Oil is known to be toxic to living organisms of all types. However, oil dispersants used to treat and control oil spills also can be harmful and lethal.
Oil dispersants are useful when oil spills occur and these dispersants are helpful in the control and management of oil spills in saline or fresh waters. Oil dispersants permit oil spills to be processed and degraded more rapidly by creating oil-dispersant-water interfaces. Oil dispersants remove oil from the water surface and cause it to sink into the water column. Also, subsurface oil masses subjected to underwater dispersants are prevented from rising to the surface. Both surface and subsurface oil dispersants contribute to the formation of distinct underwater oil plumes.
Oil Dispersant Chemical Composition of COREXIT
Listed below are the EPA-listed components (epa.gov) contained in the two major COREXIT products used by BP for the Gulf of Mexico oil spill.
COREXIT Oil Dispersant – Biochemical Composition
1,2-Propanediol (CAS: 57-55-6)
Ethanol, 2-butoxy-* (CAS: 111-76-2)
Butanedioic acid, 2-sulfo-, 1,4-bis(2-ethylhexyl) ester, sodium salt (1:1) (CAS: 577-11-7)
Sorbitan, mono-(9Z)-9-octadecenoate (UCAS: 1338-43-8)
Sorbitan, mono-(9Z)-9-octadecenoate, poly(oxy-1,2-ethanediyl) derivs. (CAS: 9005-65-6)
Sorbitan, tri-(9Z)-9-octadecenoate, poly(oxy-1,2-ethanediyl) derivs. (CAS: 9005-70-3 )
Propanol, 1-(2-butoxy-1-methylethoxy)- (CAS: 29911-28-2 2)
Distillates (petroleum), hydrotreated light (CAS: 64742-47-8 )
(*Note: Ethanol, 2-butoxy- is not contained in Corexit 9500 and the CAS numbers provided above are registry numbers of the American Chemical Society)
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In summary, the major components of COREXIT are essentially butanedioic acid, butoxyethanol, propanediol, propanol, sorbitan (octadecenoate compounds and derivatives) and some light petroleum distillates. Depending on the concentration, each of these products alone has some toxic or lethal characteristics.
Oil Dispersant Toxicity Lab Tests
The EPA has established specific laboratory procedures to evaluate the toxicity of the 18 different dispersants currently approved for use to treat oil spills. These lab tests involve the following major aspects:
test organisms (one specific species of fish and one specific species of crustacean)
serial diluted concentrations of dispersant or oil to yield known parts per million (ppm)
introduction of test organisms and timed exposure for 48 and 96 hours
observation and recording of live and dead test organisms after the 48- and 96-hr exposure and comparison with controls not exposed to either dispersant or dispersant-oil combination
Oil Dispersant Lab Methods and Results
The healthy fish and the crustaceans are counted and added in defined numbers to the test and control containers. Control containers contain neither the dispersant nor the oil and controls serve to determine if anything abnormal is happening in the test system. Typically, all control animals survive in the control containers. Experimental test containers harbor the diluted dispersant or dispersant-oil materials at the different, measured concentrations in ppm.
Cited here below are actual lab results in parts per million for dispersant alone and dispersant mixed with fuel oil. Notice that the dispersant alone requires higher ppm to cause death than the combination of fuel oil and dispersant. This shows that this combination is more dangerous than dispersant alone. No results are given for fuel oil alone. This control is omitted for these tests:
COREXIT® EC9500A was tested on the fish Menidia beryllina and the crustacean Mysidopsis bahia and the LC50 (ppm) was 25.20 at 96-hr and 32.23 48-hr respectively for each species.
COREXIT® EC9500A and No. 2 Fuel Oil (1:10) mixed tested similarly with Menidia beryllina and the crustacean Mysidopsis bahia yielded an LC50 of 2.61 at 96-hr and 3.40 at 48-hr.
(Data above is adapted from epa.gov. Accessed June 11, 2010.)
Oil Dispersants and Animal and Human Toxicity
Oil, dispersants and oil-dispersant mixtures are known to have toxicity for marine animals in their natural environments (response.restoration.noaa.gov. Accessed June 11, 2010) However, the overall and detailed long-term effects of these chemicals and mixtures on marine animals is not documented.
People using oil dispersants are advised to use:
a half face filter mask or an air-supplied breathing apparatus (protects respiratory tissues of the nose, throat, bronchi and lungs)
nitrile or PVC gloves, coveralls, boots for skin protection
chemical splash goggles for eye safety
Product warnings from the manufacturer clearly indicate the possible dangers of contact with concentrated or diluted dispersants. Therefore, skin, respiratory and ocular damage is possible when exposed to oil dispersants.
In summary, dispersants alone, or when combined and interacting with oil, pose hazards to animals and humans. Long term studies on the effects of these chemicals on individuals and populations is lacking and it may be hypothesized that internal tissue damage to essential organs such as liver, kidneys and intestines of animals and humans may well occur. The EPA is expected to make some of these determinations following the current BP Gulf spill.
Read more at Suite101: Oil Dispersant Toxic Effects on Animals and Humans | Suite101.com http://suite101.com/article/oil-dispersant-toxic-effects-on-plants-animals-and-humans-a247831#ixzz21W7VqTJE