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
