Influence of indoor environmental parameters on phthalate concentrations in bedrooms

This study investigated the influence of three indoor environmental parameters: ventilation (expressed as air exchange rate, h^-1), temperature, and relative humidity, on phthalate concentration in dust and in estimated airborne. We monitored environmental parameters and collected dust samples in 327 bedrooms in Tianjin, China. Air exchange rates were estimated using occupants-generated CO₂ as a tracer gas. Six common phthalates were analyzed as components of dust: Diethyl Phthalate (DEP), Di-isobutyl Phthalate (DiBP), Di-n-Butyl Phthalate (DnBP), Benzyl Butyl Phthalate (BBzP), Di (2-Ethylhexyl) Phthalate (DEHP) and Di-isononyl Phthalate (DiNP). Phthalate concentrations were compared among environmental parameters categorized as low (below median) and high (above median) using Mann-Whitney U tests. Quantitative associations of phthalate concentrations with environmental parameters were further explored with exponential fittings based on a binning method. We observed a dilution effect of ventilation on low molecular weight phthalates, which was significant for DiBP, whose concentration decreased by 32 % with an increase in air exchange rate (Δ = 1 h^-1). We found a positive association between phthalate concentrations and indoor air temperature; the dust-phase phthalate concentration increased by 11 %, for each 1 °C increase in indoor air temperature. The results indicate that continuous ventilation may be an effective strategy to reduce concentrations of the more volatile phthalates in homes. A higher indoor temperature may lead to increased phthalate concentrations in home environments.