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Chemicals management
Since dioxins are chemically stable and fat soluble, they concentrate in body fat after ingestion and build up under conditions of long-term exposure, both in animals and humans, and accumulate as they move through the food chain. They are also transferred in breast milk to infants. These properties mean that even low levels of dioxins in the environment may eventually pose risks to animals and humans.
Experimental studies have reported a number of effects to occur in animals following exposure to dioxins. Among the most significant are: endometriosis (occurrence of uterus lining in areas other than the uterus, e.g. ovaries), effects on the nervous system, developmental and reproductive effects, and impairment of the immune system.
Research also suggests that people occupationally exposed to very high levels of dioxins have a higher risk of developing cancers later in life. Both the US Environmental Protection Agency and the World Health Organization (WHO) have classified TCDD, the most toxic dioxin, as a known human carcinogen or cancer-causing agent.
Exposure to high levels of dioxins can lead to chloracne, a severe acne-like skin condition. However, the exact impact of dioxins on people's health is not yet known, and there is currently no clear indication that dioxins are causing increased disease in the general population.
The information gathered by the National Dioxins Program will be used to estimate the extent to which people are exposed to dioxins, and determine the best actions Australia can take to reduce our exposure to dioxins.
International studies have concluded that around 95 per cent of human exposure occurs through our consumption of food as shown in Figure 1. People may also be exposed through breathing in air contaminated by dioxins from smoke, factory or incinerator emissions or from uncontrolled hazardous waste sites containing dioxins.
Figure 1. Sources and pathways of dioxins
Dioxins are generally not taken up or absorbed by plants but may settle on the surfaces of the leaves. Dioxins can then enter the food chain when animals eat the contaminated leaves. In aquatic environments, filter-feeding animals can absorb dioxins when they filter sediments or particulate matter floating in the water.
The dioxins are then absorbed into the animal fat. Dioxins increase in concentration as they migrate up the food chain; this is referred to as bio-accumulation.
When people eat food contaminated with dioxins they remain in the body's fat stores. Foods likely to contain dioxins are those that contain fat, such as dairy products, meat and meat products, fish, eggs, breast milk and infant formula.
No. A healthy, balanced diet that is low in fat will reduce the risk of exposure to dioxins. Eliminating fats completely however, is not recommended. It is likely that we all have some dioxins in our bodies. Unfortunately there are no safe or effective treatments to get rid of dioxins that may be in our bodies now. Dioxins are eventually metabolised, or broken down and excreted from our bodies over many years.
Yes. Breast milk is the best food for babies, especially in their first six months. This is the advice of the WHO and the National Health and Medical Research Council (NHMRC) in Australia. Breast milk may contain low levels of dioxins because of its fat content, but all babies are exposed to dioxins even if they are not breastfed. Alternative foods for babies, such as infant formula, may also contain dioxins because they may also contain fat. Several studies around the world in areas where dioxin levels are known to be high, have still shown that breastfed babies are healthier than those fed infant formula.
Internationally, in June 2001, the Joint Food and Agriculture Organisation and WHO Expert Committee on Food Additives concluded that given the long time it takes for dioxins to break down, it is only possible to assess their health risk by measuring how much has been consumed over a month or more. The Committee decided to express the tolerable intake of dioxins as a monthly value - the provisional tolerable monthly intake or PTMI. They recommended a PTMI of 70 pg dioxin toxic equivalents (TEQ)/kg body weight as a reference value to which a human can be exposed over his or her lifetime without harm.
The Therapeutic Goods Administration and the NHMRC propose an Australian health standard Tolerable Monthly Intake (TMI) of 70 pg TEQ/kg body weight for dioxins. The proposal is accessible through the NHRMC's homepage at http://www.nhmrc.gov.au.
This is number 3 of 4 Fact Sheets on the National Dioxin Program
For more information contact:
National Dioxins Program
Chemical Policy Section
Department of the Environment, Water, Heritage and the Arts
GPO Box 787
CANBERRA ACT 2601
E-mail: dioxins@environment.gov.au
Internet: http://www.deh.gov.au/industry/chemicals/dioxins/index.html
April 2005