Impact of Clothing on Dermal Exposure to Phthalates: Observations

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Impact of clothing on dermal exposure to phthalates: observations and insights from sampling both skin and clothing Mengyan Gong, Charles J. Weschler, and Yinping Zhang Environ. Sci. Technol., Just Accepted Manuscript • DOI: 10.1021/acs.est.6b00113 • Publication Date (Web): 23 Mar 2016 Downloaded from http://pubs.acs.org on March 23, 2016

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Environmental Science & Technology

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Impact of clothing on dermal exposure to phthalates: observations and insights from sampling both skin and clothing

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Mengyan Gong1,2, Charles J. Weschler1,2,3*, Yinping Zhang1,2*

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Department of Building Science, Tsinghua University, Beijing, China Beijing Key Laboratory of Indoor Air Quality Evaluation and Control, Beijing, China 3 Environmental and Occupational Health Sciences Institute, Rutgers University, Piscataway, New Jersey, USA 2

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Corresponding Authors (Y.P.Z.) Address: Department of Building Science, Tsinghua University, Beijing, China; Fax: +86 10 6277 3461; Phone: +86 10 6277 2518 (O); email: [email protected] (C.J.W.) Environmental and Occupational Health Sciences Institute, Rutgers University, Piscataway, New Jersey, 07722; Fax: +01 732 445-0116; Phone: +01 848 445-2073; email: [email protected]

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ACS Paragon Plus Environment


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Table of Contents Art

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Abstract

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Clothing can either retard or accelerate dermal exposure to phthalates. To investigate the

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impact of clothing on dermal exposure to six phthalates (DMP/DEP/DiBP/DnBP

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/BBzP/DEHP) in real environments, two sets of experiments have been conducted: (1)

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Skin wipes were collected from 11 adults to examine the phthalate levels on both

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bare-skin (hand/forehead) and clothing-covered body locations (arm/back/calf); (2) Five

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adults were asked to wear just-washed jeans for 1 day (1st experiment), 5 days (2nd

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experiment) and 10 days (3rd experiment). Phthalates levels on their legs were measured

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on selected days during the wearing period, and phthalate levels in the jeans were

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measured at the end of each experiment and again after washing. Measured phthalate

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levels on body locations covered by clothing were lower than on uncovered locations, but

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still substantial. Dermal uptake would be underestimated by a factor of two to five if

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absorption through body locations covered by clothing were neglected. Phthalate levels in

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the jeans and on the legs increased with the wearing time. However, the levels in the

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jeans and on the legs were not strongly correlated, indicating that other pathways, e.g,

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contact with bedding or bedclothes, likely contribute to the levels on the legs. The

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efficiency with which laundering washing removed phthalates from the jeans increased

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with decreasing Kow; median values ranged from very low (< 5%) for DEHP to very high

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(~ 75%) for DMP. 3



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Introduction

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Phthalates have been widely used in various industrial and consumer products. Higher

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molecular weight phthalates, such as di(2-ethylhexyl) phthalate (DEHP) and butyl benzyl

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phthalate (BBzP), are mainly used as plasticizers in polyvinyl chloride (PVC) and other

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polymers, while lower molecular weight phthalates, such as dimethyl phthalate (DMP)

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and diethyl phthalate (DEP) are often used as solvents or carriers in personal care

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products, varnishes, and coatings1, 2. Di(n-butyl) phthalate (DnBP) and di(isobutyl)

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phthalate (DiBP) are used in both applications1, 2. The occurrence of phthalate

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metabolites in human urine indicates that people are widely exposed to phthalates2-4.

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Exposure to selected phthalates has been associated with adverse health effects, including

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reproductive and developmental effects5, 6, respiratory problems7, endocrine system

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disruption8, 9, children’s altered neurodevelopment10, 11, obesity12 and the development of

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diabetes13. Phthalate exposure occurs through inhalation, dermal absorption and ingestion.

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Dietary ingestion appears to be the dominant pathway for DEHP14-16, while for DMP,

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DEP, DnBP, DiBP and BBzP, other exposure pathways appear to make significant

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contributions 3, 17-22.

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Compared with ingestion and inhalation exposure, dermal exposure to phthalates has

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received little attention. This may be partially due to the use of inappropriate methods

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(percent absorbed)23, coupled with substantial challenges in assessing dermal absorption24. 4


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To complicate matters, the resulting biologically effective dose to organs may differ for

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different exposure pathways25. Several studies have assessed dermal exposure to

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phthalates via contact with dust/soil and consumer products17, 18, 21, 26-29 and have found

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that for DMP, DEP, and BBzP, dermal contact may contribute significantly to total

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exposure. Recent studies have indicated that dermal absorption from air is also a

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significant pathway for DEP, DiBP and DnBP17,

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understanding regarding the impact of clothing on dermal exposure to phthalates, these

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studies either assumed that dermal absorption on body locations covered by clothing

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could be neglected17, 18, 21, 27-29 or assumed that clothing had no influence on dermal

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exposure17,

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estimated that dermal absorption contributed 3-7% of total phthalate uptake if

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clothing-covered skin was neglected compared to 10-20% of total uptake if somewhat

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attenuated dermal uptake occurred under clothing-covered skin. Hence, arbitrary

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assumptions regarding the presence of phthalates on clothing-covered skin can result in

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large uncertainties in the assessment of dermal exposure to phthalates.

20, 29-33

20, 29-33

. However, given the lack of

. Based on phthalate levels measured in hand wipes, Gong et al.19

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Several experimental studies have examined how clothing may influence dermal

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uptake of chemicals from air or by transfer from treated fabrics. Piotrowski et al.34 found

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that clothing reduced dermal exposure to gas phase nitrobenzene by 20-30%, and had no

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significant influence on dermal exposure to gas phase phenol35. Several studies found

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permethrin uptake resulted from wearing permethrin impregnated clothing36-38. Blum et 5



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al.39 found that metabolites of tris(2,3-dibromopropyl) phosphate increased significantly

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in the urine of children who wore clothing treated with this flame retardant. An in vitro

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dermal absorption study has reported ‘every-day’’ clothing is effective at reducing

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exposure to organophosphates40. Recently, Morrison et al.22 conducted a human exposure

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study to examine the influence of clothing on dermal exposure to DEP and DnBP. They

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found that, compared to bare-skinned subjects, a volunteer wearing clean clothing had 1/3

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the uptake of DEP and 1/5 the uptake of DnBP. In contrast, when the volunteer wore

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clothing that had been previously exposed to these phthalates, his uptake was a factor of 3

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larger for DEP and a factor of 6.5 larger for DnBP. In other words, depending on its

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history, clothing can either retard or accelerate dermal uptake of phthalates. In day-to-day

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life, phthalates can sorb to clothing from the air, deposit onto clothing with airborne

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particles, or be transferred to clothing through contact with contaminated surfaces. These

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processes are influenced by multiple factors, including phthalate concentrations in

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different environmental media, clothing fabric, clothing weave, efficacy of laundering,

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storage location and time, duration of wear, how closely the clothing fits, and human

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behavior. However, we are aware of no studies that have examined the impact of clothing

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on dermal exposure to phthalates in real environment.

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The aims of the present study are to: 1) measure the levels of six commonly used

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phthalates (DMP, DEP, DiBP, DnBP, BBzP and DEHP) at naked and clothing-covered

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body locations, 2) measure phthalate levels in clothing and examine potential correlations 6


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with levels on underlying skin, 3) examine the influence of wearing time on both

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phthalate levels in jeans and on underlying skin, and 4) measure the fraction of phthalates

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removed by laundering. The results are expected to increase basic understanding of the

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impact of clothing on dermal exposure to phthalates, and to also be of use in future

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assessment of exposure via the dermal pathway.

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Methods

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Two sets of experiments were conducted. All subjects were students in the

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Department of Building Science, Tsinghua University. Fudan University’s ethical review

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board approved the study protocol prior to collection of the skin wipe samples

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(IRB00002408 & FWA00002399) and all the subjects gave their informed consent before

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the experiment.

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Phthalate levels on different body locations

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In our previous study41, phthalate levels in skin wipes were measured on bare skin

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locations (hand and forearm) for 10 male and 10 female adults; there were no significant

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differences between males and females. For the present study, 11 male adults were

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recruited. As in the previous study, all participants were asked not to use any skincare

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products from rising in the morning until sampling in the afternoon, not to wash the skin

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wipe locations at least four hours prior to sampling, and to try to stay in the department

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building until sampling. The wipe procedure was similar to the process described in a US 7



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Environment Protection Agency (EPA) study42 and our previous studies19, 41. Briefly, a

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pre-cleaned gauze pad (8 cm × 8 cm) was wetted with 5 ml isopropyl alcohol, and then

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used to wipe (four successive wipes) the targeted body location. As shown in Figure 1,

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skin wipes in the present study were taken from both bare-skin (forehead, right & left

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back-of-hand, and right & left palm) and clothing-covered skin (right & left forearm,

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right & left calf, and back). The sampled area of the hand was estimated by tracing its

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outline on cross-hatched graph paper, while for other body locations a fixed area was

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sampled by affixing flexible templates to the area sampled. The areas of the template

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openings were 266 cm2 for the forearms, legs, and back, and 70 cm2 for the forehead.

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Each sample was spiked with isotopically labeled recovery standards (diethyl

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phthalate-d4 (DEP-d4), di(iso-butyl) phthalate-d4 (DiBP-d4), and di(2-ethylhexyl)

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phthalate-d4 (DEHP-d4)) immediately after sampling. The skin wipe samples were stored

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in a 60 mL pre-cleaned brown glass jar at -36oC until analysis. A field blank wipe was

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prepared for each adult by soaking a pre-cleaned gauze pad in isopropyl alcohol and

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placing it directly into a brown glass jar. Skin wipe samples were analysed for six

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phthalates by GC/EI-MS, using methods described previously19. The samples in the

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previous study were collected during the ‘summer’ (June, 2013 to July, 2013), while the

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samples in present study were collected during the ‘winter’ (November, 2014). Figure 1. Sampled body locations in summer (previous study19) and winter (present

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study). ‘n’ represents the number of subjects. 132 133

Phthalate levels in clothing and on skin surfaces Since jeans are commonly worn clothing and people tend to wear them for a long

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time between washes, they were the target clothing in these experiments. Levi 501™ 100%

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cotton jeans (about 560g/pair) were purchased from an online retail store in China. The

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jeans were washed together using a normal washing machine with cold tap water and

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liquid washing detergent for about 40 min and dried naturally by hanging them on a

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balcony. After drying about 2 cm ⅹ 2 cm pieces were cut from the washed jeans on the

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front of the right side to determine the initial levels of phthalates in jeans before wearing,

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and then the jeans were immediately wrapped with aluminium foil and stored at room

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temperature until distributing them to subjects (within 3 hours). Five adults were asked to

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wear the freshly washed jeans for 1 day (1st experiment), different freshly washed jeans

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for 5 days (2nd experiment) and four of them wore still different freshly washed jeans for

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10 days (3rd experiment). Skin wipes from both their right calf and right thigh were

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collected around 5 pm on selected days during the wearing period. At the end of each

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experiment, one approximately 4 cm ⅹ 4 cm piece was cut from the front of the right

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thigh and another was cut from the front of the right calf for each jean to determine the

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amount of phthalates sorbed during the wearing period. The sampling design and

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sampling times are illustrated in Figure 2. In addition, to examine the influence of

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laundering on the phthalate levels in jeans, the jeans were washed immediately after the

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conclusion of each experiment and dried naturally on a balcony for 15 hours; 4 cm ⅹ 4

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cm pieces were then cut from the washed and dried jeans on the front of the right side.

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Each piece was weighed and spiked with recovery standards (DEP-d4, DiBP-d4, and

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DEHP-d4) immediately after sampling. The jeans samples were also stored in 60 mL

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pre-cleaned brown glass jars at -36oC until analysis. Corresponding blank samples were

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prepared by preparing empty brown jars. The skin wipe and jeans samples were analysed

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using methods similar to those described in our previous study41. Figure 2. Illustration of the experimental design. Legend at bottom.

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Data analysis

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The average recoveries for DEP-d4, DiBP-d4 and DEHP-d4 of blanks and samples were

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68%-103% and 74%-112% respectively. Samples with recovery rates less than 50% or

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larger than 130% were excluded from further statistical analysis; this was less than 5% of

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the samples. Details on the blanks are presented in the Table S1. Both the reported levels

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in skin wipes and jeans have been adjusted by subtracting the average mass in the blank

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and then dividing by the extraction recovery rates. Method detection limits (MDLs) were

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calculated as three times the standard deviation of the field blanks and, when phthalates

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were not detected in the field blanks, the laboratory instrument detection limit was used

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as the MDL (i.e., signal-to-noise ratio of 3). All non-detected values were substituted with

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one-half the MDL for statistical analysis. Statistical analyses were performed using the

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SPSS statistics software package, V. 22.0, with statistical significance defined at the p =

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0.05 level.

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Results and Discussion

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Phthalate levels at bare and clothed body locations

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Detailed information on phthalate levels on different body locations for winter samples

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(present study) and summer samples (previous study; ref 41) are presented in Tables S2-S3

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in the SI. DMP, DEP and BBzP are not included in Tables S2-S3 because of their low

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detection frequency ( 0.05) between

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the levels of DEHP on left and right forearms, left and right back-of-hands, and left and

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right palms for either season. The levels between the left and right calf are also not

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significantly different (only sampled in winter). In addition, the levels on the left and

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right sides of different body locations (forearm, back of hand, palm, and calf) are

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significantly correlated for all three compounds (see Tables S4-S6 in SI), which implies

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that phthalate levels on the left and right side of the body were a consequence of similar

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exposure pathways. Hence, subsequent comparisons of levels on different body locations

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have been made based on the log-transformed average concentrations for the left and

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right side of the body. The Paired Samples t-test indicates that the phthalate levels

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significantly differed at different body locations, with palm > back-of-hand > forearm >

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forehead for DEHP in summer and palm ≈ back-of-hand > forehead > forearm ≈

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back > calf for DEHP in winter; palm > back-of-hand > forearm for DiBP and DnBP in

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summer, and palm ≈ back-of-hand > forearm > back ≈ calf for DiBP and DnBP in

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winter ( ‘>’ is used when p < 0.05, ‘≈’ is used when p > 0.05).

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In both summer and winter, the levels of all three phthalates on the back-of-hand and

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palm are significantly correlated (see Tables S4-S6 in SI). However, phthalates levels on

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the palm are about 2 times higher than on the back-of-hand in summer, while phthalate 12


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levels on back-of-hand and palm are not significantly different in winter. Further study is

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needed to properly interpret these observations. In summer, phthalate levels on the

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back-of-hand and forearm are correlated, while such correlations are not observed in

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winter. This may reflect more statistical power in summer (n = 20) than in winter (n = 11).

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Alternately, it may reflect the fact that the forearm was clothed in winter but not in

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summer. Hence, during the summer direct contact transfer or absorption from air occurs

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for both the back-of-hand and forearm, while in winter this is not the case. In both

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summer and winter, phthalate levels on the palm and forearm are not correlated, possibly

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due to differences in the relative importance of contact transfer to the palm versus the

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forearm. Somewhat surprisingly, given the differences in sample size, DEHP levels on

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the forehead are correlated with levels on the back of either hand as well as on the left

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palm in winter but not in summer. Figure 3. Box-whisker plots for phthalate levels, determined by skinwipes, on different body locations. l/rforearm, l/rcalf, l/rbhand, and l/rpalm represents left/right forearm, left/right calf, left/right back-of-hand, and left/right palm respectively.

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Table 1 presents ratios of phthalate levels at different body locations to that on the

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hand (palm and back-of-hand averaged). For a given body location, the ratios for DiBP

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and DnBP are similar, and are higher than the ratios for DEHP. This latter observation

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may reflect the fact that both direct contact transfer and indirect transfer from air

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contribute to DiBP and DnBP on the calf, forearm, back and forehead; in contrast, there

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are kinetic constraints for DEHP transfer from air to skin30, 44 and contact transfer is

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likely the dominant contributor to DEHP at these locations. For those locations covered

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by clothing (calf, forearm and back), this may also be partially due to slower effective

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diffusion of DEHP through clothing45.

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Dermal absorption of phthalates has been estimated based on measured skin wipe

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levels and the ratios shown in Table 1, with several assumptions (see detailed information

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in section S1 of the SI). Figure S1 contrasts whole body dermal absorption (clothed and

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bare skin) with dermal absorption only through bare skin. This comparison indicates that

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dermal absorption of DiBP, DnBP and DEHP will be underestimated by a factor of two to

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three in the summer and two to five in the winter if absorptions through body locations

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covered by clothing are neglected. The underestimation is larger for DiBP and DnBP than

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DEHP, reflecting the differences among the ratios shown in Table 1. These results

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indicate the importance of including body locations covered by clothing when making

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assessments of dermal uptake of phthalates.

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Phthalate levels in clothing and on legs

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The levels of DiBP, DnBP and DEHP in both the thigh and calf area of the jeans are

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shown in Figure 4 (see Table S7 for actual values for each subject), while the levels of

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DMP and DEP are shown in Figure S2. DEHP was the most abundant phthalate with

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levels much larger than those for DnBP and DiBP, which in turn were larger than those 14


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for DEP and DMP. Phthalate levels in the jeans increased with wearing time. The

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magnitude of this increase was larger for DEHP, DnBP and DiBP, the phthalates with

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lower vapor pressures (median values of ratios between the levels in jeans at the end of

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the 3rd and 1st experiment for DEHP, DnBP, DiBP, DEP and DMP were: thigh – 18, 4, 5, 2

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and 2; calf – 3, 2, 2, 2 and 2). The capacity of the jeans for phthalates increases as the

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partition coefficient between clothing and air increases. This partition coefficient

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increases with decreasing vapor pressure and increasing Koa45. The more volatile

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phthalates (DMP, DEP and perhaps the butyl isomers) may have approached the capacity

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of the jeans, while the jeans can adsorb more of the less volatile phthalates, such as DEHP.

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The levels of DMP and DEP on thigh and calf area are not significantly different.. The

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levels of DEHP, DnBP and DiBP on the thigh area tend to be higher than those on the calf

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area of the jeans, possibly due to greater hand-to-jean contact for the thigh area. There

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former may also be more skin surface lipids on the thigh area, which contacts the

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underlying skin more than the calf area; skin oil has been shown to increase the

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partitioning between clothing and air for lipophilic SVOCs46. This should be tested in

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future studies. The levels on the thighs of the jeans correlate with levels on the calf of the

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jeans, as shown in Tables S8-S10 of SI, suggesting that similar pathways contribute to the

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levels at both sites. Figure 4 Phthalate levels in jeans (µg/g) and skin wipes (µg/m2 of skin) at of the

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conclusion of each experiment. The symbols represent results for individual subjects (S1-S5). ‘JC/JT’ represents ‘phthalate levels in the calf/thigh area of the jeans’; ‘SC/ST’ represents ‘phthalate levels on the calf/thigh as measured with skin wipes’. 261

Using values reported in the literature45, 47for partition coefficients between cotton

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clothing and different gas phase phthalates, coupled with reported gas phase

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concentrations in Chinese offices and homes28, we have estimated the amount of DnBP,

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DiBP and DEHP that one would expect to find on clothing equilibrated with its

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environment (details of these calculations are presented in section S2 and Table S11 of the

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SI). The resulting estimates (0.9 µg/g for DiBP, 2.0 µg/g for DnBP, and 81 µg/g for DEHP)

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are within a factor of ten of median levels we have measured in this study for jeans that

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had been worn until the 10th day of the 3rd experiment (for DiBP, 8.9 µg/g on calf and

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11.2 µg/g on thigh; for DnBP 8.8 µg/g on calf and 9.6µg/g on thigh, and for DEHP 61

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µg/g on calf and 275 µg/g on thigh). We judge the order-of-magnitude agreement between

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estimated and measured values to be reasonable, given the variation of phthalate

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concentrations Chinese indoor air 48 coupled with uncertainty in the partition coefficients

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between jeans and air45, 47. The estimated time to accumulate equilibrium amounts of

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DiBP, DnBP and DEHP in the jeans via solely gas-phase transfer is 15 days, 60 days, and

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2100 days, respectively (Table S11). That is, transfer directly from the gas phase alone

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cannot explain the phthalates levels measured in the jeans. Another, much faster

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mechanism for transferring phthalates to the jeans is contact transfer from contaminated

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surfaces, which can occur as quickly as the time required for jeans to rub contaminants

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from a surface. Since exposed indoor surfaces tend to be cleaned less frequently than

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jeans are washed, there is more time for indoor surfaces to sorb phthalates from the gas

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phase between cleanings – there is more time for the thermodynamic activity of

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phthalates in surface films to approach those in air (see Figure 2 in ref 30). Furthermore,

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the surfaces of phthalate plasticized materials (e.g., synthetic leather, vinyl upholstery,

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PVC furniture), can have phthalate activities that exceed gas phase activities.

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The levels of DiBP, DnBP and DEHP obtained from skin wipes of the thigh and

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calf of each subject at the end of experiments 1-3 are also shown in Figure 4, while the

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levels for all samples are shown in Figure S3. In contrast to the levels in jeans, the

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phthalate levels on the skin of the thigh and calf were not significantly different. DEHP

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levels on the skin increased from 1 day of wear (1st exp) to 5 days of wear (2nd exp) to 10

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days of wear (3rd exp); DnBP on the skin increased from 1 day to 5 days of wear, and

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then only slightly from 5 to 10 days of wear; DiBP on skin only showed an increase from

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1 to 5 days of wear. The phthalate levels on skin wipes from the thigh correlate with

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levels on the skin wipes from the calf, as shown in Tables S8-S10 of the SI. Phthalate

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levels on the thigh or calf areas of the jeans do not correlate with levels from the

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corresponding skin wipes of the thigh or calf (Tables S8-S10 of SI), except for DiBP

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levels in “jeans-calf” with “skin-calf”, and both DiBP and DEHP levels in “jeans-calf” 17



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with “skin-thigh”. Although the subjects wore the jeans for approximately 12h/day (based

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on daily activity logs), other sources such as personal care products, bedclothes and

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bedding may contribute significantly to levels on the legs. In the present experiment, the

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subjects slept about 8h/day (activity logs). Phthalate levels in the microenvironment of a

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bed have been reported to be higher than concentrations in the room air49. In addition, the

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subjects showered almost every day (sometime after the sampling), which may impact

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phthalate levels on skin.

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Efficiency with which laundering removes phthalates in jeans

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For each of the five phthalates, the fraction removed from the jeans by laundering

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(including both the washing and drying cycles) is shown in Figure S4. The levels of DMP,

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DEP, DiBP and DnBP in the jeans decreased as a consequence of laundering, while

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DEHP levels in some jeans actually increased. The jeans may have contacted DEHP

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sources during washing or drying (e.g., detergent from plastic container, plastic surfaces

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in the washing machine, plastic drying racks, the air itself). Figure 5 illustrates that the

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efficiency with which the entire laundering process removes phthalates from the jeans

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increases as the Kow of a given phthalate decreases. Presumably, this correlation is driven

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by the washing cycle of the laundering process. The median values for removal efficiency

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range from very low (< 5%) for DEHP to very high (~ 75%) for DMP, consistent with the

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fact that phthalates with lower Kow will have larger solubilities in water. The adjusted R2

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for the weighted linear regression (using standard error of removal efficiency as the 18


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weighing factor) between log Kow and removal efficiency is 0.70. With the exception of

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DEHP, the removal efficiencies are not significantly different between the thigh and calf

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regions of the jeans. Removal efficiency is influenced by many factors, including the

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nature of the fabric, the cleaning method (e.g, temperature of water, washing time), the

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loading of the contaminant and the drying method (e.g. drying naturally or machine

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drying using hot-air). However, our preliminarily results indicate that for phthalates with

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large Kow’s other measures besides machine washing with typical laundry detergents are

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needed to reduce levels in the jeans and consequent dermal exposure. Figure 5 Correlation between Log Kow of phthalate and removal efficiency (mean±SD) due to laundering. (Values of Log Kow are taken from Table 4 in Cousins & Mackay50; these are 1.61, 2.54, 2.27, 2.26, 7.73 for DMP, DEP, DiBP, DnBP and DEHP, respectively.)

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Limitations and future studies

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In this first attempt to measure phthalate levels on body locations covered by

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clothing, we found that the levels on those locations are substantial and that dermal

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uptake from clothing covered skin cannot be neglected when considering total dermal

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uptake of various phthalates. However, this study has several limitations, and much

330

remains to be done to more completely understand phthalate levels in wipes collected

331

from different skin surfaces – both covered and bare.

19



332

The number of participants in both sets of experiments was relatively small, which

333

limits the statistical power for detecting differences or associations and the

334

generalizability of the present study to other populations. The relative uniformity of the

335

subjects likely helped to reduce extraneous noise and potential confounding. Nonetheless,

336

we acknowledge that p-values depend on both the magnitude of the association and the

337

sample size, and, with larger sample sizes, some of the associations may differ from those

338

reported in this paper. Furthermore, we have conducted a number of statistical tests

339

comparing the phthalate levels on different body locations, which may result in a multiple

340

comparisons problem.

341

Although phthalate levels on forehead, forearm, back, calf and hands have been

342

measured, phthalate levels on more locations, e.g. chest, thigh and feet, would increase

343

the understanding of whole body dermal exposure. It would also be valuable to measure

344

phthalate levels at the same location, both clothed and bare, under otherwise identical

345

conditions. Furthermore, the present study used one type of clothing (jeans), one type of

346

fabric (cotton) and the subjects were exposed in one campus setting; each of these

347

categories should be expanded.

348

Airborne phthalate concentrations were not measured in the present study, although

349

such measurements would have been especially valuable in the jean experiments. Future

350

studies in which phthalate levels are measured in the air (including personal air), on

351

frequently contacted indoor surfaces, in clothing and on skin would improve 20


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352

understanding of the sources of phthalates in jeans and on skin. Measurement of key

353

parameters, e.g. diffusion coefficients through clothing/bedding, partition coefficients

354

between clothing/bedding and air, particle deposition rates onto clothing/bedding, and

355

contact transfer rates from contaminated surfaces to both skin and clothing, would be

356

valuable. Mass transfer models are needed to predict phthalate transfer from

357

clothing/bedding to skin via direct contact or transport across air gaps between skin and

358

fabric51.

359

The impact of clothing on transdermal permeability52 warrants further study. More

360

field studies measuring the amounts of various phthalates sorbed to clothing/bedding that

361

has been stored in drawers, on shelves or hung in closets would be informative, as would

362

measurements of phthalates in clothing at the time the clothes are freshly washed and

363

after periods (days, weeks, months) of storage. Chamber studies, which compare

364

phthalate levels on the same body location with and without clothing, would allow for the

365

investigation of influencing variables under defined and controlled conditions. Human

366

behavior is also anticipated to play an important role in determining levels on skin

367

surfaces (e.g., frequency with which clothing is worn and washed, frequency with which

368

bedding is washed and changed, frequency of bathing, amount of skin covered by

369

clothing, type of clothing worn). Finally, measurements of removal efficiencies for

370

laundering and showering will aid in developing strategies to reduce levels of various

371

manmade chemicals in skin surface lipids. 21



372

Acknowledgements

373

We thank the subjects for participating in this study, and Dr. Zhuohui Zhao for

374

presenting the study protocol to Fudan University’s ethical review board for review and

375

approval. Financial support was provided by the Natural Science Foundation of China

376

(51136002 and 51521005), Tsinghua University’s Initiative for Scientific Research

377

(20121088010) and the Special Fund of the Key Laboratory for Eco Planning & Green

378

Buildings, Ministry of Education (2013B-2).

379

Supporting Information

380

The supporting information is available free of charge via the internet at http://

381

pubs.acs.org. This information includes additional details on the phthalate levels in blank

382

samples (Table S1), phthalate levels on different body locations in summer and winter

383

(Table S2-S3), Spearman correlation coefficients between phthalate levels on different

384

body locations (Table S4-S6), dermal uptake estimation (Section S1 and Figure S1),

385

phthalate levels in jeans samples of each subject (Table S7 and Figure S2), phthalate

386

levels in skin wipes of each subject (Figure S3), Spearman correlation coefficients

387

between phthalate levels in jeans and skin (Table S8-S10), estimation of amount absorbed

388

at equilibrium and time to equilibrium (Section S2 and Table S11), removal efficiency of

389

phthalates from jeans through laundering (Figure S4).

22


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30


and Day E. W., Eds.; CRC

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Figure Captions

549

Figure 1. Sampled body locations in summer (previous study19) and winter (present

550

study). ‘n’ represents the number of subjects.

551

Figure 2. Illustration of the experimental design. Legend at bottom.

552

Figure 3. Box-whisker plots for phthalate levels, determined by skinwipes, on different

553

body locations. l/rforearm, l/rcalf, l/rbhand, and l/rpalm represents left/right forearm,

554

left/right calf, left/right back-of-hand, and left/right palm respectively.

555

Figure 4 Phthalate levels in jeans (µg/g) and skin wipes (µg/m2 of skin) at of the

556

conclusion of each experiment. The symbols represent results for individual subjects

557

(S1-S5). ‘JC/JT’ represents ‘phthalate levels in the calf/thigh area of the jeans’; ‘SC/ST’

558

represents ‘phthalate levels on the calf/thigh as measured with skin wipes’.

559

Figure 5 Correlation between Log Kow of phthalate and removal efficiency (mean±SD)

560

due to laundering. (Values of Log Kow are taken from Table 4 in Cousins & Mackay50;

561

these are 1.61, 2.54, 2.27, 2.26, 7.73 for DMP, DEP, DiBP, DnBP and DEHP,

562

respectively.)

31



563

Figure 1

564

32


Page 32 of 43

Page 33 of 43

565


Figure 2

566

33



567

Figure 3

568

34


Page 34 of 43

Page 35 of 43

569


Figure 4

570

35



571

Figure 5

572

36


Page 36 of 43

Page 37 of 43

573 574 575


Table 1. Geometric means (95% CIa) for the ratios of phthalate levels at different body locations to that on the hand

DEHP

DiBP

DnBP

calf/hand

forearm/hand

back/hand

forehead/hand

Summer

b

0.32(0.22-0.45)

b

0.23(0.15-0.35)

Winter

0.17(0.10-0.29)

0.27(0.17-0.43)

0.24(0.15-0.39)

0.49(0.31-0.75)

Summer

b

0.44(0.27-0.74)

b

c

Winter

0.23(0.11-0.47)

0.48(0.27-0.86)

0.61(0.35-1.06)

c

Summer

b

0.38(0.23-0.61)

b

c

Winter

0.27(0.18-0.42)

0.48(0.34-0.69)

0.57(0.42-0.78)

c

Ratios were calculated for each subject and then the geometric means were calculated. a: The 95% confidence interval was back-calculated from the log-transformed data. b: The phthalate levels on the calf were not measured in summer. c: Ratios that include DiBP and DnBP on the forehead are not reported due to their low detection frequency (< 30%) at this location.

576

37



TOC Art 84x47mm (300 x 300 DPI)


Page 38 of 43

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Figure 1. Sampled body locations in summer (previous study19) and winter (present study). ‘n’ represents the number of subjects. 68x47mm (300 x 300 DPI)



Figure 2. Illustration of the experimental design. Legend at bottom. 84x47mm (300 x 300 DPI)


Page 40 of 43

Page 41 of 43


Figure 3. Box-whisker plots for phthalate levels, determined by skinwipes, on different body locations. l/rforearm, l/rcalf, l/rbhand, and l/rpalm represents left/right forearm, left/right calf, left/right back-of-hand, and left/right palm respectively. 84x170mm (300 x 300 DPI)



Figure 4 Phthalate levels in jeans (µg/g) and skin wipes (µg/m2 of skin) at of the conclusion of each experiment. The symbols represent results for individual subjects (S1-S5). ‘JC/JT’ represents ‘phthalate levels in the calf/thigh area of the jeans’; ‘SC/ST’ represents ‘phthalate levels on the calf/thigh as measured with skin wipes’. 84x194mm (300 x 300 DPI)


Page 42 of 43

Page 43 of 43


Figure 5 Correlation between Log Kow of phthalate and removal efficiency (mean±SD) due to laundering. (Values of Log Kow are taken from Table 4 in Cousins & Mackay50; these are 1.61, 2.54, 2.27, 2.26, 7.73 for DMP, DEP, DiBP, DnBP and DEHP, respectively.) 84x69mm (300 x 300 DPI)


Impact of Clothing on Dermal Exposure to Phthalates: Observations

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