There are 3200 litres of the poisonous dispersant Corexit 9527 used during the Rena being stored in 200litre drums at the Port of Tauranga.

The dispersant is being stored by the BOP Regional Council for Maritime NZ, along with a range of other equipment that may be used in a Tier 2 oil spill response.

The dispersant was used during the Rena oil disaster off the coast of Tauranga.

Its use would be aimed at larger offshore spills if the conditions and oil was appropriate, says the regional council.

The United Kingdom banned the use of Corexit dispersants in 1998 and Sweden has a blanket ban on all dispersants in the marine environment, according to earlier SunLive reports at the time the Rena grounded in October 2011.

This week's 60 Minutes programme revisits the Corexit toxicity reports claiming serious illnesses and deaths of people in the Gulf of Mexico following the 2010 oil spill there.

Corexit's toxic properties were public domain when the dispersant was used on the Rena oil spill in the days following its grounding on the Astrolabe Reef.

At the time Maritime New Zealand trialled the dispersant Corexit 9500 and a very small amount of Corexit 9527 on heavy fuel oil spilled from the Rena in the earliest days of the response, says Maritime NZ spokesman Steve Rendle.

The dispersants were used according to the NZ Guidelines for the Use of Oil Spill Dispersants, under controlled conditions in deep water around 20km offshore from the mainland, in the vicinity of the Astrolabe Reef.

Corexit's dispersal from a helicopter in the Bay of Plenty was stopped after three days because it was not effective in the prevailing conditions. No other chemicals were used to break down oil during the response.

MNZ has not received any peer-reviewed scientific or medical data that confirms the statements made in the 60 Minutes programme, says Steve. However, MNZ regularly reviews new information and studies on dispersant use and its effects. This information helps guide MNZ's dispersant use.

MNZ worked closely with Bay of Plenty Public Health authorities throughout the Rena response to ensure any public health concerns were addressed appropriately. MNZ has received no reports of any cases of ill health linked to either the oil or dispersant, says Steve.

Peer-reviewed publications regarding Corexit products show its components break down relatively quickly, and MNZ would not expect it to have on-going effects on the water or coastal areas.

Council says there is a comprehensive and ongoing monitoring programme into the effects of the Rena oil spill that show Bay of Plenty waters are recovering well.

Reports are that Corexit trials on the heavy fuel oil leaked from the Rena proved inconclusive with it failing to work on oil that's been in the ocean for more than three or four hours.

Crude oil is toxic and its chemical ingredients can damage every system in the body. Dispersant chemicals can also affect many of the same organs. This can increase the risk and severity of harm. http://www.sciencecorps.org/crudeoilhazards.htm#Disp

The combination of a dispersants and crude oil can be more toxic than either alone, since they have many of the same toxic properties. In addition, based on the basic properties of dispersants, they may make it easier for crude oil to enter the body, enter cells, and cause damage.