Occupational contact dermatitis caused by aniline epoxy resins in the aircraft industry

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1 Contact Dermatitis riginal Article CD Contact Dermatitis ccupational contact dermatitis caused by aniline epoxy resins in the aircraft industry Maria Pesonen 1, Katri Suuronen 1, Riitta Jolanki 1, Kristiina Aalto-Korte 1, uti Kuuliala 1, Maj-Len Henriks-Eckerman 2, Ilona Valtanen 3 and Kristiina Alanko 1 1 ccupational Medicine, Finnish Institute of ccupational Health (FIH), Helsinki, Finland, 2 Work Environment Development, FIH, Turku, Finland, and 3 Tampere ccupational Health rganization, Mänttä, Finland doi: /cod Summary Background. Tetraglycidyl-4,4 -methylenedianiline (TGMDA) is an aniline epoxy resin used in, for example, resin systems of pre-impregnated composite materials (prepregs) of the aircraft industry. Allergic contact dermatitis caused by TGMDA in prepregs has been described previously. bjectives. To report on 9 patients with occupational allergic contact dermatitis caused by TGMDA in epoxy glues used in helicopter assembly. Methods. The patients were examined with patch testing at the Finnish Institute of ccupational Health in The first patient was diagnosed by testing both components of two epoxy glues from the workplace, and was also tested with glue ingredients, including TGMDA. The following patients were tested with the glues and TGMDA. The resin parts of the glues were analysed for their epoxy compounds, including TGMDA. Results. All of the patients had a patch test reaction to one or both of the resin parts of the TGMDA-containing glues. Eight of them had a strong allergic reaction to TGMDA, and one had a doubtful reaction to TGMDA. Two of the patients also had an allergic reaction to triglycidyl-p-aminophenol (TGPAP), another aniline epoxy resin, which was not present in the TGMDA-containing glues. Conclusions. In aircraft industry workers with suspected occupational dermatitis, aniline epoxy resins should be considered and patch tested as possible contact allergens. Key words: allergic contact dermatitis; glues; helicopter assembly;, -diglycidyl-4-glycidyloxyaniline; tetraglycidyl-4,4 -methylenedianiline. Epoxy resin compounds are well-known and frequent causes of allergic contact dermatitis. Exposure and sensitization to epoxy compounds often occur in an occupational setting (1). Among the epoxy resin compounds, Correspondence: Maria Pesonen, ccupational Medicine, Finnish Institute of ccupational Health, Topeliuksenkatu 41 aa, FI Helsinki, Finland. Tel: ; Fax: maria.pesonen@ttl.fi Funding: o external funding. Conflicts of interests: The authors declare no conflict of interests. Accepted for publication 21 March 2015 the most common causes of occupational contact dermatitis are the diglycidyl ether of bisphenol A epoxy resins, followed by polyamine hardeners, reactive diluents, and non-diglycidyl ether of bisphenol A-type epoxy resins (non-dgeba-rs) (2, 3). The non-dgeba-rs include diglycidyl ether of bisphenol F epoxy resins, cycloaliphatic epoxy resins, and aniline epoxy resins; the latter are also referred to as aromatic glycidyl amines. Aniline epoxy resins are mainly used for special purposes, such as aircraft and military applications. The aniline epoxy resins triglycidyl-p-aminophenol (TGPAP; also called, -diglycidyl-4-glycidyloxyaniline, CAS no ) (4 8) and, -tetraglycidyl-4,4 -methy Contact Dermatitis, 73,

2 CCUPATIAL TGMDA ALLERGY PESE ET AL. lenedianiline [TGMDA; also called 4,4 -methylenebis (, -diglycidylaniline), CAS no ] (7 9) have been reported as causes of allergic contact dermatitis in the aircraft industry (Fig. 1). Previously, allergic contact dermatitis caused by TGMDA has been reported in workers who handle composite materials pre-impregnated with a TGMDA-containing epoxy resin system (prepregs) (7 9). Here, we report a series of 9 patients with occupational contact dermatitis caused by glues that contained TGMDA and that were used in helicopter assembly at an aircraft plant. Materials and Methods Patch testing We performed the patch tests with Finn Chambers (SmartPractice, Phoenix, AZ, USA), according to the recommendations of the ICDRG. We read the tests two or three times (on days 2, 3, and 4, or on days 2, 3, and 6, or on days 2 and 5), depending on the day of the week on which the test patches were applied. Patch tests were performed with, for example, a modified baseline series, a plastic and glue series, and an epoxy chemical series, as well as with the patients own workplace materials and with individual test substances, such as the glue ingredients, including TGMDA (Epikote Resin 496; Momentive Specialty Chemicals B.V., Rotterdam, The etherlands; 100% of TGMDA). The TGPAP (purity of 90.0%) and, -diglycidylaniline (DGA; CAS no ; Fig. 1) tested in the epoxy chemical series were obtained from Sigma-Aldrich (St Louis, M, USA). As the Finn Chambers (area 0.5 cm 2 )and 20 mg of test preparation (applied by hand) were used in patch testing, we estimate that the dose of TGMDA was 0.4 mg/cm 2 with 1% in petrolatum, and 0.8 mg/cm 2 with 2% in petrolatum. Chemical analyses The resin parts of the two epoxy glues, Glue 1 and Glue 2 of patient 1, and samples of an uncured prepreg and the sanding dust of a cured composite from the workplace were dissolved in acetone for analysis. The levels of TGPAP and DGA were determined by gas chromatography mass spectrometry, and the level of TGMDA was determined with liquid chromatography with ultraviolet detection. For quantification, external standards in acetone were prepared from the pure test substances. The detection limit, which depends on the amount of the compound to be analysed, was approximately <0.001% for TGPAP and DGA. Results Patient cases ine patients with facial and eyelid dermatitis were referred to the Finnish Institute of ccupational Health in by their occupational physician. The patients worked as mechanics at a Finnish aircraft plant, and were involved in helicopter assembly, which involved the use of two-component epoxy glues and a carbon fibre-reinforced epoxy prepreg. The first 3 patients and their examinations are described in detail. The patch test results and details of the test substances are shown in Table 1. In all of the patients, the strongest patch test reactions to TGMDA, TGPAP, DGA and the tested epoxy glues were seen at the final reading. Patient 1 was sent to work as a trainee in helicopter assembly in another European country. He used two-component epoxy glues while working inside the helicopters. After 8 months of the assembly work, he developed an itchy, reddish eyelid dermatitis, which healed during weekends and reappeared after a few days at work. The eyelid dermatitis cleared completely after the patient stopped working with the epoxy glues. Patch tests were performed with a modified baseline series, a plastic and glue series, an epoxy chemical series, and the patient s own workplace materials, including two-component epoxy glues (Glue 1 and Glue 2). Allergic patch test reactions were seen to DGA in the epoxy chemical series and to the resin part of Glue 1 (Table 1). According to the material safety data sheets, the resin parts of both of the glues contained 30 60% TGMDA, as well as diglycidyl ether of bisphenol A (DGEBA) (30 60% in Glue 1; 10 30% in Glue 2). Therefore, we obtained TGMDA for patch testing. In further patch tests, the patient did not react to DGEBA and diglycidyl ether of bisphenol F, but did react to TGPAP in the epoxy chemical series, and had a doubtful (?+) reaction to TGMDA 1% pet. (Table 1). TGPAP and DGA were not identified in Glue 1 and Glue 2. Patient 2 had worked in helicopter assembly for 4 months. He regularly used Glue 1 in his work, and once a month he also used Glue 2. He developed scaly facial dermatitis, which healed during sick leave but recurred as an oedematous eyelid dermatitis 3 days after he returned to work. He was then transferred to other work tasks that did not involve handling epoxy products. After this, the facial dermatitis did not reoccur. n patch testing, he had positive reactions to both of the epoxy glues, TGMDA, DGA, and TGPAP. He also had a doubtful reaction to DGEBA (Table 1). As for patient 1, exposure to aniline epoxy resins other than TGMDA was not identified. 114 Contact Dermatitis, 73,

3 CCUPATIAL TGMDA ALLERGY PESE ET AL. (a) Tetraglycidyl-4,4 -methylenedianiline (TGMDA; 4,4 -methylenebis(,-diglycidylaniline; CAS no ) (b) Triglycidyl-p-aminophenol (TGPAP;, -diglycidyl-4-glycidyloxyaniline; CAS no ) (c) Fig. 1. Chemical structures of (a) tetraglycidyl-4,4 -methyl enedianiline, (b) triglycidyl-paminophenol, and (c), - diglycidylaniline., -Diglycidylaniline (DGA; CAS no ) Patient 3 worked for a few months as a trainee in helicopter assembly in another European country, and continued the same work after returning to Finland. He also used Glue 1 and Glue 2. He mixed the components of the glues in small, open containers, and applied them inside the aircraft. He wore disposable nitrile rubber gloves and, as a respiratory protective device, a half-mask covering his mouth and nose. After 10 months in helicopter assembly work, he developed facial and eyelid dermatitis, which healed during sick leave and recurred when he returned to work and handled the epoxy glues. Even after he started to avoid handling Glue 1 and Glue 2, he still had recurrent mild eyelid dermatitis when working in the same room in which the glues were mixed and handled. nce, he worked inside a helicopter in a cramped space in which the glues were simultaneously used by another worker, and developed eyelid oedema and dermatitis, which took several days to heal. We performed patch tests with a baseline series, a plastic and glue series, and an epoxy chemical series, but obtained negative results. Positive patch test reactions were seen to the resin parts of Glue 1, Glue 2, and TGMDA (Table 1). Later, 6 more patients (Table 1) were referred for examinations because of the occurrence of facial and eyelid dermatitis when they handled Glue 1 and Glue 2 during helicopter assembly. The patients reported wearing natural or nitrile rubber protective gloves when mixing and applying Glue 1 and Glue 2, which were used in small amounts. In addition to facial eczema, 1 of them had eczema on his wrists, which healed after he started using gloves with extended cuffs, and another had an episode of dermatitis on his forearm where Glue 1 had been spilled. After the aniline epoxy glues had been established as the cause of the workers dermatitis, preventive measures were introduced in the plant. The specific glues could not be replaced, but the glue mixing table was transferred to the corner of the room and equipped with a ventilation hood, and the workers started using a powered air-filtering respiratory protective device with a hood that covered the face whenever the working space allowed it. Since these measures were adopted, no new cases of contact allergy to TGMDA have occurred at this plant. Contact Dermatitis, 73,

4 CCUPATIAL TGMDA ALLERGY PESE ET AL. Table 1. Results of patients patch tests with epoxy compounds Patient no./year of examination DGEBA 1% pet. Patch test reactions to epoxy compounds DGA 1% pet. TGMDA pet. TGPAP pet. Glue 1 resin part pet. Glue 2 resin part pet. 1/ egative + 1%?+ 1% + 5% ++ 5% egative 0.32% egative 0.5% % + 2% egative 0.1% egative 0.25%?+ 0.5% % egative 0.01% egative 2/2005?+ ++ 1% T 1% ++ 5% ++ 5% % % % % % % % % % %?+ 0.01%?+ 3/2005 egative egative 1% % egative 5% ++ 5% % % egative 1.67% % + 0.1% % % % % egative 4/2006 egative + 1% ++?+ 2% ++ 2% % % % %?+ 5/2006 egative egative 1% ++ egative 2% ++ 2% % % % egative 0.01% egative 6/2008 egative egative 0.25% + egative 0.5% + 0.5% %?+ 0.16% %?+ 0.05%?+ 7/2008 egative egative 0.25% ++ egative 1% ++ 1% % % % % % egative 0.05%?+ 8/2009?+ egative 1% ++ egative 1% ++ 1% % % % % % % % % % % % egative 9/2009 egative egative 1% ++ egative 1% ++ 1% % % % % % % % % % % % egative Shown are the strongest reactions, which, in all patients, were recorded on the final patch test reading: day 4 in patients 1, 3, and 7; day 5 in patient 4; and day 6 in patients 2, 5, 6, 8, and 9. DGA,, -diglycidylaniline; DGEBA, diglycidyl ether of bisphenol A; TGMDA,, -tetraglycidyl-4,4 -methylenedianiline; TGPAP,, -diglycidyl-4-glycidyloxyaniline; T, not tested. Patch tests in control subjects Patch tests with the resin part of Glue 1 at 5%, 1.67% and 0.5% in pet. in 20 control subjects gave negative results. Analyses of the glues and solid materials Epoxy oligomer analyses of the resin parts of Glue 1 and Glue 2 showed that both glues contained DGEBA (61% and 34%, respectively), and TGMDA (25% and 54%, 116 Contact Dermatitis, 73,

5 CCUPATIAL TGMDA ALLERGY PESE ET AL. respectively), but not TGPAP or DGA. Uncured prepreg contained 10.5% TGMDA, and sanding dust of cured prepreg contained 0.075% TGMDA. Discussion TGMDA resin is costly, but, because of its specific chemical and physical properties, such as high heat resistance and durability, it is used in special applications in, for example, the military and the aerospace industry (10). Prepreg is a term used for a composite material pre-impregnated with a resin system. The most commonly used prepregs are impregnated with epoxy resin, and remain tacky until cured, and often require cold storage and a combination of pressure and heat to fully cure. Both TGMDA and TGPAP have been identified as constituents in the prepregs used in the aircraft industry (7, 8). Contact allergy to aniline epoxy resins has been previously reported in aircraft industry workers who handle prepregs. Burrows et al. (9) examined an outbreak of dermatitis among workers in an aircraft factory using prepregs that contained TGMDA. Seven of the 10 workers patch tested with TGMDA had a positive reaction to it. Lembo et al. (7, 11) described the examinations of workers with dermatitis in another aircraft factory. Having identified TGMDA as a component of a prepreg material used in the factory, they patch tested TGMDA in 11 workers, 9 of whom showed a positive reaction to it. More recently, a patient with occupational allergic contact dermatitis caused by TGMDA and TGPAP in prepregs in the aircraft industry has also been described (8). In addition, occupational contact allergy to TGMDA has previously been reported in 2 workers in wind turbine rotor manufacture, where the moulds for the rotor blades were constructed of glass fibre sheets impregnated with TGMDA (12). otably, these patients were patch test-negative for DGEBA-R. We present a series of 9 patients with occupational contact dermatitis of the face and eyelids caused by TGMDA in the epoxy glues used in an aircraft plant. In addition to TGMDA, the glues also contained DGEBA-R, but none of the 9 patients had a clear contact allergy to DGEBA-R. All of them had allergic patch test reactions to one or both of the glues that contained TGMDA (Glue 1 and Glue 2), and 8 had an allergic reaction (++) to TGMDA, tested as 1% pet. or 0.32% pet. as the highest concentration. ne patient (patient 1) showed only a doubtful reaction to TGMDA 1% pet., but reacted positively to TGPAP and DGA. In the case of patient 1, further patch testing with TGMDA at a higher concentration of 2% in pet. might have been helpful in order to clarify whether the doubtful reaction to TGMDA 1% pet. actually represented contact allergy. In patient 1, the diagnosis of occupational allergic contact dermatitis caused by the TGMDA-containing epoxy glue was based on patient history, an allergy-suggestive patch test reaction (++)to the glue containing TGMDA, the absence of TGPAP and DGA in the glue, and the doubtful reaction to TGMDA 1% pet. According to the analyses, Glue 1 and Glue 2 did not contain TGPAP or DGA. TGPAP, which has previously been reported as a contact allergen in the aircraft industry in prepregs (6 8), glues (4), and an epoxy resin system used in lamination (5), was present in a glue and in prepreg materials used by other workers in the plant. As none of the 3 patients with positive patch test reactions to TGPAP could confirm direct exposure to the products containing TGPAP, their patch test reactions might be attributable to indirect or some other unidentified exposure, or may have resulted from cross-reactivity between the aniline epoxy resins. DGA was not identified in any products in the plant, and reactions to DGA therefore probably represent cross-allergy, although previous exposure to it cannot be ruled out. ur patients had mixed the epoxy glue components themselves, and worked with the TGMDA-containing glues inside the helicopters in poorly ventilated conditions. The primary sensitization to TGMDA is likely to have occurred because of unintentional skin contact with the uncured glues during mixing of the glue components or during application of the glue inside the helicopter, for example to the ceiling. Small droplets of glue may have fallen from the ceiling onto the workers faces. When the components of TGMDA glues are mixed together, they become hot, owing to an exothermic reaction, and small droplets of the glue may vaporize, causing airborne exposure, which may be sufficient to cause allergic contact dermatitis in a previously sensitized subject. This may explain the airborne pattern of our patients allergic contact dermatitis. As an additional source of exposure, all of the surfaces of the working premises were covered with a fine grinding dust from the cured prepreg materials. These varied patterns of exposure emphasize the need for careful occupational hygiene measures in the epoxy composite industry. As far as we are aware, this is the first report of occupational contact dermatitis caused by TGMDA in epoxy glues used in helicopter assembly. However, 2 of our patients had previously worked as trainees in helicopter assembly in two other European countries, and reported similar cases of dermatitis in these workplaces. When aircraft industry workers with suspected occupational contact allergy are examined, aniline epoxy resins should be considered and patch tested as possible contact allergens. According to our experience, testing the resin part of the glue at a concentration of 2% may be a practical alternative to testing with the specific allergen. Contact Dermatitis, 73,

6 CCUPATIAL TGMDA ALLERGY PESE ET AL. References 1 Geier J, Krautheim A, Uter W, Lessmann H, Schnuch A. ccupational contact allergy in the building trade in Germany: influence of preventive measures and changing exposure. Int Arch ccuup Environ Health 2011: 84: Jolanki R, Estlander T, Kanerva L. 182 patients with occupational allergic epoxy contact dermatitis over 22 years. Contact Dermatitis 2001: 44: Aalto-Korte K, Suuronen K, Kuuliala, Henriks-Eckerman M L, Jolanki R. Screening occupational contact allergy to bisphenol F epoxy resin. Contact Dermatitis 2014: 71: Bruze M, Edenholm M, Engstrom K, Svensson G. ccupational dermatoses in a Swedish aircraft plant. Contact Dermatitis 1996: 34: Jappe U, Geier J, Hausen B M. Contact vitiligo following a strong patch test reaction to triglycidyl-p-aminophenol in an aircraft industry worker: case report and review of the literature. Contact Dermatitis 2005: 53: Mathias C G. Allergic contact dermatitis from a nonbisphenol A epoxy in a graphite fiber reinforced epoxy laminate. J ccup Med 1987: 29: Ayala F, Lembo G, Balato, Patruno C, Scognamiglio G, Strazzullo G, De Stefano S. The use of laboratory methods in contact dermatitis induced by composite materials.contact Dermatitis 1990: 22: Kanerva L, Jolanki R, Estlander T, Henriks-Eckerman M, Tuomi M, Tarvainen K. Airborne occupational allergic contact dermatitis from triglycidyl-p-aminophenol and tetraglycidyl-4,4 -methylene dianiline in preimpregnated epoxy products in the aircraft industry. Dermatology 2000: 201: Burrows D, Fregert S, Campbell H, Trulsson L. Contact dermatitis from the epoxy resins tetraglycidyl-4,4 -methylene dianiline and o-diglycidyl phthalate in composite material. Contact Dermatitis 1984: 11: Pham H Q, Marks M J. Epoxy resins. In: Ullmann s Encyclopedia of Industrial Chemistry, 7th edition: Weinheim, Wiley-VCH Verlag GmbH & Co, 2012: Lembo G, Balato, Cusano F, Baldo A, Ayala F. Contact dermatitis to epoxy resins in composite material. In: Current Topics in Contact Dermatitis,FroschPJ, Dooms-Goossens A, Lachapelle J M, Rycroft R J G, Scheper R J (eds): ew York, Springer-Verlag, 1989: pp Pontén A, Carstensen, Rasmussen K, Gruvberger B, Isaksson M, Bruze M. Epoxy-based production of wind turbine rotor blades: occupational contact allergies.dermatitis 2004: 15: Contact Dermatitis, 73,

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