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Australian Government: National Measurement InstituteAustralian Government: National Measurement Institute
National Measurement Institute
      

Persistent Organic Pollutants

bushfireSeveral research projects are currently underway which focus on establishing persistent organic pollutants (POP) levels in humans and the environment using direct sampling and ‘passive’ sampling methods to enable extremely low detection limits. Our partners include the National Center for Environmental Toxicology (University of Queensland), Edith Cowan University, the NSW Government and CSIRO. Published results can be found here.

We also analyse dioxins, furans, PCBs, PBDEs and other persistent organic pollutants in a range of materials at ultra-trace levels. This initiative ensures our technical leadership in the Australian analytical market and exemplifies our continued commitment to the support of trade and industry, environment and public health.

For further information email dioxins@measurement.gov.au.

Dioxins, Furans, PCBs and PBDEs

See www.dioxin20xx.org for relevant publications.

The term dioxin or furan technically refers to the basic structure of the molecule, which is composed of carbon and oxygen. Through reactions involving halogens such as chlorine or bromine, dioxins and furans acquire toxic properties. Almost all research on halogenated dioxins and furans has focused on chlorinated species — polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs). There are 75 different PCDDs and 135 different PCDFs, each compound has a distinct number and configuration of chlorine atoms (see Figure 1). These differences in chemical structure produce varying levels of toxicity among the PCDD/F family.

dibenzo-p-dioxin             dibenzofuran

Figure 1. Structures of PCDDs and PCDFs (1-9 indicate the possible positions of the chlorine atoms)

The general terms 'dioxins' and 'dioxin' are assumed to refer collectively to PCDD/Fs and this has recently been extended by the World Health Organization (WHO) to include a number of 'dioxin-like' polychlorinated biphenyls (PCBs) (see Figure 2).

Polychlorinated biphenyls

Figure 2. Structures of PCBs (numbers 2-6 (2’-6’) indicate the possible positions of the chlorine atoms at ortho(o), meta(m) and para(p) positions)

Dioxins are formed as unintentional by-products of industrial processes involving chlorine such as waste incineration, chemical and pesticide manufacturing, smelting and pulp and paper bleaching where elemental chlorine is still used in the process. PCBs on the other hand are commercially produced and used in a number of industrial applications including insulating fluids or resins in transformers and capacitors, heat transfer fluids, hydraulic fluids, solvent extenders, flame retardants and dielectric fluids. The production of PCBs was banned in western countries in the late 1970s but they still persist widely in the environment.

The polybrominated diphenyl ethers (PBDEs) are a prominent family of brominated flame retardants and are produced in three commercial formulations, known as ‘penta’, ‘octa’ and ‘deca’, based on the amount of bromination in the mixture. In many cases, PBDEs are not chemically bound to consumer products and are released to the environment through indoor air, household dust and during e-waste and textile recycling. Once in the environment PBDEs bioaccumulate in the food chain and can be detected in humans.

Structures of polybrominated diphenyl ethers

Figure 3. Structures of PBDEs, indicating the possible positions of the bromine atoms

PBDEs are not manufactured in Australia, but it has been estimated that over 500 tonnes are imported each year, of which 340 tonnes are PBDEs. In addition, the amount of PBDEs in imported articles used in both domestic and in industrial applications is unknown.

Power plantDioxins, furans and dioxin-like PCBs have been shown to be toxic at extremely low levels with the International Agency for Research on Cancer announcing in 1997 that 2,3,7,8-tetrachlorodibenzo-p-dioxin was carcinogenic to humans. These compounds are fat soluble, extremely persistent, bioaccumulate through the food chain and are ubiquitous. Approximately 90% of human exposure is through our diet with food from animal origin being the predominant source. The risks of toxicity and environmental contamination have resulted in a heightened awareness of dioxins and associated compounds internationally.

On 23 May 2001, Australia together with over 150 other countries signed the Stockholm Convention on Persistent Organic Pollutants. This convention provides the impetus for all countries to reduce and/or eliminate emissions of the so-called 'dirty dozen' compounds, namely, dioxins, furans, PCBs and the following organochlorine pesticides (DDT, aldrin, dieldrin, endrin, chlordane, heptachlor, hexachlorobenzene, mirex and toxaphene) and to create regulatory frameworks that address concerns for public health and the environment. Australia ratified the convention on 20 May 2004.

In 2009, nine chemicals were added to the Stockholm Convention, with four of these having exemptions for specific uses or recycling/stockpile reduction activities. The new compounds are:

  • lindane (a pesticide)
  • alpha hexachlorocyclohexane and beta hexachlorocyclohexane (by-products of lindane production)
  • chlordecone (another pesticide)
  • hexabromobiphenyl (a flame retardant widely used in consumer goods)
  • pentachlorobenzene (a fungicide intermediate and a flame retardant)
  • pentabromodiphenyl ethers and octabromodiphenyl ethers (PBDEs, flame retardants)
  • perfluorooctane sulfonate (PFOS) which is a non-stick surface coating

WHO has identified a number of dioxins, furans and PCBs that represent the highest risk to public health in terms of their toxicological properties at concentrations as low as parts per quadrillion (ppq). Click here for more information on ppb, ppt and ppq.