Dioxins
Last updated 12 April 2010
What are dioxins?
The word ‘dioxin’ refers to a group of chemical compounds sharing similar chemical structures, properties and biological properties. Several hundred of these compounds exist and are members of three related families:
- Polychlorinated dibenzo-p-dioxins (PCDDs)
- Polychlorinated dibenzofurans (PCDFs)
- Certain co-planar polychlorinated biphenyls (dioxin-like PCBs)
Why are they of concern?
Dioxins accumulate in the fat of animals and humans and are persistent in the environment. Certain of the dioxins are toxic to various degrees. The dioxins identified as toxic have been linked with a number of cancer and non-cancer health effects including reproductive effects and suppression of the immune system.
How are they produced and what are the major sources?
Dioxins are not deliberately produced but are released into the environment mainly as by‑products of combustion or certain chemical production processes. Based on the Inventory of Dioxin Emissions in Australia (National Dioxins Program Technical Report No. 3, 2004 (external site), ten sources accounted for 96% of all emissions in Australia for those sources that were selected for study in the Inventory.
These were biomass burning (70%), pulp and paper production (6%), waste burning and accidental fires (5.4%), zinc production (2.7%), fossil fuel power plants (2.3%), aluminium production (2%), sewage and sewage treatment (1.8%), metal ore sintering (1.7%), medical waste incineration (1.6%) and household heating and cooking with wood (1.2%). The Inventory did not consider possible dioxin contamination of pesticides since such contamination was considered to be very small.
What levels of dioxins do we have in Australia?
The levels of dioxins in the Australian population are low by international standards. Determining dioxin levels in human blood is a common measure. When compared with levels found in other OECD countries, Australians have one of the lowest body burdens of dioxins in human blood in the world. Levels of dioxins in human milk were also low in Australia.
For more information, see:
- Dioxins in the Australian population: levels in blood, technical report No. 9 (external site)
- Dioxins in the Australian population: levels in human milk, technical report No. 10 (external site)
How are we exposed to dioxins?
It has been estimated that, for those sources studied, over 96% of dioxins present in the Australian environment originated from emissions to the air from bushfires and a variety of industrial processes.
These dioxins settle on plant, soil and water surfaces and can enter the food chain when animals eat leaves, soils or sediments that contain dioxins. These compounds accumulate in the fat of animals and humans over the course of their lives. Human exposure comes mainly from eating animal fats such as in meat (including fish), milk and eggs.
Is our food safe?
Yes. A study by Food Standards Australia New Zealand in 2004 found that on the basis of the available data and taking into account all the inherent uncertainties and limitations, the public health and safety risk from exposure to dioxins in food is very low.
For more information on dioxins in food, see Food Standards Australia and New Zealand (external site). For information on the National Action Plan for Addressing Dioxins in Australia, see Department of Sustainability, Environment, Water, Population and Communities.
Doesn’t the APVMA routinely monitor pesticides for dioxins?
Pesticides have not been routinely monitored for dioxins in Australia or overseas. As a result of improvements to manufacturing methods in the last 20 years, dioxin impurities in pesticides were believed to be at levels below what might be a human health concern for agricultural workers and bystanders. They were also believed to make a very low contribution to overall annual dioxin emissions to the environment.
The dioxins human health risk assessment (2004) indicated that dioxin levels in the tissues of Australians are among the lowest by world standards and are decreasing. Further, the national assessment did not recommend any additional dioxin monitoring. Dioxins as impurities in pesticides have been thought to be adequately controlled by requiring proper manufacturing methods and by identifying expected levels for each impurity early in the registration process. This same approach is used by regulators overseas.