A sensitivity analysis using alternative toxic equivalency factors to estimate U.S. dietary exposures to dioxin-like compounds

Abstract

EPA recommends sensitivity analyses when applying the toxic equivalency factor (TEF) method to evaluate exposures to dioxin-like compounds (DLCs). Applying the World Health Organization's (WHO) 2005 TEF values and estimating average U.S. daily dietary intakes of 25 DLCs from eight food categories, we estimate a toxic equivalency (TEQ) intake of 23 pg/day. Among DLCs, PCB 126 (26%) and 1,2,3,7,8-PeCDD (23%) dominate TEQ intakes. Among food categories, milk (14%), other dairy (28%), beef (25%), and seafood (18%) most influenced TEQ intakes. We develop two approaches to estimate alternative TEF values. Based on WHO's assumption regarding TEF uncertainty, Approach1 estimates upper and lower TEFs for each DLC by multiplying and dividing, respectively, its individual TEF by ± half a log. Based on compiled empirical ranges of relative potency estimates, Approach2 uses percentile values for individual TEFs. Total TEQ intake estimates using the lower and upper TEFs based on Approach1 were 8 and 68 pg TEQ/day, respectively. The 25th and 75th percentile TEFs from Approach2 yielded 12 and 28 pg TEQ/day, respectively. The influential DLCs and food categories remained consistent across alternative TEFs, except at the 90th percentile using Approach2. We highlight the need for developing underlying TEF probability distributions.

Keywords: 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD); 2,3,7,8-tetrachlorodibenzo-p-dioxin; Cij; DLC average concentrations in each food category; DLC intake estimate for each food category; DLCs; Dietary intake; Dioxin-like compounds (DLCs); Dose addition; EPA; Eij; HpCDF; HxCDD; HxCDF; PCBs; PCDDs; PCDFs; PeCDD; REP; Relative estimates of potency (REP); SI; Sensitivity analysis; Supplementary Information; TCDD; TEF; TEF(A); TEF(B); TEF(L); TEF(U); TEQ; TEQ(A)(j); TEQ(AT); TEQ(L); Toxic equivalency (TEQ); Toxic equivalency factor (TEF); U.S.; U.S. Environmental Protection Agency; United States; WHO; World Health Organization; alternative TEF value based on the percentile used (e.g., where (“A”) indicates the percentile—10th, 25th, 50th, 75th, 90th); alternative daily TEQ intake rate estimates for the jth food category; alternative total daily TEQ intake estimates; baseline TEF value; dioxin-like compounds; f(j); fat fraction estimates for each food category; food ingestion rate for each food category; heptachlorodibenzofuran; hexachlorodibenzo-p-dioxin; hexachlorodibenzofuran; lower TEF value; lower TEQ value; pentachlorodibenzo-p-dioxin; polychlorinated biphenyls; polychlorinated dibenzo-p-dioxins; polychlorinated dibenzofurans; r(j); relative estimates of potency; toxic equivalency factor; toxicity equivalence; upper TEF value.