Transdermal Uptake of Diethyl Phthalate and Di( n -butyl) Phthalate Directly from Air: Experimental Verification

Abstract

BackgroundFundamental considerations indicate that, for certain phthalate esters, dermal absorption from air is an uptake pathway that is comparable to or greater than inhalation. Yet this pathway has not been experimentally evaluated and has been largely overlooked when assessing uptake of phthalate esters.ObjectivesThis study investigated transdermal uptake, directly from air, of diethyl phthalate (DEP) and di(n-butyl) phthalate (DnBP) in humans.MethodsIn a series of experiments, six human participants were exposed for 6 hr in a chamber containing deliberately elevated air concentrations of DEP and DnBP. The participants either wore a hood and breathed air with phthalate concentrations substantially below those in the chamber or did not wear a hood and breathed chamber air. All urinations were collected from initiation of exposure until 54 hr later. Metabolites of DEP and DnBP were measured in these samples and extrapolated to parent phthalate intakes, corrected for background and hood air exposures.ResultsFor DEP, the median dermal uptake directly from air was 4.0 μg/(μg/m3 in air) compared with an inhalation intake of 3.8 μg/(μg/m3 in air). For DnBP, the median dermal uptake from air was 3.1 μg/(μg/m3 in air) compared with an inhalation intake of 3.9 μg/(μg/m3 in air).ConclusionsThis study shows that dermal uptake directly from air can be a meaningful exposure pathway for DEP and DnBP. For other semivolatile organic compounds (SVOCs) whose molecular weight and lipid/air partition coefficient are in the appropriate range, direct absorption from air is also anticipated to be significant.CitationWeschler CJ, Bekö G, Koch HM, Salthammer T, Schripp T, Toftum J, Clausen G. 2015. Transdermal uptake of diethyl phthalate and di(n-butyl) phthalate directly from air: experimental verification. Environ Health Perspect 123:928–934; http://dx.doi.org/10.1289/ehp.1409151

Measurements of dermal uptake of nicotine directly from air and clothing

“…On the other hand, wearing clean clothing after exposure is anticipated to significantly reduce absorption due to transfer of nicotine from skin lipids to clothing (Weschler et al, 2015;Morrison et al, 2016). Given such transfer to clothing, the absorbed mass measured in this study is likely within a factor of five of the maximum anticipated absorption (neglecting ionization).…”

“…It corresponds to 413 µg/m 2 of body surface area for participant 1 (67 years old) and 368 µg/m 2 for participant 2 (35 years old) (see section S2 Dermal uptake estimate in Supporting Information for body surface areas). Weschler et al (2015) reported increasing dermal uptake from air of two phthalates with increasing age. It is also noteworthy that participant 1 showered late in the evening on the day of exposure, while in order to increase uptake, participant 2 decided to shower in the evening of the following day.…”

“…During all exposure sessions, the participants breathed clean air through a hood. The breathing arrangement was identical to that described in Weschler et al (2015). All participants were non-smokers and were not exposed to environmental tobacco smoke (ETS) during the days prior to the exposure and during the subsequent urine collection period.…”

Dermal Uptake from Airborne Organics as an Important Route of Human Exposure to E-Waste Combustion Fumes

“…Furthermore, concentrations of urinary metabolites due to dermal uptake from airborne contaminants, such as low molecular weight phthalates and 2-butoxyethanol, were roughly equal to or even greater than those from inhalation exposure. 11,12 Technically, exposure risks through dietary intake, dust ingestion, and inhalation for local residents or workers can be substantially reduced with proper protective measures, such as avoiding consumption of locally contaminated foods, washing hands before eating and wearing respiratory protection mask. Therefore, human dermal uptake from airborne organic contaminants is deemed significant in inducing health risk for residents dwelling in e-waste recycling zones, but has not been examined adequately.…”

“…Upon 6 h human exposure to diethyl phthalate (DEP) and di(n-butyl) phthalate (DnBP) vapor in a chamber, 11 the median dermal and inhalation uptakes of DEP directly from air were 4.0 and 3.8 μg (μg m −3 in air) −1 , respectively, whereas those of DnBP were 3.1 and 3.9 μg (μg m −3 in air) −1 . Furthermore, the concentrations of DEP and DnBP metabolites in human urine samples from both dermal uptake and inhalation increased quickly, with inhalation inducing slightly greater metabolite concentrations than dermal uptake.…”