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Toxic dispersants in Gulf oil spill creating hidden marine crisis

Tom Levitt and Nicole Edmison

6th September, 2010

More than 200 million tons of crude oil have gushed into the Gulf of Mexico since the rupture of Deepwater Horizon. The chemicals used to clean up the spill have received less attention but could have devastating long-term effects on the marine ecosystem

Nearly two million gallons of controversial oil dispersants have been applied to the waters of the Gulf in an attempt to break up the spill – by far the largest use of such chemicals in history.

Oil dispersants are composed of two main ingredients: solvents and surfactants. With the aid of wave action, solvents work to reduce the surface tension of slicks, breaking the oil into droplets so the surfactants can penetrate the mass more deeply. 



Surfactants quickly work to coat the outside of the droplets to prevent them clumping together again. Very small drops of oil are then capable of moving away from the surface of the water and dispersing throughout the water column. 



However, this process of dispersing oil neither eliminates nor decreases its toxicity. In fact it creates a much more toxic cocktail of oil and chemical dispersant. Experts say this cocktail mix is now beginning a slow but sure degradation of the ecosystem from the bottom up. Despite this environmental officials in the US have allowed them to be used on an unprecedented scale.

Tiny droplets of combined oil and dispersant adhere to plankton, says Dr Susan Shaw, founder and director of the Marine Environmental Research Institute (MERI). The plankton-eaters then indiscriminately gobble up the tainted particles while fish-eaters consume the poisoned plankton eaters, and so on through the marine food web.

Close links to oil industry


Two main dispersants have been in use in the Gulf of Mexico since late April. Corexit 9527 was used until supplies ran out, to be replaced with Corexit 9500. Both are products of Nalco Energy Services LP, whose board of directors is made up of former and current BP, Exxon, Monsanto and Lockheed executives. Nalco is a corporate affiliate of BP.

Questions were asked of Corexit 9527’s toxicity following its use in the cleanup of the Exxon Valdez oil spill, with cleanup workers reportedly suffered health problems, including blood in their urine, as well as kidney and liver disorders linked to 2-Butoxyethanol, the main ingredient of Corexit 9527.

On 20 May the US Environmental Protection Agency (EPA) sent BP a directive: to choose a less toxic dispersant from an approved list on the National Contingency Plan Product Schedule. Of the 18 different dispersants on the list, five were found to be less toxic, more effective and in reasonable supply. Two were found in a laboratory setting to be 100 per cent effective at dispersing Southern Louisiana crude oil.

In contrast, Corexit 9527 and Corexit 9500 are respectively 63.4 per cent and 54.7 per cent effective but BP continued to use them, arguing that they were the only dispersants in reasonable supply.

A history of damage


This is not the first time the use of chemical dispersants has been questioned.

The use of dispersants in the Exxon Valdez spill in 1989, the worst oil spill in US history before the Gulf of Mexico disaster, has been linked to the decimation of native kelp and barnacle populations in the near-shore environments of Prince William Sound. 



With the kelp and barnacles gone, invasive species were free of competition and took over the near-shore areas. The invasives lacked the holding power of the native species, however, and were wiped out after the first major storm system made its way through the sound. By that time, the invasives had become the foundation of the food chain for sea ducks – with their food source destroyed, hundreds of thousands were lost and their populations have yet to recover.

Despite the concerns, chemical dispersants have been used in approximately 24 per cent of all documented oil spills from tankers since the late 1960s, with the total amount used rarely reported.

Furthermore a review of the International Tanker Owners Pollution Federation Limited database, a non-profit response group that consults on marine spills of oil, chemicals and other hazardous substances, shows that of the 258 marine incidents they were involved with between 1995 and 2005, 18 per cent involved the use of dispersants.

An 'ill-conceived' experiment

The Center for Biological Diversity (CBD) accuse the US government of conducting an ‘ill-conceived experiment’ and criticise US officials for allowing dispersants to be used at depths where their impacts have never been tested and could ‘cripple’ the gulf ecosystem.



‘If larval fish, for example, succumb to the toxins found in dispersed oil, what will their predators eat? What will the animals that eat those animals eat? That is a daunting question to contemplate in an ecosystem that’s considered one of the most biodiverse in the world, and which provides more than one-fifth of US seafood production,’ said CBD senior attorney Andrea Treece.



The EPA claim ‘not to have seen significant environmental impacts from the use of dispersants so far and none of the currently authorised dispersants appear to show significant endocrine-disrupting activity.’

Another watchdog, the Environmental Working Group (EWG), say the effects have not even begun to be made clear yet. ‘There remain large uncertainties about dispersant usage at the sea floor, the effects of large plums of oil and the potential of dispersed oil to effect the food web.  Just because the oil is gone from the surface does not mean we are in the clear,’ said senior scientist David Andrews.

Drew Wheelan, conservation coordinator for the American Birding Association, has been reporting from the Gulf Coast since the beginning of the spill. On 4 August he came upon a massive fish die-off near Fourchon, Louisiana, that may be the tip of the dispersant iceberg.

‘One of the main problems with [dispersants] is that they use large amounts of oxygen from the system when they break down,’ he says. ‘They have sprayed much of this stuff very close to shore here.’

A recent analysis of 11 years of oil-dispersant-related studies by the Prince William Sound Regional Citizens’ Advisory Council backs this up and says, ‘dispersants act physically and irreversibly on the respiratory organs, and reversibly, depending on exposure time, on the nervous system’ of marine life.’

It says there is also a lack of any studies on the long-term impacts of dispersants on the marine ecosystem and that testing for genotoxicity and endocrine disruption was not being done.



The Marine Environmental Research Institute (MERI) is attempting its own toxic assessment of the cocktail effect on the Gulf ecosystem – from phytoplankton, fish and birds to marine mammals and humans – and Dr Shaw said she agreed with others suggesting that ‘we have not even begun’ to see the impacts of the spill on Gulf wildlife.


‘Corexit is transporting the oil into every membrane and every system of [animals’] bodies and we’ll see a lot of different unpleasant effects,’ she says.

Safe alternatives?


The EPA say it has now started testing for the combined cocktail effects of oil and dispersants in the Gulf of Mexico. But the EWG say this is the wrong way round.

‘In a catastrophe situation such as the Gulf oil spill the government/EPA should fully understand the benefits and cost of dispersant usage and act…It should have known the long term health effects on aquatic systems,’ said Dr Andrews.

In the US, New Jersey senator Frank Lautenberg has recently introduced legislation that could bring an end to the use of untested toxic chemicals in oil dispersants. The Safe Dispersants Act seeks to address shortcomings in current federal law by requiring advanced testing to determine their long-term effects on human and marine health, eliminating the use of unsafe chemicals and requiring the disclosure of ingredients.

Whatever the outcome of this legislation there may be already be alternatives available for future oil spills. Researchers in Brazil, a world-leader in new deepwater drilling technology, are in the patenting stages of a new cleanup method that involves converting glycerin into a powder. Glycerin powder turns oil into a plastic-like substance that can easily be scooped up from water, then separated back into its usable constituent forms using kerosene.

Useful links
Prince William Sound Regional Citizens’ Advisory Council

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