Dioxins in Total Diet Survey 2001 Samples: Your Questions Answered

This survey was carried out to allow up-to-date dietary intakes of dioxins and dioxin-like PCBs from the whole diet to be estimated, and to check that controls on releases of these chemicals to the environment are being effective.

Analysis was carried out on samples collected for the 2001 Total Diet Study (TDS). The TDS is a model of the typical UK diet. A total of 121 categories of food and drink are specified for inclusion in the Total Diet. These are assigned to one of 19 broad food groups, such as carcass meat, miscellaneous cereals and eggs. Foods are grouped so that commodities known to be susceptible to contamination (such as offal and fish) are kept separate, as are foods which are consumed in large quantities, such as bread, potatoes and milk.

Dioxins and dioxin-like PCBs are chemicals with different degrees of dioxin-like toxicity. The use of Toxic Equivalency Factors (TEFs) allows concentrations of the less toxic compounds to be expressed as an overall equivalent concentration of the most toxic dioxin, 2,3,7,8-TCDD. These toxicity-weighted concentrations are then summed to give a single concentration expressed as a Toxic Equivalent (TEQ). The system of TEFs used in the UK and a number of other countries is that set by the World Health Organization (WHO), and the resulting overall concentrations are referred to as WHO-TEQs.

Dioxins and dioxin-like PCBs were found at low levels in all the food groups analysed. The highest concentrations were found in the animal fat-containing food groups such as meat, fish and eggs. This was expected as these chemicals are known to bioaccumulate in the food chain.

In July 2002 limits were set by the European Commission (EC) for dioxins in foods that contribute significantly to the total dietary intake of these chemicals. The limits are as follows: meat (1-3 nanograms WHO-TEQ/kilogram fat basis), liver (6 ng WHO-TEQ/kg fat basis), fish (4 ng WHO-TEQ/kg fresh weight), eggs (3 ng WHO-TEQ/kg fat basis), milk and milk products (3 ng WHO-TEQ/kg fat basis), fats and oils depending on type (0.75-3 ng WHO-TEQ/kg fat basis). The EC has also set lower action levels for dioxins in these foods. If these are exceeded work must be carried out to identify and eliminate the source of contamination. These limits and action levels are to be reviewed by December 2004.

Levels of dioxins in all those foods for which limits have been set are within the limits. The TDS food group samples are all composite samples of different foods of varying fat contents. For example, the milk products food group contains low fat cottage cheese and yoghurt, and cream and butter with higher fat contents.

At present there are no limits for dioxin-like PCBs in food. It is anticipated that by December 2004, when the limits for dioxins in food are due to be reviewed, they will be expanded to include dioxin-like PCBs.

A Tolerable Daily Intake (TDI) is the maximum amount of a contaminant that can be eaten every day over the whole lifetime without causing harm.

The estimated average dietary intake by adults in the UK has fallen from 1.8 picograms WHO-TEQ/kg of body weight per day to 0.9 pg WHO-TEQ/kg of body weight per day between 1997 and 2001. The new TDI, which took effect in November 2001, is 2 pg WHO-TEQ/kg of body weight per day.

The average dietary intakes by adults, children and all but the youngest age group of toddlers (1.5 to 2.5 years) of dioxins and dioxin-like PCBs via the total diet in 2001 were all within the UK TDI. Overall, at any point in time, only 1.1% of adults, 10% of children and 37% of toddlers are estimated to exceed the UK TDI. By comparison, in 1997 it was estimated that 35% of adults, 62% of children and 97% of toddlers exceeded the UK TDI. Dietary intakes of dioxins and dioxin-like PCBs are anticipated to decline further still in the future as controls on releases of the chemicals to the environment continue to take effect.

Intakes in the UK are similar to those in the EU and USA.

The tolerable daily intake is the amount that may be consumed every day over the whole lifetime without causing harm. The levels in the body take many years to build up and these intakes in children are not expected to be harmful provided that the average intake over a prolonged period is within the TDI. Based on the results of this survey, parents are advised that they do not need to change their children’s diets because of the presence of dioxins and PCBs in food.

There is very little scope for removal of dioxins and PCBs from foods once they have entered the food chain. It is generally agreed that the best method of preventing dioxins and PCBs from entering the food chain is to control releases of these chemicals to the environment.

Dioxins have never been produced intentionally but are unwanted by-products resulting from various combustion processes. Most dioxins are spread through the air, and in recent years there has been considerable effort to reduce industrial emissions of dioxins with considerable success. PCBs were formerly used in electrical equipment, but their production and general use ceased in the 1970s and is now banned. The only remaining use of PCBs in the UK is sealed inside some older electrical equipment but these PCBs must be phased out and destroyed under the UK PCB Regulations.

Over the past ten years there has been a tenfold decrease in industrial emissions under Environment Agency control. Municipal waste incinerators were the most significant source of atmospheric emissions and these have fallen by 97% to less than 1% of the UK total.

UK surveys show that in the past 20 years, human dietary exposure to both dioxins and PCBs fell by around 85%.

UK emissions of dioxins from industrial sources are now estimated to be the same as from domestic sources with accidental, agricultural and domestic fires and fireworks now emitting the most dioxins in the UK.

As dioxins and PCBs do not break down easily, they persist in the environment and it is likely to take many years for the control measures to have full effect.

In October 2002 the Government carried out a consultation on future measures that could be taken to further reduce environmental and human exposure. Under the Stockholm Convention, the Department of Environment, Food and Rural Affairs (DEFRA) will be producing an action plan to reduce dioxins in the environment and consumer dietary exposure to these chemicals, taking into account responses from the consultation. DEFRA is currently investigating the cost effectiveness of potential measures to achieve these reductions.

Animals and fish take up dioxins and PCBs present in their food and from any soil or sediment they may eat during feeding. These compounds then pass into the milk, meat, fish and eggs, concentrating in the fat component.

Animal fat in milk, meat, fish, eggs (and their products) is the main source of dioxins and PCBs in the diet. The levels of dioxins and PCBs in any individual's diet will vary depending on the amounts and types of foods they eat.

Dioxins and PCBs are found at low levels in all foods, including foods that are important sources of nutrients. The Agency’s advice is that the benefits of a healthy, balanced diet, outweigh any risks from dioxins and PCBs. The Agency does not recommend extreme consumption of any food.

Dioxins and PCBs have no immediate effect on health, even at the highest levels found in foods. The potential risks to health come from long-term exposure to high levels. They can cause a wide range of effects in animals, including cancer and effects on the immune and reproductive systems. However, it appears people may be less sensitive.