Health & Environmental Research Online (HERO)


Glycols (25265-71-8, 110-98-5, & 24800-44-0)


135 References Were Found:

Book/Book Chapter
Book/ Chapter

Propanediols

Authors: Sullivan, CJ; Kuenz, A; Vorlop, KD (2018) In Ullmann's Encyclopedia of Industrial Chemistry. Wiley-VCH Verlag GmbH & Co.. HERO ID: 4940399

[Less] 1,2‐Propanediol, [57‐55‐6], propylene glycol, HOCH2CH(CH3)OH, is very similar to ethylene glycol in . . . [More] 1,2‐Propanediol, [57‐55‐6], propylene glycol, HOCH2CH(CH3)OH, is very similar to ethylene glycol in its physical and chemical properties (→ Ethylene Glycol). The first reported description of 1,2‐propanediol was by Wurtz in 1859 1.

Industrial‐scale synthesis of 1,2‐propanediol from propylene oxide (→ Propylene Oxide) and water began in the 1930s. Current production uses this same process, which leads simultaneously to di‐ and tripropylene glycols. The worldwide capacity for 1,2‐propanediol was predicted at 2.56 × 106 t in 2017 2.

1,2‐Propanediol finds use in diverse applications, such as unsaturated polyesters (→ Polyester Resins, Unsaturated) for thermoset composites, food chemistry, food processing equipment, cosmetics, pharmaceuticals, as well as deicers and automotive antifreeze components (→ Antifreezes).

The "refereed" or "peer review" status of a journal comes from the Ulrichsweb Global Serials Directory (http://ulrichsweb.serialssolutions.com/), as supplied by the publisher. The term refers to the system of critical evaluation of manuscripts/articles by professional colleagues or peers. The content of refereed publications is sanctioned, vetted, or otherwise approved by a peer-review or editorial board. The peer-review and evaluation system is utilized to protect, maintain, and raise the quality of scholarly material published in serials. Publications subject to the referee process are assumed, then, to contain higher quality content than those that are not.
Peer Reviewed Journal Article

Topical delivery of anthramycin I. Influence of neat solvents

Authors: Haque, T; Rahman, KM; Thurston, DE; Hadgraft, J; Lane, ME (2017) European Journal of Pharmaceutical Sciences 104:188-195. HERO ID: 4947114

[Less] Anthramycin (ANT) was the first pyrrolobenzodiazepine (PBD) molecule to be isolated, and is a potent . . . [More] Anthramycin (ANT) was the first pyrrolobenzodiazepine (PBD) molecule to be isolated, and is a potent cytotoxic agent. Although the PBD family has been investigated for use in systemic chemotherapy, their application in the management of actinic keratoses (AK) or skin cancer has not been investigated to date. In the present work, anthramycin (ANT) was selected as a model PBD compound, and the skin penetration of the molecule was investigated using conventional Franz diffusion cells. Finite dose permeation studies of ANT were performed using propylene glycol (PG), 1,3-butanediol (BD), dipropylene glycol (DiPG), Transcutol P® (TC), propylene glycol monocaprylate (PGMC), propylene glycol monolaurate (PGML) and isopropyl myristate (IPM). The skin penetration of BD, DiPG, PG and TC was also measured. Penetration of ANT through human skin was evident for TC, PG and PGML with the active appearing to "track" the permeation of the vehicle in the case of TC and PG. Deposition of ANT in skin could be correlated with skin retention of the vehicle in the case of IPM, PGMC and PGML. These preliminary findings confirm the ability of ANT to penetrate human skin and, given the potency of the molecule, suggest that further investigation is justified. Additionally, the findings emphasise the critical importance of understanding the fate of the excipient for the rational design of topical formulations.

Archival Material
Archival Material

HSDB: Dipropylene glycol

Author: NLM (2015) Available online at http://toxnet.nlm.nih.gov/cgi-bin/sis/search2/r?dbs+hsdb:@term+@DOCNO+2658. (Nov 2, 2018). [Website] HERO ID: 4940366

[Less] Identification and Use: Dipropylene Glycol is used as medication, as an antifreeze agent, in air sanitation, . . . [More] Identification and Use: Dipropylene Glycol is used as medication, as an antifreeze agent, in air sanitation, and as a stabilizer in cosmetic preparations. It is also used as an intermediate for polyester resins, solvent extraction of aromatic hydrocarbons, steam set printing inks, stabilizer in cosmetics. As an inert ingredient, dipropylene glycol facilitates delivery of formulated pesticide chemical products that are used as herbicides, fungicides, insecticides, growth regulators and attractants on various commodities. It is also used in targeting odor-causing bacteria, animal pathogenic bacteria (G- and G+ vegetative), and animal viruses. Human Toxicity Studies: Repeated application of a shaving preparation containing 7.2% dipropylene glycol did not induce sensitization in 50 subjects when applied in 24/48 hr (presumably covered) patches, 3 days/wk for 3 weeks, followed by a challenge patch after a 2 wk rest period. Covered 48 hr application of a 50% solution of dipropylene glycol (DiPG; unspecified solvent) caused irritation in 14 of 34 persons and was equivocally irritant in a further 17. No local effects were induced when 20% DiPG in petrolatum was in 48 hr covered contact with the skin of an unspecified number of volunteers. Similarly, no effects were observed in 59 subjects exposed to a shaving preparation containing 7.2% DiPG in a 4 wk controlled use test or in 101 subjects following 48 hr uncovered contact, repeated after 2 wk in conjunction with exposure to UV light. However, the same shaving preparation in 48 hr covered contact with the skin, caused mild irritation in 6 of 101 subjects, with an additional two subjects also giving mild reactions when the patch was applied 2 wk later. It is more acutely depressant to CNS than ethylene, diethylene or propylene glycol. A case of a 32-year-old man who ingested more than 500 mL of dipropylene glycol-containing Fantasia fog solution (High Energy Lighting, Houston, TX) and subsequently developed acute renal failure, polyneuropathy, and myopathy. The toxicological profiles of monopropylene glycol (MPG), dipropylene glycol (DPG), tripropylene glycol (TPG) and polypropylene glycols (PPG; including tetra-rich oligomers) are collectively reviewed, and assessed considering regulatory toxicology endpoints. None of the glycols reviewed presented evidence of carcinogenic, mutagenic or reproductive/developmental toxicity potential to humans. Animal Toxicity Studies: Undiluted /dipropylene glycol/ caused mild irritation when 500 mg was applied to rabbit skin for 24 hours. When dipropylene glycol was applied repeatedly for prolonged periods (10 applications in 12 days) to skin of rabbits it had negligible irritating action and there was no indication that toxic quantities were absorbed through intact skin. Rabbits /were given/ 2-4 g/kg bw administered iv for 1-21 days. Two animals died at the fourth day with lesions in the kidneys. The remaining 8 were killed during the following 21 days. The kidneys of 3 animals exhibited similar lesions and one of these also had involvement of the liver. /New Zealand white/... rabbits (24/group) were artificially inseminated /and given 200, 400, 800, 1200 mg/kg bw/day by gavage on days 6-19 of gestation/. Animals were observed daily for clinical signs of toxicity. Mean food and body weights were calculated for each group on gestation days (GD) 0, 6, 9, 12, 15, 25, and 30. All animals were killed on GD 30 and examined for maternal body and organ weights, implant status, fetal weight, sex and morphological development. No maternal lethality occurred in the study. Pregnancy rates were 95%, 83%, 91%, and 82% in the control to high dose dipropylene glycol (DPG) groups, respectively. No effect that could be attributed to exposure to DPG was noted on maternal body weight, food consumption, or clinical signs. Necropsy of the maternal animals revealed no effects on kidney and liver weights. In utero DPG exposure did not affect the frequency of post-implantation loss, mean fetal body weight per litter, or external, visceral, or skeletal malformation. NOEL >1200 mg/kg/day. /Tested externally on eyes, rated numerically on scale of 1 to 10 according to degree of injury observed after 24 hr, paying particular attention to condition of cornea. Most severe injuries have been rated 10/. Rats received 12% /dipropylene glycol/ in the diet for 15 weeks. The treatment resulted in depression of running activity. Moderate degenerative changes in kidneys were found. ...The concentration of 10% /dipropylene glycol/ in drinking water caused death in some animals. Histology examination revealed hydropic degeneration of kidney tubular epithelium and liver parenchyma. Rats were not affected by 5% dipropylene glycol in their drinking water for 77 days. ...Administration level of 10%, some died with hydropic degeneration of kidney tubular epithelium and liver parenchyma. ...Effects were similar to those of diethylene glycol but less severe and less uniformly produced. Time-mated /Sprague-Dawley/ rats were dosed with /800, 2000, or 5000 mg/kg/day dipropylene glycol/ (DiPG) or the distilled deionized water vehicle /by gavage/. Animals were observed daily beginning on gestation day (GD) 6 for clinical signs of toxicity. All sperm-positive rats were killed on GD20. The maternal body, liver and intact uterus were weighed and corpora lutea were counted. The fetuses were examined in detail. Maternal toxicity and lethality were observed at 2000 and 5000 mg/kg/day (mortality rate: 4% and 9%), establishing the maternal NOAEL as 800 mg/kg/day. There were no significant differences between the DiPG exposed groups and the control. NOAEL was 5000 mg/kg/day. DiPG has no teratogenetic or embryonal effect. Dipropylene glycol markedly stimulated choleresis, /SRP: Secretion of bile/, when injected intraduodenally at 1 mL/kg into rats. Propylene glycol and dipropylene glycol were tested for mutagenic or genotoxic potential and found to be negative in a battery of studies: a bacterial gene mutation assay using Salmonella typhimurium, and in vitro Chinese hamster ovary (CHO) mutation assay, an in vitro Chinese hamster ovary (CHO) chromosomal aberration assay and an in vitro sister chromatid exchange assay. Dogs... after survival of repeated gastric dosage of dipropylene glycol showed only moderate degenerative changes in kidneys and only minimal evidence of liver damage. Ecotoxicity Studies: /Authors/ were able to feed chicks a diet containing 5% dipropylene glycol for 27 days without adverse effects. The chicks were unable to use it as an energy source.

The "refereed" or "peer review" status of a journal comes from the Ulrichsweb Global Serials Directory (http://ulrichsweb.serialssolutions.com/), as supplied by the publisher. The term refers to the system of critical evaluation of manuscripts/articles by professional colleagues or peers. The content of refereed publications is sanctioned, vetted, or otherwise approved by a peer-review or editorial board. The peer-review and evaluation system is utilized to protect, maintain, and raise the quality of scholarly material published in serials. Publications subject to the referee process are assumed, then, to contain higher quality content than those that are not.
Peer Reviewed Journal Article

Identification of toxicants in cinnamon-flavored electronic cigarette refill fluids

Authors: Behar, RZ; Davis, B; Wang, Y; Bahl, V; Lin, S; Talbot, P (2014) Toxicology In Vitro 28:198-208. HERO ID: 4088550

[Less] In a prior study on electronic cigarette (EC) refill fluids, Cinnamon Ceylon was the most cytotoxic . . . [More] In a prior study on electronic cigarette (EC) refill fluids, Cinnamon Ceylon was the most cytotoxic of 36 products tested. The purpose of the current study was to determine if high cytotoxicity is a general feature of cinnamon-flavored EC refill fluids and to identify the toxicant(s) in Cinnamon Ceylon. Eight cinnamon-flavored refill fluids, which were screened using the MTT assay, varied in their cytotoxicity with most being cytotoxic. Human embryonic stem cells were generally more sensitive than human adult pulmonary fibroblasts. Most products were highly volatile and produced vapors that impaired survival of cells in adjacent wells. Cinnamaldehyde (CAD), 2-methoxycinnamaldehyde (2MOCA), dipropylene glycol, and vanillin were identified in the cinnamon-flavored refill fluids using gas chromatography–mass spectrometry and high-pressure liquid chromatography (HPLC). When authentic standards of each chemical were tested using the MTT assay, only CAD and 2MOCA were highly cytotoxic. The amount of each chemical in the refill fluids was quantified using HPLC, and cytotoxicity correlated with the amount of CAD/product. Duplicate bottles of the same product were similar, but varied in their concentrations of 2MOCA. These data show that the cinnamon flavorings in refill fluids are linked to cytotoxicity, which could adversely affect EC users.

The "refereed" or "peer review" status of a journal comes from the Ulrichsweb Global Serials Directory (http://ulrichsweb.serialssolutions.com/), as supplied by the publisher. The term refers to the system of critical evaluation of manuscripts/articles by professional colleagues or peers. The content of refereed publications is sanctioned, vetted, or otherwise approved by a peer-review or editorial board. The peer-review and evaluation system is utilized to protect, maintain, and raise the quality of scholarly material published in serials. Publications subject to the referee process are assumed, then, to contain higher quality content than those that are not.
Peer Reviewed Journal Article

A toxicological review of the propylene glycols

Authors: Fowles, JR; Banton, MI; Pottenger, LH (2013) Critical Reviews in Toxicology 43:363-390. HERO ID: 3038211

[Less] The toxicological profiles of monopropylene glycol (MPG), dipropylene glycol (DPG), tripropylene glycol . . . [More] The toxicological profiles of monopropylene glycol (MPG), dipropylene glycol (DPG), tripropylene glycol (TPG) and polypropylene glycols (PPG; including tetra-rich oligomers) are collectively reviewed, and assessed considering regulatory toxicology endpoints. The review confirms a rich data set for these compounds, covering all of the major toxicological endpoints of interest. The metabolism of these compounds share common pathways, and a consistent profile of toxicity is observed. The common metabolism provides scientific justification for adopting a read-across approach to describing expected hazard potential from data gaps that may exist for specific oligomers. None of the glycols reviewed presented evidence of carcinogenic, mutagenic or reproductive/developmental toxicity potential to humans. The pathologies reported in some animal studies either occurred at doses that exceeded experimental guidelines, or involved mechanisms that are likely irrelevant to human physiology and therefore are not pertinent to the exposures experienced by consumers or workers. At very high chronic doses, MPG causes a transient, slight decrease in hemoglobin in dogs and at somewhat lower doses causes Heinz bodies to form in cats in the absence of any clinical signs of anemia. Some evidence for rare, idiosyncratic skin reactions exists for MPG. However, the larger data set indicates that these compounds have low sensitization potential in animal studies, and therefore are unlikely to represent human allergens. The existing safety evaluations of the FDA, USEPA, NTP and ATSDR for these compounds are consistent and point to the conclusion that the propylene glycols present a very low risk to human health.

Book/Book Chapter
Book/ Chapter

Glycol ethers: Ethers of propylene, butylene glycols, and other glycol derivatives

Author: Cragg, ST (2012) In Bingham, E; Cohrssen, B (Eds.), Patty's toxicology: Volume 4 (6th, pp. 789-877). Hoboken, NJ: John Wiley & Sons. HERO ID: 4851358

[Less] There are five U.S. manufacturers of propylene glycol ether derivatives shown in Table 1. This table . . . [More] There are five U.S. manufacturers of propylene glycol ether derivatives shown in Table 1. This table also lists the trade names for these materials.

The ethers of mono‐, di‐, tri‐, and polypropylene glycol are prepared commercially by reacting propylene oxide with the alcohol of choice in the presence of a catalyst. They may also be prepared by direct alkylation of the selected glycol with an appropriate alkylating agent such as a dialkyl sulfate in the presence of an alkali.

The monoalkyl ethers of propylene glycol occur in two isomeric forms, the alpha or beta isomer. The alpha isomer is a secondary alcohol (on the middle carbon of the propane backbone) that forms the ether linkage at the terminal alcohol of propylyene glycol. This alpha isomer is predominant during synthesis. The beta isomer is a primary alcohol with the ether linkage formed at the secondary alcohol. The toxicological significance of the alpha and beta isomers of propylene glycol is discussed later in this narrative. The monoalkyl ethers of dipropylene glycol occur in four isomeric forms. The commercial product Dowanol® DPM Glycol Ether is believed to be a mixture of these but to consist to a very large extent of the isomer in which the alkyl group has replaced the hydrogen of the primary hydroxyl group of the dipropylene glycol, which is a secondary alcohol. The internal ether linkage is between the 2 position of the alkyl‐etherized propylene unit and the primary carbon of the other propylene unit, thus leaving the remaining secondary hydroxyl group unsubstituted. In the case of dipropylene glycol monomethyl ether, the primary isomer is 1‐(2‐methoxy‐1‐methylethoxy)‐2‐propanol. The monoalkyl ethers of tripropylene glycol can appear in eight isomeric forms. The commercial product Dowanol® TPM Glycol Ether, however, is believed to be a mixture of isomers consisting largely of the one in which the alkyl group displaces the hydrogen of the primary hydroxyl group of the tripropylene glycol and the internal ether linkages are between secondary and primary carbons. The known physical properties of the most common ethers are given in Tables 5 and 8.

The methyl and ethyl ethers of these propylene glycols are miscible with both water and a great variety of organic solvents. The butyl ethers have limited water solubility but are miscible with most organic solvents. This mutual solvency makes them valuable as coupling, coalescing, and dispersing agents. These glycol ethers have found applications as solvents for surface coatings, inks, lacquers, paints, resins, dyes, agricultural chemicals, and other oils and greases. The di‐ and tripropylene series also are used as ingredients in hydraulic brake fluids.

Occupational exposure would normally be limited to dermal and/or inhalation exposure. The toxicological activity of the propylene glycol‐based ethers generally indicates a low order of toxicity. Under typical conditions of exposure and use, propylene glycol ethers pose little hazard. As with many other solvents, appropriate precautions should be employed to minimize dermal and eye contact and to avoid prolonged or repeated exposures to high vapor concentrations.

The propylene glycol ethers (PGEs), even at much higher exposure levels, do not cause the types of toxicity produced by certain of the lower molecular weight ethylene glycol ethers (EGEs). Specifically, they do not cause damage to the thymus, testes, kidneys, blood, and blood‐forming tissues as seen with ethylene glycol methyl and ethyl ethers. In addition, the propylene glycol ethers induce neither the development effects of certain of the methyl‐ and ethyl‐substituted ethylene glycol‐based ethers nor the hemolysis and associated secondary effects seen in laboratory animals with EGEs.

Other propylene glycol ethers also exhibit a similar lack of toxicity. For example, propylene glycol ethyl ether (PGEE) and its acetate do not cause the critical toxicities of testicular, thymic, or blood injury and do not produce birth defects. Propylene glycol tertiary‐butyl ether (PGTBE) also has been tested and fails to elicit these toxicities or birth defects in rats exposed by inhalation to substantial concentrations.

The methyl, ethyl, and n‐butyl ethers of butylene glycol considered herein are prepared by reacting the appropriate alcohol with the so‐called straight‐chain butylene oxide, consisting of about 80% 1,2 isomer and about 20% 2,3 isomer in the presence of a catalyst. They are colorless liquids with slight, pleasant odors. The methyl and ethyl ethers are miscible with water, but the butyl ether has limited solubility. All are miscible with many organic solvents and oils; thus, they are useful as mutual solvents, dispersing agents, and solvents for inks, resins, lacquers, oils, and greases. Industrial exposure may occur by any of the common routes.

The common esters and diesters of the polyols are prepared commercially by esterifying the particular polyol with the acid, acid anhydride, or acid chloride of choice in the presence of a catalyst. Mono‐ or diesters result, depending on the proportions of each reactant employed. The ether esters are prepared by esterifying the glycol ether in a similar manner. Other methods can also be used.

The acetic acid esters have remarkable solvent properties for oils, greases, inks, adhesives, and resins. They are widely used in lacquers, enamels, dopes, adhesives, and in fluids to dissolve plastics or resins as applied by lacquer, paint, and varnish removers.

Generally speaking, the fatty acid esters of the glycols and glycol ethers, in either the liquid or vapor state, are more irritating to the mucous membranes than those of the parent glycol or glycol ethers. However, once absorbed into the body, the esters are hydrolyzed and the systemic effect is quite typical of the parent glycol or glycol ethers.

It should be noted that the nitric acid esters of glycols are highly toxic and exert a physiological action quite different from that of the parent polyols.

The nitric acid esters of glycols are not typical of the esters or ether esters of organic acids and are considered separately in this chapter. They are used as explosives, usually in combination with nitroglycerin, to reduce the freezing point.

Industrial exposures of consequence are most likely to occur through the inhalation of vapors, but may also occur through contact with the eyes and skin. With the dinitrate, a serious hazard exists from absorption through the skin.

The "refereed" or "peer review" status of a journal comes from the Ulrichsweb Global Serials Directory (http://ulrichsweb.serialssolutions.com/), as supplied by the publisher. The term refers to the system of critical evaluation of manuscripts/articles by professional colleagues or peers. The content of refereed publications is sanctioned, vetted, or otherwise approved by a peer-review or editorial board. The peer-review and evaluation system is utilized to protect, maintain, and raise the quality of scholarly material published in serials. Publications subject to the referee process are assumed, then, to contain higher quality content than those that are not.
Peer Reviewed Journal Article

Safety assessment of propylene glycol, tripropylene glycol, and PPGs as used in cosmetics

Authors: Fiume, MM; Bergfeld, WF; Belsito, DV; Hill, RA; Klaassen, CD; Liebler, D; Marks, JG; Shank, RC; Slaga, TJ; Snyder, PW; Andersen, FA (2012) International Journal of Toxicology 31:245S-60S. [Review] HERO ID: 3036587

[Less] Propylene glycol is an aliphatic alcohol that functions as a skin conditioning agent, viscosity decreasing . . . [More] Propylene glycol is an aliphatic alcohol that functions as a skin conditioning agent, viscosity decreasing agent, solvent, and fragrance ingredient in cosmetics. Tripropylene glycol functions as a humectant, antioxidant, and emulsion stabilizer. Polypropylene glycols (PPGs), including PPG-3, PPG-7, PPG-9, PPG-12, PPG-13, PPG-15, PPG-16, PPG-17, PPG-20, PPG-26, PPG-30, PPG-33, PPG-34, PPG-51, PPG-52, and PPG-69, function primarily as skin conditioning agents, with some solvent use. The majority of the safety and toxicity information presented is for propylene glycol (PG). Propylene glycol is generally nontoxic and is noncarcinogenic. Clinical studies demonstrated an absence of dermal sensitization at use concentrations, although concerns about irritation remained. The CIR Expert Panel determined that the available information support the safety of tripropylene glycol as well as all the PPGs. The Expert Panel concluded that PG, tripropylene glycol, and PPGs ≥3 are safe as used in cosmetic formulations when formulated to be nonirritating.

Book/Book Chapter
Book/ Chapter

Glycols

Author: Cavender, FL (2012) In Bingham, E; Cohrssen, B; Powell, CH (Eds.), Patty's toxicology. John Wiley & Sons. HERO ID: 4731313


Technical Report
Technical Report

Data submitted to EPA: substantial risk reports: human health: acute toxicity: dipropylene glycol (25265-71-8)

Author: U.S. EPA (2011) HERO ID: 4940287


The "refereed" or "peer review" status of a journal comes from the Ulrichsweb Global Serials Directory (http://ulrichsweb.serialssolutions.com/), as supplied by the publisher. The term refers to the system of critical evaluation of manuscripts/articles by professional colleagues or peers. The content of refereed publications is sanctioned, vetted, or otherwise approved by a peer-review or editorial board. The peer-review and evaluation system is utilized to protect, maintain, and raise the quality of scholarly material published in serials. Publications subject to the referee process are assumed, then, to contain higher quality content than those that are not.
Peer Reviewed Journal Article

Dermal penetration of propylene glycols: Measured absorption across human abdominal skin in vitro and comparison with a QSAR model

Authors: Fasano, WJ; ten Berge, W; Banton, MI; Heneweer, M; Moore, NP (2011) Toxicology In Vitro 25:1664-1670. HERO ID: 3039551

[Less] The dermal penetration of undiluted monopropylene glycol (MPG) and dipropylene glycol (DPG) has been . . . [More] The dermal penetration of undiluted monopropylene glycol (MPG) and dipropylene glycol (DPG) has been measured in vitro using human abdominal skin under conditions of infinite dose application, and the results compared with predictions from the SKINPERM QSAR model (ten Berge, 2009). The measured steady-state penetration rates (J(ss)) for MPG and DPG were 97.6 and 39.3 mu g/cm(2)/h, respectively, and the permeability coefficients (K(p)) were 9.48 x 10(-5) cm/h for MPG and 3.85 x 10(-5) cm/h for DPG. In comparison, the SKINPERM model slightly over-predicted J(ss) and K(p) for MPG and DPG by between 2.6- and 5.1-fold, respectively. The model predictions of 254 mu g/cm(2)/h and 24.6 x 10(-5) cm/h for MPG, and 202 mu g/cm(2)/h and 19.8 x 10(-5) cm/h for DPG were in fairly good agreement with the measured values. Further, the model predicted a J(ss) of 101 mu g/cm(2)/h and a Kp of 9.9 x 10(-5) cm/h for the homologue tripropylene glycol. Assuming that the measured J(ss) was the same under conditions of finite dose application (taken to be 10 mu L/cm(2)) and was maintained over a 24-h period (both conservative assumptions), the relative dermal absorption of the applied dose was estimated to be 23% (0.96%/h) for MPG and 9% (0.39%/h) for DPG. However, the extrapolation for MPG may be further overestimated due to possible residence in the stratum corneum under infinite conditions of exposure that would not be applicable to a finite loading dose. (C) 2011 Elsevier Ltd. All rights reserved.