In vitro dermal absorption of di(2-ethylhexyl) adipate (DEHA) in a roll-on deodorant using human skin.

In vitro dermal absorption experiments were conducted using a roll-on deodorant that contains 1.56% di(2-ethylhexyl) adipate (DEHA), a plasticizer widely used in consumer products. Human skin specimens were fitted in Bronaugh flow-through Teflon diffusion cells. The diffusion cells were maintained at 32 °C to reflect the skin temperature. Two amounts (low dose: 5 mg of the product; high dose: 100 mg) were applied, in triplicate, each on four different human skins. DEHA was determined in the receiver solution at 6-h intervals, using headspace solid-phase microextraction gas chromatography-mass spectrometry (GC-MS). After 24 h, the experiment was terminated and masses of DEHA in the skin depot, skin wash, and upper and lower chambers of the diffusion cell were determined. A significant portion of applied DEHA, 28% in the low amount application and 34% in the high one, was found in the skin depot. In comparison, only 0.04% and 0.002% of applied DEHA were found in the receiver solutions for the low and high doses, respectively. Under our experimental conditions, an apparent steady-state flux of low DEHA mass penetrating from skin into the receiver solution was observed with a penetration rate of 2.2 ng/cm(2)/h for both the low and high doses. The average mass recovery was 81% for the low dose application and 56% for the high dose.

Phthalates in cosmetic and personal care products: concentrations and possible dermal exposure.

Phthalates are multifunctional chemicals that are used in a variety of consumer products including cosmetic and personal care products. This study aims at determining phthalate levels in cosmetic and personal care products obtained from the Canadian market. Overall 252 products including 98 baby care products were collected at retail stores in several provinces across Canada in year 2007. These products included fragrances, hair care products (hair sprays, mousses, and gels), deodorants (including antiperspirants), nail polishes, lotions (body lotions and body creams), skin cleansers, and baby products (oils, lotions, shampoos and diaper creams). Samples were extracted with different organic solvents, depending on the types of the products, followed by gas chromatography-mass spectrometry (GC-MS) analysis. Of the 18 investigated phthalates, diethyl phthalate (DEP), dimethyl phthalate (DMP), diisobutyl phthalate (DiBP), di-n-butyl phthalate (DnBP) and di(2-ethylhexyl) phthalate (DEHP) were detected. The detection frequencies were in the following order: DEP (103 out of 252 products)>DnBP (15/252)>DiBP (9/252)>DEHP (8/252)>DMP (1/252). DEP was detected in almost all types of surveyed products with the highest levels (25,542 µg/g, equal to 2.6%) found in fragrances. DnBP was largely present in nail polish products with the highest concentration of 24,304 µg/g (2.4%). DnBP was also found in other products such as hair sprays, hair mousses, skin cleansers and baby shampoos at much lower concentrations (36 µg/g and less). Levels of other detected phthalates were generally low in the products. Based on these values, daily dermal exposure dosage to five phthalates was estimated for three age groups, female adults (60 kg); toddlers (0.5-4 years) and infants (0-6 months), through the use of cosmetic and personal care products. The exposure estimation, however, was based on existing products use pattern data, instead of probabilistic model based population use distribution. For female adults, the maximal daily exposure of 78 µg/kg bw/d was determined for DEP. The maximal daily exposure was much lower for the other four phthalates (DEHP, 0.82 µg/kg bw/d; DnBP, 0.36 µg/kg bw/d; and DMP, 0.03 µg/kg bw/d). The exposure for DiBP was not calculated due to its very low levels (<10 µg/g) in products. Toddlers and infants in this case had a maximal daily exposure to DEP of 20 and 42 µg/kg bw/d, respectively.

A novel "by difference" method for assessing dermal absorption of polycyclic aromatic hydrocarbons from soil at federal contaminated sites.

A highly precautionary cost-effective method for estimating dermal absorption using data from 24-h skin soap washes from in vitro dermal absorption tests in Bronaugh flow-through diffusion cells with human skin is reported. Skin was dosed with 16 U.S. Environmental Protection (EPA) priority polycyclic aromatic hydrocarbons (PAH) applied in mixture each at 2 µg/ml (ppm) in acetone without soil. Concurrent tests were conducted with an unspiked aqueous suspension of PAH-contaminated soil obtained from a Canadian federal contaminated site. Percentage dermal absorption was estimated "by difference" from the applied dose and that detected by high-performance liquid chromatography (HPLC) in 24-h skin soap washes. The dermal absorption for 11 PAH ranged from 71 to 88.3% without and with soil, respectively. Lower absorption was found for 5 PAH in soil, in the range of 26.4 to 60.8%. Data could not be corrected for evaporative loss due to inconsistent data from Tenax adsorbent. Corroboratory gas chromatography/mass spectroscopy (GC/MS) tests are needed. Previously published in vitro data from the authors' laboratory supported use of the "by difference" method.

Contaminated soils (III): in vitro dermal absorption of ethylene glycol and nonylphenol in human skin.

Dermal absorption of contaminants from soils at federal contaminated sites in Canada was investigated using one hydrophile, (14)C-ethylene glycol (EG), and one lipophile, (14)C-nonylphenol (NP). In vitro dermal absorption of EG and NP was examined in dermatomed (0.4-0.5 mm) human skin using Bronaugh Teflon flow-through cells with Hanks HEPES buffered (pH 7.4) receiver solution with 4% bovine serum albumin (BSA). Tests were conducted under occlusive conditions with and without a commercial gardening soil spiked with EG or NP applied to skin at a soil load of 5 mg/cm(2). With percent absorption in skin depot included, a total of 9.9 + or - 6.28% (n = 6) and 34.8 + or - 8.47% (n = 6) absorption of EG with and without soil, respectively, and 20.6 + or - 5.56% (n = 7) and 41.1 + or - 6.46% (n = 7) of NP, with and without soil, respectively, were obtained. For tests without soil a reverse pattern was observed with significantly lower percent absorption into the receiver than depot with the lipophile NP, but significantly higher percent absorption in receiver versus depot for the hydrophile EG. This pattern was different in tests with soil, and caution needs to be exercised when extrapolating data from in vitro tests conducted without soil in human health risk assessments at contaminated sites.

Effect of cold storage on in vitro human skin absorption of six 14C-radiolabeled environmental contaminants: benzo[a]pyrene, ethylene glycol, methyl parathion, naphthalene, nonyl phenol, and toluene.

Dermal absorption of human breast skin obtained fresh from a local hospital was tested before and after freezer storage at -19 degrees C for 30 or 60 d. Dermatomed skin (0.4-0.5 mm) was tested in vitro using the Bronaugh flow-through diffusion cells perfused at 1.5 ml/h with receiver solution (Hanks HEPES buffered basal saline containing 4% bovine serum albumin [BSA]). Six 14C-radiolabeled chemicals ranging in lipophilicity were tested, including benzo[a]pyrene (BaP), ethylene glycol (EG), methyl parathion (MP), naphthalene (Nap), nonyl phenol (NP), and toluene (Tol). There was significantly lower percent dermal absorption into the receiver solution for two of the six chemicals (BaP and Tol) with the skin depot excluded. However, with percent dermal absorption defined as that including the skin depot, with the exception of the BaP data for skin frozen 30 d, there was no significant difference between percent dermal absorption data for fresh unfrozen controls and those stored frozen for all 6 test chemicals for both 30 and 60 d freezer storage times. These results suggested with skin depot included that freezer storage may have potential for preserving human skin for in vitro absorption tests of environmental contaminants; however, optimal freezer storage conditions such as temperature and storage duration and their effects on skin viability and dermal metabolism need to be determined.

Contaminated soils (II): in vitro dermal absorption of nickel (Ni-63) and mercury (Hg-203) in human skin.

Dermal absorption of heavy metal soil contaminants was tested in vitro with chloride salts of radioactive nickel (Ni-63) and mercury (Hg-203). Aqueous soil suspensions, spiked with either Ni-63 or Hg-203, were applied to fresh viable human breast skin tissue in Bronaugh diffusion cells perfused with Hanks HEPES buffered (pH 7.4) receptor containing 4% bovine serum albumin (BSA). Receptor fractions were collected every 6 h for 24 h when skin was soap washed. Tests were conducted concurrently in triplicate with and without soil for each skin specimen. Mean percent dermal absorption including the skin depot for Ni-63 was 1 and 22.8% with and without soil, respectively, while for Hg-203, values of 46.6 and 78.3% were obtained. Excluding the skin depot and considering only absorption in receptor, there was 0.5 and 1.8% absorption of Ni-63 with and without soil, respectively, and 1.5 and 1.4% for Hg-203. The potential bioavailability of the skin depot is discussed in relation to dermal exposure to these metals in contaminated soil.

In vitro dermal absorption of methyl salicylate, ethyl parathion, and malathion: first responder safety.

In vitro tests with fresh dermatomed (0.3 to 0.4 mm thick) female breast skin and one leg skin specimen were conducted in Bronaugh flow-through Teflon diffusion cells with three chemicals used to simulate chemical warfare agents: 14C-radiolabeled methyl salicylate (MES), ethyl parathion (PT), and malathion (MT), at three dose levels (2, 20, and 200 mM). Tests were conducted at a skin temperature of 29 degrees C using a brief 30-min exposure to the chemical and a 6.5-h receivor collection period. Rapid absorption of all three chemicals was observed, with MES absorbed about 10-fold faster than PT and MT. For MES, PT, and MT, respectively, there was 32%, 7%, and 12% absorption into the receivor solution (Hank's HEPES buffered saline with 4% bovine serum albumin [BSA], pH 7.4) at the low dose (2 mM), 17%, 2%, and 3% at the medium dose (20 mM), and 11%, 1%, and 1% at the high dose (200 mM) levels. Including the skin depot for MES, PT, and MT, respectively, there was 40%, 41%, and 21% (low dose), 26%, 16%, and 8% (medium dose), and 13%, 19%, and 10% (high does) absorption. Efficacy of skin soap washing conducted at the 30 min exposure time ranged from 31% to 86%, varying by chemical and dose level. Skin depot levels were highest for the relatively lipophilic PT. "Pseudo" skin permeability coefficient (K(p)) data declined with dose level, suggesting skin saturation had occurred. An in-depth comparison with literature data was conducted and risk assessment of first responder exposure was briefly considered.

Contaminated soils (I): In vitro dermal absorption of benzo[a]pyrene in human skin.

Dermal absorption of the lipophile and potential carcinogen benzo[a]pyrene (BaP) in soils from contaminated sites was simulated in vitro using human skin exposed to 14C-BaP-spiked soil. This study is the first in a series of tests at Health Canada with several soil contaminants spanning a wide range of lipophilicity conducted with viable human skin. Breast skin was obtained fresh from a local hospital and dermatomed to a thickness of 0.4-0.5 mm. Teflon Bronaugh diffusion cells were perfused with HEPES buffered Hanks saline (pH 7.4) with 4% bovine serum albumin (BSA) and fractions were collected at 6-h intervals for up to 24 h exposure either to 14C-BaP applied in acetone or spiked in a commercial gardening soil. As skin depot 14C levels were still high at 24 h, the study was repeated for up to 42 h to examine skin depot bioavailability. Skin was washed with soapy water at 24 h in both the 24- and 42-h studies. Exposure to 14C-BaP both with and without soil was conducted in triplicate with skin specimens from at least 4 patients. In the 24-h exposure tests including the skin depot there was 15 and 56% absorption with and without soil, respectively. The lower total percent absorption from the spiked soil applied to skin resulted from lower depot absorption of 8% with and 45% without soil. Data for 42-h studies were similar and revealed no significant decrease in skin depot levels. Including the 42-h depots there was 16 and 50% absorption with and without soil, respectively, with respective depots of 7 and 39%. As there was no significant difference between the 24- and 42-h depots both with and without soil, the data suggest the depot for BaP was not bioavailable for at least the additional 18-h post soap wash exposure. The bioavailability of BaP is discussed in relation to previous in vitro and in vivo studies in perspective with dermal exposure to contaminated soils.

Skin decontamination: Importance of the wash-in effect.

That skin washing/decontamination may increase percutaneous absorption is commonly referred to as the 'wash-in' (W-I) effect. This article traces the development of the W-I effect both in vivo and more recently in vitro. The mechanism(s) responsible for this effect are examined particularly in relation to the laboratory method used in vitro. The importance of the W-I effect is presented and it is recommended that caution be practiced when skin is washed as the W-I effect may increase both local cutaneous and general systemic toxicity. Experimental data on a wide variety of chemicals are urgently needed.

Determination of dermal absorption QSAR/QSPRs by brute force regression: multiparameter model development with Molsuite 2000.

Accurate dermal quantitative structure-activity/property relationship (QSAR/QSPR) models are needed to predict percutaneous absorption of environmental contaminants. The Molsuite 2000 chemistry modeling software (ChemSW, Fairfield, CA) was used to model the Flynn component of the Kirchner in vitro human skin permeability coefficient (K(p)) data. This Kirchner- derived Flynn (K/F) database was updated to include recent literature data quality recommendations. A K/F data subset consisting of nondrug compounds was used to further optimize the developed QSPR models. The statistical fit of the models was excellent with r(2) values up to.89 for a three-descriptor parameter K/F database model and up to.96 for a four- parameter model of the data subset. A one-parameter transform model using only logarithm octanol-water partition coefficient (log K(o/w)) was also developed for the data subset (r(2) =.87). Molecular volume (MV) descriptors were not shown to be superior to molecular weight in conventional two-parameter models with log K(o/w) but may be superior in multiparameter models. A previously nonreported descriptor, surface tension in water (STW), was found to provide optimal multiparameter models. The developed models passed PRESS cross-validation and could be useful for predicting environmental systemic dermal exposure.

Automated in vitro dermal absorption (AIDA): development of a cost-effective diffusion cell.

A new diffusion cell design is reported for conducting in vitro dermal absorption tests. This disposable cell was inexpensive to construct and reduces the risk of inter-test cross-contamination. A disadvantage was that the polymer material used adsorbed the lipophilic test compound, 14C-nonyl phenol. Data is presented for absorption of tritiated water and 14C-nonyl phenol in a dialysis membrane model, Snakeskin and for tritiated water in human skin (Kp = 6.3 +/- 0.78 cm/h x 10(-3)). Further testing is needed to evaluate the capacity of the 'Dispo' cell for use with lipophilic test chemicals.

Low molecular weight cyclic volatile methylsiloxanes in cosmetic products sold in Canada: implication for dermal exposure.

Low molecular weight cyclic volatile methylsiloxane (cVMS) compounds have been used in a variety of cosmetics and personal care products and many other consumer products. The study provides information on the levels of cVMSs in cosmetics and personal care products sold in Canada with an attempt to estimate the consumer dermal exposure to cVMSs from these products. The levels of four cVMS compounds, hexamethylcyclotrisiloxane (D3), octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), and dodecamethylcyclohexasiloxane (D6) were determined in 252 cosmetics and personal care products collected from retail stores in several provinces in Canada. These products included fragrances, hair care products, deodorants and antiperspirants, nail polishes, lotions, skin cleansers and a variety of baby products (baby oils, baby lotions, baby shampoos, and diaper creams). Samples were extracted with different organic solvents depending on the nature of the products followed by gas chromatograph-mass spectrometry (GC-MS) analysis. D3, D4, D5 and D6 were found in 0.8%, 4.8%, 14.3%, and 9.1% of the products, respectively. D5 was the most predominant cVMS with the highest concentration of 680 mg/g in an antiperspirant. D5 was also found to have the highest concentration in baby products (150 mg/g in a diaper cream). Several approaches were used to estimate consumer dermal exposure to cVMSs. A wide range of exposure estimates were derived as a result of the uncertainty in adsorption efficiency and penetration rates of cVMSs in human skin as well as in the degree of evaporative loss during products use.