Dermal and pulmonary absorption of propan-1-ol and propan-2-ol from hand rubs

American Journal of Infection Control 40 (2012) 250-7 Contents lists available at ScienceDirect American Journal of Infection Control American Journal of Infection Control journal homepage: www.ajicjournal.org Major article Dermal and pulmonary absorption of propan-1-ol and propan-2-ol from hand rubs Harald Below PhD a, *, Ivo Partecke MD b, Nils-Olaf Huebner MD a, Nora Bieber MD a, Thomas Nicolai a, Alexander Usche a, Ojan Assadian MD, DTMH a, Elke Below PhD c, Günter Kampf MD a, d, Wolfram Parzefall PhD e, Claus-Dieter Heidecke MD, PhD b, Dariusz Zuba PhD f, Vincent Bessonneau g, Thomas Kohlmann PhD h, Axel Kramer MD, PhD a a Institute of Hygiene and Environmental Medicine, Ernst Moritz Arndt University, Greifswald, Germany Department of Surgery, Clinic of General, Visceral, Vascular and Thoracic Surgery, Ernst Moritz Arndt University, Greifswald, Germany c Institute of Forensic Science, Ernst Moritz Arndt University, Greifswald, Germany d BODE Chemie GmbH, Scientific Affairs, Hamburg, Germany e Institute of Cancer Research, Medical University of Vienna, Vienna, Austria f Institute of Forensic Research, Krakow, Poland g Environmental and Health Research Laboratory, French School of Public Health, Rennes, France h Institute for Community Medicine, Ernst Moritz Arndt University, Greifswald, Germany b Key Words: Alcohol Blood level Metabolites Hand hygiene Risk assessment Toxicology Background: It has been shown that nontoxic concentrations of ethanol are absorbed after hand hygiene using ethanol-based hand rubs. This study investigated whether absorption of propan-1-ol and propan2-ol from commercially available hand rubs results in measurable concentrations after use. Methods: The pulmonary and dermal absorption of propanol during hand rubs was investigated. Rubs contained 70% (w/w) propan-1-ol, 63.14% (w/w) propan-2-ol, or 45% (w/w) propan-2-ol in combination with 30% (w/w) propan-1-ol. Results: Peak median blood levels were 9.15 mg/L for propan-1-ol and 5.3 mg/L for propan-2-ol after hygienic hand rubs and 18.0 mg/L and 10.0 mg/L, respectively, after surgical hand rubs. Under actual surgical conditions, the highest median blood levels were 4.08 mg/L for propan-1-ol and 2.56 mg/L for propan-2-ol. The same procedure performed with prevention of pulmonary exposure through the use of a gas-tight mask resulted in peak median blood levels of 1.16 mg/L of propan-1-ol and 1.74 mg/L of propan-2-ol. Conclusion: Only minimal amounts of propanols are absorbed through the use of hand rubs. Based on our experimental data, the risk of chronic systemic toxic effects caused by hand rubs is likely negligible. However, our study did not evaluate the consequences of long-term daily and frequent use of hygienic hand rubs. Copyright Ó 2012 by the Association for Professionals in Infection Control and Epidemiology, Inc. Published by Elsevier Inc. All rights reserved. * Address correspondence to Harald Below, PhD, Institute of Hygiene and Environmental Medicine, Ernst Moritz Arndt University, Walther Rathenau Strasse 49a, 17489 Greifswald, Germany. E-mail address: below@uni-greifswald.de (H. Below). I.P. and N.-O.H. contributed equally to this article. This study was supported by grants from Antiseptica, Pulheim, Germany; Bode Chemie, Hamburg, Germany; B. Braun Medical, Sempach, Switzerland; Ecolab Deutschland, Düsseldorf, Germany; Lysoform Dr. Hans Rosemann, Berlin, Germany; and Schülke & Mayr, Norderstedt, Germany. Conflict of interest: G.K. is a paid employee of Bode Chemie, Hamburg, Germany. The other authors have no conflicts of interest to disclose. Given that hands are the primary vehicle for transmission of microbial pathogens causing infections, hand hygiene is essential for infection control in any health care setting,1-10 as well as in the community.11-13 Most alcohol-based hand rubs contain ethanol, propan-1-ol or propan-2-ol, or a combination of these alcohols.1,2,10 In previous studies of hand rubs with ethanol-based formulations, under extreme test conditions usually not encountered in the health care setting, 0.5%-2.3% of the applied ethanol was absorbed, resulting in blood levels of <30 mg/L (0.023%). Although absorption was found, in practice the use of ethanol-based hand rubs is considered safe.14,15 0196-6553/$36.00 - Copyright Ó 2012 by the Association for Professionals in Infection Control and Epidemiology, Inc. Published by Elsevier Inc. All rights reserved. doi:10.1016/j.ajic.2011.03.009 H. Below et al. / American Journal of Infection Control 40 (2012) 250-7 Comparable blood levels were found for propan-2-ol; in a study using a commercial hand rub applied every 10 minutes over a 4-hour period, subjects’ blood levels of propan-2-ol ranged from 0.5 to 1.8 mg/L.16 Leeper et al17 reported that after extensive epidermal application of 273 g of propan-2-ol, only 0.9% was absorbed within 10 hours. In contrast, Brown et al18 found negligible blood levels of propan-2-ol in subjects who applied a hygienic hand rub 30 times in a 1-hour period. Propanol-2-ol also was not detec\table in the breath of these subjects. However, the Brown et al study used a method that is approximately 30-fold less sensitive than the method used in the study of Turner et al16 and in the present study. The dermal and inhalation absorption of propan-2-ol is supported by case reports on intoxication.19-22 After preoperative skin antisepsis in pediatric surgery, serum levels of up to 12.2 mg/L (mean, 5.0  3.37 mg/L) were documented by Wittmann et al.23 Compared with propan-2-ol, the data on absorption of propan1-ol is even scantier. On isolated human epidermis, the following constants of permeability have been determined: 800 cm/hour for ethanol, 1,200 cm/hour for propan-1-ol, and 1,350 cm/hour for propan-2-ol.24,25 Peschel et al26 demonstrated that after modified surgical hand rubs with propanol-containing products with and without the ingestion of alcoholic beverages, propan-2-ol and propan-1-ol levels could disturb the analysis of congeners. Measured propan-1-ol levels were generally 0.2-1.8 mg/L, with levels pf 8.8 mg/L and 14 mg/L measured in 2 subjects. The aim of the present experimental study was to determine the absorbed amounts of propan-2-ol and propan-1-ol from the use of commercially available hand rubs. The primary goal is to assess the toxicological risk from the absorption data. We tested 3 hand rubs containing propan-1-ol alone, propan-2-ol alone, and both in combination under the same worst-case conditions as in our previous study examining ethanol absorption,14 as well as under clinical conditions with and without pulmonary exposure. METHODS Study design and setting All 3 experiments had a controlled blinded design and were approved by the Ethics Committee of the Board of Physicians of Mecklenburg-Pomerania, University of Greifswald (BB 07/09). In experiment 1, under a worst-case model of excessive hygienic or surgical hand rubs, hand rub application was performed in a 37 m3 room with 2 open windows and an open door, without controlled air exchange during applications. Between hand rub applications, participants were placed in a second room in which the use of alcohol-based hand rubs was not permitted. Blood samples were collected in another separate room. Experiment 2 involved surgical hand rubs, including a hygienic hand rub on entering the surgical theatre. Absorption was determined during the routine surgical program, which included 3 interventions of approximately 90 minutes each. Blood samples were collected in the doctors’ lounge in the surgical suite. Experiment 3 was performed in the same manner as in experiment 2, but pulmonary exposure was prevented through the use of a gas-tight mask (X-plore 4390 with A2 filter; Draeger, Lübeck, Germany) during hand rub application and while the surgeon was in the wash room. Participants Twelve participants (6 males, 6 females) participated in experiment 1, 10 surgeons (6 males, 4 females) participated in experiment 2, and 10 participants (6 males, 4 females) participated in experiment 3. For all experiments, inclusion criteria were age at 251 least 18 years and the ability to perform a standardized application according to European Standard EN 1500:1997.27 Exclusion criteria were defined as visible skin lesions on hands or arms, skin disease, alimentary intake of ethanol, and use of cosmetics in any form within 24 hours before the start of a test and on the day of the test. Furthermore, individuals with diabetes mellitus, pregnant or lactating women, and individuals who participated in a clinical experiment within 30 days before the start of the study also were excluded. To exclude potential oral alcohol consumption by participants, we also determined the ethanol levels of all participants during the 3 experiments. Written consent was obtained from all participants. Hand rubs Three commercially available hand rubs were tested: hand rub P1 (Skinman Sensitive, 70% w/w propan-1-ol; Ecolab, Düsseldorf, Germany), hand rub P2 (Manorapid ready for use, 63.14% w/w propan-2-ol; Antiseptica, Pulheim, Germany), and hand rub P1P2 (Sterillium Classic Pure, 45% w/w propan-2-ol in combination with 30% w/w propan-1-ol and 0.2% w/w mecetronium etilsulfate; Bode Chemie, Hamburg, Germany). All hand rubs were applied in both hygienic and surgical hand rubs. The hand rubs did not contain any fragrance or dye but a mixture of skin care components. Hand rub application In experiment 1, both hygienic hand rubs and surgical hand rubs were performed with P1P2 and P2, because at the time that this experiment was conducted, a hand rub containing only propan1-ol was not commercially available. Hands were washed with nonmedicated neutral soap and dried thoroughly immediately before the start of the experiment. For each hygienic hand rub, 4 mL of hand rub was applied in the test room to both hands and rubbed in for 30 seconds according to the standard rub-in procedure described in EN 1500:1997.27 After waiting for 1 minute outside the test room, this procedure was repeated. A total of 20 hygienic hand rubs were performed, resulting in a total exposure time of 10 minutes over a 30-minute period. The surgical hand rub experiments were started 7 days after the hygienic hand rub experiments. Here, 4 mL of hand rub was applied to the hands and rubbed on the hands and forearms. This procedure was repeated 5 times, with the hands and forearms kept covered with the hand rub for the recommended application time of 3 minutes.28 After a 5-minute wait outside the test room, the procedure was repeated. A total of 10 surgical hand rubs were performed, resulting in a total exposure time of 30 minutes over an 80-minute period. For hygienic and surgical hand rubs, each hand rub was tested individually on one of 2 consecutive test days. At the end of each test day, a skin care cream (Neutrogena; Johnson & Johnson, Düsseldorf, Germany) was applied to the treated skin areas. For experiments 2 and 3, when entering the surgical theater, a hygienic hand rub was performed. This hygienic hand rub was performed for 30 seconds with the same hand rub as used for the surgical hand rub. Then, 10 minutes later, a surgical hand rub with an application time of 1.5 minutes was performed before each of 3 consecutive 90-minute surgical interventions. The exact volume of the product applied for both the hygienic hand rub and the 3 surgical hand rubs was noted and used to calculate the absorption rate. After the hand rub application and air-drying, surgical gloves and gowns were donned. 252 H. Below et al. / American Journal of Infection Control 40 (2012) 250-7 Blood sampling RESULTS In all experiments, skin antisepsis was performed with an alcohol-free skin antiseptic (7.5% povidone-iodine solution, Braunol; B Braun, Melsungen, Germany) before blood sampling with a peripheral intravascular catheter (Inside-W, 18 GA; BD, Sandy, UT). Baseline samples were obtained before the first hand rub. In experiment 1, samples were obtained at 2.5, 5, 10, 20, 30, 60, and 90 minutes after the last hygienic hand rub or at 5, 10, 20, 30, 60, 90, and 120 minutes after the last surgical hand rub. In experiments 2 and 3, blood samples were collected before the hygienic hand rub and 3 times at 90-minute intervals (after each surgical procedure), as well as at 60 and 90 minutes after the third surgical procedure. Blood samples were stored at 4 C before analysis and were analyzed within 12 hours. Quality control Chemical analysis Chemical analysis was performed using gas chromatography in a modification of the method described by Roemhild et al,14,29 which uses head-space injection (CombiPal-Autosampler; CTC Analytics, Zwingen, Switzerland) with flame-ionization detection (5890 series II gas chromatograph; Hewlett Packard, Waldbronn, Germany). In brief, 1 mL of sample or 1 mL of standard and 0.5 g of anhydrous Na2SO4 were filled in 1.5-mL head space vials and incubated for 45 minutes at 75 C. Then 2.5 mL was injected (time interval, 0.5 minute). A DB 624 column (60 m  0.32 mm  1.8 mm; J&W Scientific, Folsom, CA) was used for separation. The chromoatographic conditions were an injector temperature of 150 C, a detector temperature of 250 C, a column temperature program of 40 C for 8 minutes, followed by a ramp of 3 C/minute to 120 C (0 minutes) and then 30 C/minute to 230 C (5 minutes). Nitrogen (5.0) served as the carrier gas at a rate of 1.45 mL/minute (21.9 cm/s). For each measurement, calibration was performed according to the method of the external standard with 3 calibration points (Medidrug BGS-S, levels 1-3; Medichem, Steinenbronn, Germany) and custom-made standards in water. The latter were used for control standards and propionaldehyde, which is not included in the commercially available standards. This calibration standard was produced based on the weight of the original contents of the substances followed by dilution to the calibration level. The method’s detection limits were 0.13 mg/L for propan-1-ol, 0.03 mg/L for propan-2-ol, 0.14 mg/L for ethanol, 0.01 mg/L for acetone, and 0.02 mg/L for propionaldehyde. For all measurements, quality controls were performed using certified reference material (Medidrug BGS 2/05 S-Plus; Medichem). Parallel selected samples were analyzed in the chemical laboratory of the Institute of Forensic Medicine, University of Greifswald. Data calculation and statistical analysis Blood concentrations are expressed as median and 25% and 75% percentiles. Concentrations below the detection limit were set to 0. The amount of absorbed alcohol was calculated separately for each participant based on the method of Wittmann et al.14,23 In brief, the median amount absorbed is the product of the maximum blood level, body weight, and a sex-dependent factor (0.6 for women; 0.7 for men). The proportion of absorbed alcohol was calculated from the amount of alcohol initially applied and the percentage of that amount absorbed. P values were calculated for differences in blood concentrations in each experiment using Wilcoxon’s rank-sum test and for differences between experiments 2 and 3 using the MannWhitney U test for unpaired samples. All analyses were done using SPSS version 11.5.1 (SPSS, Munich, Germany). The results of the certified reference material analysis (n ¼ 9; propanols and acetone) and the comparison of the results of parallel samples analyzed by the chemical laboratory at the Institute of Forensic Medicine were within the limits of analytical deviation and fulfilled the requirements of an interlaboratory test. Baseline blood concentrations For each parameter, a total of 107 baseline values were determined during the 3 experiments. For propan-1-ol, 91 of 107 samples (85 %) were below the detection limit (median and 25th and 75th percentiles, <0.13 mg/L). For propan-2-ol 6, 7 of 107 samples (62.6%) were below the detection limit (median and 25th percentile, <0.03 mg/L; 75th percentile, 0.16 mg/L). For propionaldehyde, 80 samples (74.8%) had concentrations below the detection limit (median, 0.03 mg/L; 25th percentile, <0.02 mg/L; 75th percentile, 0.07 mg/L). Acetone was detectable in all 107 samples (median, 2.10 mg/L; 25th percentile, 1.57 mg/L; 75th percentile, 3.08 mg/L). The ethanol baseline values were below the detection limit in most cases (n ¼ 86; 80.4%), or at most 0.55 mg/L. Blood levels and absorbed propanols and metabolites in experiment 1 In the worst-case model, the calculated applied amounts for hygienic hand rubs were 44.25 g of propan-2-ol for P2, 30.64 g of propan-2-ol for P1P2, and 20.42 g of propan-1-ol for P1P2. Exposures for surgical hand rubs were 110.62 g of propan-2-ol for P2, 76.6 g of propan-2-ol for P1P2, and 51.05 g of propan-1-ol for P1P2 (Table 1). In experiment 1, after the hygienic hand rubs, the highest median concentrations of propan-2-ol was 5.3 mg/L (0.0042%) with P2 and 4.9 mg/L (0.0038%) with P1P2, and the highest median concentrations of propan-1-ol was 9.15 mg/L (0.0088%) with P1P2. Propan-1-ol reached its highest median concentration at 30 minutes after the last application (P1P2), and propan-2-ol reached its highest median concentration at 60 min after the last application (P2 and P1P2) (Table 1). In the worst-case model, the median blood concentrations after surgical hand rubs were higher: 5.8 mg/ L (0.0046%) with P2 and 10.0 mg/L (0.0079%) with P1P2 for propan2-ol (Table 3), and 18 mg/L (0.0173%) for propan1-ol with P1P2. Propan-1-ol reached its highest median concentration after 30 minutes (P1P2), and propan-2-ol did so after 30 minutes with P1P2 and after 60 minutes with P2 (Table 1). The median amounts of absorbed propan-2-ol were 310 mg (0.7%) with P2 and 310 mg (1.0%) with P1P2; the median amount of absorbed propan-1-ol was 600 mg (2.9%) with P1P2 (hygienic hand rub). For the surgical hand rubs, the median amount of absorbed propan-2-ol was 472 mg (0.4%) with P2 and 569 mg (0.7%) with P1P2, and that of absorbed propan-1-ol was 918 mg (1.8%) with P1P2 (Table 1). Acetone, the main metabolite of propan-2-ol, reached its maximum concentration at 60 minutes after the last application, 6.2 mg/L for P2 and 4.5 mg/L for P1P2 (hygienic hand rub). After the surgical hand rubs, the maximal median concentrations were 5.4 mg/L for P2 and 4.95 mg/L for P1P2, at 60 minutes and 90 minutes, respectively, after the last application (Table 3). Independent of the type of hand rub used, the concentration of propionaldehyde as a metabolite of propan-1-ol did not change significantly (Table 1). 253 H. Below et al. / American Journal of Infection Control 40 (2012) 250-7 Table 1 Median maximum blood concentrations of propanols and their metabolites, applied and median absorbed amounts, and proportion of propanols after 20 hygienic or 10 surgical hand rubs with formulation P2 or P1P2 from 12 participants in the worst-case model (experiment 1) Amount absorbed, mg (% of absorbed alcohol) Median maximum blood concentration Experiment Hand rub 1, HHR P2 P1P2 1, SHR P2 P1P2 Substance Time after exposure, minutes Propan-2-ol Acetone Propan-1-ol Propan-2-ol Acetone Propionaldehyde Propan-2-ol Acetone Propan-1-ol Propan-2-ol Acetone Propionaldehyde 60 60 30 60 60 10 60 60 30 30 90 60 Median (25th; 75th percentiles), mg/L 5.3 6.2 9.15 4.9 4.5 0.15 5.8 5.4 18.0 10.0 4.95 0.2 (3.2; 10.5) (3.5; 11.9) (4.87; 13.1) (3.1; 6.6) (2.5; 5.6) (0.1; 0.3) (3.27; 7.47) (4.17; 7.02) (10.55; 25.1) (5,85; 12.9) (3.02; 6.1) (0.1; 0.2) P .001 .007 .001 <.001 <.001 .002 .001 .002 <.001 <.001 <.001 .016 Median 25th percentile 44.25 310 (0.7) 225 (0.5) 20.42 30.64 600 (2.9) 310 (1.0) 410 (12.0) 229 (0.7) 110.62 472 (0.4) 321 (0.3) 575 (0.5) 51.05 76.6 918 (1.8) 569 (0.7) 703 (1.4) 364 (0.5) 1,220 (2.4) 746 (1.0) Amount applied, g 75th percentile 416 (0.9) 1,043 (5.1) 479 (1.6) HHR, hygienic hand rub; SHR, surgical hand rub. Table 2 Applied and median absorbed amounts and proportion of propanols after surgical hand rub with P1, P2 and P1P2 in experiment 2 (dermal and pulmonary absorption) and experiment 3 (dermal absorption only) Amount absorbed, mg (% of absorbed alcohol) Hand rub Substance P1 Propan-1-ol P2 Propan-2-ol P1P2 Propan-1-ol Propan-2-ol Propan-1-ol Propan-2-ol Absorption Dermal Dermal Dermal Dermal Dermal and pulmonary only and pulmonary only and pulmonary Dermal only Amount applied, g 20.1 20.1 18.25 18.25 8.43 12.64 8.43 12.64 Blood levels and absorbed propanols and metabolites in experiments 2 and 3 During the 1 hygienic hand rub and the 3 subsequent surgical hand rubs, surgeons were exposed to a mean total of 33 mL of hand rub, corresponding to a mean total propan-2-ol exposure of 18.25 g for P2 and 12.64 g for P1P2 and a mean propan-1-ol exposure of 20.1 g for P1 and 8.43 g for P1P2 (Table 2). In experiment 2, the highest median blood level of propan-1-ol was 4.08 mg/L (0.0039%; P1), and that of propan-2-ol was 2.56 mg/L (0.0025%; P1P2) (Table 3). Excluding pulmonary adsorption in experiment 3 resulted in lower median concentrations than were recorded in experiment 2, with 1.16 mg/L propan-1-ol (0.0011%; P1) and 1.74 mg/L propan-2-ol (0.0017%; P2) (Table 3). In experiment 2, the highest median absorbed amounts of propan-1-ol and propan-2-ol were 271 mg (1.3%; P1) and 92.7 mg (0.5%; P2), respectively (Table 2). The combination of propanols (P1P2) influenced absorption; thus, we found 124 mg (1.5%) propan-1-ol and 137 mg (1.1%) propan-2-ol. In experiment 3, the highest median absorbed amounts of propan-1-ol and propan-2-ol were 109 mg (0.5%) for P1, 151 mg (0.8%) for P2, and 97.6 mg (1.2%) and 129 mg (1.0%), respectively, for P1P2. The decline in the absorbed amount of propan-1-ol (from 271 mg to 109 mg) is significant (P ¼ .023), whereas the increase in the absorbed amount of propan-2-ol (from 92.7 mg to 151 mg) is salient but not significant (Table 2). The relative absorbed amount of propan-1-ol (1.2%-2.9%) was approximately 3 times higher than that of propan-2-ol (0.4%-1.1%). Absorption of propan-2-ol was approximately twice as high after application of the mixture of the 2 propanols as after application of propan-2-ol alone (Tables 1 and 2). Median, mg 271 109 92.7 151 124 137 97.6 129 (1.3) (0.5) (0.5) (0.8) (1.5) (1.1) (1.2) (1.0) 25th percentile, mg 125 55.2 72.4 87.4 67.1 87.4 45.3 64.1 (0.6) (0.3) (0.4) (0.5) (0.8) (0.7) (0.5) (0.5) 75th percentile, mg 492 174 156 177 182 181 124 159 (2.4) (0.9) (0.9) (1.0) (2.2) (1.4) (1.5) (1.3) The differences in acetone levels between experiment 2 and experiment 3 are noteworthy. In experiment 2, there was a significant increase in the blood concentration of acetone, with a maximum of 10.22 mg/L; in contrast, these were no significant changes in acetone blood levels in experiment 3 (Table 3). In experiments 2 and 3, blood levels of propionaldehyde did not increase significantly from baseline values (data not shown). DISCUSSION The literature contains little information on absorption of propanols after application of hand rubs. In contrast to some authors who found certain levels of absorption,16,26,30 others detected no propanol in the blood after application of hand rubs16,18 or skin disinfection.15 Consequently, we opted to perform a 2-step experiment. The first step was a worst-case model to clarify whether any absorption occurred, and if so, to what extent (experiment 1). In the second step, absorption was determined under clinically relevant conditions (experiment 2), and also excluding the possibility of pulmonary absorption (experiment 3). For this purpose, we used a highly sensitive analytical method.14,29 The criteria for selecting the hand rubs used were commercial availability, a pure formulation of propan-1-ol or propan-2-ol, and of the combination of the 2 propanols. Only one hand rub containing propan-1-ol was commercially available. To select the pure propan-2-ol and the combined product, we compiled a list of the 10 most-used hand rubs in Germany and chose 2 by lottery. 254 Table 3 Experiments 2 and 3 (dermal and pulmonary absorption vs dermal absorption only), median blood concentrations (mg/L) of propanols and acetone before and after surgical hand rubs with P1, P2, and P1P2 After application Hand rub P1 Substance Absorption Propan-1-ol Dermal and pulmonary <0.13 (<0.13)* Dermal only <0.13 (<0.13-0.00)* Dermal and pulmonary Dermal only Acetone P2 Propan-1-ol Propan-2-ol Acetone P1P2 Propan-1-ol Propan-2-ol <0.03 (<0.03-0.07) Dermal and pulmonary 1.85 (1.69-3.60) Dermal only 2.32 (1.87-3.09) Dermal and pulmonary Dermal only Dermal and pulmonary <0.13 (<0.13) <0.13 (<0.13) 0.13 (0.06-0.24) Dermal only 0.06 (<0.03-0.07) Dermal and pulmonary 2.15 (1.49-2.51) Dermal only 2.90 (2.38-3.63) Dermal and pulmonary <0.13 (<0.13-0.15) Dermal only <0.13 (<0.13) Dermal and pulmonary Dermal only Acetone 0.21 (0.13-0.23) 0.22 (0.04-0.399) <0.03 (<0.03-0.06) Dermal and pulmonary 2.51 (1.70-3.59) Dermal only 2.40 (1.75-2.68) First OP Second OP Third OP 60 minutes after last OP 90 minutes after last OP 2.77 (1.90-3.62) P ¼ .005 0.86 (0.54-1.21) P ¼ .005 0.60 (0.45-0.82) P ¼ .005 0.06 (<0.03-0.07) P ¼ .686 4.21 (3.29-5.44) P ¼ .074 2.03 (1.54-2.54) P ¼ .333 <0.13 (<0.13) <0.13 (<0.13) 0.92 (0.68-1.43) P ¼ .005 0.85 (0.36-1.25) P ¼ .005 4.08 (3.36-5.91) P ¼ .005 2.40 (1.96-2.93) P ¼ .017 2.14 (1.18-3.00) P ¼ .005 0.53 (0.27-0.94) P ¼ .008 2.56 (1.29-3.02) P ¼ .005 0.64 (0.49-1.22) P ¼ .007 6.42 (3.80-7.82) P ¼ .005 2.34 (1.79-2.68) P ¼ .959 4.08 (1.50-6.75) P ¼ .005 0.85 (0.51-2.17) P ¼ .005 0.90 (0.58-0.99) P ¼ .008 0.06 (<0.03-0.07) P ¼ .752 6.34 (4.60-8.88) P ¼ .007 1.99 (1.58-2.54) P ¼ .333 <0.13 (<0.13) <0.13 (<0.13) 1.50 (0.87-1.86) P ¼ .005 1.54 (0.87-2.66) P ¼ .005 6.72 (5.07-7.93) P ¼ .005 3.62 (2.26-4.62) P ¼ .386 1.21 (0.72-3.28) P ¼ .007 0.50 (0.18-2.20) P ¼ .012 1.96 (1.26-3.09) P ¼ .005 0.89 (0.63-1.90) P ¼ .005 8.54 (5.94-12.09) P ¼ .005 3.06 (2.18-3.66) P ¼ .333 3.25 (0.59-7.47) P ¼ .005 1.16 (0.38-2.39) P ¼ .005 0.55 (0.44-1.24) P ¼ .005 0.07 (<0.03-0.14) P ¼ .183 9.15 (5.64-12.78) P ¼ .008 2.21 (1.71-2.73) P ¼ .646 <0.13 (<0.13) <0.13 (<0.13) 1.70 (1.16-2.22) P ¼ .005 0.95 (0.57-1.69) P ¼ .005 9.02 (6.74-10.42) P ¼ .005 4.16 (2.91-5.54) P ¼ .053 0.51 (0.3-2.07) P ¼ .059 0.68 (0.29-1.66) P ¼ .012 1.39 (0.91-2.29) P ¼ .005 1.24 (0.50-2.20) P ¼ .013 8.14 (6.56-11.69) P ¼ .005 4.17 (3.18-5.59) P ¼ .028 0.95 (0.73-1.89) P ¼ .007 0.64 (0.15-1.03) P ¼ .012 0.46 (0.33-0.54) P ¼ .005 0.06 (<0.03-0.07) P ¼ .344 8.21 (4.12-16.96) P ¼ .005 2.13 (1.78-2.79) P ¼ .575 <0.13 (<0.13) <0.13 (<0.13) 1.00 (0.74-1.58) P ¼ .005 1.74 (1.38-2.73) P ¼ .005 8.25 (6.38-9.59) P ¼ .005 4.10 (2.58-5.29) P ¼ .059 0.3 (0.17-0.87) P ¼ .441 0.18 (<0.13-0.56) P¼0.028 0.82 (0.68-1.66) P ¼ .008 0.70 (0.43-1.20) P ¼ .007 8.81 (7.03-10.50) P ¼ .005 4.45 (3.01-6.43) P ¼ .022 0.54 (0.32-1.20) P ¼ .017 <0.13 (<0.13-0.24) P ¼ .068 0.36 (0.24-0.48) P ¼ .037 0.06 (<0.03-0.11) P ¼ .482 6.98 (4.70-13.51) P ¼ .005 1.98 (1.48-2.25) P ¼ .333 <0.13 (<0.13) <0.13 (<0.13) 0.85 (0.50-1.10) P ¼ .005 1.35 (0.54-2.36) P ¼ .005 7.93 (5.22-10.07) P ¼ .005 4.43 (2.68-5.40) P ¼ .114 0.43 (0.25-0.87) P ¼ .515 0.08 (<0.13-0.27) P ¼ .042 1.36 (0.96-1.63) P ¼ .005 0.61 (0.39-1.19) P ¼ .012 10.22 (6.80-11.93) P ¼ .005 3.96 (3.33-4.12) P ¼ .017 *The values are median alcohol concentration (25th and 75th percentiles) from 10 participants (total exposure to 33 mL; total contact time, 5 minutes). H. Below et al. / American Journal of Infection Control 40 (2012) 250-7 Propan-2-ol Before first application H. Below et al. / American Journal of Infection Control 40 (2012) 250-7 Baseline values The ethanol baseline values indicate that the participants abstained from ethanol before and during our experiments. The proportion of propan-1-ol values below the limit of detection is in line with reports in the literature and suggests a physiological, endogenous low-level blood concentration. Small amounts of propan-1-ol in the blood could not be explained by intake of alcoholic beverages.31 A strong indication that propan-1-ol may be formed under physiological conditions is the finding that after participants drank propan-1-ol-free alcoholic beverages, their propan-1-ol levels rose to detectable levels (up to 0.2 mg/L).26,31 Because ADH preferentially metabolizes ethanol, the metabolism of propan-1-ol is competitively inhibited by ethanol, which may result in an increase of measurable concentrations of propan-1-ol. The main reason that propan-1-ol is not recognized as physiological is likely its detection limit, which is 5-fold higher than that of propan-2-ol (0.13 mg/L vs 0.03 mg/L). Endogenous propan-2-ol blood levels reported in the literature vary greatly, ranging from 0.01 to 10 mg/L.23,31,32 Our results are in the lower range of this range (<0.03-0.25 mg/L; <0.000024%0.0002%). A possible reason for the presence of physiological propan-2-ol could be the reduction of acetone in certain metabolic situations, such as hunger and illness.32,33 Zuba et al34 reported that acetone, acetaldehyde, methanol, propan-2-ol, and propan-1-ol are commonly found in the blood of alcoholic patients. The origin of these substances is related mainly to their presence in alcoholic beverages as impurities (congeners), which lead to steady-state concentrations after prolonged consumption and ultimately to metabolic changes in the body. The peak concentration of propan-2-ol was 75.6 mg/L, and that of propan-1-ol was 13.5 mg/L.34 Relationship between applied and absorbed amounts We found a clear, direct correlation between the amounts applied and the amounts absorbed (Tables 1 and 2). In all 3 experiments, systemic uptake was seen, with the greatest absorption occurring in the worst-case model. In experiment 1, the increase in concentrations of propanols and their metabolites was significant at all time points studied. In experiments 2 and 3, dermal absorption also was significant at most time points, but was markedly lower than that seen in experiment 1 (Tables 1-3). The proportion of median absorbed propanols ranged from 0.4% to 2.9% (mean, 1.1%). The use of P1P2 was apparently associated with a slightly increased relative absorption rate. Risk assessment of absorbed amounts Propan-1-ol During clinical exposure, both propanols were absorbed in measurable concentrations. The median absorbed amount of propan-1-ol was 271 mg (Table 2). The highest median propan-1-ol concentration was 4.08 mg/L (experiment 2; Table 3). Blood levels after rubs with P1 reached about half the values attained after drinking alcoholic beverages containing propan-1-ol.34 In contrast to propan-2-ol, propan-1-ol is not fully accepted as a physiological compound. However, certain foods and beverages contain detectable amounts of propan-1-ol, for example, 6-73 mg/L in beer, 3-8 mg/L in malt beer, 12-68 mg/L in wine, 5-217 mg/L in fruit wine, and 94-5,773 mg/L in fruit brandy.35 The amount absorbed depends on the kind of beverage consumed. Although propan-1-ol is not usually detected in vodka and other distilled spirits, subjects have measurable concentrations after drinking these beverages.31 Typical serum propan-1-ol concentrations after 255 bolus intake (over 1-1.5 hours) with resulting blood ethanol levels of approximately 1.0%-1.3% were up to 0.05 mg/L for vodka, 0.30 mg/L for beer, 0.20 for wines, 0.40 for brandy, and 2.5 mg/L for fruit brandy.36 Because we found higher blood levels of propan-1-ol after hand rubs compared with levels reported after drinking alcoholic beverages, the risk of toxicity must be carefully considered. However, although data on the high dose range for propan-1ol toxicity have been reported,37 such data are lacking on the low dose range (see below), which is of interest here. Our data from experiments 2 and 3 show no significant increase in concentrations of propionaldehyde, the main metabolite of propan-1-ol; in no case did the blood propionaldehyde level exceed 0.1 mg/L. Thus, we conclude that propan-1-ol toxicity due to the metabolite propionaldehyde is highly unlikely. As a consequence of the European Union assessment, it is necessary to limit propan-1-ol; in scenarios with short-term and repeated exposures,38 exposure should be reduced. In the case of hand rubs, this can be achieved only by decreasing inhalation exposure, that is, by increasing room ventilation. Propan-2-ol The median absorbed amount of propan-2-ol during clinical exposure was 137 mg (experiment 2; Table 2) at a concentration of 2.56 mg/L (Table 3). In contrast to propan-1-ol, an acceptable daily intake of 2.4 mg/kg (144 mg/60 kg) has been determined for propan-2-ol.39 However, the risk of hand rubs should not be evaluated based on an acceptable daily intake, which expresses the limit for life-long intake via food and includes a safety factor of at least 100. Hand rubs are applied mainly by health care professionals, and the possible health risk depends on the actual exposure. Under our exaggerated experimental conditions, it is possible that the acceptable daily intake of propan-2-ol could be reached. This indicates that the safety factor of 100 may be somewhat uncertain, but does not imply a significant toxic risk. When used in combination with ethanol drinking, propan-2-ol and propan-1-ol have similar elimination rate constants (0.14  0.07 g kg 1h 1 vs 0.14  0.12 g kg 1h 1). Their elimination rate is in the same range as that of ethanol in social drinkers (0.15 g/kg/h). They both have a high biological half-life, 5.1  4.3 hours for propan-1-ol and 4.8  2.4 hours for propan-2-ol.34 Previous case reports on acute intoxication suggest that propan2-ol blood levels <50 mg/L are harmless. Only levels >500 mg/L are associated with mild intoxication. Patients with a blood level 1,500 mg/L are deeply comatose.19-22,40 In 2 reported cases of oral intoxication with propan-2-ol, blood levels reached 3,150 mg/L and 4,200 mg/L, which would be lethal without intensive medical care.41 These data are difficult to compare with low-level chronic exposure such as occurs from the use of hand rubs, and it is not possible to reliably determine a threshold for toxic effects after chronic exposure. The German MAK (threshold limit value) Commission has set a propan-2-ol inhalation exposure limit of 200 ppm (500 mg/m3) in the workplace; in the United States, theOccupational Safety and Health Administrationhas set this limit at 400 ppm.42 Application of 10 mL of hand rub (8 g) could achieve this value temporarily in a 20-m3 room without ventilation. Thus, potential health risks by pulmonary absorption should be minimized by appropriate ventilation. Metabolic aspects For propan-1-ol, we found a low but statistically significant increase in the main metabolite, propionaldehyde, only in the worst-case model. Surprisingly, we found increased propan-2-ol levels after application of P1, which contains only propan-1-ol (experiment 2; Table 3). In experiment 2, participants had the 256 H. Below et al. / American Journal of Infection Control 40 (2012) 250-7 greatest increase in acetone levels of any experiments. The participants did not eat during the experiment, and abstinence increased their acetone blood levels. In experiment 3, during which the participants were permitted to eat between the surgical procedures, acetone levels increased only moderately, and, accordingly, no propan-2-ol was detected (Table 3). Propan-2-ol is oxidized to acetone, which is subsequently degraded to acetate and formiate.43 Acetone is a physiological metabolite generated during ketogenesis from fatty acid breakdown44; as such, acetone was detectable at baseline levels (0.8-5.9 mg/L) on all experimental days. The great variations observed correspond with levels reported in the literature ranging from 0.01 mg/L to 10 mg/L.23,31,45 Elevated urinary acetone is a possible marker of exposure to propan-2-ol. Conversely, propan-2-ol may be produced from acetone by reductive metabolism in the presence of sufficient nicotinamide adenine dinucleotide and nicotinamide adenine dinucleotide phosphate.46 Thus, elevated levels of acetone may lead to an increase in propan-2-ol blood concentration.31,43 This metabolic pathway may explain the appearance of propan-2ol in our participants after application of P1 alone. Some authors have suggested that both propan-2-ol and acetone should be considered when evaluating physical stress.47 The “endogenous” level of propan-2-ol depends mainly on diet and disease states. The propan-2-ol level is elevated in alcoholics, but this may be a consequence of the “special” diet (ie, starvation, low-calorie food), not alcohol per se, during prolonged consumption of alcoholic beverages, resulting in metabolic disturbances. In addition, the large excess of nicotinamide adenine dinucleotide phosphate favors reduction processes. Dermal absorption without inhalation exposure During routine hand rub application, it is practically impossible to avoid inhalation exposure. Until now, the proportion of inhalation absorption was generally unknown. By preventing pulmonary absorption, the absorbed amount of propan-1-ol was significantly lower than the combined dermal and pulmonary absorption (109 mg vs 271 mg; P ¼ .023) (Table 2). After eliminating one value from a participant with inexplicably high absorption, the difference remained (P ¼ .041). This tendency was not seen with propan-2-ol. Application of P1P2 resulted in no significant change in the absorption of either propan-2-ol or propan-ol-1. Here and with application of P2 alone, the differences were not significant. Our results support the suspicion that propan-2-ol is dermally absorbed to a greater extent than propan-1-ol, which might be attributed to the higher dermal permeability coefficient of propan-2-ol (1,350 cm/hour vs 1,200 cm/hour).24,25 Unlike propan-2-ol, a large proportion of propan-1ol is absorbed through the lungs, although propan-2-ol has slightly higher volatility (8 10 6 atm.m3/mol at 25 C vs 7.4 10 6 atm.m3/ mol at 25 C). Propan-1-ol from P1P2 is apparently absorbed preferably via dermal contact. This observation may be explained by the lower volatility of P1P2 due to the mixture of 45% propan-2-ol and 30% propan-1-ol, compared with P1 which is 70% propan-1-ol. In addition, the high proportion of propan-2-ol could increase the dermal absorption of propan-1-ol. We found no uniform tendency of absorption in experiments 2 and 3, possibly due to differences in skin integrity (eg, microlesions). The small sample size (n ¼ 10) makes it difficult to draw conclusions regarding the predominant exposure pathway. In addition, individual genetic variability in metabolic enzymes might play a role in determining the internal dose of alcohols, although investigating this was beyond the scope of this study. Compared with propanolols, ethanol has lower dermal absorption24,25 and less toxicity, and it is more easily metabolized by ADH. Thus, ethanol-based preparations may be preferable in wards with a high frequency of hygienic hand rub use. Yet the differing dermal absorption and metabolization of alcohols is certainly not the only relevant factor in product selection in wards with a high frequency of hand rub use. The spectrum of antimicrobial activity, efficacy, dermal tolerance, and possible impact on compliance in hand hygiene also should be taken into account. Irrespective of the type of alcohol in a hand rub, it seems advisable to increase air exchange in the room to prevent unnecessary pulmonary absorption. This study has several limitations. The number of participants was relatively low. Dermal absorption is influenced by the integrity of the skin (undetectable microlesions) and may vary among the participants and also on different days, implying that small differences between pulmonary and dermal absorption are difficult to recognize. The chosen exposure was a 1-day application, which represents a common frequency of hand rubs in a surgical theater. We did not evaluate the consequences of daily chronic and frequent hygienic hand rubs. We also did not assess the risks to health care workers who are metabolically deficient in aldehyde dehydrogenase, a condition that could present an increased risk of toxicity. In conclusion, in the present study, propanols were absorbed at such low levels that no acute toxic symptoms could be observed and were not expected to arise in our participants. The study revealed that on average, only 0.4%-2.9% of the administered amounts of propanols were absorbed; these substances were metabolized quickly, and their concentrations rapidly decreased to physiological levels. They were rapidly eliminated after the end of exposure and did not accumulate, as also demonstrated by the nonaccumulation of propionaldehyde or acetone in experiments 2 and 3. Because long-term exposure to propanols through the application of hand rubs has yet to be investigated, and given the lack of toxicologic data, further studies are needed. In cases of alcohol dehydrogenase and/or aldehyde dehydrogenase malfunction, a different risk assessment should be conducted. References 1. Boyce JM, Pittet D. Guideline for hand hygiene in health-care settings: recommendations of the Healthcare Infection Control Practices Advisory Committee and the HICPAC/SHEA/APIC/IDSA Hand Hygiene Task Force. Infect Control Hosp Epidemiol 2002;23(12 Suppl):S3-40. 2. Kampf G, Kramer A. Epidemiologic background of hand hygiene and evaluation of the most important agents for scrubs and rubs. Clin Microbiol Rev 2004;17: 863-93. 3. Rotter M. Handwashing and hand disinfection. In: Mayhall CG, editor. Hospital epidemiology and infection control. Philadelphia: Lippincott Williams & Wilkins; 2002. p. 1727-46. 4. Hilburn J, Hammond BS, Fendler EJ, Groziak PA. Use of alcohol hand sanitizer as an infection control strategy in an acute care facility. Am J Infect Control 2003; 31:109-16. 5. Larson E. A causal link between handwashing and risk of infection? Examination of the evidence. Infect Control 1988;9:28-36. 6. Larson E. Skin hygiene and infection prevention: more of the same or different approaches? 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