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BACKGROUND: Humans are commonly exposed to multiple environmental chemicals, including tetrabromobisphenol A (TBBPA; a flame retardant), triclosan (an antimicrobial agent), and bisphenol A (BPA; polycarbonate plastics). These chemicals are readily absorbed and may interact with each other. OBJECTIVES: We sought to determine whether TBBPA, given alone or in combination with triclosan, can modulate the concentrations of BPA and 17b-estradiol (E2). METHODS: Female and male CF-1 mice were each given a subcutaneous injection of 0-27 mg TBBPA, with or without concurrent 0:33 mg triclosan, followed by dietary administration of 50 μg=kg body weight 14C-BPA. Radioactivity was measured in blood serum and tissues through liquid scintillation counting. In subsequent experiments, female and male CF-1 mice were each given a subcutaneous injection of 0 or 1 mg TBBPA and E2 was measured in urine 2-12 h after injection. RESULTS: Doses as low as 1 mg TBBPA significantly elevated 14C-BPA concentrations in the uterus and ovaries of females; in the testes, epididymides, vesicular-coagulating glands, and preputial glands of males; and in blood serum, heart, lungs, and kidneys of both sexes; urinary E2 concentrations were also elevated. Lower doses of TBBPA or triclosan that had no effects on their own elevated 14C-BPA concentrations when the two substances were given concurrently. CONCLUSION: These data indicate that TBBPA, triclosan, and BPA interact in vivo, consistent with evidence that TBBPA and triclosan inhibit enzymes that are critical for BPA and E2 metabolism. [ABSTRACT FROM AUTHOR]