VALIDATION OF A METHODOLOGY FOR MODELING PCDD AND PCDF INTAKE VIA THEFOODCHAIN

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