Levels of seven urinary phthalate metabolites in a human reference population

Using a novel and highly selective technique, we measured monoester metabol ites of seven commonly used phthalates in urine samples from a reference po pulation of 289 adult humans. This analytical approach allowed us to direct ly measure the individual phthalate metabolites responsible for the animal reproductive and developmental toxicity while avoiding contamination from t he ubiquitous parent compounds. The monoesters with the highest urinary lev els found were monoethyl phthalate (95th percentile, 3,750 ppb, 2,610 mug/g creatinine), monobutyl phthalate (95th percentile, 294 ppb, 162 mug/g crea tinine), and monobenzyl phthalate (95th percentile, 137 ppb, 92 mug/g creat inine), reflecting exposure to diethyl phthalate, dibutyl phthalate, and be nzyl butyl phthalate. Women of reproductive age (20-40 years) were found to have significantly higher levels of monobutyl phthalate, a reproductive an d developmental toxicant in rodents, than other age/gender groups (p < 0.00 5). Current scientific and regulatory attention on phthalates has focused a lmost exclusively on health risks from exposure to only two phthalates, di- (2-ethylhexyl) phthalate and di-isononyl phthalate. Our findings strongly s uggest that health-risk assessments for phthalate exposure in humans should include diethyl, dibutyl, and benzyl butyl phthalates.