Phthalates on indoor surfaces and associated exposure via surface touch behavior: Observation in university dormitories and its implications

Abstract

Phthalates are typical emerging indoor pollutants and ubiquitously distributed in the indoor air, settled dust and on surfaces. Phthalates have the potential to be transported by human hands through surface touch behaviors. Although the contribution of subsequent exposure via hand-to-mouth contact in real indoor environments has not been thoroughly characterized, it is an important factor to consider. In this study, six commonly-used phthalates (dimethyl phthalate (DMP), diethyl phthalate (DEP), di-n-butyl phthalate (DnBP), butyl benzyl phthalate (BBzP), di-2-ethylhexyl phthalate (DEHP), and di-n-octyl phthalate (DOP)) were measured in surface wipes, air and dust samples collected from university dormitories. Video-cameras were used to monitor occupants’ real surface touch behaviors. Primary surfaces being touched included desks, cellphones, keyboards and computer mice, with averaged touch frequencies ranging from 10.4 h−1 to 25.4 h−1. Phthalate levels on computer mice were the highest, with DEHP being present as the most predominant compound (mean: 2621 μg/m2). Exposures via inhalation, dust ingestion, dermal absorption and hand-to-mouth contact were further estimated using Monte-Carlo simulations. The results suggest that the exposure resulting from surface touching and subsequent hand-mouthing could contribute 35 %–55 % to total exposure for targeted phthalates, which were generally higher than intakes via dust ingestion. This study provides a better understanding of phthalate transfer through surface touch behavior, and highlights the significance of hand-to-mouth contact exposure in indoor environments.