To identify the needs of exposure information that can be fulfilled by TDS
The first objective of TDS-Exposure project is to identify clearly what kind of information TDS studies can provide for exposure and risk assessment. In the past 30 years, TDS have been implemented in different countries. The first TDS was launched in 1961 in the USA (Murray CW et al, 2008) and now TDS are used in all parts of the world. For instance, several countries including China, Korea, Japan, Cameroon, Lebanon, Canada, United Kingdom, France, Italy and the Czech Republic have organized TDS in recent years. Traditionally, TDS were mainly used to assess exposure to environmental contaminants like heavy metals or persistent organic pollutants (Kwon YM et al, 2009) and nutrients (Wang et al, 2008). However, risk assessors also need exposure information for a broad range of substances like migrants from packaging material (e.g. bisphenol A), pesticide residues and substances produced during cooking like acrylamide or furan. It is necessary to characterize
the interest and the limitations of TDS to assess exposure to all of these substances.
Development of TDS in Europe
The second objective of this project is to encourage the development of total diet studies across Europe and worldwide in order to improve the quality of chemical risk assessments and test the implementation in countries without any TDS. Today, the number of European countries with a TDS is still relatively low. United Kingdom, France, Italy and the Czech Republic are the main countries with TDS. Belgium, Spain and Sweden use duplicate portion studies only. These studies have provided a lot of exposure information and time trend analysis in the last 20 years. There is a need to encourage other European countries to launch TDS to identify determinants of exposure at international level and means to reduce these exposures, if necessary. In order to implement TDS in Europe there is a need to develop training opportunities such as summer schools for young researchers. Online training could also be developed. There is also a need to provide assistance to countries without any TDS to implement such studies. Depending on the substances considered and the level of pooling the cost of a complete TDS in a country can differ and is often over 2 million Euros. Therefore it is not possible for this consortium to develop complete TDS for all countries. However, it is possible to implement small scale TDS limited to some contaminants in different countries. This small scale implementation is the best way to determine the fieldwork and identify and resolve the difficulties that can arise in different EU countries.
Harmonization of TDS
The third objective of this project is to propose a harmonized method for total diet studies across Europe, to test it and to develop a Total Quality Management System. The methodologies used in exposure assessment often differ from one country to another for different reasons. Firstly, exposure assessment can differ because different methodologies for the dietary surveys are used. For instance, 95th or 97.5th percentiles of exposure depend on the number of days in the survey (EFSA, 2009). Secondly, exposure assessment based on TDS can differ from one country to another because of different methodologies for sampling and analysing foods in order to estimate food contamination. It is the reason why it is crucial to standardise or harmonise these two steps. Sampling strategies for food analysis need to use up to date information on foods in the market. TDS are based on analysis of food as consumed. This is the reason why there is a need for information on how the foods are stored (e.g. packaging material) and prepared at home or in restaurants in order to be representative of the food habits of the population. The chemical analysis step is also crucial because different analytical methods can lead to different results. Finally, the exposure assessment methodology needs to be harmonised. Among the main issues raised by EFSA are firstly the type of dietary survey used and secondly the statistical model applied to estimate long term exposure assessment based on short term dietary surveys. Usually dietary surveys last between one day and seven days when the chronic exposure assessment need to consider months or years of intake. Statistical methods exist to estimate the usual intake based on a limited number of survey days. There is a need to harmonise these methodologies in order to be able to compare exposure assessments based on TDS between them. The most important specifications of TDS studies will be described through the development
and implementation of a quality standard framework for TDS centres in Europe. The objective here is to develop a Total Quality management system for TDS in Europe, addressing issues like TDS team, strategy, design and resources, planning, sampling, sample preparation including cooking, sample analysis, data evaluation and exchange and the dissemination and use of results, in order to improve the quality of data and comparability between countries. Generic flowcharts and SOPs will be developed for every essential process and critical step.
To make a European TDS database available for risk assessors and risk managers
The fourth objective of the project is to build and test a European database of TDS studies useful for risk assessors and risk managers like EFSA and DG SANCO. Existing TDS results are today published in reports or scientific papers that provide only aggregate results. Risk assessors and risk managers are often not able to access fully disaggregated TDS results necessary for exposure and risk assessment. The aim of this project is to make available a European database for exposure assessment. The main producers and owners of TDS results participate in this project: IFR and FERA for the United Kingdom, Anses for France, NIPH/SZU for the Czech Republic and ISS and INRAN for Italy. This will give the opportunity to build a database that will have to be updated in the future when new TDS results become available. Outside EFSA and DG SANCO, researchers will have access to results from this database for their own research activity. This access would not be at the most disaggregated level but at a level with an easy interpretation of the data, if possible.
Estimation of dietary intake of contaminants with TDS
The fifth objective of the project is to develop or adapt existing exposure assessment models to TDS studies and to assess uncertainties. Different simple or more complex models can be applied to assess exposure by using TDS results. The main aim of these models is to estimate variability of exposure between individuals and uncertainties in order to protect the whole population. Exposure varies according to different factors like age and gender but also between dietary patterns, countries and regions. Between individuals variability is estimated through statistics like high percentiles (95th, 97.5th and 99th percentiles). One main constraint of TDS is that foods are pooled before analysis. For this reason, only mean contamination of foods can be estimated directly from the food sample analysis. Usually, a simple deterministic model is used to estimate chronic exposure by combining food consumption data at individual level with mean contamination data. A few methodological researches have been done regarding the estimation of uncertainties and variability in TDS. Because the sampling and the pooling procedure is known, it should be possible to assess uncertainties and to estimate variability of the contamination before the pooling of foods.