Legacy and emerging plasticizer profiles in kindergarten classrooms: innovative source identification and exposure assessment

Indoor exposure to plasticizers poses a growing risk to child development. Nevertheless, their contamination profiles, definitive sources, and primary exposure pathways remain inadequately understood. Herein, plasticizer concentrations and distributions across various environmental media were systematically characterized in 30 kindergarten classrooms. Results revealed that an emerging plasticizer, 2,2,4-trimethyl-1,3-pentanediol diisobutyrate, was predominant in the gas phase (median: 1304 ng/m³), while a legacy plasticizer, di(2-ethylhexyl) phthalate, exhibited the highest concentrations in particles (54.9 ng/m³), dust (624 μg/g), and on tables and chairs (258 and 134 μg/m², respectively). Indoor surfaces (e.g., desks and chairs) acted as important reservoirs of plasticizers, where frequent child contact (>50 times/h) disturbed air-surface equilibrium while simultaneously facilitating proportional redistribution of plasticizers across surfaces. Additionally, source attribution using a novel in-situ screening method identified flooring and beds as primary contributors (27%-59%), with walls and curtains also showing unexpectedly high contributions (up to 29%). Finally, exposure doses were calculated across four pathways: inhalation, dermal absorption, dust ingestion, and surface-to-hand-to-mouth contact. Notably, the often-overlooked surface-to-hand-to-mouth pathway was identified as an important pathway for low-volatility plasticizers, and even the dominant pathway for certain emerging compounds, which warrants further investigations. These findings support effective mitigation strategies: removal or avoidance of source materials represents the most direct approach to reducing indoor plasticizer, and more frequent cleaning of high-contact surfaces may further reduce children's exposure.