Exposure assessment of dioxins/furans consumed in dairy foods and fish

Dioxins/furans are ubiquitous environmental contaminants whose primary rout e of human exposure occurs via the consumption of fatty foods of animal ori gin. The US FDA conducted a market basket survey of dairy products and comm ercial fish and shellfish to obtain data on levels of 17 dioxin/furan conge ners (2, 3, 7, 8-congeners) in the US. The dairy products sampled included various cheeses (American, cheddar, Swiss, cottage), ice cream, yogurt, but ter, and milk. The finfish and shellfish (molluscs and crustacea) sampled a re those marine species consumed in the greatest amounts and include canned tuna, shrimp, cod, blue crab, and oysters. Catfish was sampled because it is the dominant aquaculture species. Samples were collected in 1995/96 and analysis for 17 dioxin/furan congeners was performed by high-resolution gas chromatography following extraction and clean-up. Limits of detection (LOD ) and quantitation (LOQ) for each congener in each food were reported. Poin t estimates of exposure were calculated using a 3- day (1-day diary plus 2- day recall) food consumption survey for eaters-only and for the general pop ulation (USDA/CSFII, 1989-92). Toxicity equivalency factors (TEFs) develope d by the World Health Organization (1997) were used to derive overall dioxi n/furan toxicity equivalents (TEQ) for each sample food. Mean estimates of TEQ exposure for each food were derived using five values for non-detects ( ND = 0; ND = 1/2 LOD or LOQ; ND = LOD or LOQ) on both a total sample and ea ters-only basis. Using zero and the LOD provide lower and upper bounds on t he range of estimated exposure, respectively. The bounds on mean dioxin int akes (pg/person/ day) calculated for consumers of specific foods were estim ated as follows (using zero or LOD for non-detects): butter (0.5-11), chees e (1.6-3.2), ice cream (4-19), yogurt (0.8-28), catfish (148-150), fish (ot her than catfish) (0.03-9), crustacea (32-35), mollusks (16.1-16.6), and sh rimp (0.09-4.5). Exposure estimates derived by the five ND-methods are stro ngly dependent on the LOD and LOQ and represent upper bound estimates of ex posure. Uncertainty in the exposure estimates is reduced with refinements i n the analytical method.