Objective To investigate the whole process of indoor phthalate exposure in households, including source identification in home environment, exposure levels, human intake, and its association with children's asthma and allergy.

Methods A questionnaire survey was conducted among children aged 0-8 years in Tianjin City and Cangzhou City, Hebei Province, China, and information on demographic features, home environment, and allergic diseases or symptoms was collected. Household indoor environment inspections were performed, and bedroom dust and urine samples were collected from all children. Gas chromatography-mass spectrometry and liquid chromatography-mass spectrometry were used to measure the concentrations of six phthalates in indoor dust (diethyl phthalateDEP, di-isobutyl phthalate DiBP, di-n-butyl phthalate DnBP, benzyl butyl phthalate BBzP, di (2-ethylhexyl) phthalate DEHP, and di- isononyl phthalate DiNP), as well as the concentrations of urinary phthalate metabolites (mono-ethyl phthalate MEP, mono-isobutyl phthalate MiBP, mono-n-butyl phthalate MnBP, mono-benzyl phthalate MBzP, mono-2-ethylhexyl phthalate MEHP, mono-(2-ethyl-5-carboxylpentyl) phthalate MECPP, mono-(2-ethyl-5-hydroxyhexyl) phthalate MEHHP, and mono-(2-ethyl-5-oxohexyl) phthalate MEOHP, mono-isononyl phthalate MiNP). The regression models were used to identify the sources of indoor phthalates and to assess their health effect.

Results A total of 398 children aged 0-8 years were enrolled in the study. DEHP, DnBP, and DiBP were identified as the main indoor phthalates, with a median concentration of 126.9, 40.8, and 16.3 μg/g, respectively, in dust, and their corresponding metabolites in the urine of children were MECPP, MiBP, and MnBP, with a median concentration of 43.9, 31.7, and 25.8 μg/L, respectively. The linear regression analysis indicated that modern building materials (e.g., laminated wood flooring and PVC-framed windows) and cosmetics might be the indoor sources of household DiBP, DnBP, and DEHP exposure. The indoor intake of DiBP and DnBP accounted for 20% and 40%, respectively, of their own total intake. Exposure to indoor DiBP was significantly associated with asthma in children (aOR=2.26, 95%CI: 1.02-5.03).

Conclusion Modern building materials and cosmetics in households may release phthalates and thus increase the risk of allergic diseases or symptoms in children.