OIL SLICK: There is concern about the effects on the environment of using dispersant to break up oil from the stranded ship Rena.
Dispersants ‘worse than oil’
by MICHELLE COOKE
The dispersants being used to break up the hundreds of tonnes of oil leaking from the grounded Rena could be “more harmful than the oil itself”.
Maritime New Zealand (MNZ) has used Corexit 9500 to help break up the oil, but University of Southampton oceanography lecturer Dr Simon Boxall said using dispersants could cause unnecessary harm.
The UK banned the use of Corexit dispersants in 1998 and Sweden has a blanket ban on all dispersants in the marine environment, Boxall said.
“In their raw form some dispersants can be very toxic and I believe will do more harm than good,” he said.
“They are more harmful than the oil itself and they are not less toxic than dishwashing liquid.
“Dishwashing liquid doesn’t carry hazchem advice and you don’t wear protective clothing and masks to do the washing up. In this case – with limited knowledge of the region – I’d advise caution on use of dispersants.”
But Environment Minister Nick Smith said Corexit was no more toxic than dishwashing liquid and had been approved by the Environmental Protection Agency.
He said at least 1800 litres of the chemical dispersant had been used with variable results.
In New Zealand, Corexit can be used in sea water but not fresh water.
Boxall has studied the Erika oil spill on France’s Brittany coast in 1999 and the MV Braer oil spill in the Shetland Islands in 1993.
He said oil broke up naturally after the Erika oil spill and “little human intervention took place”.
He estimated last night that it should take between four and six weeks for the oil to be naturally dispersed.
But another 300 tonnes have since leaked into the ocean, which means the natural process could take longer.
He said the stormy weather was “both a pro and con”. While it hindered the salvage operation, it would also help disperse the oil.
MNZ started using Corexit last week to disperse the oil from the Rena, but was also looking at using alternative dispersants.
National on scene commander Rob Service said last week that despite initial indications that dispersant testing had proved effective, further analysis had confirmed Corexit was not dispersing the oil.
MNZ said on its website chemical dispersants were an “important option” and should always be considered in the most effective “first stage” of the response strategy.
A spokesperson for MNZ said results from a trial of Corexit on Thursday and Friday proved inconclusive and while it planned to use it this morning, the weather hindered that operation.
Corexit is dispersed from the air, but it was too cloudy to fly today.
Helicopters have been on standby all day, waiting for a break in the weather so spraying could continue.
The chemical only worked on fresh oil and would not work on oil that had been in the ocean for more than three or four hours.
“If it’s still coming out tomorrow then we’ll continue to use it,” the spokesperson said.
Commonwealth Scientific and Industrial Research Organisation (CSIRO) research scientist Professor Nic Bax, who leads the Biodiversity Hub at the University of Tasmania, said nature would play its part but dispersants could also be helpful in breaking up the oil.
“Dispersants used to be quite toxic but now are considered to be much less toxic than the oil itself, so the main environmental decision regarding their use is determining where the oil will have least harm.”
“Spilt oil that remains at the surface will gradually be dispersed by natural physical processes at least in high energy environments. Oil that reaches low energy environments or gets buried in sediments may persist for several years.”
The University of Houston in Texas is currently researching new types of dispersants which are more environmentally friendly.
