Acute and chronic dietary exposure assessments
GEMS/Food data used to assess dietary exposure of chemicals in food
The role of dietary exposure assessments has grown significantly in light of the World Trade Organization (WTO) "Agreement on the Application of Sanitary and Phytosanitary Measures" (SPS Agreement). The SPS Agreement further requires that sanitary and phytosanitary measures should be based on sound scientific risk assessment.
Dietary exposure assessments combine food consumption data with data on the concentration of chemicals in food. The resulting dietary exposure estimate is then compared with the relevant toxicological or nutritional reference value for the food chemical of concern. Assessments may be undertaken for acute or chronic exposures where short-term exposure covers a period of 24 hours, and long-term exposure covers average daily exposure over the entire lifetime.
Dietary exposure assessments can be used both to evaluate the intake of chemical hazards and the intake of nutrients. When assessing nutrients the default assumptions used tend to underestimate exposure compared to the default assumptions used for potentially toxic food chemicals which tend to overestimate exposure. For some nutrients, two assessments may be necessary due to the specific need to look at both nutrient adequacy and the potential to exceed upper safety levels of the nutrient.
The general equation for both acute and chronic dietary exposure would be expressed as follows:
The data required for assessing dietary exposure are determined by the objective of the assessment. Dietary exposure can be assessed for chemicals before the chemical has been approved for use (pre-regulation), after a chemical has potentially been in the food supply for years (post-regulation), or for chemicals that are present naturally in foods. In the first case, chemical concentration data are available or estimated from the registrant/manufacturer. In the other two cases, additional chemical concentration data could be obtained from food in the market place.
WHO under the GEMS Food programme develops databases for the purpose of acute and chronic exposure assessment which include data on the consumption of large portions of commodities by the general population and children ages 6 and under. Consumption figures were provided by Australia, France, The Netherlands, Japan, South Africa, Thailand, the United Kingdom of Great Britain and Northern Ireland (UK) and the United States of America (USA) as well as the age distribution and mean body weights for the relevant groups. In addition, data on unit weight and per cent edible portion were provided by Belgium, France, Japan (unit weight only), Sweden, the UK and the USA. For chronic exposure assessment, the GEMS Food programme developed the clustering of various dietary patterns within 13 so called cluster diets GEMS/Food Consumption Cluster Diets, August 2006.