Health risk assessment of exposures to a high molecular weight plasticizer present in automobile interiors

This study provides an exposure and risk assessment of diundecyl phthalate (DUP), a high molecular weight phthalate plasticizer present in automobile interiors. Total daily intake of DUP was calculated from DUP measured in wipe samples from vehicle seats from six automobiles. Four of the vehicles exhibited atypical visible surface residue on the seats. Two vehicles with no visible surface residue were sampled as a comparison. DUP was the predominant organic compound identified in each of the wipes from all seats. A risk assessment of DUP via oral, dermal, and inhalation routes resulting from contact with automobile seats was conducted. The mean, standard deviation, and maximum DUP concentrations on the seats with visible surface residue were 6983 ± 7823 μg/100 cm² and 38300 μg/100 cm², respectively. The mean and 95th percentile of the mean for daily cumulative dose of DUP for all exposure routes for the seats with no visible surface residue ranged from 7 × 10^-4 to 4 × 10^-3 mg/kg-day and from 8 × 10^-4 to 5 × 10^-3 mg/kg-day, respectively. For seats with visible surface residue, cumulative doses ranged from 2 × 10^-3 to 2 × 10^-2 mg/kg-day and from 4 × 10^-3 to 2 × 10^-2 mg/kg-day, respectively. The estimated daily intake (contact or absorbed dose) of DUP from automobile seats were far lower than the NOAELs reported in and derived from animal studies, and are well below the reported Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH) Derived No Effect Levels (DNELs) for the general population. Based on this analysis, using virtually any benchmark for evaluating safety, exposure to DUP via automobile seat covers did not pose a measureable increased health-risk in any population under any reasonably plausible exposure scenario.