Integrated Evidence of Environmental Occurrence and Human Exposure to Citrate Plasticizers

Citrate-based plasticizers such as acetyl tributyl citrate (ATBC) and acetyl triethyl citrate (ATEC) are alternatives to phthalates, yet human exposure data remain scarce. ATBC and ATEC are metabolized to acetyl dibutyl citrate (ADBC) and acetyl diethyl citrate (ADEC), which represent relatively specific biomarkers of their respective parent compounds, whereas dibutyl citrate (DBC) and diethyl citrate (DEC) may reflect combined exposure to multiple acetylated and nonacetylated citrate plasticizers and therefore have lower specificity. This study analyzed household dust (n = 47) and urine (n = 363) from 121 participants across three seasons to characterize population-level exposure. In dust, four parent plasticizers, including ATBC, ATEC, tributyl citrate (TBC), and triethyl citrate (TEC) were quantified, with ATBC detected in 37% of samples and concentrations reaching 93.98 μg/g (95th percentile). Four urinary metabolites, ADBC, DBC, ADEC, and DEC, were quantified. In urine, DBC and DEC were detected in over 70% of samples. Mixed-effects modeling showed a significant association between urinary ADBC and DBC, consistent with a shared metabolic pathway. The median estimated daily intake of ATBC from dust ingestion and dermal contact was 0.50 ng/kg bw/day, several thousand times lower than the European Food Safety Authority tolerable daily intake, indicating negligible risk. These findings provide integrated environmental and biomonitoring evidence of human exposure to citrate plasticizers and highlight the need for continued toxicological evaluation.