaster but we and many other environmental groups have serious concerns about their use.
From:
Oil Spill Dispersants: Efficacy and Effects (2005)
by Ocean Studies Board (OSB)
Dispersants are mixtures of solvents, surfactants, and other additives that are applied to oil slicks to reduce the oil-water interfacial tension (NRC, 1989; Clayton et al., 1993)… Reduction of the interfacial tension between oil and water by addition of a dispersant promotes the formation of a larger number of small oil droplets when surface waves entrain oil into the water column. These small submerged oil droplets are then subject to transport by subsurface currents…
In other words the dispersants act like mustard or egg yolk in salad dressing to break up the oil into little droplets that will mix with the water and allow those little droplets of oil to sink down into the water column and to the sea floor.
So once the oil sinks everything is fine right?
Well, no, not really. The oil is still in the marine environment and can still impact fish and bottom dwelling organisms and potentially allow toxic materials to move up the food chain as bottom dwelling organisms become contaminated and then are preyed upon by large organisms like crabs and shrimp and then the crabs and shrimp are preyed upon by fish, the fish by larger fish etc., this is called bio-accumulation.
More from:
Oil Spill Dispersants: Efficacy and Effects (2005)
by Ocean Studies Board (OSB)
One of the most difficult decisions that oil spill responders and natural resources managers face during a spill is evaluating the environmental trade-offs associated with dispersant use. The objective of dispersant use is to transfer oil from the water surface into the water column. When applied before spills reach the coastline, dispersants will potentially decrease exposure for surface dwelling organisms (e.g., seabirds) and intertidal species (e.g., mangroves, salt marshes), while increasing it for water-column (e.g., fish) and benthic species (e.g., corals, oysters).
In other words the dispersants may help to decrease shoreline impacts but will increase impacts to things that live under the water.
This is obviously a big concern to those of us who enjoy eating oysters, crabs, shrimp, speckle trout, redfish and all of the other wonderful seafood that comes from the Gulf and Louisiana’s coastal estuaries.
Another concern we have about the dispersants is that they themselves are toxic. We have learned from the Natural Resources Defense Council that the dispersant being used in the Deepwater Horizon disaster is Corexit 9500.
From the Corexit 9500 Materials Safety Data Sheet:
MATERIAL SAFETY DATA SHEET
PRODUCT
COREXIT® 9500
APPLICATION :
OIL SPILL DISPERSANT
NFPA 704M/HMIS RATING
HEALTH : 1 / 1
FLAMMABILITY : 1 / 1
0 = Insignificant 1 = Slight 2 = Moderate 3 = High 4 = Extreme
COMPOSITION/INFORMATION ON INGREDIENTS
Our hazard evaluation has identified the following chemical substance(s) as hazardous.
Hazardous Substance(s)
Distillates, petroleum, hydrotreated light
Propylene Glycol
Organic sulfonic acid salt
HAZARDS IDENTIFICATION
**EMERGENCY OVERVIEW**
WARNING
Combustible.
Keep away from heat. Keep away from sources of ignition – No smoking. Keep container tightly closed. Do not get in eyes, on skin, on clothing. Do not take internally. Avoid breathing vapor. Use with adequate ventilation. In case
of contact with eyes, rinse immediately with plenty of water and seek medical advice. After contact with skin, wash immediately with plenty of soap and water.
Wear suitable protective clothing.
Clearly any workers handling this product need to be supplied with the proper protective gear.
Corexit 9500 is also known to be toxic to marine life. A report written by Anita George-Ares and James R. Clark for Exxon Biomedical Sciences, Inc. entitled Acute Aquatic Toxicity of Three Corexit Products states that, “Corexit 9500, Corexit 9527, and Corexit 9580 have moderate toxicity to early life stages of fish, crustaceans and mollusks (LC50 or EC50 – 1.6 to 100 ppm*).”
We hope that the EPA and US Fish and Wildlife Service are closely monitoring the use of these products and monitoring for impacts to the environment.
A further area of concern is the unprecedented deployment of dispersants into the leaking oil at the site of the leaks almost 5,000 feet below the surface.
The oil spill Unified Command reported on May 1, 2010 that response crews worked through the night using an ROV to dispense 3,000 gallons of sub-surface dispersant at a rate of nine gallons per minute. BP and NOAA are evaluating the results of the test procedure to determine its feasability for continued use.
The Unified Command also reported that, as of May 1, 2010, 142,914 gallons of dispersant have been deployed and an additional 68,300 gallons are available.
If you see anything fishy happening on your waterways don’t hesitate to call the Lower Mississippi Riverkeerp hotline at 1-866-MSRIVER
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