Background <p>Phthalate exposure may affect human health, with particular concerns for children.</p> Objective <p>The purpose of this study is to investigate the exposure to phthalates in Chinese residential indoor environments and to estimate the contribution of indoor environmental exposure to the daily total intake of phthalates among children on a person-by-person basis.</p> Methods <p>We measured phthalate metabolite concentrations in the urine of 324 Chinese children aged 0–8 years, and parent phthalate mass fractions in settled dust collected from the children’s bedrooms. Concentrations of phthalates in the air (particulate and gas phase) were estimated from phthalate levels in the dust using equilibrium partitioning. The daily intakes of four phthalates, di-2-ethylhexyl phthalate (DEHP), diethyl phthalate (DEP), di-n-butyl phthalate (DnBP), and diisobutyl phthalate (DiBP), were estimated from concentrations of metabolites in urine. The intakes attributable to residential indoor environmental exposure via air and dust were calculated for three exposure routes, dermal absorption, inhalation, and ingestion.</p> Results <p>The primary residential indoor intake routes for lower molecular weight phthalates DnBP, DiBP, and DEP were dermal absorption from air (median 0.12, 0.09, and 0.01 µg/d/kg-bw, respectively) and inhalation (median 0.13, 0.09, and 0.02 µg/d/kg-bw, respectively). For DEHP, a high molecular weight phthalate, dust ingestion was the predominant intake route (median 0.10 µg/d/kg-bw). Residential indoor exposures to DiBP and DnBP respectively contributed 20% and 40% to their total intake in Chinese children, with increasing trend among younger children.</p> Significance <p>The findings identify residential indoor environments as important contributors to overall phthalate exposure in Chinese children, and highlight the significance of residential exposure in evaluating the health effects of phthalates.</p> Impact <p>This paper highlights the contribution of residential indoor environment to phthalate exposure among Chinese children. Residential indoor exposure to DiBP and DnBP contributes substantially to the total intake of these compounds among Chinese children aged 0 to 8 years. Considering the endocrine disrupting effects of these compounds, risk management strategies should consider exposures occurring in indoor environments.</p> Highlights <p><UnorderedList Mark="Bullet"> <ItemContent> <p>Dermal uptake from air is comparable or even larger than inhalation intake for low molecular weight phthalates.</p> </ItemContent> <ItemContent> <p>Exposures in the indoor environment contribute meaningfully to the total phthalate exposure of children.</p> </ItemContent> <ItemContent> <p>One of the first that measured phthalate concentrations in indoor dust and their metabolites in urine for the same Chinese study population.</p> </ItemContent> </UnorderedList></p>