UK United Kingdom

Sydney Harbour’s toxic legacy shows value of green safety net

The story of dioxin contamination of Sydney Harbour shows us the great value of the green safety net of environmental law. The laws that form this green safety net, particularly federal laws, have recently…

The NSW Government recommends not eating fish caught west of Sydney Harbour Bridge. Gord McKenna/Flickr

The story of dioxin contamination of Sydney Harbour shows us the great value of the green safety net of environmental law.

The laws that form this green safety net, particularly federal laws, have recently been under attack as “green tape”.

This term has become a negative political slogan that represents a sustained attempt to whittle away the protections that have been established, particularly over the past 20 years.

The federal government’s decision to shelve plans to devolve approval powers under its main environmental laws to state governments is sure to re-ignite this attack.

The irony of this sustained political attack on environmental law is that it is the very success of these laws in maintaining or restoring a healthy environment in Australia that has bred the complacency underpinning the attacks.

Many people have forgotten the problems that these laws were created to solve. The danger is that when such laws succeed in maintaining and restoring a healthy environment, they are taken for granted and, over time, holes in the safety net are allowed to grow.

The story of Sydney Harbour’s toxic legacy is timely to remember in this context.

Dioxin contamination of Sydney Harbour

Dioxins are a group of persistent environmental pollutants that accumulate in the food chain, mainly in the fatty tissue of animals. They are highly toxic and can cause reproductive and developmental problems; damage the immune system; interfere with hormones and also cause cancer.

The dioxin contamination of Sydney Harbour comes largely from a former industrial site at Rhodes adjacent to Homebush Bay.

Source of dioxin contamination in Sydney Harbour. Adapted from GoogleEarth

A long history of bad site management

The history of bad management of the site is explained in detail in the technical reports for the remediation of Homebush Bay.

From 1928 until its closure in 1986, the site was used for the manufacture of a wide range of highly toxic chemicals, including timber preservatives, herbicides, pesticides and plastics.

For the latter half of its operating life, the site was owned by Union Carbide Australia Ltd, although the company changed its name following the Bhopal gas disaster at the Union Carbide India Ltd pesticide plant in 1984.

From 1949 until 1976, the site was used to manufacture the herbicides 2,4,5-T and 2,4-D, the ingredients for Agent Orange that was used as a defoliant in the Vietnam War.

As a result of both chemical manufacturing and the use of contaminated fill for reclamation, soil and groundwater on the site were highly contaminated by various chemicals, including dioxins.

Overflow during reclamation and uncontrolled release of stormwater and wastewater into Homebush Bay, as well as possible spills while loading and unloading ships, also contributed to heavy contamination of the bay by dioxins and other chemicals.

This occurred until about 1970, when site management was improved to comply with new environmental laws. Extensive remediation of the site has since been carried out.

Union Carbide factory at Rhodes adjacent to Homebush Bay in the 1960s. Rhodes Remediation Projects

The toxic legacy

While the heavily contaminated former Union Carbide site has been extensively remediated, dioxins from the site have spread throughout the sediments at the bottom of Sydney Harbour.

Dioxins formed as a by-product of the manufacture of timber preservatives and 2,4,5-T at the site have been linked by a characteristic chemical profile to the dioxin contamination in other parts of Sydney Harbour. The site appears to be the major source of these contaminants in the harbour.

It is impracticable to remediate the extensive area of the harbour that is contaminated.

Dioxins from the contaminated sediments enter the marine food chain and are accumulated in fish, prawns and other organisms. The only practicable means to ‘remove’ the contaminants from the marine food chain is to allow other, clean sediments to cover the contaminants. For much of the harbour, this process will take decades.

Fishing banned for decades to come

Fishing bans have been in place around Homebush Bay since 1989, and were extended to parts of the Parramatta River in 1990.

The extent of contamination from the site was not recognised until 2006, when all commercial fishing was banned in Sydney Harbour after tests revealed elevated levels of dioxin in fish and crustaceans in the harbour.

Recreational fishing in the Harbour has not been banned but, based on advice from an expert panel, the NSW government recommends that:

  • No fish or crustaceans caught west of the Sydney Harbour Bridge should be eaten.

  • For fish caught east of the Sydney Harbour Bridge, generally no more than 150 grams per month should be consumed, except for species for which specific higher consumption limits have been established (for example, 1,200 grams of sand whiting).

A NSW government study suggested that much of Sydney Harbour remains contaminated by dioxins at levels that will make eating fish from much of the harbour unsafe for decades.

Environmental regulation is difficult

Regulating a site such as the former Union Carbide factory is difficult. It requires government agencies with the technical and administrative capability as well as the legal powers to do the job.

It is easy to look back and think, “how could the government have missed this happening?” but it is important to recognise in this context that the Union Carbide factory was one of thousands of industrial sites spread across an enormous geographic area.

It is easy to forget that lax laws in the past led to serious environmental problems.

Certainly all environmental laws should be subject to regular review to make them as efficient, effective and equitable as is practicable. That approach is simply what standard texts on policy design recommend.

But attacking the green safety net of environmental laws as “green tape” fails to recognise the history of environmental problems.

It also fails to recognise that our current laws need to be strengthened in many areas, not weakened. A glaring example of this is the profound inadequacy of our response to the unrivalled threat of climate change.

So, next time you walk barefoot on a clean beach and go for a swim in the ocean, spare a thought for the value of the green safety net of environmental law that is working to maintain the health of these places.

Editorial note: This is an abridged version of an article published in the November/December 2012 issue of Precedent.

Join the conversation

16 Comments sorted by


    Written & authorised by William Bourke, Sydney

    The best green tape safety net we can now implement is population policy reform.

    1. Chris McGrath

      Senior Lecturer at University of Queensland


      The article was mainly about maintaining the green safety net of existing environmental laws but I agree with you that sustainable population policies are a critical missing component in the existing system.

      The fact that there are holes in the existing system is a reason to strengthen it though, not a reason to weaken it as is proposed by opponents of environmental regulation.


      Written & authorised by William Bourke, Sydney


      Agreed Chris. Apologies for not addressing the article more specifically... but population is the missing link in most discussions around environmental protection and sustainability. We should include it in all such discussions because, in the long run, all major environmental battles will be lost unless we tackle population.

  2. Phillip Lawrence

    PhD Scholar at University of Sydney

    Its frustrating that no major NGO will get involved in this issue. Probably because the President Emeritus of WWF International was also on the board of Union Carbide during the terrible Bhopal explosion and the Dioxin pollution of Sydney harbor. A problem a bit too close to home I suppose.

    1. Chris McGrath

      Senior Lecturer at University of Queensland

      In reply to Phillip Lawrence

      I'm not sure what an NGO can do here as there does not seem to be much more that can be done about the problem than is already being done by the NSW Government.

      They stopped the source of the contaminants and spent a lot of money decontaminating the site at Rhodes and Homebush Bay. It appears to be impracticable to decontaminate the large area of the harbour that is affected. So the ban on commercial fishing and recommendations against eating fish and crustaceans appears to be the only remaining management options available.

      I have not read about WWF's position on this but I would presume they would follow the views of the WHO and NSW Government.

      Greenpeace is a major NGO and it has campaigned on the issue in the past. I'm not sure about the other NGOs.

      What do you think the NGOs should be doing?

  3. Michael Brown

    Professional, academic, company director

    It is always interesting to go back and review the science on these topics which had plenty of publicity at the time, but not much subsequently. Often the initial research results are not confirmed, and this is the case with dioxin. Here are the results of the latest studies:
    "The update of a cohort of US herbicide producers generated negative results overall....the update of a similar Dutch cohort did not…

    Read more
    1. Chris McGrath

      Senior Lecturer at University of Queensland

      In reply to Michael Brown

      Michael, your lack of concern for this issue stands in stark contrast to the NSW Government and the World Health Organisation's views.

      Your dismissal of the problem so easily is very rash and your concluding, poorly aimed shot at the IPCC suggests that you are trolling here.

      The chemical name for dioxin is 2,3,7,8- tetrachlorodibenzo para dioxin (TCDD) but, as in my article, the name "dioxins" is often used for the family of structurally and chemically related polychlorinated dibenzo para…

      Read more
  4. Tom James


    Thank you Chris for another great article. Short, concise and very evidence based.

    This case is a good example of which Australia's commercial and recreational fishing community (not all but many) should consider before attacking existing and proposed environmental regulation.

    As an avid recreational fisherman, I have observed the widespread stark opposition to environmental regulation such as MPA's. Although, MPA's are a completely separate issue, they serve the same purpose, to protect the ecosystems which provide the resources Australians love to exploit. They must understand that these policies are not implemented to oppress, but to ensure that similar outcomes of the "Sydney Dioxin" case (a ban on fishing) will not need to be repeated in other regions.

  5. Comment removed by moderator.

  6. Max Finlayson

    Director, Institute for Land, Water and Society at Charles Sturt University

    Chris, thanks for providing a clear outline of the benefits of a green safety net. I know full well from my own experiences in water quality sampling how we have managed to turn around some of the pollution trends of the past. Including in our coastal waters. We have managed this because we have had a green safety net. Yes, we should review it at regular intervals, and establish what is now needed, in the light of the evidence. Then make an informed decision. And a public decision using the mechanism that exist under the green net. Best wishes

  7. Max Finlayson

    Director, Institute for Land, Water and Society at Charles Sturt University

    Chris, I'd like more information on your comments about the near impossibility of cleaning up the Sydney harbour pollution that you have mentioned. Was the Union Carbide site remediated using public or industry funds? And do we have sufficient ecotoxicological and risk assessment data for the wider harbour? Do we need further data? Or do we already have sufficient information (and ongoing assessment) about this problem? Thanks

    1. Chris McGrath

      Senior Lecturer at University of Queensland

      In reply to Max Finlayson

      Those are really good questions Max.

      There is a lot of information on the remediation of Homebush Bay at

      An enormous amount of work went into the clean-up. My understanding is that Union Carbide paid from some of the remediation but a large part of it was born by the NSW Government. Some of the contamination pre-dated Union Carbide's ownership of the site.

      A lot of ecotoxicology work for the harbour has been done by Gavin Birch at the University of…

      Read more
  8. Ann Cunningham

    Commissioning Editor

    Thanks Chris for such an important and informative piece - just beautifully written and sourced too.

    For those interested - ABC NSW 7.30 report did very good coverage of the effect of dioxins on Sydney harbour's commercial fishers and their families back in 2006.

    1. Chris McGrath

      Senior Lecturer at University of Queensland

      In reply to Ann Cunningham

      Thanks Ann, I wasn't aware of the 7.30 Report covering the issue in 2006.

      As a Queenslander, I only became aware of the dioxin contamination of Sydney Harbour in 2010 when I read the excellent article by Ann Davies in the Sydney Morning Herald that I linked to:

      I was travelling through Sydney and just happened to pick up a copy of the SMH. I was shocked by it and I have used it ever since when teaching about pollution laws as it is a story that really brings home the importance of our environmental legal system.

  9. Dean Ashby

    Company Owner at Ezestore Storage Sydney

    It is rather sad that such activities have contaminated the waters of Sydney Harbour. I was having this conversation with some friends when we went sailing one weekend. The boat was in a cheap storage nearby, which was very surprising knowing that it is in the CBD, and the conversation started when we finally got on the waters of Sydney Harbour. One of us onboard was an environmentalist, and explained to us not only about the toxin in the waters, but also other concerns like conservation and climate change, among others. I have learned a lot from these, and I am now thinking about how to get involved in this in my own way. Probably, I will start with my kids – bring them to a science museum, or the like.