Validation of a methodology for modelling PCDD and PCDF intake via the foodchain

The US EPA foodchain exposure methodology has been assessed, linking background concentrations of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) in the atmosphere with eventual intake of these chemicals by humans via the foodchain. The methodology is assessed against background environmental concentrations of PCDD/Fs and the background daily adult intake of PCDD/Fs in the UK diet comprising meats, vegetables, dairy produce, fish and miscellaneous food groups. The environmental fate and transport of PCDD/Fs is estimated for each of the seventeen, 2,3,7,8-positional PCDD/F isomers individually from the atmospheric burden in the atmosphere and into the environmental medium or food product of interest. The model predicts PCDD/F deposition rate and soil concentration to within +/-50% of the measured I-TEQ values. For grass, the model underpredicts PCDD/F concentrations but the lack of a reliable and coherent data set precludes further investigation as to the likely causes. The model performs well on food products, with the exception of potatoes (under-predicts by a factor of 20) and 'other' vegetables (underpredicts by a factor of 3). The total modelled PCDD/F intake via the diet is 61 pg I-TEQ day-1 as opposed to the measured intakes of 69 pg I-TEQ day-1 (excluding plant foods) and 81 pg day-1 (including data for plant foods measured in a previous survey, and not representative of contemporary exposures). The major contributor to total PCDD/F intake is via milk and milk products, accounting for about 40% of the daily dietary intake. 'Hidden' fats and oils account for 35% of the PCDD/F intake, followed by the ingestion meat and meat products (12%). As a group, vegetables do not appear to contribute significantly to the total adult background intake of PCDD/Fs via the diet.